On deriving p-mode parameters for inclined solar-like stars

Thanks to their high quality, new and upcoming asteroseismic observations - with CoRoT, Kepler, and from the ground... - can benefit from the experience gained with helioseismology. We focus in this paper on solar-like oscillations, for which the inclination of the rotation axis is unknown. We present a theoretical study of the errors of p-mode parameters determined by means of a maximum-likelihood estimator, and we also analyze correlations and biases. We have used different, complementary approaches: we have performed either semi-analytical computation of the Hessian matrix, fitting of single mean profiles, or Monte Carlo simulations. We give first analytical approximations for the errors of frequency, inclination and rotational splitting. The determination of the inclination is very challenging for the common case of slow rotators (like the Sun), making difficult the determination of a reliable rotational splitting. Moreover, due to the numerous correlations, biases - more or less significant - can appear in the determination of various parameters in the case of bad inclination fittings, especially when a locking at 90 degrees occurs. This issue concerning inclination locking is also discussed. Nevertheless, the central frequency and some derived parameters such as the total power of the mode are free of such biases.Comment: 9 pages, 6 figures, to appear in A&

On the detection of Lorentzian profiles in a power spectrum: A Bayesian approach using ignorance priors

Aims. Deriving accurate frequencies, amplitudes, and mode lifetimes from stochastically driven pulsation is challenging, more so, if one demands that realistic error estimates be given for all model fitting parameters. As has been shown by other authors, the traditional method of fitting Lorentzian profiles to the power spectrum of time-resolved photometric or spectroscopic data via the Maximum Likelihood Estimation (MLE) procedure delivers good approximations for these quantities. We, however, show that a conservative Bayesian approach allows one to treat the detection of modes with minimal assumptions (i.e., about the existence and identity of the modes). Methods. We derive a conservative Bayesian treatment for the probability of Lorentzian profiles being present in a power spectrum and describe an efficient implementation that evaluates the probability density distribution of parameters by using a Markov-Chain Monte Carlo (MCMC) technique. Results. Potentially superior to "best-fit" procedure like MLE, which only provides formal uncertainties, our method samples and approximates the actual probability distributions for all parameters involved. Moreover, it avoids shortcomings that make the MLE treatment susceptible to the built-in assumptions of a model that is fitted to the data. This is especially relevant when analyzing solar-type pulsation in stars other than the Sun where the observations are of lower quality and can be over-interpreted. As an example, we apply our technique to CoRoT observations of the solar-type pulsator HD 49933.Comment: 12 pages, 11 figures, accepted for publication in Astronomy and Astrophysic

Exoplanets or Dynamic Atmospheres? The Radial Velocity and Line Shape Variations of 51 Pegasi and Tau Bootis

Because of our relatively low spectral resolution, we compare our observations with Gray's line bisector data by fitting observed line profiles to an expansion in terms of orthogonal (Hermite) functions. To obtain an accurate comparison, we model the emergent line profiles from rotating and pulsating stars, taking the instrumental point spread function into account. We describe this modeling process in detail. We find no evidence for line profile or strength variations at the radial velocity period in either 51 Peg or in Tau Boo. For 51 Peg, our upper limit for line shape variations with 4.23-day periodicity is small enough to exclude with 10 sigma confidence the bisector curvature signal reported by Gray & Hatzes; the bisector span and relative line depth signals reported by Gray (1997) are also not seen, but in this case with marginal (2 sigma) confidence. We cannot, however, exclude pulsations as the source of 51 Peg's radial velocity variation, because our models imply that line shape variations associated with pulsations should be much smaller than those computed by Gray & Hatzes; these smaller signals are below the detection limits both for Gray & Hatzes' data and for our own. Tau Boo's large radial velocity amplitude and v*sin(i) make it easier to test for pulsations in this star. Again we find no evidence for periodic line-shape changes, at a level that rules out pulsations as the source of the radial velocity variability. We conclude that the planet hypothesis remains the most likely explanation for the existing data.Comment: 44 pages, 19 figures, plain TeX, accepted to ApJS (companion to letter astro-ph/9712279

Calculation of Spectral Darkening and Visibility Functions for Solar Oscillations

