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  • 1
    Electronic Resource
    Electronic Resource
    A Morphometric Study of the Structural Characteristics of the Aorta in Pigs Using an Image Analysis Method (2002)
    Oxford UK : Blackwell Science Ltd.
    Anatomia, histologia, embryologia 31 (2002), S. 0 
    Details
    ISSN: 1439-0264
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The objective of this study was to evaluate multiple structural characteristics, in addition to vasa vasorum density, in different aortic regions. The aorta of healthy Landrace pigs was divided into four thoracic and three abdominal segments. Transverse sections were reserved for morphometric analysis. Image analysis showed the aortic diameter, the thickness of the media, the number of elastic lamellae and the thickness of elastic membranes being reduced with increased distance from the heart (P 〈 0.05). The average thickness of lamellar units remained constant in the thoracic, but increased in the abdominal aorta (P 〈 0.05). The number of lamellar units, contained in the avascular zone of the media, and the density of vasa vasorum decreased peripherally (P 〈 0.05), still the average thickness of the avascular zone was invariant. In conclusion, the anatomical properties of the vessel wall alter through the aorta, being optimal for the varying stresses to which the aorta is subjected along its length. The distinct aortic parts may exhibit inherent morphological features, responsible for the various pathological processes that affect the aorta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0264.2002.00356.x
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  • 2
    Electronic Resource
    Electronic Resource
    Variational bounds of elastic constants in transversely isotropic plates (1998)
    Springer
    Archive of applied mechanics 68 (1998), S. 445-456 
    Details
    ISSN: 1432-0681
    Keywords: Key words spectral decomposition ; transverse isotropy ; plate ; strain energy ; plane eigenangle ; elastic constants ; fracture toughness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The spectral decomposition of the fourth-rank compliance tensor S for transversely isotropic plates yields three eigenvalues, together with a new dimensionless parameter ω p , called the plane eigenangle. These constitute the essential parameters for an invariant description of the elastic behaviour of anisotropic plates. In this paper, a study of the variational bounds imposed by thermodynamical constraints on the values of the elastic constants is presented. Furthermore, a theoretical definition of the longitudinal shear modulus G L is introduced in terms of the elastic constants E L , E T and v L as a means of checking the validity of the experimentally measured value of G L . Finally, it is shown that the plane eigenangle ω p is the only necessary parameter required for a monoparametric indication of the elasticity and toughness of transversely isotropic plates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004190050178
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Spectral decomposition of the compliance fourth-rank tensor for orthotropic materials (2000)
    Springer
    Archive of applied mechanics 70 (2000), S. 289-306 
    Details
    ISSN: 1432-0681
    Keywords: Key words Spectral decomposition ; compliance tensor ; orthotropic medium ; Euler angles ; elastic strain energy ; Poisson's ratios ; quasi-isotropic medium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The compliance tensor related to orthotropic media is spectrally decomposed and its characteristic values are determined. Further, its idempotent tensors are estimated, giving rise to energy orthogonal states of stress and strain, thus decomposing the elastic potential in discrete elements. It is proven that the essential parameters, required for a complete characterisation of the elastic properties of an orthotropic medium, are the six eigenvalues of the compliance tensor, together with a set of three dimensionless parameters, the eigenangles θ, ϕ and ω. In addition, the intervals of variation of these eigenangles with respect to different values of the elastic constants are presented. Furthermore, bounds on Poisson's ratios are obtained by imposing the thermodynamical constraint on the eigenvalues to be strictly positive, as specified from the positive-definite character of the elastic potential. Finally, the conditions are investigated under which a family of orthotropic media behaves like a transversely isotropic or an isotropic one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004199900066
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    Paper (German National Licenses)
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