Increased hydrogen production by Escherichia coli strain HD701 in comparison with the wild-type parent strain MC4100

Hydrogen production by Escherichia coli is mediated by the formate hydrogenlyase (FHL) complex. E. coli strain HD701 cannot synthesize the FHL complex repressor, Hyc A. Consequently, it has an up-regulated FHL system and can, therefore, evolve hydrogen at a greater rate than its parental wild type, E. coli MC4100. Resting cells of E. coli strain HD701 and MC4100 were set up in batch mode in\ud phosphate buffered saline (PBS) to decouple growth from hydrogen production at the expense of sugar solutions of varying composition. Strain HD701 evolved several times more hydrogen than MC4100 at glucose concentrations ranging from 3 to 200 mM. The difference in the amount of H2 evolved by both strains decreased as the concentration of glucose increased. The highest rate of H2 evolution by strain HD701was 31ml h−1 ODunit −1 l−1 at a glucose concentration of 100 mM.With strain MC4100, the highest ratewas 16ml h−1 ODunit −1 l−1 under these conditions. Experiments using industrial wastes with a high sugar content yielded similar results. In each case, strain HD701\ud evolved hydrogen at a faster rate than the wild type, showing a possible potential for commercial hydrogen production

Estimation par Maximum de Vraisemblance du sous espace clutter dans un bruit hétérogène rang faible avec application au STAP

National audienceDans le contexte d'une cible noyée dans un clutter hétérogène de rang faible plus un bruit blanc gaussien, les méthodes de filtrage rang faible requièrent moins de données secondaires que les méthodes classiques pour atteindre des performances équivalentes. Le filtre de rang faible est notamment composé du projecteur sur le sous espace clutter. Celui ci étant en pratique inconnu, il est nécessaire de l'estimer. Nous proposons dans ce papier un estimateur par maximum de vraisemblance du projecteur sur le sous espace clutter pour un bruit composé d'un cluter SIRV (Spherically Invariant Random Vectors) de rang faible et d'un bruit blanc gaussien. Les performances de ce nouvel estimateur sont testées sur des simulations de validation ainsi qu'une application de Space Time Adaptive Processing (STAP) [1]

Leading Order Calculation of Shear Viscosity in Hot Quantum Electrodynamics from Diagrammatic Methods

We compute the shear viscosity at leading order in hot Quantum Electrodynamics. Starting from the Kubo relation for shear viscosity, we use diagrammatic methods to write down the appropriate integral equations for bosonic and fermionic effective vertices. We also show how Ward identities can be used to put constraints on these integral equations. One of our main results is an equation relating the kernels of the integral equations with functional derivatives of the full self-energy; it is similar to what is obtained with two-particle-irreducible effective action methods. However, since we use Ward identities as our starting point, gauge invariance is preserved. Using these constraints obtained from Ward identities and also power counting arguments, we select the necessary diagrams that must be resummed at leading order. This includes all non-collinear (corresponding to 2 to 2 scatterings) and collinear (corresponding to 1+N to 2+N collinear scatterings) rungs responsible for the Landau-Pomeranchuk-Migdal effect. We also show the equivalence between our integral equations obtained from quantum field theory and the linearized Boltzmann equations of Arnold, Moore and Yaffe obtained using effective kinetic theory.Comment: 45 pages, 22 figures (note that figures 7 and 14 are downgraded in resolution to keep this submission under 1000kb, zoom to see them correctly

MAXIMUM LIKELIHOOD ESTIMATION OF CLUTTER SUBSPACE IN NON HOMOGENEOUS NOISE CONTEXT

International audienceIn the context of a disturbance composed of a Low Rank (LR) clutter plus a white Gaussian noise, the corresponding LR filters used to detect a target embedded in this disturbance needs less training vectors than classical methods to reach equivalent performance. Unlike the classical one which is based on covariance matrix of the noise, the LR filter is based on the clutter subspace projector. In this paper, we propose a new estimator of the clutter subspace projector for a disturbance composed of a LR Spherically Invariant Random Vectors (SIRV) plus a zero mean white Gaussian noise that does not require prior information on the SIRV's texture. Numerical simulations validate the introduced estimator, and its performance and robustness are tested on a Space Time Adaptive Processing (STAP) simulation

MAXIMUM LIKELIHOOD ESTIMATION OF CLUTTER SUBSPACE IN NON HOMOGENEOUS NOISE CONTEXT

International audienceIn the context of a disturbance composed of a Low Rank (LR) clutter plus a white Gaussian noise, the corresponding LR filters used to detect a target embedded in this disturbance needs less training vectors than classical methods to reach equivalent performance. Unlike the classical one which is based on covariance matrix of the noise, the LR filter is based on the clutter subspace projector. In this paper, we propose a new estimator of the clutter subspace projector for a disturbance composed of a LR Spherically Invariant Random Vectors (SIRV) plus a zero mean white Gaussian noise that does not require prior information on the SIRV's texture. Numerical simulations validate the introduced estimator, and its performance and robustness are tested on a Space Time Adaptive Processing (STAP) simulation

