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  • 1
    Electronic Resource
    Electronic Resource
    Anisotropic glasslike characteristics of strontium barium niobate relaxors (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 490-496 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The complex dielectric response of strontium barium niobate relaxor ferroelectrics has been studied as a function of orientation and composition. The dielectric response was found to be strongly dependent on orientation, in distinct comparison to the nearly orientation-independent response found for Pb-based perovskite relaxors. Investigations of the temperature dependence of the high-field polarization behavior found that the square-to-slim loop hysteresis transition occurred rapidly with increasing temperature. In addition, no deviations from Curie–Weiss behavior were found, however two distinct linear regions were observed. An anisotropic dielectric glasslike model involving the freezing of heterophase fluctuations is then discussed in reference to the data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357100
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  • 2
    Electronic Resource
    Electronic Resource
    Electrical transport properties of CoSi2 and Co(SixGe1−x)2 films formed by different methods (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 5427-5432 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical transport properties of CoSi2 and Co(SixGe1−x)2 thin films formed by solid state interaction and co-evaporation in the range of 4–300 K were studied. The Hall effect data indicate a hole carrier conduction in all samples. The rapid thermal annealed CoSi2 exhibits a typical metallic conduction with a residual resistivity of 3.3-μΩ-cm and room-temperature (RT) resistivity of 15 μΩ cm. The co-evaporated CoSi2 and Co(Si0.9Ge0.1)2 films after low temperature annealing up to 250 °C show a low resistivity of 70–80 μΩ cm at RT and change little down to 4 K. The hole carrier density of all the samples studied has values close to 2–3×1022 cm−3, while the carrier Hall mobility has large differences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350200
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  • 3
    Electronic Resource
    Electronic Resource
    High critical current densities in YBa2Cu3O7−x thin films formed by metalorganic chemical vapor deposition at 730 °C (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 648-650 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: YBa2Cu3O7−x superconducting thin films with a critical current density of 2.3×106 A/cm2 at 77.7 K and 0 T were prepared by a metalorganic chemical vapor deposition process. The films were formed in situ on LaAlO3 at a substrate temperature of 730 °C in 2 Torr partial pressure of N2O. Resistivity and magnetic susceptibility measurements of the as-deposited films show a sharp superconducting transition temperature of 89 K with a narrow width of less than 1 K. Critical current densities were measured by the dc transport method with a patterned bridge of 120 μm×40 μm. Both x-ray diffraction and high-resolution electron microscopy measurements indicate that films grew epitaxially with the c axis perpendicular to the surface of the substrate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104557
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  • 4
    Electronic Resource
    Electronic Resource
    Positron annihilation and internal surfaces (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 1334-1335 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Doppler broadened gamma spectra from positron annihilations in alumina and several zeolites were measured as a function of internal surfaces. In all cases, the gamma line shape parameter was found to vary proportionally with surface area. The results greatly enhance the potential of using positron annihilation spectroscopy as a microprobe for surface studies of porous materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109722
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  • 5
    Electronic Resource
    Electronic Resource
    T-Cell Immunity to Acetylcholine Receptor and its Subunits in Lewis Rats over the Course of Experimental Autoimmune Myasthenia Gravis (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Scandinavian journal of immunology 37 (1993), S. 0 
    Details
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Lymph nodes, spleen and thymus obtained from Lewis rats were examined over the course of experimental autoimmune myasthenia gravis (EAMG) for the distribution and the number of antigen-reactive CD4+ T helper cells which, upon recognition of Torpedo acetylcholine receptor (AChR) or the α, β, γ or δ subunits of Torpedo AChR, responded by secretion of interferon-gamma (IFN-γ). T cells with these specificities were detected in these three immune organs. Numbers were highest in lymph nodes. In spleen and thymus, numbers of antigen-reactive T cells did not differ. T cells reacting against the intact AChR were more frequent than T cells recognizing any of the subunits. The immunogenicity between the four subunits did not differ, with the exception that the α subunit induced a slightly higher T-cell response. No restriction of the T-cell repertoire to the four subunits was detected during early compared to late phases of EAMG. The AChR and subunit-reactive T cells could—via secretion of effector molecules including IFN-γ—play an important role in the initiation and perpetuation of EAMG. and consequently also of human myasthenia gravis. T cells with the same specificities were also detected in control animals injected with adjuvant only, but at much lower numbers which were within the range of T cells recognizing the control antigen myelin basic protein. They could represent naturally occurring autoimmune T cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3083.1993.tb02580.x
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  • 6
    Electronic Resource
    Electronic Resource
