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  • 1985-1989  (92)
  • 1915-1919  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Identification of vortex motions in turbulent mixing of choked jets (1988)
    Springer
    Experiments in fluids 6 (1988), S. 335-343 
    Details
    ISSN: 1432-1114
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A specially adapted schlieren system is used to generate fluctuating signals which respond strongly to large scale coherent components of a turbulent mixing jet flow and which have a relatively reduced response to random disturbances. The schlieren signals also provide a direct indication of the presence of vortex-like structures in the turbulent mixing layers by virtue of the phase relationship of the schlieren signals to the pressure field. This system gives a clear resolution of the fluctuating periodic effects associated with vortex structures in the flow from a choked convergent nozzle. It has thus been possible to determine that vortex-like eddies are associated with the feedback screech mechanism, and also generate periodic disturbances due to their passage through the diamond shaped wave structure in the flow. The regular disturbances in the flow move at 0.77 of the fully expanded flow velocity. Phase spectral observations demonstrate clearly the vortex like structure of coherent disturbances in the flow by virtue of the quadrature phase relation between the schlieren and microphone signals. Movement of the sensing microphone in the pressure field external to the flow shows disturbance propagation at the acoustic velocity, and also shows that disturbances at Strouhal numbers above 0.7 emanating from the inner mixing zone can be identified by an additional time delay to reach the microphone and only influence the microphone when it is located downstream of the flow sensing schlieren system due to confinement of pressure disturbances within Mach cones of the flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00538825
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  • 2
    Electronic Resource
    Electronic Resource
    Taxonomy of Plant-Pathogenic Coryneform Bacteria (1986)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Phytopathology 24 (1986), S. 115-140 
    Details
    ISSN: 0066-4286
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.py.24.090186.000555
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  • 3
    Electronic Resource
    Electronic Resource
    Large magnetic hysteresis in a melt-textured Y-Ba-Cu-O superconductor (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 584-586 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Melt-textured YBa2Cu3O7−δ superconductor with a long and well-aligned grain structure is shown to exhibit magnetic hysteresis at 77 K which is the largest ever reported for bulk polycrystalline Y-Ba-Cu-O. The large ΔM resulted in a magnet-like behavior as well as a strong suspension phenomenon. It is shown, contrary to the previous reports, that the suspension behavior observed in Y-Ba-Cu-O is a generic consequence of large grain size, and not due to the presence of Ag oxide or Ag particles. There appears to be no substantial enhancement in flux pinning and Jc by these particles. Comparisons of magnetization behavior in various YBa2Cu3O7−δ samples (polycrystals, silver-oxide doped, melt-textured, and single crystals) indicated that for applied fields substantially larger than Hc1 the current flow that gives rise to the observed magnetization is intragranular. The pinning force and hence the critical current is roughly the same [Jc (magn)∼104 A/cm2] within a factor of ∼2 regardless of grain size, grain boundary configuration, presence of second phase particles, or increased dislocation and twin densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101464
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  • 4
    Electronic Resource
    Electronic Resource
    Low-resistivity contacts to bulk high Tc superconductors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2605-2607 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Convenient methods for obtaining extremely low resistivity contacts to bulk high Tc superconductors ( ρc in the range of 10−11–10−12 Ω cm2) are described. Three different configurations of silver contact metal in Y-Ba-Cu-O have been employed, i.e., embedded Ag wire, embedded Ag particles, and selectively patterned Ag clad on superconductor wire. In all three cases, the low-resistivity metallic contacts are formed in situ during the sintering or melt processing of the superconductor, thus eliminating the need for separate steps of contact preparation such as vacuum deposition of contact metal and additional heat treatment. The distribution and morphology of the silver contacts will be discussed. The measured contact resistivities in the present work are the lowest reported for the high Tc superconductors, and these methods may serve as a useful basis for important contact technologies needed for bulk superconductor applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101038
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  • 5
    Electronic Resource
    Electronic Resource
