The Effect of Women’s Bargaining Power on Child Nutrition in Rural Senegal

We examine how women’s bargaining power affects child nutritional status using data from rural Senegal. In order to correct for the potential endogeneity of women’s bargaining power we use information on a mother’s ethnicity relative to that of the community she resides in order to construct an arguably exogenous exclusion restriction. While standard OLS estimates suggest that if a mother has more bargaining power, her children will have a better nutritional status, our IV estimates indicate that the true impact is underestimated if the endogeneity of bargaining power is not taken into account

They might be giants: luminosity class, planet frequency, and planet-metallicity relation of the coolest Kepler target stars

We estimate the stellar parameters of late K and early M type Kepler target stars. We obtain medium resolution visible spectra of 382 stars with Kp-J>2 (~K5 and later spectral type). We determine luminosity class by comparing the strength of gravity-sensitive indices (CaH, K I, Ca II, and Na I) to their strength in a sample of stars of known luminosity class. We find that giants constitute 96+-% of the bright (Kp<14) Kepler target stars, and 7+-3% of dim (Kp>14) stars, significantly higher than fractions based on the stellar parameters quoted in the Kepler Input Catalog (KIC). The KIC effective temperatures are systematically (110 +15 -35} K) higher than temperatures we determine from fitting our spectra to PHOENIX stellar models. Through Monte Carlo simulations of the Kepler exoplanet candidate population, we find a planet occurrence of 0.36+-0.08 when giant stars are properly removed, somewhat higher than when a KIC log(g)>4 criterion is used (0.27+-0.05). Lastly, we show that there is no significant difference in g-r color (a probe of metallicity) between late-type Kepler stars with transiting Earth-to-Neptune sized exoplanet candidates and dwarf stars with no detected transits. We show that a previous claimed offset between these two populations is most likely an artifact of including a large number of misidentified giants.Comment: Accepted to Ap

Quorum Sensing Controls Swarming Motility of Burkholderia glumae through Regulation of Rhamnolipids.

International audienceBurkholderia glumae is a plant pathogenic bacterium that uses an acyl-homoserine lactone-mediated quorum sensing system to regulate protein secretion, oxalate production and major virulence determinants such as toxoflavin and flagella. B. glumae also releases surface-active rhamnolipids. In Pseudomonas aeruginosa and Burkholderia thailandensis, rhamnolipids, along with flagella, are required for the social behavior called swarming motility. In the present study, we demonstrate that quorum sensing positively regulates the production of rhamnolipids in B. glumae and that rhamnolipids are necessary for swarming motility also in this species. We show that a rhlA- mutant, which is unable to produce rhamnolipids, loses its ability to swarm, and that this can be complemented by providing exogenous rhamnolipids. Impaired rhamnolipid production in a quorum sensing-deficient B. glumae mutant is the main factor responsible for its defective swarming motility behaviour

Burkholderia thailandensis harbors two identical rhl gene clusters responsible for the biosynthesis of rhamnolipids

<p>Abstract</p> <p>Background</p> <p>Rhamnolipids are surface active molecules composed of rhamnose and β-hydroxydecanoic acid. These biosurfactants are produced mainly by <it>Pseudomonas aeruginosa </it>and have been thoroughly investigated since their early discovery. Recently, they have attracted renewed attention because of their involvement in various multicellular behaviors. Despite this high interest, only very few studies have focused on the production of rhamnolipids by <it>Burkholderia </it>species.</p> <p>Results</p> <p>Orthologs of <it>rhlA</it>, <it>rhlB </it>and <it>rhlC</it>, which are responsible for the biosynthesis of rhamnolipids in <it>P. aeruginosa</it>, have been found in the non-infectious <it>Burkholderia thailandensis</it>, as well as in the genetically similar important pathogen <it>B. pseudomallei</it>. In contrast to <it>P. aeruginosa</it>, both <it>Burkholderia </it>species contain these three genes necessary for rhamnolipid production within a single gene cluster. Furthermore, two identical, paralogous copies of this gene cluster are found on the second chromosome of these bacteria. Both <it>Burkholderia </it>spp. produce rhamnolipids containing 3-hydroxy fatty acid moieties with longer side chains than those described for <it>P. aeruginosa</it>. Additionally, the rhamnolipids produced by <it>B. thailandensis </it>contain a much larger proportion of dirhamnolipids versus monorhamnolipids when compared to <it>P. aeruginosa</it>. The rhamnolipids produced by <it>B. thailandensis </it>reduce the surface tension of water to 42 mN/m while displaying a critical micelle concentration value of 225 mg/L. Separate mutations in both <it>rhlA </it>alleles, which are responsible for the synthesis of the rhamnolipid precursor 3-(3-hydroxyalkanoyloxy)alkanoic acid, prove that both copies of the <it>rhl </it>gene cluster are functional, but one contributes more to the total production than the other. Finally, a double Δ<it>rhlA </it>mutant that is completely devoid of rhamnolipid production is incapable of swarming motility, showing that both gene clusters contribute to this phenotype.</p> <p>Conclusions</p> <p>Collectively, these results add another <it>Burkholderia </it>species to the list of bacteria able to produce rhamnolipids and this, by the means of two identical functional gene clusters. Our results also demonstrate the very impressive tensio-active properties these long-chain rhamnolipids possess in comparison to the well-studied short-chain ones from <it>P. aeruginosa</it>.</p

