7,026 research outputs found

    An Intrinsic Approach to Forces in Magnetoelectric Media

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    This paper offers a conceptually straightforward method for the calculation of stresses in polarisable media based on the notion of a drive form and its property of being closed in spacetimes with symmetry. After an outline of the notation required to exploit the powerful exterior calculus of differential forms, a discussion of the relation between Killing isometries and conservation laws for smooth and distributional drive forms is given. Instantaneous forces on isolated spacetime domains and regions with interfaces are defined, based on manifestly covariant equations of motion. The remaining sections apply these notions to media that sustain electromagnetic stresses, with emphasis on homogeneous magnetoelectric material. An explicit calculation of the average pressure exerted by a monochromatic wave normally incident on a homogeneous, magnetoelectric slab in vacuo is presented and the concluding section summarizes how this pressure depends on the parameters in the magnetoelectric tensors for the medium.Comment: 25 pages, 3 figures, to appear in Il Nuovo Cimento B, proceedings of GCM8, Catania (Oct 2008) - References added, minor corrections mad

    Aeronomy report no. 73: Analysis of sounding rocket data from Punta Chilca, Peru

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    A technique is described for measuring electron concentrations in the lower portion of the ionosphere above Punta Chilca. A radio-propagation experiment for measuring Faraday rotation is combined with a dc/Langmuir probe experiment for measuring electron current. The results obtained from the analysis of radio and probe data from Nike Apache 14.532, which was launched at 20:26 UT on May 28, 1975, at a solar zenith angle of 60 deg are presented. A comparison of the profiles of electron concentration indicates that the value of the maximum ionization in the D region under quiet conditions is proportional to the square of the cosine of the solar zenith angle

    Grain legume evaluation

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    Pea variety evaluation, 89NM20, 89EB22, 89KA68, 89N334, 89EB24, 89SC27, 89A24, 89EB33, 89EB25. Grain legume species evaluation, 89NM21, 89MO41, 89N25, 89MC9, 89NM21, 89A22. Faba bean evaluation, 89MO42, 89A23, 89MC10, 89EB27, 89SG22 Grain legume agronom

    Trends in the use of payment instruments in the United States

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    In 2003, for the first time, the number of electronic payments in the United States exceeded the number of check payments--a result of substantial growth in electronic payments (especially by debit card) and a decline in check payments. The shift toward electronic payments suggests that, as with other large economies, many payments formerly made by check are now being made with electronic payment instruments. As in past years, however, the value of checks far exceeded the value of commonly used electronic payments. ; Comparisons among groups of depository institutions of different types and sizes suggest that the distribution of payments of different types is linked in part to the types of customers those institutions tend to serve. For example, at credit unions, which generally serve individuals rather than businesses, checks accounted for a smaller proportion of account debits, and debit card payments and ATM withdrawals accounted for a larger proportion, than at institutions of other types. ; Overall, "on us" check payments, those for which the payer and payee used the same institution, declined slightly. The rate at which checks are returned also declined, while the rate of returned ACH payments--almost twice that of checks--increased, in part because of new types of ACH payments, including ACH transactions initiated with a check. ; Data gathered in 2004 also reveal some differences among geographic regions. Debit card use was substantially greater, and check use substantially lower, in the West than in other regions. In contrast, debit card use was considerably less common in the Northeast, and the decline in check payments since 2000 was less pronounced in that region. ; Indirect evidence--data on ATM withdrawals and cash back from debit card payments--suggests that cash remains a popular means of making payments. Industry data showing increases in ATMs and ATM transactions appear to reflect a shift toward greater use of ATMs and less use of checks to obtain cash, and do not necessarily indicate an increase in the use of cash.Payment systems ; Checks

    Aspects of quantum energy and stress in inhomogeneous unbounded dielectric continua

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    This article explores a number of issues associated with the problem of calculating and detecting electromagnetic quantum induced energy and stress in a stationary dielectric material with a smooth inhomogeneous polarizability. By concentrating on a particular system composed of an ENZ-type (epsilon-near-zero) meta-material, chosen to have a particular anisotropic and smooth inhomogeneous permittivity, confined in an infinitely long perfectly conducting open rectangular waveguide, we are able to deduce analytically from the source-free Maxwell’s equations and their boundary conditions a complete set of bounded harmonic electromagnetic evanescent eigen-modes and their associated eigen-frequencies. Since these solutions prohibit the existence of asymptotic scattering states in the guide, the application of the conventional Lifshitz approach to the Casimir stress problem becomes uncertain. An alternative approach is adopted based upon the spectral properties of the system and a regularization scheme constructed with direct applicability to more general systems composed of dielectrics with smooth inhomogeneous permittivities and open systems that may only admit evanescent modes. This more general scheme enables one, for the first time, to prescribe precise criteria for the extraction of finite quantum expectation values from regularized mode sums together with error bounds on these values, and is used to derive analytic or numeric results for regularized electromagnetic ground state expectation values in the guide

    GSFC short pulse radar, JONSWAP-75

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    In September 1975, the Goddard Space Flight Center operated a short pulse radar during ocean wave measuring experiments off the coast of West Germany in the North Sea. The experiment was part of JONSWAP-75. The radar system and operations during the experiment are described along with examples of data

