519 research outputs found

    Devoted Heroes: Muslim Superheroes, Comics, and Fundamentalism

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    When Superman leapt onto newsstands, he brought religiosity with him, specifically Christian and Jewish religiosity. From his creators’ Jewish backgrounds, to the Christian imagery read into him, Superman is a symbol of how religion can intersect with the comic book medium. Debates still erupt over the question: is Superman Jewish? This is reductionist, at best. It begs the question, what does it mean to say that a character is religious? What is the question referencing? The diegetic religion of the character? The religious affiliation of who the character is based on? The writers and artists of the comic? How closely the character’s traits and story mimic religious traits and stories? Through these follow up questions it becomes clear that our initial question is far more complicated than it may first have appeared

    European climate response to tropical volcanic eruptions over the last half millennium

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    We analyse the winter and summer climatic signal following 15 major tropical volcanic eruptions over the last half millennium based on multi-proxy reconstructions for Europe. During the first and second post-eruption years we find significant continental scale summer cooling and somewhat drier conditions over Central Europe. In the Northern Hemispheric winter the volcanic forcing induces an atmospheric circulation response that significantly follows a positive NAO state connected with a significant overall warm anomaly and wetter conditions over Northern Europe. Our findings compare well with GCM studies as well as observational studies, which mainly cover the substantially shorter instrumental period and thus include a limited set of major eruptions

    The Relativistic Factor in the Orbital Dynamics of Point Masses

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    There is a growing population of relativistically relevant minor bodies in the Solar System and a growing population of massive extrasolar planets with orbits very close to the central star where relativistic effects should have some signature. Our purpose is to review how general relativity affects the orbital dynamics of the planetary systems and to define a suitable relativistic correction for Solar System orbital studies when only point masses are considered. Using relativistic formulae for the N body problem suited for a planetary system given in the literature we present a series of numerical orbital integrations designed to test the relevance of the effects due to the general theory of relativity in the case of our Solar System. Comparison between different algorithms for accounting for the relativistic corrections are performed. Relativistic effects generated by the Sun or by the central star are the most relevant ones and produce evident modifications in the secular dynamics of the inner Solar System. The Kozai mechanism, for example, is modified due to the relativistic effects on the argument of the perihelion. Relativistic effects generated by planets instead are of very low relevance but detectable in numerical simulations

    A Survey of Air-to-Ground Propagation Channel Modeling for Unmanned Aerial Vehicles

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    In recent years, there has been a dramatic increase in the use of unmanned aerial vehicles (UAVs), particularly for small UAVs, due to their affordable prices, ease of availability, and ease of operability. Existing and future applications of UAVs include remote surveillance and monitoring, relief operations, package delivery, and communication backhaul infrastructure. Additionally, UAVs are envisioned as an important component of 5G wireless technology and beyond. The unique application scenarios for UAVs necessitate accurate air-to-ground (AG) propagation channel models for designing and evaluating UAV communication links for control/non-payload as well as payload data transmissions. These AG propagation models have not been investigated in detail when compared to terrestrial propagation models. In this paper, a comprehensive survey is provided on available AG channel measurement campaigns, large and small scale fading channel models, their limitations, and future research directions for UAV communication scenarios

    Phenomenology of the Lense-Thirring effect in the Solar System

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    Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in Astrophysics and Space Science (ApSS). Some uncited references in the text now correctly quoted. One reference added. A footnote adde

    Radioscience simulations in General Relativity and in alternative theories of gravity

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    In this communication, we focus on the possibility to test GR with radioscience experiments. We present a new software that in a first step simulates the Range/Doppler signals directly from the space time metric (thus in GR and in alternative theories of gravity). In a second step, a least-squares fit of the involved parameters is performed in GR. This software allows one to get the order of magnitude and the signature of the modifications induced by an alternative theory of gravity on radioscience signals. As examples, we present some simulations for the Cassini mission in Post-Einsteinian gravity and with the MOND External Field Effect.Comment: 4 pages; Proceedings of "Les Rencontres de Moriond 2011 - Gravitation session

    The Pioneer Anomaly

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    Radio-metric Doppler tracking data received from the Pioneer 10 and 11 spacecraft from heliocentric distances of 20-70 AU has consistently indicated the presence of a small, anomalous, blue-shifted frequency drift uniformly changing with a rate of ~6 x 10^{-9} Hz/s. Ultimately, the drift was interpreted as a constant sunward deceleration of each particular spacecraft at the level of a_P = (8.74 +/- 1.33) x 10^{-10} m/s^2. This apparent violation of the Newton's gravitational inverse-square law has become known as the Pioneer anomaly; the nature of this anomaly remains unexplained. In this review, we summarize the current knowledge of the physical properties of the anomaly and the conditions that led to its detection and characterization. We review various mechanisms proposed to explain the anomaly and discuss the current state of efforts to determine its nature. A comprehensive new investigation of the anomalous behavior of the two Pioneers has begun recently. The new efforts rely on the much-extended set of radio-metric Doppler data for both spacecraft in conjunction with the newly available complete record of their telemetry files and a large archive of original project documentation. As the new study is yet to report its findings, this review provides the necessary background for the new results to appear in the near future. In particular, we provide a significant amount of information on the design, operations and behavior of the two Pioneers during their entire missions, including descriptions of various data formats and techniques used for their navigation and radio-science data analysis. As most of this information was recovered relatively recently, it was not used in the previous studies of the Pioneer anomaly, but it is critical for the new investigation.Comment: 165 pages, 40 figures, 16 tables; accepted for publication in Living Reviews in Relativit

    Deployment operation procedures for the WHOI Ice-Tethered Profiler

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    Deployed and fixed to a suitable multi-year ice floe, the Ice-Tethered Profiler (ITP) can sustain near-real time measurements of upper ocean temperature and salinity for up to three years. Incorporating a specifically designed winch system and deployment apparatus that is both light weight and easily assembled or disassembled on a ship or at a deployment site, the ITP can be deployed in less than four hours by either transporting the gear and field personnel to the deployment site via aircraft, or by lowering the gear over the side of a ship and hauling on the ice. Using daily satellite imagery (if available), visual reconnaissance flights, and ice surveying, the choice of an appropriate ice floe is a necessity to select a site that will sustain the system for a prolonged period of time (depending upon the instrument sampling rate). If available, the helicopter is the preferable method for surveying different sites and for deployment operations. Working from a ship typically limits the distance and selection of ice floes. Pre-deployment procedures include powering and configuring the ITP instruments and preparing the apparatus for transport to the deployment site. Specific deployment methods include the assembly and disassembly of the ITP winch, proper placement of the total ITP deployment apparatus, ‘Yale Grip’ braiding and slipping techniques, and testing the Iridium and Inductive communication links. The operations described here provide a safe and efficient manner to easily deploy the WHOI ITP.Funding was provided by the National Science Foundation under Grant No. OCE-0324233 and by the Office of Polar Programs under award numbers ARC-0519899 and ARC-0631951
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