Calculations of spectral darkening and visibility functions for the brightness oscillations of the Sun resulting from global solar oscillations are presented. This has been done for a broad range of the visible and infrared continuum spectrum. The procedure for the calculations of these functions includes the numerical computation of depth-dependent derivatives of the opacity caused by p modes in the photosphere. A radiative-transport code was used for this purpose to get the disturbances of the opacities from temperature and density fluctuations. The visibility and darkening functions are obtained for adiabatic oscillations under the assumption that the temperature disturbances are proportional to the undisturbed temperature of the photosphere. The latter assumption is the only way to explore any opacity effects since the eigenfunctions of p-mode oscillations have not been obtained so far. This investigation reveals that opacity effects have to be taken into account because they dominate the violet and infrared part of the spectrum. Because of this dominance, the visibility functions are negative for those parts of the spectrum. Furthermore, the darkening functions show a wavelength-dependent change of sign for some wavelengths owing to these opacity effects. However, the visibility and darkening functions under the assumptions used contradict the observations of global p-mode oscillations, but it is beyond doubt that the opacity effects influence the brightness fluctuations of the Sun resulting from global oscillations

Polysorbate 80 Inhibition of Pseudomonas aeruginosa Biofilm Formation and Its Cleavage by the Secreted Lipase LipA

Surface-associated bacterial communities known as biofilms are an important source of nosocomial infections. Microorganisms such as Pseudomonas aeruginosa can colonize the abiotic surfaces of medical implants, leading to chronic infections that are difficult to eradicate. Our study demonstrates that polysorbate 80 (PS80), a surfactant commonly added to food and medicines, is able to inhibit biofilm formation by P. aeruginosa on a variety of surfaces, including contact lenses

Toxicokinetics of bisphenol-S and its glucuronide in plasma and urine following oral and dermal exposure in volunteers for the interpretation of biomonitoring data

The measurement of bisphenol-S (BPS) and its glucurono-conjugate (BPSG) in urine may be used for the biomonitoring of exposure in populations. However, this requires a thorough knowledge of their toxicokinetics. The time courses of BPS and BPSG were assessed in accessible biological matrices of orally and dermally exposed volunteers. Under the approval of the Research Ethics Committee of the University of Montreal, six volunteers were orally exposed to a BPS-d8 deuterated dose of 0.1 mg/kg body weight (bw). One month later, 1 mg/kg bw of BPS-d8 were applied on 40 cm2 of the forearm and then washed 6 h after application. Blood samples were taken prior to dosing and at fixed time periods over 48 h after treatment; complete urine voids were collected pre-exposure and at pre-established intervals over 72 h postdosing. Following oral exposure, the plasma concentration–time courses of BPS-d8 and BPSG-d8 over 48 h evolved in parallel, and showed a rapid appearance and elimination. Average peak values (±SD) were reached at 0.7 ± 0.1 and 1.1 ± 0.4 h postdosing and mean (±SD) apparent elimination half-lives (t½) of 7.9 ± 1.1 and 9.3 ± 7.0 h were calculated from the terminal phase of BPS-d8 and BPSG-d8 in plasma, respectively. The fraction of BPS-d8 reaching the systemic circulation unchanged (i.e. bioavailability) was further estimated at 62 ± 5% on average (±SD) and the systemic plasma clearance at 0.57 ± 0.07 L/kg bw/h. Plasma concentration–time courses and urinary excretion rate profiles roughly evolved in parallel for both substances, as expected. The average percent (±SD) of the administered dose recovered in urine as BPS-d8 and BPSG-d8 over the 0–72 h period postdosing was 1.72 ± 1.3 and 54 ± 10%. Following dermal application, plasma levels were under the lower limit of quantification (LLOQ) at most time points. However, peak values were reached between 5 and 8 h depending on individuals, suggesting a slower absorption rate compared to oral exposure. Similarly, limited amounts of BPS-d8 and its conjugate were recovered in urine and peak excretion rates were reached between 5 and 11 h postdosing. The average percent (±SD) of the administered dose recovered in urine as BPS-d8 and BPSG-d8 was about 0.004 ± 0.003 and 0.09 ± 0.07%, respectively. This study provided greater precision on the kinetics of this contaminant in humans and, in particular, evidenced major differences between BPA and BPS kinetics with much higher systemic levels of active BPS than BPA, an observation explained by a higher oral bioavailability of BPS than BPA. These data should also be useful in developing a toxicokinetic model for a better interpretation of biomonitoring data

