Artificial cochlea and acoustic black hole travelling waves observation: Model and experimental results

An inhomogeneous fluid structure waveguide reproducing passive behaviour of the inner ear is modelled with the help of the Wentzel–Kramers–Brillouin method. A physical setup is designed and built. Experimental results are compared with a good correlation to theoretical ones. The experimental setup is a varying width plate immersed in fluid and terminated with an acoustic black hole. The varying width plate provides a spatial repartition of the vibration depending on the excitation frequency. The acoustic black hole is made by decreasing the plate׳s thickness with a quadratic profile and by covering this region with a thin film of viscoelastic material. Such a termination attenuates the flexural wave reflection at the end of the waveguide, turning standing waves into travelling waves

The three lipocalins of egg-white: only Ex-FABP inhibits siderophore-dependent iron sequestration by Salmonella Enteritidis

Salmonella Enteritidis is the most prevalent food-borne pathogen associated with egg-related outbreaks in the European Union. During egg colonization, S. Enteritidis must resist the powerful anti-bacterial activities of egg white (EW) and overcome ovotransferrin-imposed iron-restriction (the most important anti-bacterial mechanism of EW). Many pathogens respond to iron restriction by secreting iron-chelating chemicals called siderophores but EW contains a siderophore-sequestering “lipocalin” protein (Ex-FABP) that is predicted to limit the usefulness of siderophores in EW. S. Enteritidis produces two siderophores: enterobactin, which is strongly bound by Ex-FABP; and the di-glucosylated enterobactin-derivative, salmochelin (a so-called “stealth” siderophore), which is not recognized by Ex-FABP. Thus, production of salmochelin may allow S. Enteritidis to escape Ex-FABP-mediated growth inhibition under iron restriction although it is unclear whether its EW concentration is sufficient to inhibit pathogens. Further, two other lipocalins (Cal-γ and α-1-ovoglycoprotein) are found in EW but their siderophore sequestration potential remains unexplored. In addition, the effect of EW lipocalins on the major EW pathogen, S. Enteritidis, has yet to be reported. We overexpressed and purified the three lipocalins of EW and investigated their ability to interact with the siderophores of S. Enteritidis, as well as their EW concentrations. The results show that Ex-FABP is present in EW at concentrations (5.1 μM) sufficient to inhibit growth of a salmochelin-deficient S. Enteritidis mutant under iron restriction but has little impact on the salmochelin-producing wildtype. Neither Cal-γ nor α-1-ovoglycoprotein bind salmochelin or enterobactin, nor do they inhibit iron-restricted growth of S. Enteritidis. However, both are present in EW at significant concentrations (5.6 and 233 μM, respectively) indicating that α-1-ovoglycoprotein is the 4th most abundant protein in EW, with Cal-γ and Ex-FABP at 11th and 12th most abundant. Further, we confirm the preference (16-fold) of Ex-FABP for the ferrated form (Kd of 5.3 nM) of enterobactin over the iron-free form (Kd of 86.2 nM), and its lack of affinity for salmochelin. In conclusion, our findings show that salmochelin production by S. Enteritidis enables this key egg-associated pathogen to overcome the enterobactin-sequestration activity of Ex-FABP when this lipocalin is provided at levels found in EW

Les séries fluvio-éoliennes du "Cutler Group" :: Permien (Utah, USA). Modèle architectural et expression des unités génétiques

National audienceL'essor qu'a connu la stratigraphie séquentielle dans les environnements continentaux a permis de définir des modèles architecturaux pour des séries fluvio-lacustres. Plus récemment, les modèles proposés ont intégré les dépôts éoliens dans les systèmes continentaux côtiers ou lacustres (préservation de l'éolien vs variations de la table d'eau, e.g. Carr-Crabaugh & Kocurek, 1998) ou dans les systèmes continentaux endoréiques (préservation de l'éolien vs climat (e.g. Clemmensen et al., 1998) ou préservation de l'éolien vs accommodation et flux de sédiments, e.g. Bourquin et al., 2009). Cependant, peu de modèles discutent les variations de préservation des dépôts éoliens par rapport aux environnements continentaux associés (fluvial, lac, playa) afin de prédire un modèle architectural des dépôts éoliens (du réservoir au bassin) en fonction du contexte géodynamique. L'objectif de cet exposé est de contraindre l'expression des unités génétiques et de proposer un modèle architectural montrant les variations de préservation des dépôts éoliens en fonction du contexte tectonique, climatique et eustatique. L'étude des séries du Permien inférieur, " Cutler Group ", du " Paradox Basin " (SE Utah), caractérisées par des dépôts fluvio-éoliens (e.g. Condon, 1997), a été réalisée à partir de 5 sections sédimentologiques. Elles sont localisées sur un profil proximal représenté par des dépôts dominés fluvial jusqu'à des dépôts dominés éolien dans le domaine distal (e.g. Mountney & Jagger, 2004). Une étude sédimentologique et stratigraphique détaillée permet de proposer une évolution spatiale et temporelle des environnements de dépôt. Nous avons ainsi mis en évidence (1) les variations d'expression des unités génétiques d'un environnement proximal à un environnement distal en climat semi-aride, (2) plusieurs modèles architecturaux montrant l'évolution verticale depuis un contexte de bassin côtier, à dunes éoliennes faiblement préservées, vers des environnements plus continentaux dominés éolien puis vers des systèmes fluvio-lacustres à faible préservation des dépôts éoliens

