Isotopic composition of atmospheric nitrate in a tropical marine boundary layer

Long-term observations of the reactive chemical composition of the tropical marine boundary layer (MBL) are rare, despite its crucial role for the chemical stability of the atmosphere. Recent observations of reactive bromine species in the tropical MBL showed unexpectedly high levels that could potentially have an impact on the ozone budget. Uncertainties in the ozone budget are amplified by our poor understanding of the fate of NOx (= NO + NO2), particularly the importance of nighttime chemical NOx sinks. Here, we present year-round observations of the multiisotopic composition of atmospheric nitrate in the tropical MBL at the Cape Verde Atmospheric Observatory. We show that the observed oxygen isotope ratios of nitrate are compatible with nitrate formation chemistry, which includes the BrNO3 sink at a level of ca. 20 ± 10% of nitrate formation pathways. The results also suggest that the N2O5 pathway is a negligible NOx sink in this environment. Observations further indicate a possible link between the NO2/NOx ratio and the nitrogen isotopic content of nitrate in this low NOx environment, possibly reflecting the seasonal change in the photochemical equilibrium among NOx species. This study demonstrates the relevance of using the stable isotopes of oxygen and nitrogen of atmospheric nitrate in association with concentration measurements to identify and constrain chemical processes occurring in the MBL

Holistic optimisation of noise reducing devices

International audienceThe work presented in this paper is part of the QUIESST European project, in which one of the objective is to perform multi-objective holistic optimisations of noise reducing devices. We present here optimisation results concerning the extrinsic performances of noise barriers. The performances under interest are acoustical, economical and environmental. The variety of noise barriers considered is very wide, ranging from straight and flat barriers, to rough or capped barriers. A total number of nine noise reducing device families are optimised. Acoustical performances are obtained from numerical calculations: the Boundary Element Method (in 2D) is used to obtain relative sound pressure levels at a set of receivers in different situations. Theses situations include road and rail sources; rural and urban cases; flat, embanked and depressed topographies. The economical performance is calculated according to the maintenance cost of the different materials in use in the barrier. Four environmental performances indicators are considered; their calculation is based on a life-cycle assessment analysis. All performances are expressed as a gain (or loss) relative to a reference screen. It is shown that the optimisation procedure allows one to obtain a wide variety of optimised noise reducing devices, and hence provides a helpful design tool by allowing one to focus on specific parameters

α-Li3InF6, a ternary fluoride with a new structure type

InF6 octahedra sharing common corners with [Li2F6], create an approximately hexagonally packed framework in the plane (1 0 0). The antiferroelectric behaviour evident from dielectric studies is confirmed by the antiparallel displacements of In and Li atoms from octahedral centres. This structure is mainly featured by the disorder observed in the lightest atoms...

Early defect in the expression of mouse sperm DNAJ 1, a member of the DNAJ/heat shock protein 40 chaperone protein family, in the spinal cord of the wobbler mouse, a murine model of motoneuronal degeneration

Prevention of protein misfolding is ensured by chaperone proteins, including the heat shock proteins (HSP) of the DNAJ/HSP40 family. Detection of abnormal protein aggregates in various neurodegenerative diseases has led to the proposal that altered chaperone activity contributes to neurodegeneration. Msj-1, a DNAJ/HSP40 protein located around the spermatozoa acrosome, was recently found to be down-regulated in the testis of wobbler mutant mice. Wobbler is an unidentified recessive mutation which triggers progressive motoneuron degeneration with abnormal intracellular protein accumulations, and defective spermatozoa maturation. Here, we examined Msj-1 expression in the spinal cord of the mutants and their controls. Msj-1 transcripts were amplified by reverse transcription-polymerase chain reaction from mutant and wild-type spinal cord RNA. Sequencing of Msj-1 coding region revealed no change in the mutant. In contrast, decreased Msj-1 mRNA levels were observed in five to six-week-old wobbler mice spinal cord, when motoneuron degeneration is at its apex, as compared to controls. A similar decrease was observed in two-week-old wobbler spinal cord, when the number of motoneurons is still unaltered, indicating that the decreased mRNA content is intrinsic to the mutant and not simply related to the loss of cells expressing Msj-1. Assays of Msj-1 protein levels yielded similar results. Immunofluorescent labeling revealed numerous Msj-1-ir motoneurons in five-week-old control spinal cord while no signal was observed in age-matched wobbler. Our results show, therefore, that Msj-1 expression is down-regulated in both organs affected by the wobbler mutation, the CNS and the testis, and that this defect precedes the first histological signs of motoneuron degeneration. These results provide the first example of an association between transcriptional repression of a chaperone protein and a neurodegenerative process

Synthesis and microstructural studies of Er3+^3+-doped fluorozirconate devitrified glasses

Internet is becoming more and more widely used for the design and delivery of course material. This relatively new technology makes extensive use of cybertexts, taken here in the generic sense of digitized texts, images and sounds. In designing web sites for their courses, professors can now rely on new tools which benefit and facilitate their work. Our presentation addresses issues related to these functions and particularly to the design and use of e-texts (e-packs) with the leading platform WebCT (Web Course Tools). Data used in our presentation are extracted from a Canadian survey and from our own experience with undergraduate courses

Doublecortin mutation leads to persistent defects in the Golgi apparatus and mitochondria in adult hippocampal pyramidal cells

International audienc

Spin transition in Co3+ by optical absorption and time-resolved spectroscopy under pressure: An appraisal of the different spin states

This work investigates the electronic structure of CoF3 by optical absorption and its relationship with the ground-state spin and the Jahn-Teller (JT) effect exhibited by Co3+(d6) in octahedral coordination (CoF6)3-. The results are compared with other Co3+ fluorides and oxides, where Co3+ is high spin (HS) and low spin (LS), respectively. In CoF3 we detect an absorption band with a doublet structure at 1.89eV (657nm) and 1.45eV (855nm) at 2.5GPa, which is associated with the T e JT effect on the 5T2 HS ground state. Absorption measurements under pressure have been carried out around the HS-LS (5T2 1A1) spin crossover transition in the 0-20 GPa range. We show that the JT effect is stable in a wide pressure range. No sign of intermediate spin (3T1, 2 states) is observed in the explored pressure range