A simple laser system for atom interferometry

We present here a simple laser system for a laser cooled atom interferometer, where all functions (laser cooling, interferometry and detection) are realized using only two extended cavity laser diodes, amplified by a common tapered amplifier. One laser is locked by frequency modulation transfer spectroscopy, the other being phase locked with an offset frequency determined by an Field-Programmable Gate Array (FPGA) controlled Direct Digital Synthesizer (DDS), which allows for efficient and versatile tuning of the laser frequency. Raman lasers are obtained with a double pass acousto-optic modulator. We demonstrate a gravimeter using this laser system, with performances close to the state of the art

The "missing link": a 4-day period transiting exoplanet around OGLE-TR-111

We report the discovery of a transiting hot Jupiter around OGLE-TR-111, from our radial velocity follow-up of OGLE transiting candidates in Carina. The planet has a mass of 0.53 +- 0.11 M_J and a radius of 1.0 +0.13-0.06 R_J. Three transiting exoplanets have already been found among OGLE candidates, all with periods near 1.5 days. The planet presented here, with P=4.0 days, is the first exoplanet detected by transits with the characteristics of a "normal" hot Jupiter, as found in abundance by radial velocity surveys The radius of OGLE-TR-111b and the scarcity of hot Jupiters detected among OGLE transit candidates tend to indicate that the case of HD209458b, with a radius of 1.4 R_J, is exceptional, with most hot Jupiters being smaller.Comment: 4 pages, 4 figures, to be published in A&A Letter

Characteristics And Variability Of Storm Tracks In The North Pacific, Bering Sea And Alaska

Thesis (Ph.D.) University of Alaska Fairbanks, 2009Storm activity in the North Pacific, Bering Sea and Alaska regions is investigated using various automated storm tracking and parameter extraction algorithms. Specific, novel details of storm activity throughout the year are presented. The influence of major climatic drivers is considered, including the Pacific/North American Index and sea ice variability. Details of synoptic-scale forcing on a specific, severe storm event are considered in the context of how different tracking algorithms are able to depict the event. New storm climatology results show that the inter-seasonal variability is not as large during spring and autumn as it is in winter. Most storm variables exhibited a maxima pattern that was oriented along a zonal axis. From season to season this axis underwent a north-south shift and, in some cases, a rotation to the northeast. Barotropic processes have an influence in shaping the downstream end of storm tracks and, together with the blocking influence of the coastal orography of northwest North America, result in high lysis concentrations, effectively making the Gulf of Alaska the "graveyard" of Pacific storms. Summer storms tended to be longest in duration. Temporal trends tended to be weak over the study area. Sea surface temperature did not emerge as a major cyclogenesis control in the Gulf of Alaska. Positive sea-ice anomalies in the Sea of Okhotsk were found to decrease secondary cyclogenesis, shift cyclolysis locations westward, and alter the North Pacific subtropical jet. In the Atlantic, a negative North-Atlantic-Oscillation-like pattern is observed; these results were confirmed by experiments on the ECHAM5 Atmospheric Global Circulation Model driven with sea-ice anomalies in the Sea of Okhotsk. The destructive west Alaska storm of autumn 1992, which flooded Nome, was investigated using two storm tracking algorithms: NOAA's (National Oceanic and Atmospheric Administration) current operational algorithm and the Melbourne algorithm. Manual tracking was performed as a control. The main storm location features were captured by both algorithms, but differed in the genesis and lysis location. The NOAA algorithm broke the event into two. This storm was shown to have been affected by a blocking high that influenced how the tracking algorithms handled the event

Description d'Acnodon senai n. sp. du Rio Jari (Brésil, Amapa) et redescription d'A. normani (Teleostei, serrasalmidae)

#Acnodon senai n. sp., décrite du rio Jari (Brésil, Amapa), est une espèce proche de #A. normani Gosline, 1951 décrite du rio Tocantins. Ces deux espèces ont un museau pointu, une bouche terminale et deux séries de dents du prémaxillaire nettement séparées. Ces caractères les différencient de #A. oligacanthus (Müller et Troschel, 1844), décrit du Surinam, chez qui le museau est arrondi, la bouche infère et les séries prémaxillaires accolées. Les branchiospines, rigides et bordées d'une membrane simple chez #A. normani, sont souples et bordées d'une membrane lobulée chez #A. senai$. (Résumé d'auteur

Le genre Serrasalmus (Pisces, Serrasalmidae) dans le bas Tocantins (Brésil, Parà), avec la description d'une espèce nouvelle, S. geryi, du bassin Araguaia-Tocantins

