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  • Articles: DFG German National Licenses  (3)
  • 1985-1989  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Reflection and transmission of plane waves by a layer of compact inhomogeneities (1988)
    Springer
    Pure and applied geophysics 128 (1988), S. 101-118 
    Details
    ISSN: 1420-9136
    Keywords: Reflection ; transmission ; plane waves ; compact inhomogeneities ; cracks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Reflection and transmission of elastic wave motion by a layer of compact inhomogeneities has been analyzed. For identical inhomogeneities whose geometrical centers are periodically spaced, the problem has been formulated and solved rigorously. The reflected and transmitted longitudinal and transverse wave motions have been expressed as superpositions of wavemodes, where each wavemode has its own cut-off frequency. At its cut-off frequency a mode converts from a standing into a propagating wavemode. The standing wavemodes decay exponentially with distance to the plane of the centers of the inhomogeneities. At small frequencies only the lowest order modes of longitudinal and transverse wave motion are propagating. Reflection and transmission coefficients have been defined in terms of the coefficients of the zeroth-order scattered wavemodes. These coefficients have been computed by a novel application of the Betti-Rayleigh reciprocal theorem. They are expressed as integrals over the surface of a single inhomogeneity, in terms of the displacements and tractions on the surface of the inhomogeneity. The system of singular integral equations for the surface fields has been solved numerically by the boundary integral equation method. Curves show the reflection and transmission coefficients for the reflected and transmitted longitudinal and transverse waves as functions of the frequency. Some results are also presented for planar distributions of cracks whose spacing and size are random variables. Finally, dispersion relations are discussed for solids which are completely filled with periodically spaced inhomogeneities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01772592
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Boundary-integral equation method for elastodynamic scattering by a compact inhomogeneity (1989)
    Springer
    Computational mechanics 5 (1989), S. 129-144 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The set of singular integral equations which relates unknown fields on the surface of the scatterer to a time-harmonic incident wave is solved by the boundary element method. The general method of solution is discussed in some detail for scattering by an inclusion. Results are presented for a spherical cavity, and for a soft and a stiff spherical inclusion. Fields on the surface of the scatterer are compared with previous results obtained by different methods. Back-scattered and forward-scattered displacement fields are presented, both as a function of position at fixed frequency, and as a function of frequency at fixed position. The quasi-static approximation is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01046482
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Ca overload and the action of calcium sensitive proteases, phospholipases and prostaglandin E2 in myocardial cell degradation (1985)
    Springer
    Basic research in cardiology 80 (1985), S. 303-315 
    Details
    ISSN: 1435-1803
    Keywords: calcium entry ; myocardial cell injury ; membrane permeability ; calcium-activated neutral protease ; calcium-dependent phospholipases ; cyclooxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The mechanism of Ca overload-induced myocardial cell injury under hypoxia was examined for the involvement of calcium-activated neutral proteases (CANP), calcium-dependent phospholipases (CDP) or prostaglandins with measuring45Ca entry, intake of biologically inert dye, nigrosin, into the cultured myocytes, as was useful for the quantification of sarcolemma permeability, and the release of creatine phosphokinase (CPK) to the culture medium. A Ca channel blocker, verapamil (1 and 10 μg/ml) or a Ca ionophore, A 23187 (0.5 to 4 μg/ml) dose-dependently decreased or increased both the Ca entry and nigrosin intake in accordance with the CPK release. Furthermore, the inhibitors against CANP, NCO-700 (2 and 20 μg/ml) that was demonstrated to permeate sarcolemma using14C-labelled reagent, against CDP, mepacrine (1 and 10 μg/ml) or against cyclooxygenase, indomethacin (1 and 10 μg/ml) caused no effect on the Ca entry, nigrosin intake nor CPK release under hypoxia. These results suggest that the Ca overdose into the myocardial cells potentiates their injury and it is not primarily related to the activation of CANP, CDP nor cyclooxygenase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01907906
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    Paper (German National Licenses)
    Fulltext
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