17,241 research outputs found

    Dynamical Structure of the Molecular Interstellar Medium in an Extremely Bright, Multiply Lensed z ≃ 3 Submillimeter Galaxy Discovered with Herschel

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    We report the detection of CO(J = 5 → 4), CO(J = 3 → 2), and CO(J = 1 → 0) emission in the strongly lensed, Herschel/SPIRE-selected submillimeter galaxy (SMG) HERMES J105751.1+573027 at z = 2.9574 ± 0.0001, using the Plateau de Bure Interferometer, the Combined Array for Research in Millimeter-wave Astronomy, and the Green Bank Telescope. The observations spatially resolve the molecular gas into four lensed images with a maximum separation of ~9" and reveal the internal gas dynamics in this system. We derive lensing-corrected CO line luminosities of L'_(CO(1-0)) = (4.17 ± 0.41), L'_(CO(3-2)) = (3.96 ± 0.20), and L'_(CO(5-4)) = (3.45 ± 0.20) × 10^(10) (μL/10.9)^(–1) K km s^(–1) pc^2, corresponding to luminosity ratios of r_(31) = 0.95 ± 0.10, r_(53) = 0.87 ± 0.06, and r_(51) = 0.83 ± 0.09. This suggests a total molecular gas mass of M_(gas) = 3.3×10^(10) (α_(CO)/0.8) (μ_L/10.9)^(–1) M_☉. The gas mass, gas mass fraction, gas depletion timescale, star formation efficiency, and specific star formation rate are typical for an SMG. The velocity structure of the gas reservoir suggests that the brightest two lensed images are dynamically resolved projections of the same dust-obscured region in the galaxy that are kinematically offset from the unresolved fainter images. The resolved kinematics appear consistent with the complex velocity structure observed in major, "wet" (i.e., gas-rich) mergers. Major mergers are commonly observed in SMGs and are likely to be responsible for fueling their intense starbursts at high gas consumption rates. This study demonstrates the level of detail to which galaxies in the early universe can be studied by utilizing the increase in effective spatial resolution and sensitivity provided by gravitational lensing

    SAMplus: adaptive optics at optical wavelengths for SOAR

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    Adaptive Optics (AO) is an innovative technique that substantially improves the optical performance of ground-based telescopes. The SOAR Adaptive Module (SAM) is a laser-assisted AO instrument, designed to compensate ground-layer atmospheric turbulence in near-IR and visible wavelengths over a large Field of View. Here we detail our proposal to upgrade SAM, dubbed SAMplus, that is focused on enhancing its performance in visible wavelengths and increasing the instrument reliability. As an illustration, for a seeing of 0.62 arcsec at 500 nm and a typical turbulence profile, current SAM improves the PSF FWHM to 0.40 arcsec, and with the upgrade we expect to deliver images with a FWHM of 0.34\approx0.34 arcsec -- up to 0.23 arcsec FWHM PSF under good seeing conditions. Such capabilities will be fully integrated with the latest SAM instruments, putting SOAR in an unique position as observatory facility.Comment: To appear in Proc. SPIE 10703 (Ground-based and Airborne Instrumentation for Astronomy VII; SPIEastro18

    Using the Sound Card as a Timer

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    Experiments in mechanics can often be timed by the sounds they produce. In such cases, digital audio recordings provide a simple way of measuring time intervals with an accuracy comparable to that of photogate timers. We illustrate this with an experiment in the physics of sports: to measure the speed of a hard-kicked soccer ball.Comment: 3 pages, 4 figures, Late

    Classification of algebras with minimal quadratic growth of identities

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    The main goal of this paper is to prove that the five algebraswhich were used in [3] to classify (up to PI-equivalence) thealgebras whose sequence of codimensions is bounded by a linear functiongenerate the only five minimal varieties of quadratic growth

    Mathematical modeling of the thermal degradation kinetics of vitamin C in cupuaçu (Theobroma grandiflorum) nectar