    Synthesis of Kentucky’s Traveler Information Systems

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    After the United States Department of Transportation (USDOT) petitioned the Federal Communications Commission (FCC) to establish a dedicated phone number for real-time travel information services, the abbreviated 511 dialing code was founded in July 2000. The FCC reasoned that 511 services could reduce traffic congestion, air pollution, and the inefficient use of fossil fuels. 511 would, in turn, improve traveler safety. In 2010, the Federal Highway Administration (FHWA) mandated a set of requirements for systems that deliver real-time traffic information to the public. States DOTs were asked to comply with this mandate by November 2014. Many states, in addition to maintaining websites, also have dedicated mobile apps and a social media presence (e.g., one or multiple Twitter accounts) that communicate data on traffic and road conditions. Analysis of 511 usage data indicated that the number of phone calls received has dropped sharply since the mid-2000s. Conversely, the amount of traffic handled by KYTC’s websites and mobile apps has increased. Like the phone system, websites and mobile apps garner the most traffic during the winter months. Discussions with KYTC 511 stakeholders revealed that phone system will be less relevant — although necessary to maintain, particularly in rural areas. There was significant consensus among KYTC stakeholders about the strengths of the state’s current approach to delivering traffic information, and a number of improvements were put forward to enhance it in the future. A survey of Kentucky drivers revealed that a majority get their traffic information through digital content providers. Services such as Google and Waze are popular for retrieving maps and driving directions, while television and radio play an important role still, especially for the provision of information during hazardous weather. Government-provided services (i.e., 511, TRIMARC) are less popular among drivers, and only garner a fraction of the traffic of online services and traditional media. Discussions with other state DOTs revealed that many other states are currently in the process of rethinking their 511 and traveler information systems. Many plan to retool these over the next 2–3 years. While there was agreement among state DOTs that they will continue to provide authoritative traveler information, how they carry out this mandate is somewhat unclear

    56Ni dredge-up in the type IIp Supernova 1995V

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    We present contemporary infrared and optical spectra of the plateau type II SN 1995V in NGC 1087 covering four epochs, approximately 22 to 84 days after shock breakout. The data show, for the first time, the infrared spectroscopic evolution during the plateau phase of a typical type II event. In the optical region P Cygni lines of the Balmer series and of metals lines were identified. The infrared (IR) spectra were largely dominated by the continuum, but P Cygni Paschen lines and Brackett gamma lines were also clearly seen. The other prominent IR features are confined to wavelengths blueward of 11000 \AA and include Sr II 10327, Fe II 10547, C I 10695 and He I 10830 \AA. We demonstrate the presence of He I 10830 \AA on days 69 and 85. The presence of this line at such late times implies re-ionisation. A likely re-ionising mechanism is gamma-ray deposition following the radioactive decay of 56Ni. We examine this mechanism by constructing a spectral model for the He I 10830 \AA line based on explosion model s15s7b2f of Weaver & Woosley (1993). We find that this does not generate the observed line owing to the confinement of the 56Ni to the central zones of the ejecta. In order to reproduce the He I line, it was necessary to introduce additional upward mixing of the 56Ni, with 10^{-5} of the total nickel mass reaching above the helium photosphere. In addition, we argue that the He I line-formation region is likely to have been in the form of pure helium clumps in the hydrogen envelope.Comment: Accepted for publication in MNRAS, 32 pages including 11 figures (uses psfig.sty - included

    Heavy X-ray obscuration in the most-luminous galaxies discovered by WISE

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    Hot Dust-Obscured Galaxies (Hot DOGs) are hyperluminous (L8−1000 μm>1013 L⊙L_{\mathrm{8-1000\,\mu m}}>10^{13}\,\mathrm{L_\odot}) infrared galaxies with extremely high (up to hundreds of K) dust temperatures. The sources powering both their extremely high luminosities and dust temperatures are thought to be deeply buried and rapidly accreting supermassive black holes (SMBHs). Hot DOGs could therefore represent a key evolutionary phase in which the SMBH growth peaks. X-ray observations can be used to study their obscuration levels and luminosities. In this work, we present the X-ray properties of the 20 most-luminous (Lbol≳1014 L⊙L_{\mathrm{bol}}\gtrsim10^{14}\, L_\odot) known Hot DOGs at z=2−4.6z=2-4.6. Five of them are covered by long-exposure (10−7010-70 ks) Chandra and XMM-Newton observations, with three being X-ray detected, and we study their individual properties. One of these sources (W0116−-0505) is a Compton-thick candidate, with column density NH=(1.0−1.5)×1024 cm−2N_H=(1.0-1.5)\times10^{24}\,\mathrm{cm^{-2}} derived from X-ray spectral fitting. The remaining 15 Hot DOGs have been targeted by a Chandra snapshot (3.1 ks) survey. None of these 15 is individually detected; therefore we applied a stacking analysis to investigate their average emission. From hardness-ratio analysis, we constrained the average obscuring column density and intrinsic luminosity to be logNH [cm−2]>23.5N_H\,\mathrm{[cm^{-2}]}>23.5 and LX≳1044 erg cm−2 s−1L_X\gtrsim10^{44}\,\mathrm{erg\,cm^{-2}\,s^{-1}}, which are consistent with results for individually detected sources. We also investigated the LX−L6μmL_X-L_{6\mu\mathrm{m}} and LX−LbolL_X-L_{bol} relations, finding hints that Hot DOGs are typically X-ray weaker than expected, although larger samples of luminous obscured QSOs are needed to derive solid conclusions.Comment: MNRAS, accepted 2017 November 29 . Received 2017 November 29 ; in original form 2017 October 11. 15 pages, 6 figure
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