B(H) Constitutive Relations Near H_c1 in Disordered Superconductors

We provide a self-contained account of the B vs. H constitutive relation near H_c1 in Type II superconductors with various types of quenched random disorder. The traditional Abrikosov result B ~ [ln (H - H_c1)]^{-2}, valid in the absence of disorder and thermal fluctuations, changes significantly in the presence of disorder. Moreover, the constitutive relations will depend strongly on the type of disorder. In the presence of point disorder, B ~ (H - H_c1)^{3/2} in three-dimensional (thick) superconductors, as shown by Nattermann and Lipowsky. In two-dimensional (thin film) superconductors with point disorder, B ~ (H - H_c1). In the presence of parallel columnar disorder, we find that B ~ exp[-C / (H - H_c1)] in three dimensions, while B ~ exp[-K / (H - H_c1)^{1/2}] in two dimensions. In the presence of nearly isotropically splayed disorder, we find that B ~ (H - H_c1)^{3/2} in both two and three dimensions.Comment: 37 pages, 12 figures included in text; submitted to Physica

Stable Ta2O5 Overlayers on Hematite for Enhanced Photoelectrochemical Water Splitting Efficiencies

Hematite (α‐Fe2O3) is one of the most promising photoanodes for water oxidation, however the efficiencies of current hematite materials remain low. Surface trap states are often reported as one of the factors which limit the activity of hematite photoelectrodes, often leading to undesirable surface pinning and trap‐mediated recombination. The deposition of ultra‐thin Al2O3 overlayers is known to enhance hematite activity through passivation of surface states, however Al2O3 is rapidly degraded at normal hematite operating pH values (pH≈13). This study reports atomic layer deposition (ALD) of Ta2O5 thin films as stable, passivating overlayers on a range of hematite photoelectrodes and demonstrates that enhanced activity correlates with observed changes in trap‐state dynamics

Quasiparticle excitations in relativistic quantum field theory

We analyze the particle-like excitations arising in relativistic field theories in states different than the vacuum. The basic properties characterizing the quasiparticle propagation are studied using two different complementary methods. First we introduce a frequency-based approach, wherein the quasiparticle properties are deduced from the spectral analysis of the two-point propagators. Second, we put forward a real-time approach, wherein the quantum state corresponding to the quasiparticle excitation is explicitly constructed, and the time-evolution is followed. Both methods lead to the same result: the energy and decay rate of the quasiparticles are determined by the real and imaginary parts of the retarded self-energy respectively. Both approaches are compared, on the one hand, with the standard field-theoretic analysis of particles in the vacuum and, on the other hand, with the mean-field-based techniques in general backgrounds.Comment: 53 pages, 4 figures. Version accepted for publication in Ann. Phy

Spitzer and ISO Galaxy Counts in the Mid-Infrared

Galaxy source counts that simultaneously fit the deep mid-infrared surveys at 24 microns and 15 microns made by the Spitzer Space Telescope and the Infrared Space Observatory (ISO) respectively are presented for two phenomenological models. The models are based on starburst and luminous infrared galaxy dominated populations. Both models produce excellent fits to the counts in both wavebands and provide an explanation for the high redshift population seen in the longer Spitzer 24 micron band supporting the hypothesis that they are luminous-ultraluminous infrared galaxies at z=2-3, being the mid-infrared counterparts to the sub-mm galaxy population. The source counts are characterized by strong evolution to redshift unity, followed by less drastic evolution to higher redshift. The number-redshift distributions in both wavebands are well explained by the effect of the many mid-infrared features passing through the observation windows. The sharp upturn at around a milliJansky in the 15 micron counts in particular depends critically on the distribution of mid-infrared features around 12 microns, in the assumed spectral energy distribution.Comment: 6 pages, 2 figures, accepted for publication MNRA

Effects of air pollution and meteorological parameters on human health in the city of Athens, Greece

The impact of air pollution (CO, NO, NO2, SO2, O3) and meteorological parameters (air temperature, humidity and atmospheric pressure) on three indicators of human morbidity (circulatory, respiratory and skin diseases) is quantified, while the sensitivity of the results to different model specifications is tested. Findings indicate that higher SO2 and CO levels significantly increase circulatory and skin diseases, respectively, while higher NO and O3 concentrations increase respiratory diseases. Air temperature is significantly associated with all human health indicators. This work highlights the need for lower air pollution standards for the city of Athens and a wider climate change policy