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L'objectif de cette recherche est de déterminer un protocole d'investigation permettant de décrire la structure de la coulée de Super Sauze le long de profils continus, en employant les méthodes électriques et TDEM (Time-Domain Electromagnetism) associées. Le passage d'une gamme de résistivité à la suivante correspond souvent aux limites des trois terrains définis par les sondages géotechniques. Les résultats présentés montrent que les méthodes employées sont adaptées à la problématique ; ils sont validés par la géotechnique. (Résumé d'auteur)

*INRA, Centre de Versailles (FRA) Diffusion du document : INRA, Centre de Versailles (FRA); National audience

The aim of our paper is to show the importance of geomagnetic data to the knowledge of the main geomagnetic field and its secular variation, and also of the temporal, in order to survey the Earth's environment. Firstly, we recall the results obtained on the high-resolution secular variation of the geomagnetic field in two sites situated in Western Europe (London and Paris) over the last four centuries. The declination data are remarkably well correlated between the two sites and can be used to construct a more complete and accurate synthetic series, in which many gaps or times with scattered or uncertain data can be amended. The built declination synthetic series is believed to be valid for much Western Europe, and information about the secular variation in this area are obtained. But, to characterise the geomagnetic field, the spatial variations are also important. To monitor the field variations, an international program has been developed since 1988. Under the INTERMAGNET program, high quality data from a global network of geomagnetic observatories are sent in near real time via satellite and computer links to world-wide collection and disseminatin points called "Geomagnetic Information Nodes" or GINs. All INTERMAGNET observatories operate with the same common specifications (resolution, filtering, sampling rate, data formats etc.) Today, the INTERMAGNET observatories data-sets of 1.0 minute values with good baselines are available within minutes and hours from about 60 observatories. Another INTERMAGNET goal is to fill out the global geomagnetic observatory distribution. In fact, a recent study specified the minimum number of equally spaced observatories needed to do a degree and order 10 spherical harmonic model of the main field. The model required a minimum of 92 observatories on about a 2,000 km spacing. Eight sites would require ocean bottom observatories... (D'après résumé d'auteur)

International audience; In France, sunflower variety trials for new varieties registration on the National List are planned in the fields as randomized complete block designs with four replicates. In this paper 119 such trials (from 1993 to 1996) are analysed as if they had been planned with a resolvable incomplete block designs (IBD) to investigate whether a different system of blocking would have been better than the one actually used. A postblocking technique (Patterson and Hunter, 1983; Ainsley et al., 1987) is used to establish a relationship between error mean squares and block size in order to predict the efficiency of IBD . It is shown that when recovering inter-block information the IBD average efficiency would have been 1.33 for five plots per block; with intra-block information only, the IBD average efficiency reaches 1.24. Block size has an effect on efficiency. The results are in accordance with those of Patterson and Hunter (1983) who recommended that the optimum block size should be roughly equal to the square root of the number of varieties in the experiment.

The aim of this study is to interpret data from vertical electrical soundings using bayesian approach of the 1 D inverse problem. Two orthogonal Schlumberger soundings were carried out on the lake Tritrivakely. By classical interpretation, thickness of first conductive layers is underestimated. Bayesian inversion method is efficient for analysis of equivalence : using two or three layers models, we obtain a well constrained estimation on resistivity of conductive layer(s) but a poorly constrained estimation on thickness. Bayesian inversion may be used also for giving a smooth model resistivity versus depth. (Résumé d'auteur)

National audience

Petroleum oil, rapeseed oil and its methyl ester derivative enhance efficacy of an Illoxan CE emulsion of diclofop-methyl on ryegrass (Lolium multiflorum Lam) by 65, 29 and 57% respectively. These adjuvants only marginally improve spray retention by plants. The abaxial leaf surface retains more spray than the adaxial surface: 3.4, 4.0, 7.3 and 6.9 times at 0, 30, 60 and 80° leaf inclination respectively. Droplet drying was 110 to 150% accelerated by both the oils and the emulsifier. This was accompanied by an increase in the spread of droplets : 3.7 times with the methyl ester derivative on a surface basis. Diclofop-methyl penetration into ryegrass (adaxial surface) was not affected by the emulsifier; was 210% increased by rapeseed oil, 310% by its methyl ester and 500% by petroleum oil. Diclofop-methyl penetration after 24 h was 20% of the applied herbicide on the adaxial surface (poorly wettable), but only 4% on the abaxial surface (highly wettable). Addition of rapeseed oil methyl ester derivative increased it to 81 and 9% respectively., Une huile minérale, une huile végétale (colza), ainsi que son ester méthylique, augmentent l’efficacité du diclofop-méthyl sur ray-grass (Lolium multiflorum Lam) respectivement de 65, 29 et 57% (fig 1). Ces adjuvants n’améliorent que peu ou pas la rétention de pulvérisation par les plantes (tableaux I, II et IV). La face abaxiale retient davantage de pulvérisation que la face adaxiale : 3,4, 4,0, 7,3 et 6,9 fois plus à, respectivement, 0, 30, 60 et 80° d’inclinaison (tableau III). Le séchage des gouttelettes déposées sur le feuillage est accéléré par les huiles ou l’émulgateur seul (de 110 à 150%) (fig 2), et leur étalement augmenté (3,7 fois en surface par l’ester méthylique) (fig 3). La pénétration du diclofop-méthyl par la face adaxiale n’est pas affectée par l’émulgateur mais est augmentée de 210% par l’huile de colza, 310% par son ester méthylique et 500% par l’huile minérale (fig 4). En 24 h, 20% du diclofop-méthyl appliqué pénètre par la face adaxiale (peu mouillable) et seulement 4% par la face abaxiale (très mouillable). L’addition d’ester d’huile de colza accroît ces valeurs à, respectivement, 81 à 9% (tableau V).

National audience