262 research outputs found

    Four new T dwarfs identified in PanSTARRS 1 commissioning data

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    A complete well-defined sample of ultracool dwarfs is one of the key science programs of the Pan-STARRS 1 optical survey telescope (PS1). Here we combine PS1 commissioning data with 2MASS to conduct a proper motion search (0.1--2.0\arcsec/yr) for nearby T dwarfs, using optical+near-IR colors to select objects for spectroscopic followup. The addition of sensitive far-red optical imaging from PS1 enables discovery of nearby ultracool dwarfs that cannot be identified from 2MASS data alone. We have searched 3700 sq. deg. of PS1 y-band (0.95--1.03 um) data to y≈\approx19.5 mag (AB) and J≈\approx16.5 mag (Vega) and discovered four previously unknown bright T dwarfs. Three of the objects (with spectral types T1.5, T2 and T3.5) have photometric distances within 25 pc and were missed by previous 2MASS searches due to more restrictive color selection criteria. The fourth object (spectral type T4.5) is more distant than 25 pc and is only a single-band detection in 2MASS. We also examine the potential for completing the census of nearby ultracool objects with the PS1 3π\pi survey.Comment: 25 pages, 8 figures, 5 table, AJ accepted, updated to comply with Pan-STARRS1 naming conventio

    A Fully Nonmetallic Gas Turbine Engine Enabled by Additive Manufacturing, Part II: Additive Manufacturing and Characterization of Polymer Composites

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    This publication is the second part of the three part report of the project entitled "A Fully Nonmetallic Gas Turbine Engine Enabled by Additive Manufacturing" funded by NASA Aeronautics Research Institute (NARI). The objective of this project was to conduct additive manufacturing to produce aircraft engine components by Fused Deposition Modeling (FDM), using commercially available polyetherimides-Ultem 9085 and experimental Ultem 1000 mixed with 10% chopped carbon fiber. A property comparison between FDM-printed and injection molded coupons for Ultem 9085, Ultem 1000 resin and the fiber-filled composite Ultem 1000 was carried out. Furthermore, an acoustic liner was printed from Ultem 9085 simulating conventional honeycomb structured liners and tested in a wind tunnel. Composite compressor inlet guide vanes were also printed using fiber-filled Ultem 1000 filaments and tested in a cascade rig. The fiber-filled Ultem 1000 filaments and composite vanes were characterized by scanning electron microscope (SEM) and acid digestion to determine the porosity of FDM-printed articles which ranged from 25 to 31%. Coupons of Ultem 9085, experimental Ultem 1000 composites and XH6050 resin were tested at room temperature and 400F to evaluate their corresponding mechanical properties. A preliminary modeling was also initiated to predict the mechanical properties of FDM-printed Ultem 9085 coupons in relation to varied raster angles and void contents, using the GRC-developed MAC/GMC program

    Millimeter-wave Signature of Strange Matter Stars

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    One of the most important questions in the study of compact objects is the nature of pulsars, including whether they consist of neutron matter or strange quark matter (SQM). However, few mechanisms for distinguishing between these two possibilities have been proposed. The purpose of this paper is to show that a strange star (one made of SQM) will have a vibratory mode with an oscillation frequency of approximately 250 GHz (millimeter wave). This mode corresponds to motion of the center of the expected crust of normal matter relative to the center of the strange quark core, without distortion of either. Radiation from currents generated in the crust at the mode frequency would be a SQM signature. We also consider effects of stellar rotation, estimate power emission and signal-to-noise ratio, and discuss briefly possible mechanisms for exciting the mode.Comment: 13 pages, Latex, one figur

    Patient focused registries can improve health, care, and science.

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    Eugene Nelson and colleagues call for registries of care data to be transformed into patient centred interactive learning systemsThis work is supported by funding from the Robert Wood Johnson Foundation (Grants: #71211 and 72313), the Cystic Fibrosis Foundation (Grant #OCONNO04Q10), and the Crohn’s and Colitis Foundation of America Quality of Care Initiative (Grant #3372). TSM was funded by the Multidisciplinary Clinical Research Center for Musculoskeletal Diseases at Dartmouth (P60 AR-062799, A. Tosteson, PI), sponsored by the National Institute for Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health. EE was funded by The Swedish Research Council for Health, Work Life and Welfare (#2014-4238). MDW is supported by a Wellcome Trust Senior Investigator award (WT09789).This is the final version of the article. It first appeared from BMJ Group via https://doi.org/10.1136/bmj.i331
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