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  • 1
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The dc conductivities of ZrO2–Y2O3 ceramic alloys (in the range 3–12 mol% of Y2O3) have been obtained from ac impedance measurements at temperatures between 250° and 370°C. The Almond–West ac conductivity model has been applied to evaluate hopping rates in this system. The migration enthalpies were evaluated and shown to increase with yttria concentration, but all values determined were shown to be lower than the corresponding activation enthalpies for conductivity. The association enthalpies thus calculated were shown to be very small in 3 mol% Y2O3–ZrO3 and to increase with yttria concentration until the yttria contents were high enough to form fully stabilized cubic zirconia. For these samples the association enthalpies are about 0.19 eV, and no longer sensitive to yttria content. The low hopping rate at high yttria concentration might be attributed to low entropy in the system, which might be attributed to the formation of vacancy clusters and/or an ordering of the structure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The tetragonality of small zirconia particles has been established by accurately measuring the tetragonality ratio (c/a) of decomposed zirconyl hydroxide, which was then calcined over a range of temperatures to produce a range of average-sized zirconia crystallite particles. The zirconia initially crystallized as a finely divided cubic phase, which, as the calcination temperature increased, gradually developed an increase in c/a.At temperatures 〉800°C, the c/avalue reached a critical value; thereafter, the tetragonal symmetry was stabilized.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: SiC-particle-reinforced MgO composites have been fabricated by hot pressing, and the thermal diffusivities of the composites measured in the temperature range 200–1000°C using a laser flash technique. The thermal conductivity of the composites was calculated by multiplying the diffusivity with density and with heat capacity. The Eshelby inclusion model has been examined, and an equation suitable for particulate composites with porosity has been derived using the multiphase Eshelby model. The model also considers the interfacial thermal condition. Good agreement was obtained between the predictions and the experimental results of the thermal conductivity of the composites, even for various levels of porosity in the composites. Crystal defects, observed in the composites, influenced the thermal conductivity, resulting in a deviation from isothermal interfacial condition. This was reflected in the interfacial thermal parameter,β used in the modeling, and the predicted value of β was in the range of 3–10, depending on the thermal conductivity of SiC used for the calculations.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 9047-9056 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A framework for micromechanics investigation of randomly oriented ellipsoidal inclusion composites has been proposed and established, based on the eigenstrain concept introduced by Eshelby, and the equivalent inclusion method. The average residual stress and strain and the average stress and strain, in both the matrix and the inclusions, have been derived relative to the mismatch of elastic moduli, thermal-expansion coefficients, and the shape of the ellipsoid. The inclusion shape has a significant effect on the stress and strain field, with the smallest effect generated by a spherical inclusion. An expression for the relationship between the average stress and strain and the inclusion shape has been formulated. The multiphase inclusion composite model has also been established. As an example, the thermal-expansion coefficient for randomly oriented ellipsoidal inclusion composites has been derived and related to the inclusion content, shape and elastic moduli. In Part II of this work, the elastic moduli of the inclusion composites are formulated and discussed. © 1996 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 9057-9063 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The elastic moduli of composites containing randomly oriented ellipsoidal inclusions are derived, calculated from the average stress and the average strain in the matrix and the inclusions, obtained using a modified Eshelby model. The quantitative expressions for the elastic moduli of the composite are obtained in relation to the volume fraction, the shape, and the elastic moduli of the inclusions. Specific cases are discussed: First, the elastic moduli of the materials containing randomly oriented penny-shaped microcracks are derived and compared with those obtained by Budiansky and O'Connell [Int. J. Solids Struct. 12, 81 (1976)] and Nemat-Nasser and Hori. The general expressions for the elastic moduli of multiphase inclusion composites and the effect of porosity or in the form of isolated voids on the elastic moduli of homogeneous materials and inclusion containing composites are derived. Experimental results have been employed to compare the predictions with engineering materials. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 30 (1995), S. 3050-3056 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A highly textured (Bi, Pb)2Sr2Ca2Cu3Ox superconductor has been prepared and the hardness, deformation and microcracking of the material explored using Vickers indentation. The present study has investigated the hardness anisotropy of the highly textured material on cross-sections of the specimen which have been chosen to give specific low-index orientations. The hardness was found to decrease as the indentation rotated from 0 ° (a diagonal of the indent parallel to the direction of the texturing) to 45 ° (the angle between a diagonal of the indent and the direction of the texturing). The square shape of the indent also changed with rotation from 0 ° to 45 °. The hardness anisotropy has been attributed to the influence of elastic and plastic anisotropy in the polycrystalline materials. In addition, a weakness in the grain-boundary bonding results in the movement of adjacent grains by a sliding mechanism which dominated the indentation anisotropy effect. The presence of microcracking in the grain and at the grain boundary was found to affect the hardness anisotropy.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    The protein journal 18 (1999), S. 709-719 
