Evaluation of the inter-annual variability of stratospheric chemical composition in chemistry-climate models using ground-based multi species time series

The variability of stratospheric chemical composition occurs on a broad spectrum of timescales, ranging from day to decades. A large part of the variability appears to be driven by external forcings such as volcanic aerosols, solar activity, halogen loading, levels of greenhouse gases (GHG), and modes of climate variability (quasi-biennial oscillation (QBO), El Niño-Southern Oscillation (ENSO)). We estimate the contributions of different external forcings to the interannual variability of stratospheric chemical composition and evaluate how well 3-D chemistry-climate models (CCMs) can reproduce the observed response-forcing relationships. We carry out multivariate regression analyses on long time series of observed and simulated time series of several traces gases in order to estimate the contributions of individual forcings and unforced variability to their internannual variability. The observations are typically decadal time series of ground-based data from the international Network for the Detection of Atmospheric Composition Change (NDACC) and the CCM simulations are taken from the CCMVal-2 REF-B1 simulations database. The chemical species considered are column O3, HCl, NO2, and N2O. We check the consistency between observations and model simulations in terms of the forced and internal components of the total interannual variability (externally forced variability and internal variability) and identify the driving factors in the interannual variations of stratospheric chemical composition over NDACC measurement sites. Overall, there is a reasonably good agreement between regression results from models and observations regarding the externally forced interannual variability. A much larger fraction of the observed and modelled interannual variability is explained by external forcings in the tropics than in the extratropics, notably in polar regions. CCMs are able to reproduce the amplitudes of responses in chemical composition to specific external forcings. However, CCMs tend to underestimate very substantially the internal variability and hence the total interannual variability for almost all species considered. This lack of internal variability in CCMs might partly originate from the surface forcing of these CCMs by analysed SSTs. The results illustrate the potential of NDACC ground-based observations for evaluating CCMs

HIGH PERMEABILITY IRON-BASED METALLIC GLASSES FOR GROUND FAULT INTERRUPTERS

Les verres métalliques à base de FeBSi présentent une perméabilité élevée à la fréquence du secteur. Une substitution de 2 à 3 at % de Cr et de Mo au Fe diminue l'aimantation de 0,l à 0,2 T/% at. mais améliore considérablement la coercitivité et les pertes. Après un recuit longitudinal les alliages substitués présentent une coercitivité de 0,3 à 0,7 A/m et une perméabilité de 300.000 à 400.000 à 60 Hz, alors que les alliages FeBSi sont moins performants. Un recuit transversa1 des alliages substitués conduit à une perméabilité égale sous une excitation bipolaire ou unipolaire de 60 Hz. La diminution dans les pertes provient de celles concernant les pertes par hystérésis.FeBSi-based metallic glasses are known to exhibit high permeability for line frequency excitation. The substitution of 2-3 atom percent of Cr or No for Fe in these glasses decreases saturation magnetization by 0.1-0.2 T/at.% but substantially improves coercivity, permeability, and core loss at low to moderate induction levels. When longitudinally annealed, the substituted alloys exhibit coercivities of 0.3-0.7 A/m and 60 Hz permeabilities of 300,000-400,000, compared with the 1 A/m and 200,000 typical of FeBSi plasses. A transverse anneal of the substituted alloys results in nearly equal permeabilities under either bipolar or unipolar 60 Hz excitation. The improvement in 60 Hz properties is largely due to the decrease in the hysteresis component of loss

METALLIC HYDRIDES.Magnetic properties of laves-phase rare earth hydrides

La diffraction des neutrons montre que l'introduction d'hydrogène dans les composés RFe2 (R = Tm, Ho, et Er) diminue sensiblement la température de Curie moyenne et résulte en une réduction du moment à 0 K sur le site de terre rare. Le moment de la terre rare se désordonne à une température inférieure à la température critique macroscopique dans ErFe2H3,5. Le moment à 0 K du sous-réseau de fer dans ErFe2H3,5 est essentiellement le même que celui trouvé pour le composé non hydruré et reste sensiblement constant jusqu'à approximativement 0,8 Tc.Neutron scattering results show that the introduction of hydrogen into RFe2 compounds (R = Tm, Ho, and Er) significantly lowers the overall Curie temperature and produces a reduced 0 K moment on the rare earth site. The rare earth spins disorder at a temperature lower than the bulk Tc in ErFe3H3.5. The 0 K iron sublattice moment in ErFe2H3.5 is essentially the same as that found in the non-hydride compounds and remains nearly constant to approximately 0.8 Tc

Assembly of a π–π stack of ligands in the binding site of an acetylcholine-binding protein

Acetylcholine-binding protein is a water-soluble homologue of the extracellular ligand-binding domain of cys-loop receptors. It is used as a structurally accessible prototype for studying ligand binding to these pharmaceutically important pentameric ion channels, in particular to nicotinic acetylcholine receptors, due to conserved binding site residues present at the interface between two subunits. Here we report that an aromatic conjugated small molecule binds acetylcholine-binding protein in an ordered π-π stack of three identical molecules per binding site, two parallel and one antiparallel. Acetylcholine-binding protein stabilizes the assembly of the stack by aromatic contacts. Thanks to the plasticity of its ligand-binding site, acetylcholine-binding protein can accommodate the formation of aromatic stacks of different size by simple loop repositioning and minimal adjustment of the interactions. This type of supramolecular binding provides a novel paradigm in drug design. © 2013 Macmillan Publishers Limited. All rights reserved

Post-Soviet studies and the transition: the case of the Russian economy

The disintegration of the Soviet Union meant that an essential object of study for research analysing centralised planning disappeared and the reference point for a lot of work dealing with the comparison of economic systems was lost. It could be assumed that such a structural alteration might lead to reduced interest in Russian studies and a crisis for the scientific community involved. The purpose of this study is to test this idea and to show how the scientific community interested in post-Soviet studies has changed during the transition period.