Scientific rationale of a Saturn probe mission

We describe the main scientific goals to be addressed by future in situ exploration of Saturn

Global gene-expression analysis of the response of Salmonella Enteritidis to egg-white exposure reveals multiple egg-white-imposed stress responses

Chicken egg white protects the embryo from bacterial invaders by presenting an assortment of antagonistic activities that combine together to both kill and inhibit growth. The key features of the egg-white anti-bacterial system are iron restriction, high pH, antibacterial peptides and proteins, and viscosity. Salmonella enterica serovar Enteritidis is the major pathogen responsible for egg-borne infection in humans, which is partly explained by its exceptional capacity for survival under the harsh conditions encountered within egg white. However, at temperatures up to 42 ˚C, egg white exerts a much stronger bactericidal effect on S. Enteritidis than at lower tempertaures, although the mechanism of egg-white-induced killing is only partly understood. Here, for the first time, the impact of exposure of S. Enteritidis to egg white under bactericidal conditions (45 ˚C) is explored by global-expression analysis. A large-scale (18.7% of genome) shift in transcription is revealed suggesting major changes in specific aspects of S. Enteritidis physiology: induction of egg-white related stress-responses (envelope damage, exposure to heat and alkalinity, and translation shutdown); shift in energy metabolism from respiration to fermentation; and enhanced micronutrient provision (due to iron and biotin restriction). Little evidence of DNA damage or redox stress was obtained. Instead, data are consistent with envelope damage resulting in cell death by lysis. A surprise was the high degree of induction of hexonate/hexuronate utilisation genes, despite no evidence indicating the presence of these substrates in egg white

Numerical and experimental investigation of the acoustic black hole effect for vibration damping in beams and elliptical plates

Flexural waves in beams and plates slow down if their thickness decreases. Such property was successfully used for establishing the theory of acoustic black holes (ABH). In fact, in the case of a sharpened edge having a power-law profile, it can be shown that the refection coefficient of a wave propagating towards the sharpened edge can be equal to zero. However, manufacturing such profiles is always related to truncations and imperfections that undermine ABH. It is known though that the use of a thin absorbing film drastically improves the damping effect of ABH. The aim of the current paper is to show numerically and experimentally the capability of ABH to provide structural damping without introducing additional mass. The dynamic behaviour of a non uniform Euler-Bernoulli beam is described using a Riccati equation for the beam impedance, which leads to the reflection matrix of the sharpened edge of the beam. The influence of length of the profile, thickness and length of the absorbing film are evaluated as realistically as possible and optimised numerically in order to reduce wave reflection from the edge. Keeping in mind the numerical results, an elliptic plate with a pit of power law profile placed at one of its focuses has been designed and tested. As a result, both numerical simulations and experimental measurements show significant reduction of vibration levels

Non-linear analysis of GeneChip arrays

The application of microarray hybridization theory to Affymetrix GeneChip data has been a recent focus for data analysts. It has been shown that the hyperbolic Langmuir isotherm captures the shape of the signal response to concentration of Affymetrix GeneChips. We demonstrate that existing linear fit methods for extracting gene expression measures are not well adapted for the effect of saturation resulting from surface adsorption processes. In contrast to the most popular methods, we fit background and concentration parameters within a single global fitting routine instead of estimating the background before obtaining gene expression measures. We describe a non-linear multi-chip model of the perfect match signal that effectively allows for the separation of specific and non-specific components of the microarray signal and avoids saturation bias in the high-intensity range. Multimodel inference, incorporated within the fitting routine, allows a quantitative selection of the model that best describes the observed data. The performance of this method is evaluated on publicly available datasets, and comparisons to popular algorithms are presented

