1,553 research outputs found

    Stanford telemetry monitoring experiment on Lunar Explorer 35 Final report

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    Explorer 35 data analysis including occultation study and antenna pattern interpretation along with electromagnetic property experiment

    Noncommutative resolutions of discriminants

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    We give an introduction to the McKay correspondence and its connection to quotients of Cn\mathbb{C}^n by finite reflection groups. This yields a natural construction of noncommutative resolutions of the discriminants of these reflection groups. This paper is an extended version of E.F.'s talk with the same title delivered at the ICRA.Comment: 15 pages, 4 figures. Final version to appear in Contemporary Mathematics 705, "Representations of Algebras

    Radar studies of the planets

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    The radar measurements phase of the lunar studies involving reflectivity and topographic mapping of the visible lunar surface was ended in December 1972, but studies of the data and production of maps have continued. This work was supported by Manned Spacecraft Center, Houston. Topographic mapping of the equatorial regions of Mars has been carried out during the period of each opposition since that of 1967. The method comprised extended precise traveling time measurements to a small area centered on the subradar point. As measurements continued, planetary motions caused this point to sweep out extensive areas in both latitude and longitude permitting the development of a fairly extensive topographical map in the equatorial region. Radar observations of Mercury and Venus have also been made over the past few years. Refinements of planetary motions, reflectivity maps and determinations of rotation rates have resulted

    Improving our understanding of the Spitzer Space Telescope's pointing drifts

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    Spitzer observations of exoplanets routinely yield photometric accuracies of better than one part in 10,000. However, the attainable precision is limited in part by pointing drifts, which have the effect of moving the target to less stable or less-well characterized regions of Spitzer’s IRAC detector arrays. Here we examine a large sample of observing sequences in an effort to identify the causes of these pointing drifts. We find that short term and higher order drifts are correlated on various time scales to the temperatures of components in and around the spacecraft bus, and are most likely due to very slight angular displacements of the star trackers. Despite the constraints imposed by a limited pool of targets, such pointing drifts are best mitigated by optimal scheduling, minimizing large and/or lengthy excursions in telescope pitch angle within 24 hours of a high-precision photometry sequence. Such an effort is currently being initiated by the Spitzer Science Center

    Comparative analysis of the growth and biological activity of a respiratory and atheroma isolate of reveals strain-dependent differences in inflammatory activity and innate immune evasion

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    En el año 2010, como contraparte de los festejos del centenario de la Revolución mexicana, el poeta Jorge Esquinca invitó a treinta y cuatro poetas a participar en una antología titulada País de sombra y fuego. La relevancia de este ejercicio poético proviene de la pregunta que lo estructura: ¿Existe todavía en el vocablo Patria un núcleo generador de significado?A través del análisis de estos poemas y de los tópicos que prevalecen en ellos, es posible conocer el doloroso México que perciben los poetas mexicanos y la forma en que la poesía mexicana contemporánea del siglo XXI lo nombra.In 2010, as a counterpart to the festivities related to the 100th anniversary of the Mexican Revolution, the poet Jorge Esquinica invited thirty-four poets to participate in an anthology titled País de sombra y fuego. The relevance of this poetic exercise stems from the very question which gives it structure. Is the word Motherland still relevant in today's world?Through an analysis of these poems and the themes that prevail in them, it is possible to discover how these anthologized Mexican poets view their country nowadays and how they address its main issues.A l’any 2010, com a contrapart dels festejos del centenari de la Revolució mexicana, el poeta Jorge Esquinca va convidar trenta-quatre poetes a participar en una antologia titulada País de sombra y fuego. La rellevància d’aquest exercici poètic prové de la pregunta que l’estructura: existeix encara en el terme Pàtria un nucli generador de significat? A través de l’anàlisi d’aquests poemes i dels tòpics que prevalen en ells, és possible conèixer el dolorós Mèxic que perceben els poetes mexicans i la forma en què la poesia mexicana contamporània del segle XXI ho nombra

    Commercial-off-the-shelf simulation package interoperability: Issues and futures

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    Commercial-Off-The-Shelf Simulation Packages (CSPs) are widely used in industry to simulate discrete-event models. Interoperability of CSPs requires the use of distributed simulation techniques. Literature presents us with many examples of achieving CSP interoperability using bespoke solutions. However, for the wider adoption of CSP-based distributed simulation it is essential that, first and foremost, a standard for CSP interoperability be created, and secondly, these standards are adhered to by the CSP vendors. This advanced tutorial is on an emerging standard relating to CSP interoperability. It gives an overview of this standard and presents case studies that implement some of the proposed standards. Furthermore, interoperability is discussed in relation to large and complex models developed using CSPs that require large amount of computing resources. It is hoped that this tutorial will inform the simulation community of the issues associated with CSP interoperability, the importance of these standards and its future

    Spitzer/IRAC Observations of the Variability of Sgr A* and the Object G2 at 4.5 microns

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    We present the first detection from the Spitzer Space Telescope of 4.5 micron variability from Sgr A*, the emitting source associated with the Milky Way's central black hole. The >23 hour continuous light curve was obtained with the IRAC instrument in 2013 December. The result characterizes the variability of Sgr A* prior to the closest approach of the G2 object, a putative infalling gas cloud that orbits close to Sgr A*. The high stellar density at the location of Sgr A* produces a background of ~250 mJy at 4.5 microns in each pixel with a large pixel-to-pixel gradient, but the light curve for the highly variable Sgr A* source was successfully measured by modeling and removing the variations due to pointing wobble. The observed flux densities range from the noise level of ~0.7 mJy rms in a 6.4-s measurement to ~10 mJy. Emission was seen above the noise level ~34% of the time. The light curve characteristics, including the flux density distribution and structure function, are consistent with those previously derived at shorter infrared wavelengths. We see no evidence in the light curve for activity attributable to the G2 interaction at the observing epoch, ~100 days before the expected G2 periapsis passage. The IRAC light curve is more than a factor of two longer than any previous infrared observation, improving constraints on the timescale of the break in the power spectral distribution of Sgr A* flux densities. The data favor the longer of the two previously published values for the timescale.Comment: 13 pages, 10 figures, 2 tables, accepted for publication in the Ap
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