On the Nature of Small Planets around the Coolest Kepler Stars

We constrain the densities of Earth- to Neptune-size planets around very cool (Te =3660-4660K) Kepler stars by comparing 1202 Keck/HIRES radial velocity measurements of 150 nearby stars to a model based on Kepler candidate planet radii and a power-law mass-radius relation. Our analysis is based on the presumption that the planet populations around the two sets of stars are the same. The model can reproduce the observed distribution of radial velocity variation over a range of parameter values, but, for the expected level of Doppler systematic error, the highest Kolmogorov-Smirnov probabilities occur for a power-law index alpha ~ 4, indicating that rocky-metal planets dominate the planet population in this size range. A single population of gas-rich, low-density planets with alpha = 2 is ruled out unless our Doppler errors are >= 5m/s, i.e., much larger than expected based on observations and stellar chromospheric emission. If small planets are a mix of gamma rocky planets (alpha = 3.85) and 1-gamma gas-rich planets (alpha = 2), then gamma > 0.5 unless Doppler errors are >=4 m/s. Our comparison also suggests that Kepler's detection efficiency relative to ideal calculations is less than unity. One possible source of incompleteness is target stars that are misclassified subgiants or giants, for which the transits of small planets would be impossible to detect. Our results are robust to systematic effects, and plausible errors in the estimated radii of Kepler stars have only moderate impact.Comment: Accepted to the Astrophysical Journa

An All-Sky Catalog of Bright M Dwarfs

We present an all-sky catalog of M dwarf stars with apparent infrared magnitude J<10. The 8,889 stars are selected from the ongoing SUPERBLINK survey of stars with proper motion >40 mas/yr, supplemented on the bright end with the TYCHO-2 catalog. Completeness tests which account for kinematic (proper motion) bias suggest that our catalog represents ~75% of the estimated ~11,900 M dwarfs with J<10 expected to populate the entire sky. Our catalog is, however, significantly more complete for the Northern sky (~90%) than it is for the South (~60%). Stars are identified as cool, red M dwarfs from a combination of optical and infrared color cuts, and are distinguished from background M giants and highly-reddened stars using either existing parallax measurements or, if such measurements are lacking, on their location in an optical-to-infrared reduced proper motion diagram. These bright M dwarfs are all prime targets for exoplanet surveys using the Doppler radial velocity or transit methods; the combination of low-mass and bright apparent magnitude should make possible the detection of Earth-size planets on short-period orbits using currently available techniques. Parallax measurements, when available, and photometric distance estimates are provided for all stars, and these place most systems within 60 parsecs of the Sun. Spectral type estimated from V-J color shows that most of the stars range from K7 to M4, with only a few late M dwarfs, all within 20 pc. Proximity to the Sun also makes these stars good targets for high-resolution exoplanet imaging searches, especially if younger objects can be identified on the basis of X-ray or UV excess. For that purpose, we include X-ray flux from ROSAT and FUV/NUV ultraviolet magnitudes from GALEX for all stars for which a counterpart can be identified in those catalogs.Comment: 16 pages, accepted for publication in the Astronomical Journa

Prospecting in ultracool dwarfs : Measuring the metallicities of mid- and late-m dwarfs