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    The thermal degradation kinetics of both components of vitamin C, ascorbic acid (AA) and dehydroascorbic acid (DHAA), were determined in a nectar of Cupuacßu (Theobroma grandi¯orum) with 25% of pulp and 15% of sugar in water. AA was assayed by HPLC and the results showed that AA degraded into DHAA. A reversible ®rst order model described well the AA degradation data, with an activation energy of 74 5 kJ/mol and k80 C 0:032 0:003min ÿ1. DHAA kinetic behavior suggested a consecutive ®rst order reaction where DHAA was the intermediate product of AA degradation. A mechanistic model was derived to predict DHAA concentration. Rate constants were replaced by the Arrhenius equation in the model to evaluate the temperature dependence and the kinetic parameters for AA degradation, previously determined, were used. An activation energy of 65 9 kJ/mol and a k80 C of 0:013 0:003 min ÿ1 were estimated. The present ®ndings will help to predict the best Cupuacßu nectar processing conditions that minimize degradation of an important quality factor such as vitamin C

    Manual de interpretação de trilhas: explorando os conceitos de ecologia e conservação de floresta na Reserva do Caju.

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    bitstream/CPATC-2010/20867/1/doc-149.pd

    Close encounters involving RAVE stars beyond the 47 Tucanae tidal radius

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    The most accurate 6D phase-space information from the Radial Velocity Experiment (RAVE) was used to integrate the orbits of 105 stars around the galactic globular cluster 47 Tucanae, to look for close encounters between them in the past, with a minimum distance approach less than the cluster tidal radius. The stars are currently over the distance range 3.0 kpc << d << 5.5 kpc. Using the uncertainties in the current position and velocity vector for both, star and cluster, 105 pairs of star-cluster orbits were generated in a Monte Carlo numerical scheme, integrated over 2 Gyr and considering an axisymmetric and non-axisymmetric Milky-Way-like Galactic potential, respectively. In this scheme, we identified 20 potential cluster members that had close encounters with the globular cluster 47 Tucanae, all of which have a relative velocity distribution (Vrel_{rel}) less than 200 km s1^{-1} at the minimum distance approach. Among these potential members, 9 had close encounters with the cluster with velocities less than the escape velocity of 47 Tucanae, therefore a scenario of tidal stripping seems likely. These stars have been classified with a 93\% confidence level, leading to the identification of extratidal cluster stars. For the other 11 stars, Vrel_{rel} exceeds the escape velocity of the cluster, therefore they were likely ejected or are unassociated interlopers.Comment: 10 pages, 6 figures, 2 table, Accepted for publication in MNRA

    Um modelo integrado de gestão do risco agrícola para o Brasil.

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    O seguro agrícola é um dos mais importantes instrumentos para o desenvolvimento do setor agrícola, pois, ao permitir proteção ao produtor rural contra efeitos adversos de eventos ambientais e do mercado torna-se indispensável à estabilidade da renda, à geração de emprego e ao desenvolvimento tecnológico. No setor agrícola, além do risco de mercado, existem diversas outras fontes que a tornam uma atividade eminentemente arriscada. A principal delas se refere ao fato de que a atividade agrícola é altamente dependente de condições ambientais de difícil controle pelo homem, de modo que as variáveis climáticas e sua interação com fatores bióticos podem influenciar sobremaneira o resultado final da safra. A realidade histórica mostra que o seguro agrícola permite ao produtor rural manter sua renda na ocorrência de um sinistro, o que é fundamental para o setor agrícola e a sociedade em geral

    Point-contact spectroscopy on URu2_2Si2_2

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    Tunnel and point contact experiments have been made in a URu2_2Si2_2 single crystal along the c-axis. The experiments were performed changing temperature and contact size in a low temperature scanning tunneling microscope. A resonance develops at the Fermi level at T60T\sim 60 K. This resonance splits and becomes asymmetric when the 17.5 K phase transition is crossed. These results are consistent with the existence of Kondo like bound states of the U4+^{4+} ionic configurations and the conduction electrons. Below the transition, these configurations are split by the development of quadrupolar ordering. The peak separation can be interpreted as a direct measurement of the order parameter. Measurements on a policrystalline UAu_2Si_2$ sample are also reported, with a comparative study of the behavior of both materials.Comment: 4 pages (Latex) + 2 postscript figure
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