Hyperpolarizability effects in a Sr optical lattice clock

We report the observation of the higher order frequency shift due to the trapping field in a $^{87}$Sr optical lattice clock. We show that at the magic wavelength of the lattice, where the first order term cancels, the higher order shift will not constitute a limitation to the fractional accuracy of the clock at a level of $10^{-18}$. This result is achieved by operating the clock at very high trapping intensity up to $400$kW/cm$^2$ and by a specific study of the effect of the two two-photon transitions near the magic wavelength

Non-destructive measurement of the transition probability in a Sr optical lattice clock

We present the experimental demonstration of non-destructive probing of the 1S0-3P0 clock transition probability in an optical lattice clock with 87Sr atoms. It is based on the phase shift induced by the atoms on a weak off-resonant laser beam. The method we propose is a differential measurement of this phase shift on two modulation sidebands with opposite detuning with respect to the 1S0-1P1 transition, allowing a detection limited by the photon shot noise. We have measured an atomic population of 10^4 atoms with a signal to noise ratio of 100 per cycle, while keeping more than 95% of the atoms in the optical lattice with a depth of 0.1 mK. The method proves simple and robust enough to be operated as part of the whole clock setup. This detection scheme enables us to reuse atoms for subsequent clock state interrogations, dramatically reducing the loading time and thereby improving the clock frequency stability.Comment: 4 pages, 5 figure

An Optical Lattice Clock with Spin-polarized 87Sr Atoms

We present a new evaluation of an 87Sr optical lattice clock using spin polarized atoms. The frequency of the 1S0-3P0 clock transition is found to be 429 228 004 229 873.6 Hz with a fractional accuracy of 2.6 10^{-15}, a value that is comparable to the frequency difference between the various primary standards throughout the world. This measurement is in excellent agreement with a previous one of similar accuracy

The EFIGI catalogue of 4458 nearby galaxies with morphology II. Statistical properties along the Hubble sequence

The EFIGI catalogue of 4458 galaxies provides a reference database of the morphological properties of nearby galaxies, with 16 shape attributes describing their various dynamical components, their texture and environment, and with a dense sampling of all Hubble types. This catalogue allows us to derive a quantitative description of the Hubble Sequence in terms of the specific morphological features of the various types. The variations of the EFIGI morphological attributes with type confirm that the visual Hubble sequence is a decreasing sequence of bulge-to-total ratio and an increasing sequence of disk contribution to the total flux. There is nevertheless a large dispersion of approximately 5 types for a given bulge-to-total ratio, due to the fact that the Hubble sequence is primarily based on the strength and pitch angle of the spiral arms, independently from the bulge-to-total ratio. The grand spiral design is also related to a steep decrease in visible dust from types Sb to Sbc-Sc. In contrast, the scattered and giant HII regions show different strength variation patterns; hence, they do not appear to directly participate in the establishment of the Hubble sequence. The distortions from a symmetric profile also incidentally increase along the sequence. Bars and inner rings are frequent and occur in 41% and 25% of disk galaxies resp. Outer rings are twice less frequent than inner rings, and outer pseudo-rings occur in 11% of barred galaxies. Finally, we find a smooth decrease in mean surface brightness and intrinsic size along the Hubble sequence. The largest galaxies are cD, Ellipticals and Sab-Sbc spirals, whereas Sd and later spirals are nearly twice smaller. S0 are intermediate in size, and Im, cE and dE are confirmed as small objects. Dwarf spiral galaxies of type Sa to Scd are rare in the EFIGI catalogue, we only find 2 such objects.Comment: Accepted for publication in Astronomy and Astrophysics, 22 pages, 10 tables, 19 colour figures. Data available at http://www.efigi.or

Interference-filter-stabilized external-cavity diode lasers

We have developed external-cavity diode lasers, where the wavelength selection is assured by a low loss interference filter instead of the common diffraction grating. The filter allows a linear cavity design reducing the sensitivity of the wavelength and the external cavity feedback against misalignment. By separating the feedback and wavelength selection functions, both can be optimized independently leading to an increased tunability of the laser. The design is employed for the generation of laser light at 698, 780 and 852 nm. Its characteristics make it a well suited candidate for space-born lasers.Comment: 12 pages, 5 figure

Libéralité prétorienne et État minimum au Soudan

«°On ne commence à parler d'État que lorsque des hommes ou des organismes qui assurent plusieurs services publics commencent à être réunis entre eux et par là à faire masse.°» Paul Veyne, Le pain et le cirque. Sociologie d'un pluralisme politique. Au Soudan, comme ailleurs, l'édification de l'espace public n'a suivi que marginalement la voie royale de l'administration exclusive par l'État. S'appuyant largement sur la philanthropie et le civisme de ses gouvernés, le régime islamique, comme se..

La massage selon le protocol de Field: quelle plus-value sur la prise de poids des prématurés comparé aux soins dits standards ? travail de Bachelor

Introduction : Les naissances prématurées augmentent chaque année, ces naissances sont complexes et peuvent mener à de nombreuses complications et séquelles. Afin de répondre aux besoins particuliers des nouveau-nés, un aménagement de l’environnement et certaines méthodes de traitement sont intégrés à la routine de soins. Le massage est un traitement qui a fait ses preuves et devient monnaie courante dans les services de néonatologie. Nous nous sommes intéressées à un protocole de massage : le protocole de Field qui combine massage et mobilisation passive, dans le but de connaître la plus-value de ce protocole sur la prise de poids des prématurés âgés de 28 à 32 semaines d'aménorrhées. Méthode : Nous avons utilisé le design de la revue de littérature. Notre recherche s’est basée sur quatre bases de données : Pubmed, Cochrane, Pedro et Kinédoc. Nos mots-clés reprennent les grands thèmes de notre question de recherche : prématurité, gain de poids et massage. L’outcome étudié est le poids en grammes. La qualité des études a été évaluée avec la grille PEDro. Résultats : Trois articles composent notre revue de la littérature. Les trois articles montrent une augmentation du poids entre le début et la fin du traitement mais seulement deux études ont une différence significative. Conclusion : Avec le peu de littérature et la faiblesse de nos études il est difficile de se positionner quant au réel avantage de ce protocole de massage comparé à d’autres techniques mises en place dans les services de néonatologie. Cependant le massage a fait ses preuves et il devrait être intégré dans les routines de soins lorsque ce n’est pas encore le cas, pour les prématurés médicalement stables et de plus de 28 semaines. Car c’est une technique, ne nécessitant pas de matériel, abordable et qui permet de favoriser la prise de poids

Phase-locking of two self-seeded tapered amplifier lasers

We report on the phase-locking of two diode lasers based on self-seeded tapered amplifiers. In these lasers, a reduction of linewidth is achieved using narrow-band high-transmission interference filters for frequency selection. The lasers combine a compact design with a Lorentzian linewidth below 200 kHz at an output power of 300 mW. We characterize the phase noise of the phase-locked laser system and study its potential for coherent beam-splitting in atom interferometers.Comment: 7 pages, 4 figure

An accurate optical lattice clock with 87Sr atoms

We report a frequency measurement of the 1S0-3P0 transition of 87Sr atoms in an optical lattice clock. The frequency is determined to be 429 228 004 229 879 (5) Hz with a fractional uncertainty that is comparable to state-of-the-art optical clocks with neutral atoms in free fall. Two previous measurements of this transition were found to disagree by about 2x10^{-13}, i.e. almost four times the combined error bar, instilling doubt on the potential of optical lattice clocks to perform at a high accuracy level. In perfect agreement with one of these two values, our measurement essentially dissipates this doubt