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  • 1
    Digitale Medien
    Digitale Medien
    An Analytical Study of Free Convective Boundary-Layer Flow in Porous Media: The Effect of Anisotropic Diffusitivity (1997)
    Springer
    Transport in porous media 27 (1997), S. 289-304 
    Details
    ISSN: 1573-1634
    Schlagwort(e): free convection ; boundary layer ; anisotropy.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract The effect of an anisotropic thermal diffusivity tensor on the free convective boundary-layer flow in porous media is studied. Convection is induced by a generally inclined, uniformly heated surface embedded in a fluid-saturated medium. A third-order boundary-layer theory is presented in order to obtain accurate information on the effect of anisotropy on the rate of heat transfer into the porous medium. It is shown that the thickness of the resulting leading order boundary-layer flow depends on the precise nature of the anisotropy. On the other hand, the anisotropic diffusivity does not induce a fluid drift in the spanwise direction, a result which is different from that obtained in our earlier study of the effects of an anisotropic permeability. It is found that the second order temperature field does not contribute to the overall rate of heat transfer. Finally, we show that the third-order correction to the leading-order rate of heat transfer is given in terms of an explicit formula.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006576911797
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  • 2
    Digitale Medien
    Digitale Medien
    Non-Darcy Free Convection Along a Horizontal Heated Surface (1997)
    Springer
    Transport in porous media 29 (1997), S. 309-321 
    Details
    ISSN: 1573-1634
    Schlagwort(e): Non-Darcy ; free convection ; horizontal surface ; fluid inertia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract In this paper we analyse how the presence of inertia (Forchheimerform-drag) affects the steady free convective boundary layer flow over anupward-facing horizontal surface embedded in a porous medium. The surfacetemperature is assumed to display a power-law variation,x n with distance from the leading edge, x. It is shown thatthere are three distinct cases to consider: n〈0.5, n=0.5 and0.5〈n≤2. In the first case inertia dominates the flow near the leadingedge, but its effect wanes downstream. The boundary layer is self-similar inthe second case with the resulting profiles being dependent on the strengthof the inertia effect. In the third case, inertia effects grow withincreasing distance from the leading edge, and the boundary-layer thicknessis greater than when inertia is absent.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006542410627
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  • 3
    Digitale Medien
    Digitale Medien
    The relationship between Photosystem II intrinsic quantum yield and millisecond luminescence in thylakoids (1993)
    Springer
    Photosynthesis research 37 (1993), S. 131-138 
    Details
    ISSN: 1573-5079
    Schlagwort(e): luminescence ; Photosystem II ; quantum efficiency ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The relationship between charge recombination at Photosystem II (PS II), as indicated by millisecond luminescence, and PS II quantum yield was studied in spinach thylakoids during electron flow to methylviologen. Under the low magnesium conditions used, a decrease in quantum yield was observed in the absence of non-photochemical excitation quenching, and therefore cannot be due to a restriction in excitation delivery to the reaction centre. It was found that the decrease of the parameter Φp, which is a measure of the intrinsic quantum yield of ‘open’ PS II centers, correlates with an increase in luminescence per ‘open’ center. The relationship between these two parameters was the same whether Φp was manipulated by dissipation of the transthylakoid pH gradient or of the electrical potential. This indicates that the mechanism by which Φp decreases depends in the same way on the two components of the protonmotive force as does the charge recombination at PS II. Calculation of the yield of luminescence with respect to the back reaction will be necessary to determine whether the charge recombination occurs at a sufficiently high rate to be directly responsible for the Φp decrease.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02187471
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  • 4
    Digitale Medien
    Digitale Medien
    Non-photochemical quenching of chlorophyll fluorescence in the green alga Dunaliella (1990)
    Springer
    Photosynthesis research 24 (1990), S. 167-173 
    Details
    ISSN: 1573-5079
    Schlagwort(e): chlorophyll fluorescence ; photosynthesis ; Dunaliella
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The relaxation of the non-photochemical quenching of chlorophyll fluorescence has been investigated in cells of the green alga Dunaliella following illumination. The relaxation after the addition of DCMU or darkening was strongly biphasic. The uncoupler NH4Cl induced rapid relaxation of both phases, which were therefore both energy-dependent quenching, qE. The proportion of the slow phase of qE increased at increasing light intensity. In the presence of the inhibitors rotenone and antimycin the slow phase of qE was stabilised for in excess of 15 min. NaN3 inhibited the relaxation of almost all the qE. The implications of these results are discussed in terms of the interpretation of the non-photochemical quenching of chlorophyll fluorescence in vivo and the mechanism of qE.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00032596
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