Aménagements hydro-agricoles et santé (vallée du fleuve Sénégal)

La ville de Richard-Toll offre sept types de points d'eau à sa population, allant du site ouvert non aménagé (fleuve) aux bornes offrant de l'eau canalisée. Les usagers y gèrent eux-mêmes leur réserve d'eau quotidienne. Pour évaluer l'effet du site d'approvisionnement et du comportement de l'usager sur la qualité de l'eau consommée, l'eau de 14 sites, représentant les sept types de points d'eau présents dans la ville, a été échantillonnée. De plus, quatre usagers ont été associés à chaque point d'eau, et leur eau a été analysée à domicile à trois reprises, soit après entreposage de moins d'une heure, de 8 heures et de 24 heures. Les analyses ont permis de déterminer la qualité bactériologique de l'eau (coliformes fécaux), qui s'est avérée être excellente (0-10 UCG par 100 ml) à 4 des 14 points d'eau, et mauvaise (101-500 UGC par 100 ml) ou très mauvaise (> 500 UGC par 100 ml) dans les autres cas. Après entreposage de moins d'une heure, l'eau à l'origine excellente a vu sa qualité se dégrader chez la moitié (8 des 16) des usagers, alors que l'eau de mauvaise et de très mauvaise qualité s'est améliorée chez 19 des 39 usagers. Durant l'entreposage quotidien normal de 24 heures, l'eau à l'origine d'excellente qualité s'est dégradée dans 14 des 16 cas, alors que l'eau à l'origine mauvaise ou très mauvaise, s'est améliorée de façon permanente dans 14 des 35 cas. La chloration de l'eau à domicile explique certaines améliorations (5 des 14 cas). Ces résultats démontrent que si la qualité dépend au départ du site d'approvisionnement, l'usager est en mesure de l'affecter de façon positive ou négative, et ce indépendamment de la situation de départ. (Résumé d'auteur

Protein-RNA linkage and post-translational modifications of two sobemovirus VPgs

Sobemoviruses possess a viral genome-linked protein (VPg) attached to the 5' end of viral RNA. VPg is processed from the viral polyprotein. In the current study, Cocksfoot mottle virus (CfMV) and Rice yellow mottle virus (RYMV) VPgs were purified from virions and analysed by mass spectrometry. The cleavage sites in the polyprotein and thereof the termini of VPg were experimentally proven. The lengths of the mature VPgs were determined to be 78 and 79 aa residues, respectively. The amino acid residues covalently linked to RNA in the two VPgs were, surprisingly, not conserved; it is a tyrosine at position 5 of CfMV VPg and serine at position 1 of RYMV VPg. Phosphorylations were identified in CfMV and RYMV VPgs with two positionally similar locations T20/S14 and S71/S72, respectively. RYMV VPg contains an additional phosphorylation site at S41

SOPHIE+: First results of an octagonal-section fiber for high-precision radial velocity measurements

High-precision spectrographs play a key role in exoplanet searches and Doppler asteroseismology using the radial velocity technique. The 1 m/s level of precision requires very high stability and uniformity of the illumination of the spectrograph. In fiber-fed spectrographs such as SOPHIE, the fiber-link scrambling properties are one of the main conditions for high precision. To significantly improve the radial velocity precision of the SOPHIE spectrograph, which was limited to 5-6 m/s, we implemented a piece of octagonal-section fiber in the fiber link. We present here the scientific validation of the upgrade of this instrument, demonstrating a real improvement. The upgraded instrument, renamed SOPHIE+, reaches radial velocity precision in the range of 1-2 m/s. It is now fully efficient for the detection of low-mass exoplanets down to 5-10 Earth mass and for the identification of acoustic modes down to a few tens of cm/s.Comment: 12 pages, 11 figures, accepted in Astronomy and Astrophysic

The SOPHIE search for northern extrasolar planets. II. A multi-planet system around HD9446

