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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of AlxGa1−xAs/GaAs heterojunction bipolar transistor structures using cross-sectional scanning force microscopy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 1937-1942 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have characterized base-layer width and dopant distributions on cleaved cross-sections of AlxGa1−xAs/GaAs heterojunction bipolar transistor (HBT) structures using a variation of electrostatic force microscopy. The contrast observed is sensitive to the local dopant concentration through variations in the depletion layer depth extending into the sample surface, and enables delineation of individual device regions within the epitaxial layer structure with nanoscale spatial resolution. In two epitaxially grown HBT structures, one with 50 nm base width and the other with 120 nm base width, we are able to delineate clearly the emitter, base, collector, and subcollector regions, and to distinguish regions within the collector differing in dopant concentration by a factor of two. We have also distinguished clearly between the base widths in these samples and have precisely measured the difference to be 63±3 nm, in excellent agreement with the nominal difference of 70±7 nm. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372116
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  • 2
    Electronic Resource
    Electronic Resource
    The Use of an Oral Fluid Immunoglobulin G ELISA for the Detection of Helicobacter pylori Infection in Children (2002)
    Oxford, UK : Blackwell Science Ltd
    Helicobacter 7 (2002), S. 0 
    Details
    ISSN: 1523-5378
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background. Enzyme linked immunosorbent assay (ELISA) evaluation of oral fluid immunoglobulin G (IgG) antibodies to Helicobacter pylori is a unique approach for both epidemiological studies and the diagnosis of infection, especially in children. The use of oral fluid sampling to evaluate specific H. pylori IgG antibodies has advantages over serum, including reduced biohazard risk and noninvasive collection. Oral fluid sampling is fast and involves minimal patient discomfort. Since children facilitate transmission of H. pylori infection, a simple, accurate, noninvasive diagnostic test is necessary for large epidemiologic studies. The aim of our study was to evaluate a new oral fluid ELISA for detection of IgG antibodies to H. pylori in children.Materials and methods. We compared this new oral fluid ELISA with the HM-CAPTM serum ELISA and gastric biopsy histology using 779 oral fluid samples from children collected at 11 clinical sites across the United States. This cohort included 315 children symptomatic for abdominal pain and 464 asymptomatic. All samples were evaluated in a double blind manner. The oral fluid ELISA demonstrated a sensitivity of 76.2% and a specificity of 94.0% in children 2 months old to 201/2 years, as compared with the HM-CAPTM serologic assay. The assay’s sensitivity improved to 81.3% in children aged 5 or greater and the specificity remained at 94.0%. When compared with gastric biopsy histology in the same age group, the oral fluid ELISA demonstrated a sensitivity of 71.7% and a specificity of 90.4%.Results. This new oral fluid ELISA is moderately sensitive and offers a very specific method for detecting H. pylori infection in older children, but it is of little value in children under the age of 5 years.Conclusions. Overall, we conclude that this oral fluid ELISA does not appear to be a helpful clinical tool for the diagnosis of H. pylori infection in children.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1083-4389.2002.00062.x
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal noise in high-temperature superconducting-normal- superconducting step-edge Josephson junctions (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1337-1339 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated YBa2Cu3O7−δ-normal metal-YBa2Cu3O7−δ step-edge Josephson junctions that fit the resistively shunted junction model with Johnson–Nyquist thermal noise. The I-V curves are well fit over a large temperature range for junctions of varying critical current values. There is good agreement between the fitted thermal noise temperature and the measured ambient temperature. This is strong evidence that these junctions are not dominated by superconducting shorts longer than the superconducting coherence length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357798
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  • 4
    Electronic Resource
    Electronic Resource
    Anomalous compositional dependence in in situ growth of YBaCuO films at low oxygen pressure (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 756-758 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The roles of composition and oxygen pressure in in situ growth of superconducting YBaCuO films have been studied. Anomalous results are observed at low oxygen pressure. Off-stoichiometric, Ba-deficient films have superior superconducting properties and more bulk-like crystal structure compared to films made on the 1:2:3 stoichiometry. Films made at low pressure have an expanded c axis compared to the bulk value, although their Tc's are only slightly depressed. Tc and c-axis lattice parameters are reported as a function of the deposition conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104538
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  • 5
    Electronic Resource
    Electronic Resource
