2,411 research outputs found
Method for producing edge geometry superconducting tunnel junctions utilizing an NbN/MgO/NbN thin film structure
A method for fabricating an edge geometry superconducting tunnel junction device is discussed. The device is comprised of two niobium nitride superconducting electrodes and a magnesium oxide tunnel barrier sandwiched between the two electrodes. The NbN electrodes are preferably sputter-deposited, with the first NbN electrode deposited on an insulating substrate maintained at about 250 C to 500 C for improved quality of the electrode
Edge geometry superconducting tunnel junctions utilizing an NbN/MgO/NbN thin film structure
An edge defined geometry is used to produce very small area tunnel junctions in a structure with niobium nitride superconducting electrodes and a magnesium oxide tunnel barrier. The incorporation of an MgO tunnel barrier with two NbN electrodes results in improved current-voltage characteristics, and may lead to better junction noise characteristics. The NbN electrodes are preferably sputter-deposited, with the first NbN electrode deposited on an insulating substrate maintained at about 250 to 500 C for improved quality of the electrode
Accurate determination of the scattering length of metastable Helium atoms using dark resonances between atoms and exotic molecules
We present a new measurement of the s-wave scattering length a of
spin-polarized helium atoms in the 2^3S_1 metastable state. Using two-photon
photoassociation spectroscopy and dark resonances we measure the energy
E_{v=14}= -91.35 +/- 0.06 MHz of the least bound state v=14 in the interaction
potential of the two atoms. We deduce a value of a = 7.512 +/- 0.005 nm, which
is at least one hundred times more precise than the best previous
determinations and is in disagreement with some of them. This experiment also
demonstrates the possibility to create exotic molecules binding two metastable
atoms with a lifetime of the order of 1 microsecond.Comment: 4 pages, 4 figure
Tackling Big Genomics Data
Presented at Internet 2 Global Summit, Denver, CO. 7 April 2014This material is based upon work supported by the National Science Foundation under Grant No. ABI-1062432, Craig Stewart, PI. William Barnett, Matthew Hahn, and Michael Lynch, co-PIs. This work was supported in part by the Lilly Endowment, Inc. and the Indiana University Pervasive Technology Institute. Any opinions presented here are those of the presenter(s) and do not necessarily represent the opinions of the National Science Foundation or any other funding agencie
Careers in Computing and Science
This material is based upon work supported by the National Science Foundation under Grants No. ABI-1062432 Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation
Abundance of small individuals influences the effectiveness of processing techniques for deep-sea nematodes
Nematodes are the most abundant metazoans of deep-sea benthic communities, but knowledge of their distribution is limited relative to larger organisms. Whilst some aspects of nematode processing techniques, such as extraction, have been extensively studied, other key elements have attracted little attention. We compared the effect of (1) mesh size (63, 45, and 32 ÎŒm) on estimates of nematode abundance, biomass, and body size, and (2) microscope magnification (50 and 100Ă) on estimates of nematode abundance at bathyal sites (250-3100 m water depth) on the Challenger Plateau and Chatham Rise, south-west Pacific Ocean. Variation in the effectiveness of these techniques was assessed in relation to nematode body size and environmental parameters (water depth, sediment organic matter content, %silt/clay, and chloroplastic pigments). The 63-ÎŒm mesh retained a relatively low proportion of total nematode abundance (mean ±SD = 55 ±9%), but most of nematode biomass (90 ± 4%). The proportion of nematode abundance retained on the 45-ÎŒm mesh in surface (0-1 cm) and subsurface (1-5 cm) sediment was significantly correlated (P < 0.01) with %silt/clay (RÂČ = 0.39) and chloroplastic pigments (RÂČ = 0.29), respectively. Variation in median nematode body weight showed similar trends, but relationships between mean nematode body weight and environmental parameters were either relatively weak (subsurface sediment) or not significant (surface sediment). Using a low magnification led to significantly lower (on average by 43%) nematode abundance estimates relative to high magnification (P < 0.001), and the magnitude of this difference was significantly correlated (P < 0.05) with total nematode abundance (RÂČp = 0.53) and the number of small (†250 ÎŒm length) individuals (RÂČp = 0.05). Our results suggest that organic matter input and sediment characteristics influence the abundance of small nematodes in bathyal communities. The abundance of small individuals can, in turn, influence abundance estimates obtained using different mesh sizes and microscope magnifications
Tuning Characteristics And New Laser Lines In An Nd:YAP CW Laser
We have investigated the CW laser properties of Nd-doped yttrium-aluminum-perovskite (YAP) in a Kr are-lamp, pumped cavity, Seven laser transitions within the 4F3/2-4I11/2 multiplet have been observed. A simple Lyot filter is used to select the particular transitions. The tuning characteristics of the transitions at 1.0745 and 1.0845 ÎŒm were also obtained with the addition of a thin, uncoated etalon within the cavity. Tuning widths of 32 and 23 Ă
, respectively, were obtained. Copyright © 1986 IEE
Development of Low Noise THz SIS Mixer Using an Array of Nb/Al-AlN/NbTiN Junctions
We report the development of a low noise and broadband SIS mixer aimed for 1 THz channel of the Caltech Airborne Submillimeter Interstellar Medium Investigations Receiver (CASIMIR), designed for the Stratospheric Observatory for Infrared Astronomy, (SOFIA). The mixer uses an array of two 0.24 mum^2 Nb/Al-AlN/NbTiN SIS junctions with the critical current density of 30-50 kA/cm^2 . An on-chip double slot planar antenna couples the mixer circuit with the telescope beam. The mixer matching circuit is made with Nb and gold films. The mixer IF circuit is designed to cover 4-8 GHz band. A test receiver with the new mixer has a low noise operation in 0.87-1.12 THz band. The minimum receiver noise measured in our experiment is 353 K (Y = 1.50). The receiver noise corrected for the loss in the LO injection beam splitter is 250 K. The combination of a broad operation band of about 250 GHz with a low receiver noise makes the new mixer a useful element for application at SOFIA
Low-noise slot antenna SIS mixers
We describe quasi-optical SIS mixers operating in the submillimeter band (500-750 GHz) which have very low noise, around 5 h/spl nu//k/sub B/ for the double-sideband receiver noise temperature. The mixers use a twin-slot antenna, Nb/Al-Oxide/Nb tunnel junctions fabricated with optical lithography, a two-junction tuning circuit, and a silicon hyperhemispherical lens with a novel antireflection coating to optimize the optical efficiency. We have flown a submillimeter receiver using these mixers on the Kuiper Airborne Observatory, and have detected a transition of H/sub 2//sup 18/O at 745 GHz. This directly confirms that SIS junctions are capable of low-noise mixing above the gap frequency
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