17,250 research outputs found

    Radial honeycomb core

    Get PDF
    Core alleviates many limitations of conventional nacelle construction methods. Radical core, made of metals or nonmetals, is fabricated either by joining nodes and then expanding, or by performing each layer and then joining nodes. Core may also be produced from ribbons or strips with joined nodes or ribbons oriented in longitudinal planes

    CC Sculptoris: A superhumping intermediate polar

    Full text link
    We present high speed optical, spectroscopic and Swift X-ray observations made during the dwarf nova superoutburst of CC Scl in November 2011. An orbital period of 1.383 h and superhump period of 1.443 h were measured, but the principal new finding is that CC Scl is a previously unrecognised intermediate polar, with a white dwarf spin period of 389.49 s which is seen in both optical and Swift X-ray light curves only during the outburst. In this it closely resembles the old nova GK Per, but unlike the latter has one of the shortest orbital periods among intermediate polars.Comment: Accepted for publication in MNRAS; 11 pages, 19 figure

    A Comparison of Reef Fish Assemblages on the East and West Sides of Central Eleuthera, Bahamas

    Get PDF
    Eleuthera is a long, narrow crescent-shaped Atlantic margin island on the eastern extremity of the Great Bahama Bank in the central Bahamas. It is 144 km long and less than 5 km at its greatest width. Fringing reefs with substantial vertical relief (to 5 m in depths of 6 m) are found approximately 500 m offshore on the eastern side of the island facing the Atlantic Ocean. The western side of the island has stretches of rock cliffs and large fallen boulders providing substrate with similar vertical relief. No open passes exist between the two sides of the island and thus no direct larval transport from one side to the other appears possible. We compared post-settlement fish assemblages and larval supply on either side of central Eleuthera near Governor’s Harbour quarterly from July 2003 until July 2004. Twelve point-counts were performed at two replicate sites on both sides of the island to census juveniles and adults. Abundance, as well as average, maximum and minimum lengths of species present were recorded. Three light traps were moored at each of the same sites 40-50 m from the reef for three to five nights around the new moon to examine larval supply. Fish collected in the light traps were preserved and transported to the lab. They were identified, enumerated, and standard length was measured. Preliminary analyses of point-count and light trap data indicate dissimilar assemblage structure between the two sides of the island, with significantly greater fish abundance and species richness on the eastern side

    1RXS J232953.9+062814: A Dwarf Nova with a 64-minute Orbital Period and a Conspicuous Secondary Star

    Full text link
    We present spectroscopy and time-series photometry of the newly discovered dwarf nova 1RXS J232953.9+062814. Photometry in superoutburst reveals a superhump with a period of 66.06(6) minutes. The low state spectrum shows Balmer and HeI emission on a blue continuum, and in addition shows a rich absorption spectrum of type K4 +- 2. The absorption velocity is modulated sinusoidally at P_orb = 64.176(5) min, with semi-amplitude K = 348(4) km/s. The low-state light curve is double-humped at this period, and phased as expected for ellipsoidal variations. The absorption strength does not vary appreciably around the orbit. The orbital period is shorter than any other cataclysmic variable save for a handful of helium-star systems and V485 Centauri (59 minutes). The secondary is much hotter than main sequence stars of similar mass, but is well-matched by helium-enriched models, indicating that the secondary evolved from a more massive progenitor. A preliminary calculation in which a 1.2 solar-mass star begins mass transfer near the end of H burning matches this system's characteristics remarkably well.Comment: accepted to Astrophysical Journal Letters; 14 pages, 3 eps figures + 1 jpg greyscale figur

    A Hierarchical Model of Virtual Experience and Its Influences on the Perceived Value and Loyalty of Customers

    Get PDF
    Many businesses use virtual experience (VE) to enhance the overall customer experience, though extant research offers little guidance for how to improve consumers’ VE. This study, anchored in activity theory, examines key drivers of VE and its influences on value perceptions and customer loyalty. A hierarchical model indicates that VE comprises second-order variables (i.e., social presence, social capital, flow experience, and situational involvement) and third-order variables (i.e., communal and individual experience). The results obtained from a substantive model further reveal that VE positively influences perceptions of both economic and social value and thus influences loyalty in both the real world and virtual environments

    Search for the electric dipole moment of the electron with thorium monoxide

    Get PDF
    The electric dipole moment of the electron (eEDM) is a signature of CP-violating physics beyond the Standard Model. We describe an ongoing experiment to measure or set improved limits to the eEDM, using a cold beam of thorium monoxide (ThO) molecules. The metastable H3Δ1H {}^3\Delta_1 state in ThO has important advantages for such an experiment. We argue that the statistical uncertainty of an eEDM measurement could be improved by as much as 3 orders of magnitude compared to the current experimental limit, in a first-generation apparatus using a cold ThO beam. We describe our measurements of the HH state lifetime and the production of ThO molecules in a beam, which provide crucial data for the eEDM sensitivity estimate. ThO also has ideal properties for the rejection of a number of known systematic errors; these properties and their implications are described.Comment: v2: Equation (11) correcte

    An XMM-Newton observation of the nova-like variable UX UMa: spatially and spectrally resolved two-component X-ray emission

    Full text link
    In the optical and ultraviolet regions of the electromagnetic spectrum, UX Ursae Majoris is a deeply eclipsing cataclysmic variable. However, no soft X-ray eclipse was detected in ROSAT observations. We have obtained a 38 ksec XMM-Newton observation to further constrain the origin of the X-rays. The combination of spectral and timing information allows us to identify two components in the X-ray emission of the system. The soft component, dominant below photon energies of 2 keV, can be fitted with a multi-temperature plasma model and is uneclipsed. The hard component, dominant above 3 keV, can be fitted with a kT ~ 5 keV plasma model and appears to be deeply eclipsed. We suggest that the most likely source of the hard X-ray emission in UX UMa, and other systems in high mass transfer states, is the boundary layer.Comment: To appear in MNRAS Letter
    • …
    corecore