Air Quality Model Evaluation Data for Organics. 2. C_1−C_(14) Carbonyls in Los Angeles Air

As part of a larger experiment that provides a comprehensive set of observations to be used for testing air quality models for organic air pollutant transport and reaction, ambient air samples have been collected using DNPH-coated C_(18) cartridges at four urban locations and one background location in the Los Angeles area and have been analyzed for carbonyls as their DNPH derivatives. Twenty-three carbonyls have been identified and their concentrations measured:  14 aliphatic aldehydes (from formaldehyde to tetradecanal), two aromatics (benzaldehyde and m-tolualdehyde), three ketones (acetone, 2-butanone, and cyclohexanone), one unsaturated carbonyl (crotonaldehyde), and three dicarbonyls (glyoxal, methylglyoxal, and biacetyl). Another 19 carbonyls have been tentatively identified including 11 low molecular weight (MW) and intermediate MW carbonyls (of which four may be due to reactions of ambient NO, NO_2, and ozone with DNPH on the sampling cartridge), four C_4−C_6 dicarbonyls present at trace levels, and four high MW aliphatic carbonyls (C_(15)−C_(18)). Total carbonyl concentrations (4-h samples) averaged 22 ppb at the urban locations and 3.5 ppb at the background location and were highest (29 ppb) at the Azusa, CA, monitoring site that is downwind of downtown Los Angeles. Formaldehyde (urban average 5.3 ppb), acetaldehyde, and acetone accounted for 24%, 18%, and 7%, respectively, of the total carbonyls on a ppbv basis. The nine high MW carbonyls (C_8−C_(14)) accounted for 11−14% of the total carbonyls. The acetaldehyde/formaldehyde concentration ratio averaged 0.75 at the urban locations. Ranking of the measured carbonyls with respect to removal of the hydroxyl radical showed acetaldehyde to be the most important followed by formaldehyde and nonanal. Diurnal and spatial variations in ambient carbonyls levels are briefly examined and appear to be consistent with both direct emissions and in-situ formation during eastward transport over the urban area

Couplage analyse thermogravimétrique et émission acoustique pour l'étude de la corrosion haute température

National audienceAfin d'améliorer les connaissances du comportement à haute température des matériaux, le couplage de plusieurs techniques d'analyse physique in situ est une voie prometteuse. Dans ce but, des thermobalances ont été équipées d'un appareil spécifi que de mesure des signaux acoustiques émis par les échantillons dont la variation de masse est continûment mesurée sous diverses atmosphères représentatives de conditions industrielles. Les corrosions de surface à haute température sont à l'origine d'émission d'ondes acoustiques générées lors de la croissance ou de la fi ssuration de couches formées. Des mesures simultanées in situ des variations de masse et des signaux acoustiques apportent donc des informations sur ces mécanismes de corrosion haute température. L'application de cette méthodologie aux mécanismes d'oxydation, réduction ou attaque par les atmosphères carbonées (cokage) est présentée dans ce document. Une perspective de ces études est de pouvoir établir des référentiels pour une éventuelle utilisation de l'émission acoustique pour l'étude de la corrosion des équipements fonctionnant à haute température. // In order to improve the knowledge on the high temperature behaviour of materials, the coupling of in situ physical analysis is a promising way. For this purpose, thermobalances have been equipped with specific devices to measure the acoustic signals emitted by samples for which the mass variation is continuously recorded under simulated industrial atmospheres. The high temperature corrosion of materials surfaces generates acoustic emission signals associated to the growth or the cracking of the formed layers. In situ simultaneous measurements of the mass variation and the acoustic signals give information on the high temperature corrosion mechanisms involved. In this document, this methodology has been applied to the study of oxidation, reduction or attacks under carbon-rich atmosphere (coke deposition). These studies could lead to reference data for a possible application of acoustic emission for the corrosion monitoring of high temperature equipments

Air Quality Model Evaluation Data for Organics. 2. C_1−C_(14) Carbonyls in Los Angeles Air

