Scénarios d’ajustement du solde courant américain : une évaluation avec différentes calibrations de NiGEM.

L’article propose un examen de différents scénarios d’ajustement du déficit courant américain et une mesure des coûts associés pour les économies des États-Unis et de leurs partenaires.déficit courant américain, ajustement par le change, ajustement par une réduction de la demande intérieure américaine.

Invertébrés marins du lagon Néo calédonien : 3. Etude structurale de trois nouveaux diterpènes isolés du pennatulaire Cavernulina grandiflora

Three new diterpenes, related to stylatulide but non-balogenated, have been isolated from a new species of sea-pen, Cavernulina grandiflora : cavernuline (1) O-deacetylpropionyl cavernuline (5) and cavernulinine (6). The structures are proposed on the basis of spectral evidence

Identification of the major tRNAPhe binding domain in the tetrameric structure of cytoplasmic phenylalanyl-tRNA synthetase from baker's yeast

AbstractNative cytoplasmic phenylalanyl-tRNA synthetase from baker's yeast is a tetramer of the α2β2 type. On mild tryptic cleavage it gives rise to a modified ∡2β′2 form that has lost the tRNAPhe binding capacity but is still able to activate phenylalanine. In this paper are presented data concerning peptides released by this limited proteolytic conversion as well as those arising from exhaustive tryptic digestion of the truncated β′ subunit. Each purified peptide was unambiguously assigned to a unique stretch of the β subunit amino acid sequence that was recently determined via gene cloning and DNA sequencing. Together with earlier results from affinity labelling studies the present data show that the Lys 172—Ile 173 bond is the unique target of trypsin under mild conditions and that the N-terminal domain of each β subunit (residues 1–172) contains the major tRNAPhe binding sites

Unit-cell for dual-circular polarisation reflectarrays

International audience—A new unit-cell composed of two layers for dual-CP reflectarrays is proposed for the first time with the unique capability to reflect independently and simultaneously the two incident circular polarisations at the same frequency. The experimental results demonstrate that this unit-cell exhibits a 3.8% bandwidth around 8.4 GHz for a phase resolution better than 1.92 bits in LHCP and in RHCP. As a first step towards a reflectarray in dual-CP, this innovative unit-cell is studied in an array configuration. To increase the value of the maximum incidence angle up to 30°, a matching dielectric layer is placed over the cell

Exoplanet direct imaging in ground-based conditions on THD2 bench

The next generation of ground-based instruments aims to break through the knowledge we have on exoplanets by imaging circumstellar environments always closer to the stars. However, direct imaging requires an AO system and high-contrast techniques like a coronagraph to reject the diffracted light of an observed star and an additional wavefront sensor to control quasi-static aberrations, including the non common path aberrations. To observe faint objects, a focal plane wavefront sensor with a sub-nanometric wavefront control capability is required. In the past few years, we developed the THD2 bench which is a testbed for high-contrast imaging techniques, working in visible and near infrared wavelengths and currently reaching contrast levels lower than 1e-8 under space-like simulated conditions. We recently added a turbulence wheel on the optical path which simulates the residuals given by a typical extreme adaptive optics system and we tested several ways to remove quasi-statics speckles. One way to estimate the aberrations is a method called pair-wise probing where we record few images with known-shapes we apply on the adaptive optics deformable mirror. Once estimated, we seek to minimize the focal-plane electric field by an algorithm called Electric Field Conjugation. In this paper, we present the first results obtained on the THD2 bench using these two techniques together in turbulent conditions. We then compare the achieved performance with the one expected when all the quasi-static speckles are corrected.Comment: 9 pages, 3 figures, AO4ELT6 Qu\'ebec cit