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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4240-4246 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the magnetic hysteresis loops and temperature dependent trapped fields in melt-textured YBa2Cu3O7−δ samples before and after p+ and 3He++ irradiation using a Hall effect magnetometer (HEM) as well as a commercial vibrating sample magnetometer (VSM). For proper 3He++ fluence, the critical current density may be enhanced by a factor of 10. Calculations based on various critical state models show that before the irradiation, the hysteresis loops can be well accounted for by a critical current density of a modified power law field dependence Jc(T,B)=J0(T)/(1+B/B0)n with n=1/2; after the irradiation, the best fit has been achieved by using an exponential form such as Jc(T,B)=J0(T)exp(−B/B0), where B0 is a model dependent parameter. Jc and its field dependence deduced from HEM hysteresis loops are in good agreement with those deduced from the VSM loops, suggesting that the Hall effect magnetometer can be conveniently used to characterize bulk high Tc oxide superconductors.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial thin films of YBaCuO have been prepared with (1) the a axis perpendicular to (100) SrTiO3 ; (2) the c axis perpendicular to (100) SrTiO3 ; and (3) the [110] axis perpendicular to (110) SrTiO3. Films were fabricated using a multilayer deposition technique involving three electron guns containing Y, BaF2, and Cu under a pressure of 5×10−5 Torr of O2. As deposited films, which contained polycrystalline and amorphous regions, were later annealed in a furnace under a flowing O2-H2 O atmosphere. X-ray diffraction patterns as well as scanning electron microscopy and high-resolution electron microscopy images confirm that the films are highly oriented, essentially epitaxial. The a-axis oriented film exhibits zero resistance at 90 K and a critical current density of 2.9×106 A/cm2 at 4.2 K while the c-axis oriented film exhibits a Tc of 88 K and a Jc of 0.9×107 A/cm2 at 4.2K; the Jc values were determined magnetically. The [110]-orientation film shows the sharpest transition with a transition width of 1 K and zero resistance at 85 K.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 964-966 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the temperature and magnetic field dependence of the Hall mobility and transverse magnetoresistance in n-type InSb films epitaxially grown on GaAs substrates by metalorganic chemical vapor deposition. The films show a giant magnetoresistance: e.g., at 240 K the resistivity increases over 20 times at a magnetic field of 5 T; the low field coefficient of resistivity at 77 K is as high as 47.5 μΩ cm/G. The Hall mobility decreases with magnetic field and saturates at higher fields. By taking the interface carrier transport into account, the observed field dependence of the Hall mobility and magnetoresistance may be understood based on a two-layer model.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 479-481 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the Hall effect and the magnetoresistance in [110] textured Fe/Cr multilayers grown by electron beam evaporation. We have observed a strong magnetic field dependence of the Hall coefficient as well as a large magnetoresistance. In all cases the Hall voltage is positive. The ordinary Hall coefficient is positive at room temperature and changes sign at low temperatures; this is similar to the behavior of an antiferromagnet but differs from that observed in Fe-Cr alloys. The extraordinary Hall coefficient Rs is positive and varies with the resistivity ρ as Rs∝ρ2.6, suggesting the importance of interface scattering.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 1503-1505 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the results of a pulsed organometallic beam epitaxy (POMBE) process for growing complex oxide films at low background gas pressure (10−4–10−2 Torr) and low substrate temperature (600–680 °C) using organometallic precursors in an oxygen plasma environment. Our results show that POMBE can extend the capability of organometallic chemical vapor deposition to growing complex oxide films with high precision both in composition and structure without the need for post-deposition oxidation and heat treatments. The growth of phase-pure, highly oriented Y-Ba-Cu-O superconducting oxide films {[Tc (R=0)=90.5 K] and Jc (77 K, 50 K gauss)=1.1×105 A/cm2} is given as an example. Similar to the pulsed laser deposition process, the POMBE method has the potential for in situ processing of multilayer structures (e.g., junctions).
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nondestructive evaluation 11 (1992), S. 69-77 
    ISSN: 1573-4862
    Keywords: Welds ; flaw classification ; ultrasonics ; neural networks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A probabilistic neural network is used here to classify flaws in weldments from their ultrasonic scattering signatures. It is shown that such a network is both simple to construct and fast to train. Probabilistic nets are also shown to be able to exhibit the high performance of other neural networks, such as feed forward nets trained via back-propagation, while possessing important advantages of speed, explicitness of their architecture, and physical meaning of their outputs. Probabilistic nets are also demonstrated to have performance equal to common statistical approaches, such as theK-nearest neighbor method, while retaining their unique advantages.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-4897
    Keywords: Failure index ; Quadratic failure criteria ; Maximum strength ; Optimal stacking sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The quadratic failure criterion, which is intended to predict fracture, may be used as an object function for optimal stacking sequence design of laminated plate. However, calculations using a symmetric laminated plate demonstrate that Tsai-Wu theory may give incorrect optimum predictions under uniaxial loading.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 1084-1087 
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-2013
    Keywords: Ca2+ channels ; G protein ; Sympathetic ganglion ; Acetylcholine ; Noradrenaline ; Muscarinic receptors ; α-adrenergic receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Effects of acetylcholine (ACh) and noradrenaline (NA) on voltage-gated ion channels of sympathetic neurones acutely dissociated from rat superior cervical ganglion (SCG) were examined using the whole-cell voltage-clamp technique. Depolarizing voltage steps elicited two types of low- and high-voltage-activated (LVA and HVA) Ca2+ currents. Pressure applications of ACh and NA produced concentration-dependent inhibition of the HVA Ca2+ current without affecting the LVA Ca2+ current. The inhibitory action of ACh on the Ca2+ current was blocked by a muscarinic antagonist, atropine. The action of NA was suppressed by an α 2-adrenergic antagonist, yohimbine, but not by an α 1-adrenergic antagonist, prazosin. Delayed rectifying outward K+ currents and inward rectifying K+ current were not affected by either ACh or NA. Tetrodotoxin-sensitive and -insensitive Na+ currents also remained unaffected under actions of ACh and NA. When recorded with electrode containing guanosine-5′-O-(3-thiotriphosphate) (GTP-γ-S), the inhibitory actions of ACh and NA on Ca2+ currents became irreversible. After treatment of SCG neurones with pertussis toxin, the inhibitory action of ACh on the Ca2+ current was almost completely abolished, whereas the action of NA was only partially reduced. The results suggest that ACh and NA differentially inhibit the HVA Ca2+ current via different G proteins coupling muscarinic and α 2-adrenergic receptors to Ca2+ channels in rat SCG neurones.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Research in nondestructive evaluation 5 (1993), S. 111-122 
    ISSN: 1432-2110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A very general model formulation is presented in the frequency domain for the pulse-echo ultrasonic response of an arbitrary scatterer in a fluid. The transducer is modeled as a piston source and the scatterer can be located anywhere in the transducer wavefield. The model is computationally efficient and is shown to agree well with initial experiments.
    Type of Medium: Electronic Resource
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