Studying the Physical Diversity of Late-M Dwarfs with Dynamical Masses

We present a systematic study of the physical properties of late-M dwarfs based on high-quality dynamical mass measurements and near-infrared (NIR) spectra. We use astrometry from Keck NGS and LGS AO imaging to determine orbits for late-M binaries. We find that LP 349-25 (M7.5+M8) is a pair of young brown dwarfs (Mtot = 0.120 Msun) for which Lyon and Tucson evolutionary models jointly predict an age of 140+/-30 Myr. This is consistent with the age of the Pleiades, but at least LP 349-25A defies the empirical Pleiades lithium depletion boundary, implying that the system is in fact older and that evolutionary models underpredict the component luminosities. We find that LHS 1901AB (M6.5+M6.5) is a pair of very low-mass stars (Mtot = 0.194 Msun) with model-derived ages consistent with limits from its lack of activity (> 6 Gyr). Our improved orbit for Gl 569Bab (M8.5+M9) results in a higher mass for this binary (Mtot = 0.140 Msun) compared to previous work (0.125 Msun). We use these masses along with our published results for 2MASS J2206-2047AB (M8+M8) to test four sets of ultracool model atmospheres currently in use. Fitting these models to our NIR integrated-light spectra provides temperature estimates warmer by ~250 K than those derived independently from Dusty evolutionary models given the measured masses and luminosities. We propose that model atmospheres are more likely to be the source of this discrepancy, as it would be difficult to explain a uniform temperature offset over such a wide range of masses, ages, and activity levels in the context of evolutionary models. Our results contrast those of Konopacky et al. as we find an opposite and smaller mass discrepancy from what they report when we adopt their model-testing approach since our Teff estimates from fitting spectra are ~650 K higher than from their fitting of broadband photometry alone.Comment: 53 pages, 12 figures, accepted to Ap

Genome analysis of the necrotrophic fungal pathogens Sclerotinia sclerotiorum and Botrytis cinerea

Sclerotinia sclerotiorum and Botrytis cinerea are closely related necrotrophic plant pathogenic fungi notable for their wide host ranges and environmental persistence. These attributes have made these species models for understanding the complexity of necrotrophic, broad host-range pathogenicity. Despite their similarities, the two species differ in mating behaviour and the ability to produce asexual spores. We have sequenced the genomes of one strain of S. sclerotiorum and two strains of B. cinerea. The comparative analysis of these genomes relative to one another and to other sequenced fungal genomes is provided here. Their 38–39 Mb genomes include 11,860–14,270 predicted genes, which share 83% amino acid identity on average between the two species. We have mapped the S. sclerotiorum assembly to 16 chromosomes and found large-scale co-linearity with the B. cinerea genomes. Seven percent of the S. sclerotiorum genome comprises transposable elements compared t

Egg-white proteins have a minor impact on the bactericidal action of egg white toward Salmonella Enteritidis at 45°C

Salmonella enterica serovar Enteritidis is noted for its ability to survive the harsh antibacterial activity of egg white which is presumed to explain its occurrence as the major food-borne pathogen associated with the consumption of eggs and egg products. Liquid egg white is a major ingredient for the food industry but, because of its thermal fragility, pasteurization is performed at the modest temperature of 57 °C (for 2 to 6 min). Unfortunately, such treatment does not lead to sufficient reduction in S. Enteritidis contamination, which is a clear health concern when the product is consumed without cooking. However, egg white is able to limit S. Enteritidis growth due to its alkaline pH, iron deficiency and multiple antimicrobial proteins. This anti-Salmonella activity of egg white is temperature dependent and becomes bactericidal once the incubation temperature exceeds 42°C. This property is exploited in highly-promising pasteurization treatment (42-45 °C for 1 to 5 days) which achieves complete killing of S. Enteritidis. However, the precise mechanism and the role of the egg-white proteins are not fully understood. Here, the impact of exposure of S. Enteritidis to egg white-based media, with or without egg-white proteins (>10 kDa), under bactericidal conditions (45 °C) was explored by measuring survival and global expression. Surprisingly, the bactericidal activity of egg white at 45 °C was only slightly affected by egg-white proteins indicating that they play a minor role in the bactericidal activity observed. Moreover, egg-white proteins had minimal impact on the global-gene-expression response to egg white such that very similar, major regulatory responses (20% genes affected) were observed both with and without egg-white proteins following 45 min at 45°C. Egg-white proteins caused a significant change in expression for just 64 genes, including the psp and lysozyme-inhibitor responses genes which is suggestive of an early membrane perturbation effect. Such damage was supported by disruption of the proton motive force by egg-white proteins. In summary, the results suggest that low-mass components of egg white are largely responsible for the bactericidal activity of egg white at 45 °C