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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
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Surface acidity by positron annihilation lineshapes (1994)
    Springer
    Catalysis letters 26 (1994), S. 269-275 
    Details
    ISSN: 1572-879X
    Keywords: acidity ; catalysts ; positron annihilation spectroscopy ; zeolite ZSM-5
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An alternative new method to measure the specific acidity of catalytic materials with large internal surface areas by using positron annihilation spectroscopy was introduced. Results of lineshape parameter evaluations from two-dimensional angular correlation and Doppler broadened annihilation radiation measurements for a zeolite ZSM-5 were presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810599
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Assessing a farmer's decision concerning the application timing of nitrogen fertilizer (1994)
    Springer
    Environmental geology 24 (1994), S. 43-56 
    Details
    ISSN: 1432-0495
    Keywords: Nitrogen fertilizer ; Application timing ; Production risk ; Cotton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract This paper is concerned with a farmer's decision on the timing of nitrogen fertilizer application. Analytical models are developed to determine the necessary conditions for the optimal timing of the application of nitrogen fertilizer. The models, coupled with an estimated cotton yield function, are used to assess a farmer's decision on the optimal application timing of nitrogen fertilizer in cotton production. The empirical results explain various observed application timings of nitrogen fertilizer being used in cotton production in Mississippi, USA, and provide an estimate of the cost to a farmer when he or she must comply with a restriction on the timing of the application of nitrogen fertilizer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00768076
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  • 7
    Electronic Resource
    Electronic Resource
    Uniform convergence for moment problems with Fermi-Dirac type entropies (1994)
    Springer
    Mathematical methods of operations research 40 (1994), S. 239-252 
    Details
    ISSN: 1432-5217
    Keywords: linear constrained optimization ; moment problems ; uniform convergence ; best approximation ; Fermi-Dirac entropy ; Fenchel duality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract We consider the best entropic estimation to a unknown density¯x, given some of its algebraic or trigonometric moments. A uniform convergence theorem is established in this paper for such problems using Fermi-Dirac type entropic objectives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01432968
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  • 8
    Electronic Resource
    Electronic Resource
    Characteristics of high-density lipoprotein binding sites in cultured parenchymal, endothelial, and Kupffer's cells from rat liver (1994)
    Springer
    Bulletin of experimental biology and medicine 117 (1994), S. 270-272 
    Details
    ISSN: 1573-8221
    Keywords: high-density lipoproteins ; hepatocyte culture ; liver endothelium culture ; Kupffer's cell culture ; Scatchard analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Liver endothelial cells posses surface high-affinity binding sites for HDL3, whose affinity is 4 times higher than that of the sites on hepatocytes and Kupffer's cells. The maximal number of high-affinity binding sites on endothelial cells is 437 ng/mg protein, which surpasses this parameter on the hepatocyte surface several times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02444160
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  • 9
    Electronic Resource
    Electronic Resource
    FTIR investigation of cross-linking and isomerization reactions of acetylene-terminated polyimide and polyisoimide oligomers (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2005-2017 
    Details
    ISSN: 0887-6266
    Keywords: FTIR spectroscopy ; acetylene-terminated polyisoimide ; acetylene-terminated polyimide ; isoimide-imide isomerization ; cross-linking reaction ; thermal curing process ; flexibility effect ; cross-linking effect ; rate constant ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The interrelationship between the cross-linking and isoimide-imide isomerization reactions of oligomeric isoimides and imides was investigated using FTIR spectroscopy. It was found that cross-linking of the acetylene units of Thermid IP-600 retarded the local rearrangement of the isoimide to imide conversion of Thermid IP-600 compared with an aniline-terminated analog, decreasing the rate constant by a factor of about 2. The increased flexibility of both the isoimide (Thermid IP-600) and imide (Thermid FA-700) oligomers increased the cross-linking rate of the acetylene end groups by a factor of 4 and 2, respectively, over that of the more rigid imide oligomer (MC-600). With increasing conversion of the isoimide to imide linkages in Thermid IP-600, the kinetic parameters, Eα and in A, for the cross-linking reaction of this oligomer became the same as those for the oligomeric imide, Thermid MC-600. © 1994 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090321207
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