    Elastic-wave scattering and Stoneley wave localization by anisotropic imperfect interfaces between solids (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 118 (1994), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In this paper, elastic scattering and localization of guided waves on a thin anisotropic imperfect interfacial layer between two solids are studied. We have proposed a second-order asymptotic boundary condition approach to model such an interfacial layer. Here, using previous results, we derive simple stiffness-matrix representations of stress-displacement relations on the interface for the decomposed symmetric and anti-symmetric elastic motions. The stiffness matrices are given for an off-axis orthotropic layer or, equivalently, for a monoclinic interfacial layer. For the problem of scattering on such a thin anisotropic layer between identical isotropic semi-spaces the scattering matrices are obtained in explicit forms. Analytical dispersion equations for Stoneley-type interfacial waves localized in such a system are also given. Additional results are included for imperfect interfaces, such as fractured interfaces, modelled by spring boundary conditions. The applicability of the stiffness-matrix approach to the layer model is analysed by numerical comparison between the approximate and exact solutions. The numerical examples, which include reflection transmission on the interphase and dispersion curves of the interfacial waves, show that the stiffness-matrix method is a simple and accurate approach to describe wave interaction with a thin anisotropic interfacial layer between two solids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1994.tb03961.x
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  • 7
    Electronic Resource
    Electronic Resource
    Neisseria gonorrhoeae acquires mutations in analogous regions of gyrA and parC in fluoroquinolone-resistant isolates (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 14 (1994), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Neisseria gonorrhoeae homologues of gyrA and parC have been identified using hybridization probes generated from conserved regions of diverse gyrA genes. These genes have been tentatively identified as gyrA and parC, based on predicted amino acid sequence homologies to known GyrA homologues from numerous bacterial species and to ParC from Escherichia coli and Salmonella typhimurium. The gyrA gene maps to a physical location distant from the gyrB locus on the gonococcal chromosome, which is similar to the situation found in E. coli. The parC gene is not closely linked (i.e. greater than 9 kb) to an identifiable parE gene in N. gonorrhoeae. The gonococcal GyrA is slightly larger than its E. coli homologue and contains several small insertions near the O-terminus of the predicted open reading frame. A series of ciprofloxacin-resistant mutants were selected by passage of N. gonorrhoeae on increasing concentrations of the antibiotic. Sequential passage resulted in the selection of isolates with minimum inhibitory concentrations approximately 10000-fold higher than the parental strain. Mutations within gyrA resulted in low to moderate levels of resistance, while strains with high-level resistance acquired analogous mutations in both gyrA and parC. Resistance mutations were readily transferred between N. gonorrhoeae strains by transformation. The frequencies of transformation, resulting in different levels of ciprofloxacin resistance, further support the notion that both gyrA and parC genes are invoived in the establishment of extreme levels of ciprofloxacin resistance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1994.tb01297.x
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  • 8
    Electronic Resource
    Electronic Resource
    Programmed Cell Death of Neonatal Rat Retinal Ganglion cells due to Turn-Off Expression of a Novel 30-kD Trophic Factor and/or the Lack of this Factor Supplied from the Superior Colliculus (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 663 (1992), 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.1749-6632.1992.tb38704.x
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  • 9
    Electronic Resource
    Electronic Resource
    Metal-betaine interactions. XI. Structure of catena-[μ-dichloro-(triethylammonioacetato)cadmium(II)] (1992)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 48 (1992), S. 57-59 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108270191008363
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  • 10
    Electronic Resource
    Electronic Resource
    Variation of heavy metals in recent sediments from Piratininga Lagoon (Brazil): interpretation of geochemical data with the aid of multivariate analysis (1994)
    Springer
    Environmental geology 23 (1994), S. 241-247 
    Details
    ISSN: 1432-0495
    Keywords: Coastal lagoon ; Metallic concentration ; Multivariate analysis ; Depositional environment ; Anthropogenic discharge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract In the last decade, the Atlantic coast of south-eastern Brazil has been affected by increasing deforestation and anthropogenic effluents. Sediments in the coastal lagoons have recorded the process of such environmental change. Thirty-seven sediment samples from three cores in Piratininga Lagoon, Rio de Janeiro, were analyzed for their major components and minor element concentrations in order to examine geochemical characteristics and the depositional environment and to investigate the variation of heavy metals of environmental concern. Two multivariate analysis methods, principal component analysis and cluster analysis, were performed on the analytical data set to help visualize the sample clusters and the element associations. On the whole, the sediment samples from each core are similar and the sample clusters corresponding to the three cores are clearly separated, as a result of the different conditions of sedimentation. Some changes in the depositional environment are recognized using the results of multivariate analysis. The enrichment of Pb, Cu, and Zn in the upper parts of cores is in agreement with increasing anthropogenic influx (pollution).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00766738
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