Calculation of the bond ionicity in complex oxides

A technique for calculating the bond ionicity of crystalline materials using electronegativities of elements and taking into account the structure of polyhedra of the complex-oxide structure is proposed.     

Scattering of a Rayleigh wave by monopole-dipole resonators

The problem of scattering of a Rayleigh wave by a chain of identical closely spaced monopole-dipole resonators with friction is considered. The values of resonator parameters that provide the rejection of the Rayleigh wave are found. The conditions under which the Rayleigh wave is much more efficiently reflected by the dipole resonators than by the monopole ones are determined.     

Graphitic nanofillers in PMMA nanocomposites—An investigation of particle size and dispersion and their influence on nanocomposite properties

Mechanical, thermal, and electrical properties of graphite/PMMA composites have been evaluated as functions of particle size and dispersion of the graphitic nanofiller components via the use of three different graphitic nanofillers: “as received graphite” (ARG), “expanded graphite,” (EG) and “graphite nanoplatelets” (GNPs) EG, a graphitic materials with much lower density than ARG, was prepared from ARG flakes via an acid intercalation and thermal expansion. Subsequent sonication of EG in a liquid yielded GNPs as thin stacks of graphitic platelets with thicknesses of ～10 nm. Solution‐based processing was used to prepare PMMA composites with these three fillers. Dynamic mechanical analysis, thermal analysis, and electrical impedance measurements were carried out on the resulting composites, demonstrating that reduced particle size, high surface area, and increased surface roughness can significantly alter the graphite/polymer interface and enhance the mechanical, thermal, and electrical properties of the polymer matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2097–2112, 2007     

Spectral properties of some problems in mechanics of strongly nonhomogeneous media

Spectral properties of the following three homogenized problems in the mechanics of strongly nonhomogeneous media are considered: the “double porosity” problem, the oscillation problem for a mixture of two viscous compressible liquids, and the oscillation of a medium consisting of an elastic frame and a viscous liquid. For all three cases results on the structure of the spectrum and on the existence of so-called “spectral gaps” are obtained.     

Hydrodynamics of an expanding fireball

A set of relativistic hydrodynamic equations is solved numerically on the basis of the flux-corrected SHASTA method for one-, two-, and three-dimensional geometries. The accuracy of the proposed method is demonstrated via a comparison with exact analytic solutions for the one-dimensional Riemann problem and a boost-invariant longitudinal expansion in the Bjorken model. The example of an expanding three-dimensional fireball for which initial conditions approximately correspond to PbPb collisions at an energy of about 160 GeV per nucleon is considered. This example indicates that the presumed dynamics of the expansion may affect substantially the results of an analysis of in-medium properties of hadrons that relies on data from experiments with leptons.     

Korrosionstests an magnetischen Schichten und deren Beurteilung mit Hilfe ausgew?hlter oberfl?chenanalytischer Verfahren

Summary Besides functional behaviour of coatings their resistivity against corroding attack is a crucial criterion for quality. The application of special corroding and abrading tests yields after short times predictions about stability of the product in practical use. A number of tests have been applied to thin magnetic storage media. Besides tests of function and visual observations with light- and scanning electron microscopes, AES- and XPS-investigations were applied to discuss corrosion resistivity.     

Strukturelle Aspekte bei Korngrenzensegregationsuntersuchungen

Ohne Zusammenfassung

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Structural aspects for grain boundary segregation studies

     

Spurenbestimmung von Blei, Cadmium und Mangan in Honigen und Zuckern

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Trace analysis of lead, cadmium and manganese in honey and sugar

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Wir danken dem Fonds der Chemischen Industrie für finanzielle Unterstützung.     

Solution and solid-state NMR characterization of poly(p-phenylene terephthalamide)

NMR spectroscopy has been used to characterize poly(p-phenylene terephthalamide) in the solid state and in solution in sulfuric acid. Solid-state ¹³C NMR spectra illustrate that the chain structure is highly ordered in the solid state and is of lower symmetry than in solution. Solid-state ¹³C and ¹H NMR results show that only very limited motion takes place over the temperature range of ?170 to +200°C. High-resolution NMR spectra can be observed only in very dilute isotropic solutions because it is the overall rotational motion of the polymer, not segmental motion, that averages the nuclear spin interactions to their isotropic values. These results demonstrate that previous solution NMR studies that were interpreted as reflecting the presence of isotropic and anisotropic high-molecular-weight polymer phases over a wide range of concentrations actually are representative of polymer degradation.