Les auteurs font une description complémentaire détaillée de 7 espèces du genre #Serrasalmus récoltées dans le cours inférieur du rio Tocantins, au cours de 3 années de collectes trimestrielles. Une espèce nouvelle, #S. geryi, est décrite du bas Tocantins et de l'Araguaia. Tous les spécimens de #S. calmoni ont été capturés dans la zone sous influence de la marée. Les autres espèces sont distribuées sur toute la portion de cours étudiée. Un seul spécimen de #S. denticulatus a été récolté et #S. striolatus, décrit du rio Parà, n'a pas été rencontré. La présence de #S. eigenmanni, espèce différente de #S. humeralis, et la présence de #S. gibbus, espèce différente de #S. rhombeus sont confirmées. Une clé d'identification est proposée et les relations entre les espèces sont discutées. #S. eigenmanni est placée, avec #S. calmoni dans le sous-genre #Pristobrycon. Les auteurs placent #S. geryi dans le sous-genre #Serrasalmus, proposant une extension de la définition de celui-ci. (Résumé d'auteur

Hybridizing matter-wave and classical accelerometers

We demonstrate a hybrid accelerometer that benefits from the advantages of both conventional and atomic sensors in terms of bandwidth (DC to 430 Hz) and long term stability. First, the use of a real time correction of the atom interferometer phase by the signal from the classical accelerometer enables to run it at best performances without any isolation platform. Second, a servo-lock of the DC component of the conventional sensor output signal by the atomic one realizes a hybrid sensor. This method paves the way for applications in geophysics and in inertial navigation as it overcomes the main limitation of atomic accelerometers, namely the dead times between consecutive measurements

Simulating Fleet Noise for Notional UAM Vehicles and Operations in New York

This paper presents the results of systems-level simulations using Metrosim that were conducted for notional Urban Air Mobility (UAM)-style vehicles analyzed for two different scenarios for New York (NY). UAM is an aviation industry term for passenger or cargo-carrying air transportation services, which are often automated, operating in an urban/city environment. UAM-style vehicles are expected to use vertical takeoff and landing with fixed wing cruise flight. Metrosim is a metroplex-wide route and airport planning tool that can also be used in standalone mode as a simulation tool. The scenarios described and reported in this paper were used to evaluate a fleet noise prediction capability for this tool. The work was a collaborative effort between the National Aeronautics and Space Administration (NASA), Intelligent Automation, Inc (IAI), and the Port Authority of New York and New Jersey (PANYNJ). One scenario was designed to represent an expanded air-taxi operation from existing helipads around Manhattan to the major New York airports. The other case represented a farther term vision case with commuters using personal air vehicles to hub locations just outside New York, with an air-taxi service running frequent connector trips to a few key locations inside Manhattan. For both scenarios, the trajectories created for the entire fleet were passed to the Aircraft Environmental Design Tool (AEDT) to generate Day-Night Level (DNL) noise contours for inspection. Without data for actual UAM vehicles available, surrogate AEDT empirical Noise-Power-Distance (NPD) tables used a similar sized current day helicopter as the Baseline, and a version of that same data linearly scaled as a first guess at possible UAM noise data. Details are provided for each of the two scenario configurations, and the output noise contours are presented for the Baseline and reduced noise DNL cases

Une nouvelle espèce de Bryconexodon (Pisces, Characidae) décrite du bassin du Trombetas (Para, Brésil)

Une nouvelle espèce du genre #Bryconexodon Géry (#Pisces, #Characidae) est décrite du cours supérieur du Rio Trombetas (Para, Brésil). #Bryconexodon n. sp. est très voisine de #B. juruenae Guéry, 1980 par la forme et la distribution des dents, mais présente moins d'écailles en ligne latérale (13-15 contre 17-19), moins de séries d'écailles au-dessus de la ligne latérale (8-9 contre 10-12) et autour du pédoncule caudale (16-18 contre 22). L'examen de contenus stomacaux révèle que #B. trombetasi n. sp. est lépidophage. (Résumé d'auteur

Extremal properties for dissections of convex 3-polytopes

A dissection of a convex d-polytope is a partition of the polytope into d-simplices whose vertices are among the vertices of the polytope. Triangulations are dissections that have the additional property that the set of all its simplices forms a simplicial complex. The size of a dissection is the number of d-simplices it contains. This paper compares triangulations of maximal size with dissections of maximal size. We also exhibit lower and upper bounds for the size of dissections of a 3-polytope and analyze extremal size triangulations for specific non-simplicial polytopes: prisms, antiprisms, Archimedean solids, and combinatorial d-cubes.Comment: 19 page