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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Superoxide production by cultured microglia derived from neonatal rat brains and the cytotoxicity of these cells were evaluated. The chemiluminescence (photon counts) detected in the presence of MCLA, a new chemiluminescence probe, was strongly correlated with the microglial cell count. Chemiluminescence observed in this system was confirmed to originate specifically from superoxide produced by activated microglia. Phorbol myristate acetate-stimulated microglia caused a pronounced reduction of PC12h cell numbers in coculture. The addition of superoxide dismutase with catalase or the addition of deferoxamine mesylate inhibited PC12h cell death, suggesting that active oxygen species derived from superoxide generated by the microglia or iron-oxygen complex formation were responsible for the cytotoxicity. These results imply that activated microglia may participate in the progression of the pathologic process in some neurodegenerative disorders.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 885-896 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Molecular beam epitaxial (MBE) growth, structural, and electrical properties of novel epitaxial metal/semiconductor heterostructures (MSHs), consisting of monocrystalline CoAl, an intermetallic compound, and AlAs/GaAs III-V semiconductors have been studied. The CoAl with stoichiometric composition has a CsCl-type crystal structure whose lattice constant is very close to half the lattice constant of GaAs and AlAs, hence, it is a good candidate as a constituent metal in epitaxial monocrystalline metal/semiconductor heterostructures. MBE growth of CoAl thin films on AlAs/GaAs, and also semiconductor overgrowth on ultrathin CoAl films, together with structural characterizations by in situ reflection high energy electron diffractions, ex situ x-ray diffractions and cross sectional transmission electron microscopy have been explored. By optimizing the growth parameters and procedures, high quality monocrystalline CoAl/AlAs/GaAs heterostructures with atomically abrupt interfaces have been successfully grown. Furthermore, the electrical properties of such novel heterostructures as Schottky barrier heights of CoAl/AlAs/GaAs MSHs and transport properties in ultrathin buried CoAl films are described.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied structural and magnetic properties of epitaxial MnAs thin films with various thicknesses (L=1.0–200 nm) on GaAs substrates. The MnAs thin films were grown at 200–250 °C on an As-rich disordered c(4×4) (001) GaAs surface by molecular-beam epitaxy (MBE). The growth direction of the MnAs was found to be along the [1¯100] axis of the hexagonal unit cell. X-ray spectra of the MnAs at room temperature have two peaks, indicating that the present MBE-grown MnAs films consist of the hexagonal ferromagnetic phase and orthorhombic paramagnetic phase. Magnetization measurements revealed that the MnAs thin films have perfectly square hysteresis characteristics with relatively high remnant magnetization Mr=300–567 emu/cm3 and low coercive field Hc=65–926 Oe, compared with those of epitaxial MnGa and MnAl thin films reported previously.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Recent progress regarding high power negative-ion source development for fusion research at JAERI is described. Using the cesium-seeded volume production-type negative-ion sources with an electrostatic acceleration system, a stable production of multiampere negative hydrogen/deuterium ion beams and a high energy acceleration of negative hydrogen ions of 0.2 A up to 350 keV have been demonstrated. On the basis of this recent progress, the construction of a 500 keV, 22 A, deuterium negative-ion source for a neutral beam injection system for the JT-60 tokamak was initiated. Additionally, a 1 MeV, 1 A Cockcroft–Walton-type test facility has been prepared in order to demonstrate high current negative ion acceleration up to 1 MeV. Through these research and development activities, the high power negative-ion source technology sufficient for the realization of a neutral beam injection system for a fusion experimental reactor such as the International Thermonuclear Experimental Reactor, is in the planning stages.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 5914-5914 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, high-Tc oxide superconductors have been extensively studied because these materials can be applied to various electronic devices, especially highly sensitive magnetic sensors or high-speed switching elements. For such the applications, thin films with superior superconductivity and very smooth surfaces are needed. The purpose of this work is to develop an as-grown technique of Y-Ba-Sr-Cu-O films on comparatively low-temperature substrates by adopting a newly devised alternative sputtering. The sputtering apparatus was constructed by three targets and a substrate holder which was intermittently rotated and stopped facing the desired target. The targets were Y2O, BaO+SrO, and Cu or CuO. The thickness of the oxide layer alternately deposited was adjusted to the thickness of the each metal-oxide monolayer. The substrate used was a (100) plane of a single-crystal MgO. The substrate temperature Ts was changed from 450 to 600 °C. The deposition rate of the each layer was affected by Ts. Especially, the deposition of the CuO layer was very sensitive to conditions of the film growing surface: Ts and/or degree of oxidation. The film composition was adjusted by changing the deposition time of the each layer. The crystal with an oxygen-defective perovskite nucleated even at a Ts of about 500 °C. In the case of sintered bulks, a tetragonal phase was obtained when the content of Sr was comparatively large. In contrast, an orthorhombic phase was stabilized in the sputtered films. As-grown films showed a poor superconductivity. After a post-annealing in 1-atom O2 at a low temperature of about 450 °C, a sharp superconducting transition was observed above 77 K. As we increase the content of Sr, the resistivity of the film became large and semiconductive.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: New ultrathin epitaxial magnetic multilayers consisting of ferromagnetic τMnAl and nonmagnetic NiAl have been prepared on GaAs by molecular beam epitaxy. The magnetic and magneto-optic properties of these multilayers and the effect of incorporating nonmagnetic NiAl into the structure have been investigated. Perpendicular magnetization was confirmed and the remnant magnetization and coercivity were improved compared to τMnAl thin films. In addition, by systematically changing the thickness of the NiAl layer the magnetic properties could be controlled. We discuss these issues and compare the magnetic and magneto-optic properties of these structures with other epitaxial magnetic structures.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1580-1582 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Short light pulse generation from an optically pumped GaAs/AlGaAs quantum well laser is measured. The shortest pulse width achieved so far is less than 1.3 ps. In addition, it is found that the pulse from varies randomly even when the same excitation condition, which results from stochastic behavior of the spontaneous emission coupling to the lasing mode. In order to discuss these results in more detail, spatial dependent rate equations are analyzed in which the stochastic process of the spontaneous emission and the traveling effect of spontaneously generated optical wave packets are included.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1964-1966 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied template effects in molecular beam epitaxy (MBE) of ferromagnetic MnAs thin films on (001) GaAs substrates. When As2 flux was first supplied without Mn flux on the (001) GaAs prior to the MnAs growth, the surface reconstruction was disordered c(4×4), a more As-rich surface than c(4×4). The growth direction of the MnAs thin film grown on this surface is [1¯100] and the easy magnetization axis was found to be along the [1¯1¯20] of MnAs and the [110] of GaAs. In contrast, when one monolayer of Mn was first deposited on the c(4×4) GaAs surface and then As2 flux was supplied to grow MnAs, the growth direction of the MnAs thin film was found to be mainly [1¯101], and the easy magnetization axis was along the [1¯1¯20] of MnAs and the [1¯10] of GaAs, 90° different with respect to the substrate. These results indicate the importance of the very first monolayer in controlling the epitaxial orientation and magnetic properties of epitaxial ferromagnetic MnAs thin films. © 1994 American Institue of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3237-3239 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin films of polyperinaphthalene (PPN) have been obtained by Nd:YAG pulsed laser deposition with a target of perylenetetracarboxylic dianhydride. Components of the films depend on the power and wavelength of the laser light, which is verified by absorption spectra, Raman scattering spectra, and in situ mass spectra. The optimum conditions for the PPN film formation is 10 mJ cm−2 at 266 nm.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 92 (1988), S. 2390-2394 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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