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  • 1
    Electronic Resource
    Electronic Resource
    Mean field calculation of effective permeability based on fractal pore space (1992)
    Springer
    Transport in porous media 8 (1992), S. 93-97 
    Details
    ISSN: 1573-1634
    Keywords: Porous rock ; permeability ; porosity ; fractal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Effective permeability for porous rocks is calculated using mean field theory. We make two simplifying assumptions about the internal conductances in a network representation of the porous rock: (i) Pore space is characterized by a uniform fractal scaling; (ii) the internal conductances depend only on the characteristic pore sizes. Within these approximations, it is possible to derive a simple probability density for the internal conductances which is used for calculating effective permeability. Good agreement between calculations and experimental data of permeability vs. porosity is achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616894
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Implication of fractal geometry for fluid flow properties of sedimentary rocks (1992)
    Springer
    Transport in porous media 8 (1992), S. 133-147 
    Details
    ISSN: 1573-1634
    Keywords: Fractal ; multifractal ; sedimentary rocks ; permeability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract It is demonstrated that a certain amount of order can be extracted from an apparently random distribution of pores in sedimentary rocks by exploiting the scaling characteristics of the geometry of the porespace with the help of fractal statistics. A simple fractal model of a sedimentary rock is built, and is tested against both the Archie law for conductivity and the Carman-Kozeny equation for permeability. We demonstrate how multifractal scaling of pore-volume can be used as a tool for rock characterization by computing its experimentalf(α) spectrum, which can be modelled by a simple two-scale Cantor set.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617114
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    1H-NMR imaging of fimbria fornix lesions in the rat brain (1992)
    Springer
    Brain topography 5 (1992), S. 147-151 
    Details
    ISSN: 1573-6792
    Keywords: 1H-NMR imaging ; (Rat) brain ; Fimbria fornix ; Hippocampus ; Ventricle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mechanical lesions of the fimbria fornix (FF) have been widely used as a model to investigate the recovery of damaged brain tissue.1H-NMR imaging was employed to non-invasively measure changes in the brain after unilateral FF transection. Rats were subjected to NMR imaging at various times after the lesions were made. The experimental protocol included (multislice) T2-weighted and diffusion-weighted imaging thereby allowing the construction of two-dimensional maps of the relaxation time T2 (transverse or spin-spin relaxation time) and the apparent diffusion coefficient (ADC) of water. FF transection induced considerable changes in the status of the brain tissue at a number of different locations which were exclusively present in the affected hemisphere. At 1 day post-lesion the region of the lateral ventricle and hippocampus started to display pronounced changes in that T2- and diffusion-weighted images showed a hyperintensity and a hypointensity, respectively. These effects were maximal around day 2 to 4 whereafter a slow recovery towards the control situation was observed. Immediately after transection the FF lesion itself could be visualized. These early images pointed to an aspecific disruption of the tissue due to the mechanical intervention. Interestingly, however, from day 2 post-lesion a number of changes became evident in this region which seemed to be localized to specific structures, including the ventricle and hippocampus. After one month the presumably ventricular effect dominated and was predominantly localized to the anterior side of the FF lesion. These findings are indicative of pronounced changes in the status of water (e.g., in its distribution between extra- and intracellular compartments) at a number of locations distant from the site of FF transection. The mechanism by which these changes are brought about and the origin of their time-dependence remain to be elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01129042
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    Paper (German National Licenses)
    Fulltext
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