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  • 1
    ISSN: 1520-6033
    Source: ACS Legacy Archives
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 105 (1991), S. 0 
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A study is made of the dependence of the effective permeability of sand-shale reservoirs on the geometry of the shale inclusions. Numerical simulations are described in which factors such as the orientation and the degree of anisotropy of the shales, their volume fraction and the permeability contrast ratio between the shale and the sandstone were varied. Two different reservoir models were used in the simulations: one in which the shales were in the form of random, overlapping spheroidal inclusions, and one in which the shales were generated by a geostatistical technique. The computed effective permeability data are compared with a variety of analytical models in an attempt to discover ‘rules of thumb’for the estimation of the effective permeability of sand-shale reservoirs for use in a range of practical situations. The main technical way in which this study advances on previous work is in its use of a computationally efficient, random walk algorithm for calculating the effective permeability, which has enabled larger volumes to be simulated and, hence, a thorough investigation of finite-size effects to be made. Another advantage of the work reported here is the general nature of the sand-shale geometries used in the numerical simulations and the extensive comparisons with analytical models.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of oral rehabilitation 14 (1987), S. 0 
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A sample consisting of 1135 edentulous patients with clinically healthy denture bearing areas, was examined radiologically. It appears that the diagnostic yield is high whereas the expected radiation induced risk is low. Patients should therefore be examined radiologically prior to full denture construction.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 435-437 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A presentation is given of the results of two-dimensional lattice gas cellular automata (LGA) simulations for calculating the permeability for flow through periodic arrays of cylinders, where the cylinders have either a rhomboid or cruciform cross section. For the case of rhombi, the results are related via a semiempirical shape factor to analytical solutions for flow through arrays of circular cylinders. Finite size effects are studied by comparing simulation results with theory. This calibration of the LGA model then validates its use for the study of flow around cruciforms, for which there is no analytical solution. This has an important application in the mathematical modeling of flow through arrays of dendrites in the mushy region during the solidification of alloy steel.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-3017
    Keywords: biomarkers ; Bluegill ; sediment ; pollution ; EFPC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The temporal expression of various biological rsponses was determined in Bluegill SunfishLepomis macrochirus exposed under controlled laboratory conditions to sediment containing high concentrations of polynuclear aromatic hydrocarbons, polychlorinated biphenyls and heavy metals. Liver, gill, blood, kidney, brain, spleen and intestine were removed from Sunfish sampled at 1, 2, 4, 8, 16, and 40 weeks post-exposure. Biomarker data were recorded for specific proteins, enzymatic activities, DNA integrity, and histopathology. Biomarkers in the laboratory exposed fish were similar to those of indigenous Sunfish sampled from the site of origin of the contaminated sediment. Several patterns of development of biomarkers over time were also evident. For example, the responses of certain biomarkers are not time-dependent (i.e., intestine and gill ATPase activities) while that of others, such as brain ATPase activity, liver cytochrome P450 and NADPH content, stress proteins, chromatin proteins and DNA strand breaks, fluctuate over time. Still other biomarkers, such as EROD activity, zinc protoporphyrin content of the blood, and DNA adducts, showed marked increases over time. Such patterns need to be considered when comparing laboratory and field results and deciding which biomarkers to use for biomonitoring programs. Implications for natural selection and population/community level responses are also discussed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 19 (1995), S. 123-137 
    ISSN: 1573-1634
    Keywords: Effective permeability ; heterogeneity ; renormalisation group method ; random walks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The problem of upscaling permeability data from the core to the reservoir grid block scale for input into flow simulators is addressed. Two fast, approximate algorithms which have been suggested for this purpose—one based on random walks and the other on real-space renormalisation group methods—are compared using the results of numerical tests performed on 30 different heterogeneous permeability realisations in 3-D. The results show that random walks outperform renormalisation for this problem, being computationally more efficient and demonstrating significantly better accuracy for particular cases.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Transport in porous media 15 (1994), S. 251-269 
    ISSN: 1573-1634
    Keywords: Hodograph method ; 2D cresting models ; gas and water cresting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Three new applications of the hodograph method to the problem of gas and water cresting towards horizontal wells are presented: (1) A numerical technique, based on the hodograph method, is used to find the shape of the oil/water interface and values of critical heights for the problem of water cresting towards a horizontal well beneath an impermeable plane. (2) By correct implementation of the boundary conditions in the lateral edge drive model, a hodograph solution is found for which the water crest tends to a horizontal asymptote far from the well, rather than tending towards a parabolic curve as in previous approaches. The solution yields integral representations for the lengths of boundary segments and enables an explicit expression for the critical rate to be derived in terms of the distance to the constant potential boundary. (3) The problem of simultaneous gas and water cresting towards a horizontal well in a thin oil column reservoir is solved using the hodograph method, providing shapes of the free interfaces and an expression for the optimal placement of the well with respect to the interfaces.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Biotechnology letters 10 (1988), S. 285-288 
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Analysis of the amylase activity associated withCellulomonas flavigena showed that it was a cell associated activity that could be released upon sonication, it was active against amylopectin and starch but showed no activity against pullulan and only slight activity against amylose. The enzyme was also found to have liquifying activity and to be inducible.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 11 (1995), S. 805-812 
    ISSN: 1069-8299
    Keywords: solidification ; dendritic growth ; probabilistic modelling ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A model of solidification is developed from a statistical mechanics basis that incorporates nucleation of columnar and equiaxed grains, thermal and solute diffusion, and latent heat of the phase change. The model is applied to the solidification of austenitic steel. The dendritic growth of columnar and equiaxed grains is simulated, including the segregation of solute ahead of the solid-liquid interface. The irregular branched morphology of the solid forms in a manner analogous to dendritic morphologies that arise from constitutional undercooling in real materials. There is competition between columnar and equiaxed growth. When growing grains approach, the solute layer and the thermal field act to prevent them overlapping.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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