Skin manifestations among GATA2-deficient patients

International audienceGATA2 mutations have been identified in various diseases, such as MonoMAC syndrome, Emberger syndrome, familial myelodysplastic syndrome, acute myeloid leukaemia and dendritic cell, monocyte, B-cell and natural killer-cell deficiency. These syndromes present a wide range of clinical features, dominated by severe infections and haematological disorders such as myelodysplastic syndrome. Up to 70% of patients with GATA2 mutations have dermatological features, mainly genital or extragenital warts, panniculitis or erythema nodosum and lymphoedema. We report three patients presenting with common dermatological and haematological features leading to the diagnosis of GATA2 deficiency, but also with skin manifestations that have not been previously described gingival hypertrophy, macroglossitis and glossitis and granulomatous lupoid facial lesions. Dermatologists can encounter patients with GATA2 mutations and should recognize this disorder

PHIL photoinjector test line

LAL is now equiped with its own platform for photoinjectors tests and Research and Developement, named PHIL (PHotoInjectors at LAL). This facility has two main purposes: push the limits of the photoinjectors performances working on both the design and the associated technology and provide a low energy (MeV) short pulses (ps) electron beam for the interested users. Another very important goal of this machine will be to provide an opportunity to form accelerator physics students, working in a high technology environment. To achieve this goal a test line was realised equipped with an RF source, magnets and beam diagnostics. In this article we will desrcibe the PHIL beamline and its characteristics together with the description of the first two photoinjector realised in LAL and tested: the ALPHAX and the PHIN RF Guns

Fourier Analysis of Gapped Time Series: Improved Estimates of Solar and Stellar Oscillation Parameters

Quantitative helio- and asteroseismology require very precise measurements of the frequencies, amplitudes, and lifetimes of the global modes of stellar oscillation. It is common knowledge that the precision of these measurements depends on the total length (T), quality, and completeness of the observations. Except in a few simple cases, the effect of gaps in the data on measurement precision is poorly understood, in particular in Fourier space where the convolution of the observable with the observation window introduces correlations between different frequencies. Here we describe and implement a rather general method to retrieve maximum likelihood estimates of the oscillation parameters, taking into account the proper statistics of the observations. Our fitting method applies in complex Fourier space and exploits the phase information. We consider both solar-like stochastic oscillations and long-lived harmonic oscillations, plus random noise. Using numerical simulations, we demonstrate the existence of cases for which our improved fitting method is less biased and has a greater precision than when the frequency correlations are ignored. This is especially true of low signal-to-noise solar-like oscillations. For example, we discuss a case where the precision on the mode frequency estimate is increased by a factor of five, for a duty cycle of 15%. In the case of long-lived sinusoidal oscillations, a proper treatment of the frequency correlations does not provide any significant improvement; nevertheless we confirm that the mode frequency can be measured from gapped data at a much better precision than the 1/T Rayleigh resolution.Comment: Accepted for publication in Solar Physics Topical Issue "Helioseismology, Asteroseismology, and MHD Connections

Quantitative kinetics and enthalpy measurements of biphasic underflow chemical reactions by InfraRed Thermography

Abstract The scope of this paper is to present the experimental study of a well known chemical reaction in a biphasic millifluidic droplet flow by using InfraRed Thermography. This simple thermal evaluation enables the characterization of kinetics and enthalpy of exothermic chemical reactions. The originality of this work is the application of a very simple thermal model based on an homogenized thin body approximation to perform calorimetric estimations. This novel calorimeter needs a thermal calibration step to estimate the heat losses (W). Then, a correlation method is applied for the simultaneous estimation of the heat source (φ) and the characteristic coefficient due the convective effects (H). Here the estimation of the characteristic coefficient H (s −1 ) is done at each flow rate ratio (R). This procedure is applied for several chemical reaction performed at different flow rate ratios. Then, the enthalpy is estimated with an error lower than 2%. In addition, the methodology to estimate the mixing kinetics of the reaction can be pointed out by the integrated flux over the time. Finally, a non contact thermal calorimeter based on millifluidic and IR thermography was developed. It is a convenient and powerful tool for the characterization of chemical reaction performed in a droplet flow