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  • 1
    Electronic Resource
    Electronic Resource
    Growth and characterization of (111) and (001) oriented MgO films on (001) GaAs (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3276-3283 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of substrate preparation on the structure and orientation of MgO films grown on (001) GaAs using pulsed laser deposition has been investigated. Textured MgO films displaying a (111)MgO(parallel)(001)GaAs orientation relation with x-ray rocking curve full width at half maximum (FWHM) values as low as 1.8° were obtained in cases where the native GaAs surface oxide was only partially desorbed prior to growth. Reflection high-energy electron diffraction, transmission electron microscopy (TEM), and x-ray pole figure analysis of these films reveals a preferential orientation within the plane of the substrate: [11¯0]MgO(parallel)[11¯0]GaAs and [112¯]MgO(parallel)[110]GaAs. An interfacial layer (∼5 nm thick) was observed in high resolution TEM analysis, and was attributed to a remnant native GaAs oxide layer. Complete desorption of the native GaAs oxide at ∼600 °C in vacuum prior to MgO growth led to significant surface roughening due to Langmuir evaporation, and resulted in randomly oriented polycrystalline MgO films. Growth of MgO on Sb-passivated GaAs substrates, which provided smooth, reconstructed surfaces when heated to 350 °C in vacuum, resulted in cube-on-cube oriented films [i.e., (001)MgO(parallel)(001)GaAs,[100]MgO(parallel)[100]GaAs] with x-ray rocking curve FWHM values as low as 0.47°. TEM analysis of the cube-on-cube oriented films revealed evidence of localized strain fields at the MgO/GaAs interface, indicating the presence of misfit dislocations in the MgO layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352975
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  • 2
    Electronic Resource
    Electronic Resource
    Hierarchical domain structures and in situ domain migration in the antiferroelectric ceramic PLSnZT (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7261-7267 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The crystallography and microstructure of an antiferroelectric ceramic of approximate composition Pb0.97La0.02(Zr0.65Sn0.25Ti0.10)O3 have been examined. Transmission electron microscopy (TEM), x-ray, and neutron powder studies were carried out. The cell is metrically tetragonal with a c/a ratio of 0.993 when indexed to the parent cubic perovskite cell. The structure exhibits both a commensurate supercell, believed to be associated with oxygen octahedra distortions, and an incommensurate modulation. The different crystallographic variants of the tetragonal antiferroelectric phase gave rise to a hierarchy of domain structures. Charging of TEM specimens having an incomplete conductive coating caused domain migration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.354014
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  • 3
    Electronic Resource
    Electronic Resource
    Observation of gold evaporated on graphite (00.1) cleaved surfaces (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 6520-6522 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Gold evaporated on air-cleaved (00.1) graphite was observed by scanning tunneling microscopy. Most individual gold islands were not stable during scanning; some islands even appeared to translate. These observations suggest that the interaction between the gold islands and the scanning tunneling microscope tip is stronger than that between the gold and the air-cleaved graphite substrate. Some gold islands were observed to be stable. It was deduced that stable islands at steps were located on the upper layer rather than on the lower layer. It is also deduced that the alignment of the elongated gold grains in the continuous film may be related to cleavage steps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346856
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  • 4
    Electronic Resource
    Electronic Resource
    Crack formation in epitaxial [110] thin films of YBa2Cu3O7−δ and PrBa2Cu3O7−x on [110]SrTiO3 substrates (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1682-1684 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A characteristic feature of epitaxial [110] thin films of YBa2Cu3O7−δ and PrBa2Cu3O7−x on [110]SrTiO3 substrates is that the films have a tendency to crack along the (001) planes. We have studied the crack spacing as a function of deposition temperature and film thickness. The experimental data have been found to be in excellent agreement with a theoretical analysis of the crack spacings in brittle films. The study has allowed us to determine the critical thickness below which no cracks are expected to form as a function of temperature for [110] films of YBa2Cu3O7−δ, PrBa2Cu3O7−x, and YBa2Cu3O7−δ/ PrBa2Cu3O7−x bilayers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.105110
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  • 5
    Electronic Resource
    Electronic Resource
    Anomalous superperiodicity in scanning tunneling microscope images of graphite (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2396-2398 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An anomalously large periodicity has been observed in scanning tunneling microscope images of a (00.1) graphite sample. The unusual contrast has hexagonal symmetry, a periodicity of 7.7±0.2 nm and is superimposed on the usual a=0.246 nm atomic spacing of graphite. Current-voltage curves recorded in the scanning tunneling spectroscopy mode from the region showing the superperiodicity exhibit slightly more metallic behavior than those from neighboring normal regions. One possible explanation for the observed periodicity is that it is a rotational moiré pattern resulting from the overlap between a misoriented layer of graphite and the underlying graphite single crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102906
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  • 6
    Electronic Resource
    Electronic Resource