As part of a larger experiment that provides a comprehensive set of observations to be used for testing air quality models for organic air pollutant transport and reaction, ambient air samples have been collected using DNPH-coated C_(18) cartridges at four urban locations and one background location in the Los Angeles area and have been analyzed for carbonyls as their DNPH derivatives. Twenty-three carbonyls have been identified and their concentrations measured:  14 aliphatic aldehydes (from formaldehyde to tetradecanal), two aromatics (benzaldehyde and m-tolualdehyde), three ketones (acetone, 2-butanone, and cyclohexanone), one unsaturated carbonyl (crotonaldehyde), and three dicarbonyls (glyoxal, methylglyoxal, and biacetyl). Another 19 carbonyls have been tentatively identified including 11 low molecular weight (MW) and intermediate MW carbonyls (of which four may be due to reactions of ambient NO, NO_2, and ozone with DNPH on the sampling cartridge), four C_4−C_6 dicarbonyls present at trace levels, and four high MW aliphatic carbonyls (C_(15)−C_(18)). Total carbonyl concentrations (4-h samples) averaged 22 ppb at the urban locations and 3.5 ppb at the background location and were highest (29 ppb) at the Azusa, CA, monitoring site that is downwind of downtown Los Angeles. Formaldehyde (urban average 5.3 ppb), acetaldehyde, and acetone accounted for 24%, 18%, and 7%, respectively, of the total carbonyls on a ppbv basis. The nine high MW carbonyls (C_8−C_(14)) accounted for 11−14% of the total carbonyls. The acetaldehyde/formaldehyde concentration ratio averaged 0.75 at the urban locations. Ranking of the measured carbonyls with respect to removal of the hydroxyl radical showed acetaldehyde to be the most important followed by formaldehyde and nonanal. Diurnal and spatial variations in ambient carbonyls levels are briefly examined and appear to be consistent with both direct emissions and in-situ formation during eastward transport over the urban area

The RNA polymerase III-dependent family of genes in hemiascomycetes: comparative RNomics, decoding strategies, transcription and evolutionary implications

We present the first comprehensive analysis of RNA polymerase III (Pol III) transcribed genes in ten yeast genomes. This set includes all tRNA genes (tDNA) and genes coding for SNR6 (U6), SNR52, SCR1 and RPR1 RNA in the nine hemiascomycetes Saccharomyces cerevisiae, Saccharomyces castellii, Candida glabrata, Kluyveromyces waltii, Kluyveromyces lactis, Eremothecium gossypii, Debaryomyces hansenii, Candida albicans, Yarrowia lipolytica and the archiascomycete Schizosaccharomyces pombe. We systematically analysed sequence specificities of tRNA genes, polymorphism, variability of introns, gene redundancy and gene clustering. Analysis of decoding strategies showed that yeasts close to S.cerevisiae use bacterial decoding rules to read the Leu CUN and Arg CGN codons, in contrast to all other known Eukaryotes. In D.hansenii and C.albicans, we identified a novel tDNA-Leu (AAG), reading the Leu CUU/CUC/CUA codons with an unusual G at position 32. A systematic ‘p-distance tree’ using the 60 variable positions of the tRNA molecule revealed that most tDNAs cluster into amino acid-specific sub-trees, suggesting that, within hemiascomycetes, orthologous tDNAs are more closely related than paralogs. We finally determined the bipartite A- and B-box sequences recognized by TFIIIC. These minimal sequences are nearly conserved throughout hemiascomycetes and were satisfactorily retrieved at appropriate locations in other Pol III genes

Thermogravimetric experiments coupled with acoustic emission analysis dedicated to high-temperature corrosion studies on metallic alloys

International audienceHigh temperature corrosion of metallic alloys in industrial equipments, such as refinery and petrochemical equipments concerns several phenomena: oxidation, carburization... These phenomena can create stresses in the materials, the relaxation of which mostly produces transient elastic waves. Several methods enable the recording and analyzing of these transient elastic waves. Piezoelectric sensors fixed directly on the sample can record elastic waves with a low decrease in energy and frequency at ambient temperature. In case of high temperature environments, a waveguide can also be used to transmit waves from sample to sensors. For this purpose, alumina or platinum are mainly used as waveguide materials because these materials conserve the waveform. The goal of this study is to assign the elastic waves to the corrosion phenomena. This data base will then be useful for the monitoring of industrial equipment using acoustic emission methods. For this purpose, thermogravimetric analysis (TGA) has been coupled with acoustic emission (AE) devices. Simultaneous measurements of the mass variation and of the acoustic signals emitted during the corrosion of samples of the Zirconium based alloy Zircaloy 4 at high temperatures in the range of 400 °C to 900 °C can provide complementary information to increase the level of understanding of high temperature corrosion mechanisms. Our work focuses on a specific waveguide (WG) conception and on the transmission of elastic waves (acoustic signals) through the waveguide at high temperature. Results on experiments concerning the corrosion of zirconium alloy plates under oxygen atmosphere are presented

