Characterisation of the influence function non-additivities for a 1024-actuator MEMS deformable mirror

In order to evaluate the potential of MEMS deformable mirrors for open-loop applications, a complete calibration process was performed on a 1024-actuator mirror. The mirror must be perfectly calibrated to obtain deterministic membrane deflection. The actuator's stroke-voltage relationship and the effect of the non- additivity of the influence functions are studied and finally integrated in an open-loop control process. This experiment aimed at minimizing the residual error obtained in open-loop control.Comment: 6 pages, 9 figures, Proceedings of the 1st AO for ELT conference, June 2009, Pari

A constrained, globalized, and bounded Nelder-Mead method for engineering optimization

International audienceOne of the fundamental difficulties in engineering design is the multiplicity of local solutions. This has triggered much effort in the development of global search algorithms. Globality, however, often has a prohibitively high numerical cost for real problems. A fixed cost local search, which sequentially becomes global, is developed in this work. Globalization is achieved by probabilistic restarts. A spacial probability of starting a local search is built based on past searches. An improved Nelder-Mead algorithm is the local optimizer. It accounts for variable bounds and nonlinear inequality constraints. It is additionally made more robust by reinitializing degenerated simplexes. The resulting method, called the Globalized Bounded Nelder-Mead (GBNM) algorithm, is particularly adapted to tackling multimodal, discontinuous, constrained optimization problems, for which it is uncertain that a global optimization can be afforded. Numerical experiments are given on two analytical test functions and two composite laminate design problems. The GBNM method compares favorably with an evolutionary algorithm, both in terms of numerical cost and accuracy

Electron injection in a nanotube: noise correlations and entanglement

Transport through a metallic carbon nanotube is considered, where electrons are injected in the bulk by a scanning tunneling microscope tip. The charge current and noise are computed. For an infinite homogeneous nanotube, the shot noise exhibits effective charges different from the electron charge. Noise correlations between both ends of the nanotube are positive, and occur to second order only in the tunneling amplitude. The positive correlations are symptomatic of an entanglement phenomenon between quasiparticles moving right and left from the tip. This entanglement involves many body states of the boson operators which describe the collective excitations of the Luttinger liquid

Open-loop control demonstration of micro-electro-mechanical-system MEMS deformable mirror

New astronomical challenges revolve around the observation of faint galaxies, nearby star-forming regions and the direct imaging of exoplanets. The technologies required to progress in these fields of research rely on the development of custom Adaptive Optics (AO) instruments such as Multi-Object AO (MOAO) or Extreme AO (ExAO). Many obstacles remain in the development of these new technologies. A major barrier to the implementation of MOAO is the utilisation of deformable mirrors (DMs) in an open-loop control system. Micro-Electro-Mechanical-System (MEMS) DMs show promise for application in both MOAO and ExAO. Despite recent encouraging laboratory results, it remains an immature technology which has yet to be demonstrated on a fully operational on-sky AO system. Much of the research in this area focuses on the development of an accurate model of the MEMS DMs. In this paper, a thorough characterization process of a MEMS DM is performed, with the goal of developing an open-loop control strategy free of computationally heavy modelling (such as the use of plate equations). Instead, a simpler approach, based on the additivity of the influence functions, is chosen. The actuator stroke-voltage relationship and the actuator influence functions are carefully calibrated. For 100 initial phase screens with a mean rms of 97 nm (computer generated following a Von Karman statistic), the resulting mean residual open-loop rms error is 16.5 nm, the mean fitting error rms is 13.3 nm and the mean DM error rms is 10.8 nm (error reflecting the performances of the model under test in this paper). This corresponds to 11% of residual DM error

Fluctuations et courant hors-équilibre en nanophysique

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSudocFranceF

Variabilité des recommandations pour la prévention du tétanos dans les pays développés

Objectif : Comparer les recommandations officielles de l Organisation mondiale de la santé (OMS) et des pays développés, pour la prévention primaire et secondaire du tétanos. Méthode : Etude bibliographique des recommandations des ministères et instituts de santé publique de différents pays avec celles de l OMS. Analyse par Chi2 des incidences du tétanos en 2010. Résultats : La primovaccination est identique dans tous les pays étudiés mais le nombre de rappels diffère, principalement à l âge adulte. Certains pays recommandent des rappels décennaux à vie chez l adulte. D autres n en recommandent qu un ou deux, voire aucun. Pour la prise en charge des plaies, selon le pays, le nombre de doses de vaccin antitétanique souhaité et le délai depuis la dernière dose ne sont pas pris en compte de la même façon. La distinction des plaies pour caractériser le risque tétanique varie et est plus ou moins nettement définie. Ces différences entraînent des prises en charge très variables pour l administration du vaccin et des immunoglobulines antitétaniques. Seuls les Etats-Unis ont une incidence du tétanos significativement inférieure à celle des autres pays en utilisant des protocoles similaires à ceux du Canada. Malgré ces différences dans les recommandations, l incidence de la maladie a diminué considérablement dans tous les pays. Conclusion : Les recommandations pourraient sans doute être optimisées globalement pour limiter le risque d erreur, améliorer encore la couverture et diminuer les coûts et la surutilisation des produits vaccinaux. Il faudrait réévaluer la précision de la définition du risque tétanique et des facteurs de risque à prendre en compte, et améliorer les méthodes de documentation du statut vaccinal.ST ETIENNE-BU Médecine (422182102) / SudocSudocFranceF

Rolling shutter detector data flow strategies to push the limits of AO performance

Adaptive Optics (AO) improves the image quality of ground-based telescopes, by compensating in real-time for the blurring effects of atmospheric turbulence. AO systems of future Extremely Large Telescopes (ELTs) will have to operate at much bigger scales (in terms of degrees of freedom) and faster control rates (in terms of loop frequency) to realise their full potential. We have investigated and simulated an AO control methodology to stream pixels "as they come" using a rolling-shutter sCMOS camera to reconstruct 2D images. Compared to a traditional global shutter implementation, the initial results indicate the rolling shutter can reduce control loop latency by a factor of two to four, using existing hardware. This means we can detect twice the number of photons while sampling twice as slowly. Nevertheless, significant technical challenges remain in implementing the rolling functionality, especially when integrating off- The -shelf software and hardware, which is often constricted by a closed-source code base. Furthermore, as the rolling shutter readout is asynchronous, questions remain about coupling and aliasing of telescope vibrations into the imaging system, causing distortions of time and space. If successfully implemented in practice, the rolling shutter approach has the potential to allow astronomers and engineers to capture better scientific observations closer to the diffraction limit

Femtosecond pump-probe experiments on trapped flavin: Optical control of dissociation

Femtosecond pump-probe experiments are performed on flavin biomolecules isolated in an ion trap. Mass spectra of the photoinduced fragments show that the fragmentation pathways can be modified using two-color two-photon excitation. In particular, when an infrared probe pulse (810nm) is added subsequent to the first excitation step (excitation of the S1 state of flavin mononucleotide at 405nm), branching ratios between lumichrome and lumiflavin production are inverted relative to the single excitation case