    ISSN: 1573-4943
    Keywords: Biosensor ; adenylate kinase ; monoclonal antibody ; inhomogeneous ; rebinding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We monitored the interactions between pairs of molecules where the antigen adenylate kinase (AK) was immobilized on the surface of a chip and the antibody against AK, McAb3D3, was in solution. The association data that we obtained were not always accurately described by the expected pseudo-first-order reaction mechanism. A better description of the association data was achieved with a double-exponential function. Various models were applied to describe these observations: mass transport-controlled processes, inhomogeneous immobilized ligands, or inhomogeneous soluble analytes. Inhomogeneous immobilized ligands seemed to be the most likely explanation for the observed biphasic association kinetics. We simulated the kinetics of the SPR signal under the above-mentioned conditions. Plots of dR/dt versus R of the association phase showed characteristic differences between those nonlinearities resulting from mass transport limitation and those from inhomogeneous ligands. The plots of dR/dt versus R of McAb3D3 binding to immobilized AK show positive curvatures, indicating that the observed biphasic association kinetics is due to the inhomogeneity of the immobilized ligands. This is consistent with the results obtained from the comparison of various model fittings.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 12 (1993), S. 1-11 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using four hazardous dispersion models, the ability to predict Lower Flammability Distance (LFD), the distance from a release through which the released gas is present in concentration below flammable range, has been evaluated using a set of large-scale propane release field experiment data. The four models evaluated were the DEGADIS model, the SLAB model, the OME Simple Gas model and the OME Heavy Gas model (1983). The observed LFDs were compared with the predicted LFDs for three atmospheric conditions. The complete data set was broken into two parts: (1) the cyclone type releases (representing instantaneous release situations) and (2) the nozzle type releases (representing horizontal jet releases). A procedure based on the USEPA guidelines on air quality models was followed to evaluate the models.The complex models (DEGADIS and SLAB models) appear unreasonably weak in predicting LFD's compared with the relatively simple Gaussian model used in the OME Simple Gas model for instantaneous releases. The OME simple gas model is significantly better than the DEGADIS and SLAB models for cyclone type (instantaneous) releases under unstable and neutral atmospheric conditions; and the DEGASIS model is significantly better than the SLAB model for nozzle type (horizontal jet) releases under stable atmospheric conditions. Since the size of the data set is not large enough (n = 20 for cyclone type release and n = 18 for nozzle type release), it is difficult to show 95% significant differences between models.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Publication Date: 2018-04-12
    Electronic ISSN: 2475-9953
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 10
    Publication Date: 2018-03-12
    Description: The chemical diversity of physiological DNA modifications has expanded with the identification of phosphorothioate (PT) modification in which the nonbridging oxygen in the sugar-phosphate backbone of DNA is replaced by sulfur. Together with DndFGH as cognate restriction enzymes, DNA PT modification, which is catalyzed by the DndABCDE proteins, functions as a bacterial restriction-modification (R-M) system that protects cells against invading foreign DNA. However, the occurrence of dnd systems across a large number of bacterial genomes and their functions other than R-M are poorly understood. Here, a genomic survey revealed the prevalence of bacterial dnd systems: 1,349 bacterial dnd systems were observed to occur sporadically across diverse phylogenetic groups, and nearly half of these occur in the form of a solitary dndBCDE gene cluster that lacks the dndFGH restriction counterparts. A phylogenetic analysis of 734 complete PT R-M pairs revealed the coevolution of M and R components, despite the observation that several PT R-M pairs appeared to be assembled from M and R parts acquired from distantly related organisms. Concurrent epigenomic analysis, transcriptome analysis, and metabolome characterization showed that a solitary PT modification contributed to the overall cellular redox state, the loss of which perturbed the cellular redox balance and induced Pseudomonas fluorescens to reconfigure its metabolism to fend off oxidative stress. An in vitro transcriptional assay revealed altered transcriptional efficiency in the presence of PT DNA modification, implicating its function in epigenetic regulation. These data suggest the versatility of PT in addition to its involvement in R-M protection.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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