    The immunoperoxidase localization of tumour markers in ovarian cancer: the value of CEA, EMA, cytokeratin and DD9 (1991)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 98 (1991), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. Primary tumours from 40 patients with epithelial ovarian cancer, treated at St Thomas's Hospital over a 10-year period, were studied for the immunocytochemical expression of the following tumour markers in formalin-fixed paraffin embedded material: carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA), cytokeratin (CAM 5.2), and DD9. An indirect immunoperoxidase staining technique was used. All of the tumours were positive for EMA and CAM 5.2, and 30% of them were positive for both CEA and DD9. The absence of CEA and DD9 may be of value in differentiating between metastatic abdominal adenocarcinomas of ovarian origin and those of gastrointestinal origin, but no indication of prognosis was obtained using these epithelial markers. The strong and widespread staining of all of the tumours for EMA suggests that this may be a useful marker for detecting metastatic or recurrent disease by immunoscintigraphy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1991.tb10315.x
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  • 7
    Electronic Resource
    Electronic Resource
    Phase development of Tl2Ba2CaCu2O8 thin films on LaAlO3 substrates (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 3028-3030 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The evolution of phases leading to the formation of epitaxial films of nominal composition Tl2Ba2CaCu2O8 on (100) LaAlO3 by post-deposition annealing of amorphous precursor films has been investigated by examining interrupted heat-treatment samples using analytical microscopy and x-ray diffraction. The superconductor, with a composition of Tl1.8Ba2Ca0.94Cu2.6Ox, forms from a melt, which itself formed from intermediary crystalline phases during the continual loss of Tl2O. It is concluded that Tl1.8Ba2Ca0.94Cu2.6Ox, Cu2O, and Tl3Ca5Ox are in subsolidus equilibrium and that a melt phase exists between at least 780 and 860 °C under reducing conditions controlled by the Tl2O vapor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109149
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  • 8
    Electronic Resource
    Electronic Resource
    Metalorganic deposition of high critical current thin films in the Bi-Sr-Ca-Cu-O system on {100} LaAlO3 substrates (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 351-353 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconducting thin films of the two Cu-layer phase in the Pb-doped Bi-Sr-Ca-Cu-O system have been fabricated on {100} LaAlO3 single crystals by the metalorganic deposition from ethyl hexanoate precursors. Thin films given heat treatments in air at 850–860 °C had resistive transitions with a Tc of 86–89 K. The zero-field transport critical current densities were in the range of 2–4×105 A/cm−2 at 77 K and 106 A cm−2 at 45 K in 200–300-nm-thick films. In contrast to c-axis oriented films grown on {100} MgO, x-ray pole figures show that the films grown on {100} LaAlO3 are epitaxial, a result confirmed by electron channeling patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.107934
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  • 9
    Electronic Resource
    Electronic Resource
    Sites of [3H]taurine Uptake in the Rat Substantia Nigra in Relation to the Release of Taurine from the Striatonigral Pathway (1990)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 2 (1990), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The autoradiographic localization of radiolabelled taurine taken up in the rat substantia nigra in vivo together with conditions of release of the [3H]taurine taken up into brain slices were studied to determine whether they are consistent with the hypothesis that taurine may act as a neurotransmitter in the striatonigral pathway.At the light microscopic level the main cellular elements that became radiolabelled following the injection of [3H]taurine into the substantia nigra could be identified as glial cells. Electron microscope autoradiography confirmed that a subpopulation of glial cells including astrocytes, pericytes, and oligodendrocytes were radiolabelled and that neuronal perikarya were not radiolabelled. In addition, axonal elements including both terminal and preterminal boutons were found to have silver grains overlying them and were thus considered to be radiolabelled. This was supported by a quantitative analysis of the distribution of the silver grains; whereas glial elements had a significantly higher number of grains associated with them than with any other structure, axonal elements had a significantly greater number of grains than dendritic structures.Release of the preloaded [3H]taurine from superfused slices of substantia nigra occurred in response to veratridine, was calcium-dependent and was sensitive to inhibition by high magnesium concentrations or tetrodotoxin. Following the destruction of neurons in the striatum by ibotenic acid injections, although the weight of the ipsilateral substantia nigra was reduced, the uptake of [3H]taurine was not altered. In contrast to this, the veratridine-stimulated release was markedly attenuated, implying that the destruction of striatal neurons causes the loss of sites in the substantia nigra from which exogenous taurine is released.These results add further support to previous suggestions that taurine might act as a neurotransmitter or neuromodulator in the striatonigral pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1990.tb00380.x
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  • 10
    Electronic Resource
    Electronic Resource
    Neuroanatomical Characterization of a New Mutant Rat with Dopamine Depletion in the Substantia Nigra (1994)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 6 (1994), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A new mutant rat strain with movement disorders has arisen spontaneously in a closed colony of Albino–Swiss rats at the Department of Anatomy, Glasgow University. The animals possess a progressive locomotor disorder which is first apparent at around post-natal day 10. We here report that tyrosine hydroxylase immunocytochemistry demonstrates that these mutants have profound depletions in dopaminergic systems in the substantia nigra and corresponding areas of neostriatum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1994.tb01000.x
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