Magnetocapillary Swimmers

We present an experiment where three mesoscopic soft ferromagnetic beads are placed onto a liquid surface and submitted to the influence of magnetic fields. A vertical magnetic field creates a repulsion which counterbalances the capillary attraction. We show that the competition with a second, oscillating field, deforms the structure in a non reciprocal way. As a consequence, the structure is able to swim. This experiment is fully described in a fluid dynamics video attached to this submission.Comment: 5 pages, 6 figures and 2 videos for the gallery of fluid motion (The same ones but at different qualities.

Intervenir sur les souffrances au travail : acteurs et enjeux dans la durée

National audience[début du texte] La santé psychique au travail fait l’objet, depuis plusieurs années, de débats entre chercheurs, porteurs de théories sensiblement différentes, au sein de la psychologie du travail. D’une part, des études à l’échelle de l’organisation essaient de caractériser et d’expliquer, à partir de données quantitatives, les facteurs qui conduisent à différentes formes de souffrance chez les travailleurs (stress, anxiété, épression, suicide)

Comparative study of the microstructure between a laser beam melted 17-4PH stainless steel and its conventional counterpart

The aim of this work was to compare the microstructures of 17-4PH martensitic stainless steels (MSSs) obtained by conventional manufacturing (CM), and additive manufacturing (AM) using laser beam melting (LBM) process. Both materials were studied after the same H900 heat treatment. Significant differences in microstructure were observed between the two MSSs, with a higher austenite content for the AM-H900 sample, as compared to the CM-H900 sample. Transmission electron microscopy (TEM) analyses allowed to identify both retained and reversed austenite in the AM-H900 sample, but most part of the austenite detected was found to be reversed austenite. The high amount of reversed austenite in the AM-H900 sample was attributed to a heterogeneous distribution in austenite-stabilising elements in the solution heat treated AM sample, leading to a decrease in Ms value and subsequent increase in the driving force for the martensite to austenite transformation during the ageing at 480 °C. Moreover, TEM analyses highlighted thinner martensite laths for the AM-H900 steel as compared to the CM-H900 one. This was interpreted as an increase in both nucleation sites and growth rate for reversed austenite. Despite those differences in microstructure, the AM-H900 and CM-H900 samples showed similar tensile behaviour, with similar UTS and Rp0.2 values, but a decrease in the strain to fracture was observed for the AM-H900 sample, probably related to the pores and/or to intergranular carbides

Molecular Evolution of Aminoacyl tRNA Synthetase Proteins in the Early History of Life

Aminoacyl-tRNA synthetases (aaRS) consist of several families of functionally conserved proteins essential for translation and protein synthesis. Like nearly all components of the translation machinery, most aaRS families are universally distributed across cellular life, being inherited from the time of the Last Universal Common Ancestor (LUCA). However, unlike the rest of the translation machinery, aaRS have undergone numerous ancient horizontal gene transfers, with several independent events detected between domains, and some possibly involving lineages diverging before the time of LUCA. These transfers reveal the complexity of molecular evolution at this early time, and the chimeric nature of genomes within cells that gave rise to the major domains. Additionally, given the role of these protein families in defining the amino acids used for protein synthesis, sequence reconstruction of their pre-LUCA ancestors can reveal the evolutionary processes at work in the origin of the genetic code. In particular, sequence reconstructions of the paralog ancestors of isoleucyl- and valyl- RS provide strong empirical evidence that at least for this divergence, the genetic code did not co-evolve with the aaRSs; rather, both amino acids were already part of the genetic code before their cognate aaRSs diverged from their common ancestor. The implications of this observation for the early evolution of RNA-directed protein biosynthesis are discussed.National Science Foundation (U.S.) (Grant DEB 0830024)National Science Foundation (U.S.) (Grant DEB 0936234)United States. National Aeronautics and Space Administration (NASA Postdoctoral Fellowship