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  • 1995-1999  (14)
  • 1990-1994  (26)
  • 1975-1979  (18)
  • 1925-1929  (2)
  • 1
    Electronic Resource
    Electronic Resource
    The Lagrangian spectral relaxation model for differential diffusion in homogeneous turbulence (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 1550-1571 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Lagrangian spectral relaxation (LSR) model is extended to treat turbulent mixing of two passive scalars (φα and φβ) with different molecular diffusivity coefficients (i.e., differential-diffusion effects). Because of the multiscale description employed in the LSR model, the scale dependence of differential-diffusion effects is described explicitly, including the generation of scalar decorrelation at small scales and its backscatter to large scales. The model is validated against DNS data for differential diffusion of Gaussian scalars in forced, isotropic turbulence at four values of the turbulence Reynolds number (Rλ=38, 90, 160, and 230) with and without uniform mean scalar gradients. The explicit Reynolds and Schmidt number dependencies of the model parameters allows for the determination of the Re (integral-scale Reynolds number) and Sc (Schmidt number) scaling of the scalar difference z=φα−φβ. For example, its variance is shown to scale like 〈z2〉∼Re−0.3. The rate of backscatter (βD) from the diffusive scales towards the large scales is found to be the key parameter in the model. In particular, it is shown that βD must be an increasing function of the Schmidt number for Sc≤1 in order to predict the correct scalar-to-mechanical time-scale ratios, and the correct long-time scalar decorrelation rate in the absence of uniform mean scalar gradients. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870018
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  • 2
    Electronic Resource
    Electronic Resource
    Oophorectomy at the same time as hysterectomy (1995)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 102 (1995), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1995.tb11370.x
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  • 3
    Electronic Resource
    Electronic Resource
    Accuracy of methods for estimating the size of Thanatephorus cucumeris populations in soil (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 8 (1992), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. The accuracy of assays based on galactosidase and the enzyme-linked immunosorbent assay specific to Thanatephorus cucumeris were compared with techniques based on soil dilution plating and baiting in sterilized field soil. Although soil dilution plating is reasonably quantitative, it requires substantial time, material and labour. Plant baits gave inconsistent results in the estimation of T. cucumeris populations in the soil. Enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies is suitable for detecting the presence of a range of anastomosis groups (AGs) of 71 cucumeris in soil samples, but more quantitative applications seem to be limited to a very narrow range of concentrations of the fungus (0–10 μg/g). Monoclonal antibody ELISA could be used if the soil samples are routinely further diluted, provided the range of concentrations is uniformly low. An assay of β-galactosidase permits estimation of a more adequate range of concentrations (0–500 μg/g) and may be used in defined experiments using uninoculated soil samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1992.tb00887.x
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  • 4
    Electronic Resource
    Electronic Resource
    Fetal-pericardial effusion in association with congenital heart block and maternal systemic lupus erythematosus. Case report (1990)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 97 (1990), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1990.tb02555.x
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  • 5
    Electronic Resource
    Electronic Resource
    Oestrogen and androgen states in oligo-amenorrhoeic women with polycystic ovaries (1991)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 98 (1991), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. Oestrogen and androgen states have been studied in relation to ovarian morphology defined by ultrasonography in 65 women with oligo-amenorrhoea. Of the 48 women with polycystic ovaries (PCO), 44 (92%) had a withdrawal bleed following progestogen challenge (indicating oestrogenization) compared with just three (18%) of the 17 with non-PCO (P 〈 0.001). Median serum concentrations of oestradiol and oestrone were statistically significantly higher in the PCO group but the ranges overlapped widely. Of the four women with PCO but oestrogen deficiency, two were hirsute and had evidence of a severe form of the disorder. The other two were not hirsute and appeared to have hypo-thalamic dysfunction associated with weight loss overriding the disorder due to pre-existing PCO. Compared with the non-PCO group, the PCO subgroup without hirsutism (n = 31) had statistically significantly higher median values of LH, testosterone, androstendione, and dehydro-epiandrosterone sulphate concentrations, and free androgen index. Concentrations of androgen, but not LH, were significantly higher still in the PCO subgroup with hirsutism (n = 17).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1991.tb13396.x
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  • 6
    Electronic Resource
    Electronic Resource