We report the discovery of a planetary system around HD9446, performed from radial velocity measurements secured with the spectrograph SOPHIE at the 193-cm telescope of the Haute-Provence Observatory during more than two years. At least two planets orbit this G5V, active star: HD9446b has a minimum mass of 0.7 M_Jup and a slightly eccentric orbit with a period of 30 days, whereas HD9446c has a minimum mass of 1.8 M_Jup and a circular orbit with a period of 193 days. As for most of the known multi-planet systems, the HD9446-system presents a hierarchical disposition, with a massive outer planet and a lighter inner planet.Comment: 7 pages, 6 figures, 3 tables, accepted for publication in A&

Observation of the full 12-hour-long transit of the exoplanet HD80606b. Warm-Spitzer photometry and SOPHIE spectroscopy

We present new observations of a transit of the 111-day-period exoplanet HD80606b. Using the Spitzer Space Telescope and its IRAC camera on the post-cryogenic mission, we performed a 19-hour-long photometric observation of HD80606 that covers the full transit of 13-14 January 2010. We complement this photometric data by new spectroscopic observations that we simultaneously performed with SOPHIE at Haute-Provence Observatory. This provides radial velocity measurements of the first half of the transit that was previously uncovered with spectroscopy. This new data set allows the parameters of this singular planetary system to be significantly refined. We obtained a planet-to-star radius ratio R_p/R_* = 0.1001 +/- 0.0006 that is slightly lower than the one measured from previous ground observations. We detected a feature in the Spitzer light curve that could be due to a stellar spot. We also found a transit timing about 20 minutes earlier than the ephemeris prediction; this could be caused by actual TTVs due to an additional body in the system or by underestimated systematic uncertainties. The sky-projected angle between the spin-axis of HD80606 and the normal to the planetary orbital plane is found to be lambda = 42 +/- 8 degrees thanks to the fit of the Rossiter-McLaughlin anomaly. This allows scenarios with aligned spin-orbit to be definitively rejected. Over the twenty planetary systems with measured spin-orbit angles, a few of them are misaligned; this is probably the signature of two different evolution scenarios for misaligned and aligned systems, depending if they experienced or not gravitational interaction with a third body. As in the case of HD80606b, most of the planetary systems including a massive planet are tilted; this could be the signature of a separate evolution scenario for massive planets in comparison with Jupiter-mass planets.Comment: 14 pages, 9 figures, 2 tables, accepted for publication in A&

Pattern recognition of chemical waves: finding the activation energy of the autocatalytic step in the Belousov-Zhabotinsky reaction

This is the final version. Available from the American Physical Society via the DOI in this record. The Belousov-Zhabotinsky (BZ) reaction is an example of a homogeneous, nonequilibrium reaction used commonly as a model for the study of biological structure and morphogenesis. We report the experimental effects of temperature on spontaneously nucleated trigger waves in a quasi-two-dimensional BZ reaction-diffusion system, conducted isothermally at temperatures between 9.9 and 43.3 °C. Novel application of filter-coupled circle finding and localized pattern analysis is shown to allow the highly accurate extraction of average radial wave velocity and nucleation period. Using this, it is possible to verify a strong Arrhenius dependence of average wave velocity with temperature, which is used to find the effective activation energy of the reaction in accordance with predictions elaborated from the widely used Oregonator model of the BZ reaction. On the basis of our experimental results and existing theoretical models, the value for activation energy of the important self-catalyzed step in the Oregonator model is determined to be 86.58 ± 4.86 kJ mol-1, within range of previous theoretical prediction