© 2014. The American Astronomical Society. All rights reserved.Metallicity is a fundamental parameter that contributes to the physical characteristics of a star. The low temperatures and complex molecules present in M dwarf atmospheres make it difficult to measure their metallicities using techniques that have been commonly used for Sun-like stars. Although there has been significant progress in developing empirical methods to measure M dwarf metallicities over the last few years, these techniques have been developed primarily for early- to mid-M dwarfs. We present a method to measure the metallicity of mid- to late-M dwarfs from moderate resolution (R ∼ 2000) K-band (≃ 2.2 μm) spectra. We calibrate our formula using 44 wide binaries containing an F, G, K, or early-M primary of known metallicity and a mid- to late-M dwarf companion. We show that similar features and techniques used for early-M dwarfs are still effective for late-M dwarfs. Our revised calibration is accurate to ∼0.07 dex for M4.5-M9.5 dwarfs with -0.58 <[Fe/H] <+0.56 and shows no systematic trends with spectral type, metallicity, or the method used to determine the primary star metallicity. We show that our method gives consistent metallicities for the components of M+M wide binaries. We verify that our new formula works for unresolved binaries by combining spectra of single stars. Lastly, we show that our calibration gives consistent metallicities with the Mann et al. study for overlapping (M4-M5) stars, establishing that the two calibrations can be used in combination to determine metallicities across the entire M dwarf sequence.Peer reviewe

A Spectroscopic Catalog of the Brightest (J<9) M Dwarfs in the Northern Sky

We present a spectroscopic catalog of the 1,564 brightest (J<9) M dwarf candidates in the northern sky, as selected from the SUPERBLINK proper motion catalog. Observations confirm 1,408 of the candidates to be late-K and M dwarfs with spectral subtypes K7-M6. From the low \mu>40 mas/yr proper motion limit and high level of completeness of the SUPERBLINK catalog in that magnitude range, we estimate that our spectroscopic census most likely includes >90% of all existing, northern-sky M dwarfs with apparent magnitude J<9. Only 682 stars in our sample are listed in the Third Catalog of Nearby Stars (CNS3); most others are relative unknowns and have spectroscopic data presented here for the first time. Spectral subtypes are assigned based on spectral index measurements of CaH and TiO molecular bands. A comparison of spectra from the same stars obtained at different observatories however reveals that spectral band index measurements are dependent on spectral resolution, spectrophotometric calibration, and other instrumental factors. After systematic corrections and a recalibration of the subtype-index relationships, we find that we can consistently and reliably classify all our stars to a half-subtype precision. The use of corrected spectral indices further requires us to recalibrate the \zeta parameter, from which we estimate metallicities +/-0.5dex accuracy in dwarfs of subtypes M2 and earlier, and +/-0.2dex accuracy for later (M3-M5) subtypes. Existing geometric parallax measurements are extracted from the literature for 624 stars, and are used to determine spectroscopic and photometric distances for all the other stars. Our catalog will be most useful to guide the selection of the best M dwarf targets for exoplanet searches, in particular those using high-precision radial velocity measurements.Comment: To appear in the Astronomical Journal. Corrected and updated version. Data table has been expanded to include all J<9 M-dwarf candidates in the nort

Photoinduced fluidity in chalcogenide glasses at low and high intensities: A model accounting for photon efficiency

International audienceDetailed measurements of photoinduced fluidity in Ge-Se glasses were performed using a novel shear relaxation test in torsion mode. It is shown that photofluidity is significant even at a very low intensity and that there is no apparent threshold for activating the photostructural processes. Instead, the mechanism of photofluidity is described as a cumulative process involving photoinduced motions of every atom within the irradiated volume. Based on this assumption, a model is proposed, which is shown to accurately predict the power and wavelength dependence of photofluidity using a single fitting parameter n. The factor n represents the photon efficiency for inducing an atomic motion. Photofluidity experiments performed on glass fibers of various mean coordination number indicate that the process is rapidly reduced in overconstrained glasses. The values of n obtained for these glasses correlate remarkably well with the mean coordination dependence of other photostructural changes (photodarkening, photoexpansion). This indicates that the model is physically sound. Moreover, the model is shown to quantitatively describe photofluidity data from other glass systems from literature, therefore suggesting that it could be universally applied to all chalcogenide glasses

PAH under XUV excitation: an ultrafast XUV- photochemistry experiment for astrophysics

International audienceUnderstanding processes induced by XUV excitation of Polycyclic Aromatic Hydrocarbons (PAHs) is at the heart of molecular astrophysics, which aims at understanding molecular evolution in interstellar media. We used ultrashort XUV pulses to produce highly excited PAHs cations. The photo-induced dynamics is probed using a pump-probe XUV-IR spectroscopy. By studying PAH from small (naphthalene) to large (hexabenzocoronene) PAHs, we show that the dynamic is governed by the large density of states, in which many-body quantum effects are dominant