    Persistent fetal sinus bradycardia associated with maternal anti-Ro antibodies. Case report (1990)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 97 (1990), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1990.tb02506.x
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  • 7
    Electronic Resource
    Electronic Resource
    Temperature Dependent Rate Coefficient for the Cl + ClONO2 Reaction (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 13976-13983 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100038a032
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  • 8
    Electronic Resource
    Electronic Resource
    The Fokker–Planck closure for turbulent molecular mixing: Passive scalars (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1230-1244 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A turbulent-molecular-mixing closure for passive scalar mixing is derived based on the theory of diffusion in layerlike lamellar structures. The closure is formulated in terms of the Fokker–Planck (FP) equation (or an equivalent stochastic differential equation), and is to be employed in conjunction with the probability density function (pdf) balance equation appearing in the pdf methods for modeling turbulent reactive flows. Like the mapping closure, the FP closure predicts a limiting Gaussian pdf for the passive scalar concentration in isotropic turbulence. In addition, the FP closure models the joint pdf of the scalar concentration and the scalar gradient and thus predicts the scalar dissipation rate. The closure predictions for the scalar rms concentration, the marginal pdf, and the joint pdf as well as other relevant statistics have been studied by Monte Carlo simulation. The shape and temporal evolution of the marginal pdf for the scalar concentration compare favorably with published results found from direct numerical simulations and from the mapping closure. Finally, unlike the mapping closure, the FP closure is shown to easily extend to the case of multiple scalar mixing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858241
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  • 9
    Electronic Resource
    Electronic Resource
    On velocity-conditioned scalar mixing in homogeneous turbulence (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 2678-2691 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Scalar mixing models are required to model turbulent molecular mixing in full probability density function (pdf) simulations of turbulent reacting flows. Despite the existence of direct numerical simulation (DNS) data suggesting the contrary, most scalar mixing models assume that molecular mixing is independent of the instantaneous velocity, i.e., 〈D∇2φ|V,ψ〉=〈D∇2φ|ψ〉. Since in a joint velocity, composition pdf calculation the velocity is known, this assumption is unnecessary and leads to a lack of local isotropy in the scalar field. Moreover, since velocity conditioning offers a numerically tractable approach for including the effects of local anisotropy and mean velocity gradients on scalar mixing, it should be of considerable interest for the numerical simulation of scalar mixing in inhomogeneous turbulent flows. An efficient numerical implementation of velocity-conditioned scalar mixing for full pdf simulations is proposed and verified against DNS data for homogeneous turbulence (isotropic and shear flow) with a uniform mean scalar gradient. A second-moment closure relating the velocity-conditioned scalar dissipation to the scalar fluxes and Reynolds stresses that is exact in the limit of a joint Gaussian pdf is also derived for use with moment closure models. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869054
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  • 10
    Electronic Resource
    Electronic Resource
    The Lagrangian spectral relaxation model of the scalar dissipation in homogeneous turbulence (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 2364-2386 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Lagrangian pdf methods are employed to extend the spectral relaxation (SR) model of the scalar dissipation of an inert, passive scalar (1≤Sc) in homogeneous turbulence. The Lagrangian spectral relaxation (LSR) model divides wavenumber space into a finite number (the total number depending on the Taylor-scale Reynolds number Rλ and the Schmidt number Sc) of wavenumber bands whose time constants are determined from the mean turbulent kinetic energy and instantaneous turbulent energy dissipation rate. The LSR model accounts for the evolution of the scalar spectrum (viz., pdf) from an arbitrary initial shape to its fully developed form. The effect of turbulent-frequency fluctuations on the instantaneous scalar dissipation rate following a Kolmogorov-scale fluid particle is incorporated into the LSR model through a Lagrangian pdf model for the turbulent frequency. Model results are compared with DNS data for passive scalar mixing in stationary, isotropic turbulence. Two distinct causes of non-Gaussian scalar statistics are investigated: small-scale intermittency due to scalar-dissipation fluctuations at scales near the Kolmogorov scale, and transient large-scale inhomogeneities due to the form of the initial scalar spectrum at scales near the integral scale. Despite the absence of fitting parameters, the LSR model shows satisfactory agreement with available DNS data for both types of flows. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869357
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