The deuterium-to-oxygen ratio in the interstellar medium

Because the ionization balances for HI, OI, and DI are locked together by charge exchange, D/O is an important tracer for the value of the D/H ratio and for potential spatial variations in the ratio. As the DI and OI column densities are of similar orders of magnitude for a given sight line, comparisons of the two values will generally be less subject to systematic errors than comparisons of DI and HI, which differ by about five orders of magnitude. Moreover, D/O is additionally sensitive to astration, because as stars destroy deuterium, they should produce oxygen. We report here the results of a survey of D/O in the interstellar medium performed with FUSE. We also compare these results with those for D/N. Together with a few results from previous missions, the sample totals 24 lines of sight. The distances range from a few pc to ~2000 pc and log N(DI) from ~13 to ~16 (cm-2). The D/O ratio is constant in the local interstellar medium out to distances of ~150 pc and N(DI) ~ 1x10^15 cm-2, i.e. within the Local Bubble. In this region of the interstellar space, we find D/O = (3.84+/-0.16)x10^-2 (1 sigma in the mean). The homogeneity of the local D/O measurements shows that the spatial variations in the local D/H and O/H must be extremely small, if any. A comparison of the Local Bubble mean value with the few D/O measurements available for low metallicity quasar sight lines shows that the D/O ratio decreases with cosmic evolution, as expected. Beyond the Local Bubble we detected significant spatial variations in the value of D/O. This likely implies a variation in D/H, as O/H is known to not vary significantly over the distances covered in this study. Our dataset suggests a present-epoch deuterium abundance below 1x10^-5, i.e. lower than the value usually assumed, around 1.5x10^-5.Comment: 17 pages, 9 figures, 4 tables, accepted for publication in the Astrophysical Journa

The spin-orbit angles of the transiting exoplanets WASP-1b, WASP-24b, WASP-38b and HAT-P-8b from Rossiter-McLaughlin observations

We present observations of the Rossiter-McLaughlin effect for the transiting exoplanet systems WASP-1, WASP-24, WASP-38 and HAT-P-8, and deduce the orientations of the planetary orbits with respect to the host stars' rotation axes. The planets WASP-24b, WASP-38b and HAT-P-8b appear to move in prograde orbits and be well aligned, having sky-projected spin orbit angles consistent with zero: {\lambda} = -4.7 \pm 4.0{\deg}, {\lambda} = 15 + 33{\deg}/-43{\deg} and {\lambda} = -9.7 +9.0{\deg}/-7.7{\deg}, respectively. The host stars have Teff < 6250 K and conform with the trend of cooler stars having low obliquities. WASP-38b is a massive planet on a moderately long period, eccentric orbit so may be expected to have a misaligned orbit given the high obliquities measured in similar systems. However, we find no evidence for a large spin-orbit angle. By contrast, WASP-1b joins the growing number of misaligned systems and has an almost polar orbit, {\lambda} = -79 +4.5{\deg}/-4.3{\deg}. It is neither very massive, eccentric nor orbiting a hot host star, and therefore does not share the properties of many other misaligned systems.Comment: Submitted to MNRAS, 13 pages, 8 tables, 6 figures. Includes revised parameter values for WASP-38 and HAT-P-

Rossiter-McLaughlin Effect Measurements for WASP-16, WASP-25 and WASP-31

We present new measurements of the Rossiter-McLaughlin (RM) effect for three WASP planetary systems, WASP-16, WASP-25 and WASP-31, from a combined analysis of their complete sets of photometric and spectroscopic data. We find a low amplitude RM effect for WASP-16 (Teff = 5700 \pm 150K), suggesting that the star is a slow rotator and thus of an advanced age, and obtain a projected alignment angle of lambda = -4.2 degrees +11.0 -13.9. For WASP-25 (Teff = 5750\pm100K) we detect a projected spin-orbit angle of lambda = 14.6 degrees \pm6.7. WASP-31 (Teff = 6300\pm100K) is found to be well-aligned, with a projected spin-orbit angle of lambda = 2.8degrees \pm3.1. A circular orbit is consistent with the data for all three systems, in agreement with their respective discovery papers. We consider the results for these systems in the context of the ensemble of RM measurements made to date. We find that whilst WASP-16 fits the hypothesis of Winn et al. (2010) that 'cool' stars (Teff < 6250K) are preferentially aligned, WASP-31 has little impact on the proposed trend. We bring the total distribution of the true spin-orbit alignment angle, psi, up to date, noting that recent results have improved the agreement with the theory of Fabrycky & Tremaine (2007) at mid-range angles. We also suggest a new test for judging misalignment using the Bayesian Information Criterion, according to which WASP-25 b's orbit should be considered to be aligned.Comment: 20 pages, 14 tables, 10 figures. Accepted to MNRA