    Microstructure of Cu- and Y-rich YBa2Cu3O7−x thin films: Identification of the CuYO2 phase (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 1158-1160 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The CuYO2 delafossite-type structure has been identified as a second phase in thin films of Cu- and Y-rich YBa2Cu3O7−x (123) made by electron beam co-evaporation at conditions of low oxygen pressure; this phase occurs as extremely small, densely distributed, highly oriented precipitates within the 123 matrix. The smallest (sub-100 A(ring)) [00.1] oriented precipitates of this hexagonal phase are strained to give a better lattice match to the surrounding 123 structure. The results suggest that, for thin film deposition conditions of sufficiently low temperature and pressure, there may be a tie line between YBa2Cu3O7−x and CuYO2 in the equilibrium phase diagram. The size and distribution of the precipitates is such as would be expected to influence structurally sensitive superconducting transport properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104224
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetic flux noise in thin-film rings of YBa2Cu3O7−δ (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 695-697 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low-frequency magnetic flux noise in thin-film rings of YBa2Cu3O7−δ (YBCO) is measured over the temperature range 1.3–125 K by means of a dc superconducting quantum interference device (SQUID) maintained at liquid-helium temperatures. Below the transition temperature Tc of the YBCO, the spectral density of the noise scales as 1/f, where f is the frequency, and generally increases with increasing temperature. The magnitude of the noise depends strongly on the microstructure of the film, and is lowest for a sample which is predominantly oriented with its c axis perpendicular to the substrate. These results imply that SQUID's and flux transformers of YBCO must be fabricated from highly oriented films to produce good resolution at low frequencies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100643
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  • 7
    Electronic Resource
    Electronic Resource
    Feasibility of the high Tc superconducting bolometer (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 283-285 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A design analysis is given for a bolometric infrared detector that uses the resistive transition of a high-temperature superconductor as the temperature sensing element, and liquid nitrogen (LN) as the coolant. It is shown that for highly oriented c-axis films, the measured low-frequency noise causes little or no degradation of the performance. With the incoming radiation chopped at 10 Hz, noise equivalent powers (NEP) in the range (1–20)×10−12 W Hz−1/2 should be achievable. These values compare favorably with the NEP of other detectors operating at or above LN temperatures for wavelengths greater than 20 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101447
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  • 8
    Electronic Resource
    Electronic Resource
    High temperature superconductor-normal metal-superconductor Josephson junctions with high characteristic voltages (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1984-1986 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated step edge superconductor-normal metal-superconductor microbridges using YBa2Cu3O7−x(YBCO) and noble metals with critical current-normal resistance (IcRN) products as high as 10 mV and normal resistances up to 38 Ω. Our fabrication process achieves high values of the IcRN product by exploiting the anisotropy in the properties of epitaxial YBCO films, allowing contact only between normal metal and superconductor through the crystalline axes which support the largest Josephson coupling. This results in a dramatic increase in the normal resistance of a junction without decreasing its critical current. We discuss the role of the superconductor-normal metal boundary resistance on the junction electrical properties. We have coupled submillimeter wave rf currents quasioptically into junctions integrated at the feeds of noble metal planar log periodic antennas and have induced up to 7 Shapiro steps in the current-voltage characteristics with a 760 GHz beam from a far infrared laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110622
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  • 9
    Electronic Resource
    Electronic Resource
    The Proteases and Pathogenicity of Parasitic Protozoa (1993)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Microbiology 47 (1993), S. 821-853 
    Details
    ISSN: 0066-4227
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.mi.47.100193.004133
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  • 10
    Electronic Resource
    Electronic Resource
    Crystallization and preliminary X-ray diffraction studies of the influenza C virus glycoprotein (1996)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 52 (1996), S. 1041-1045 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Influenza C virus contains a single surface glycoprotein in its lipid envelope which is the hemagglutinin-esterase-fusion glycoprotein (HEF). HEF binds cell-surface receptors, is a receptor-destroying enzyme (a 9-O-acetylesterase), and mediates the fusion of virus and host cell membranes. A bromelain-released soluble form of HEF has been crystallized. Two different tetragonal forms have been identified from crystals with the same morphology [P1(3)22, a = b = 154.5, c = 414.4 Å, and P41(3)212, a = b = 217.4, c = 421.4 Å]. Both crystal forms share a common packing scheme. Synchrotron data collection and flash cooling of crystals have been used for high-resolution data collection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444996005021
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