    Bi-Sr-Ca-Cu-O high TC superconductors (abstract) (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5815-5815 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A recent paper by Maeda et al.1 reported the discovery of a new 120 K superconductor based on a rare-earth–free ceramic material in the bismuth-strontium-calcium-copper-oxide system. We have confirmed the existence of the 120-K phase in the oxide system. The resistivity-temperature curve showed a fairly well-defined double-dip shape with the first dip starting at ∼120 K and the second at ∼95 K. The transition temperature, TC(R=0), was 84 K. This material appears to contain two superconducting phases with different TC's. A pellet made from this superconductor levitates well at 77 K (liquid-nitrogen temperature) above a neodynium-iron-boron magnet with a surface magnetic field of ∼3000 Oe, thus indicating a nontrivial critical field in this material. The critical current density and its magnetic field dependence will be reported. The magnetic and mechanical behavior of the new superconductor will also be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342214
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  • 6
    Electronic Resource
    Electronic Resource
    Fabrication and properties of high-Tc superconducting wires (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5896-5898 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The discovery of high-temperature superconductivity in perovskite-related oxides has generated an enormous amount of research activity and development effort toward applications. Commercially useful bulk superconductors typically require stabilization using a normal metal cladding for reasons of electrical, thermal, and mechanical protection, and in general need to be fabricated into fine fibers and wound into a solenoid configuration. The YBa2Cu3O7−δ type compound is a ceramic material which is mechanically hard and brittle, and is difficult to fabricate into fine wires. However, this difficulty has been overcome by several fabrication methods such as powder-in-tube method (metal-clad composite), powder-coating method (metal-core composite), and molten oxide processing method. The effect of various processing steps on the structure and superconducting properties such as transition temperature and critical current density will be discussed. Some experiments to raise the high field critical current through chemistry and microstructural control will also be described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342194
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  • 7
    Electronic Resource
    Electronic Resource
    High critical currents in Y-Ba-Cu-O superconductors (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 2074-2076 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Melt-textured growth of polycrystalline YBa2Cu3O7−δ superconductor using directional solidification created an essentially 100% dense structure consisting of long, needle- or plate-shaped crystals preferentially aligned parallel to the a-b conduction plane. The new microstructure, which completely replaces the previous granular and random structure in the sintered precursor, exhibits dramatically improved transport Jc values at 77 K of ∼17 000 A/cm2 in zero field and ∼4000 A/cm2 at H=1 T (as compared to ∼500 and ∼1 A/cm2, respectively, for the as-sintered structure), with the severe field dependence of Jc ("weak-link'' problem) no longer evident in the new melt-textured material. The improvement in Jc is attributed to the combined effects of densification, alignment of crystals, and formation of cleaner grain boundaries. Microstructure and distribution of various phases present in the melt-textured material are discussed in relation to the superconducting properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99751
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  • 8
    Electronic Resource
    Electronic Resource
    Superconductivity in the Bi-Sr-Ca-Cu-O compounds with noble metal additions (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 1628-1630 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Bi-Sr-Ca-Cu-O superconductors have been doped with various noble metals and their superconducting properties have been investigated. The resistivity and magnetic susceptibility measurements on sintered Bi4Sr3Ca2Cu4O16+x containing 20% by weight of Au, Ag, or Pt-group metals indicate that Au and the Pt-group metals significantly suppress or eliminate the superconducting transition in Bi-Sr-Ca-Cu-O. Only Ag is found to be benign, maintaining both the 115 and 85 K transitions in the compound. This nonpoisoning behavior of silver is of significant technical importance because of the need for a proper stabilizing normal metal for composite superconductor wire, nonreactive crucible materials for melt processing or crystal growth, and suitable nonpoisonous substrates or barriers for thin- or thick-film superconducting devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99705
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular Genetics of the T Cell-Receptor Beta Chain (1985)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Immunology 3 (1985), S. 537-560 
    Details
    ISSN: 0732-0582
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.iy.03.040185.002541
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of Neurotensin on Endogenous Dopamine Release from Explanted Mesoaccumbens Neurons in Vitro: Selective Activation of Somatodendritic Receptor Sites (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 537 (1988), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1988.tb42136.x
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