Extensions of the SR model

The extension of the SR model to differential diffusion is outlined in Section 4.7. In an analogous fashion, the LSR model can be used to model scalars with different molecular diffusivities (Fox 1999). The principal changes are the introduction of the conditional scalar covariances in each wavenumber band 4> a4> p) and the conditional joint scalar dissipation rate matrix (e). For example, for a two-scalar problem, the LSR model involves three covariance components (/2, W V/A) and and three joint dissipation... 

The SR model introduced in Section 4.6 describes length-scale effects and contains an explicit dependence on Sc. In this section, we extend the SR model to describe differential diffusion (Fox 1999). The key extension is the inclusion of a model for the scalar covariance (4> aft p) and the joint scalar dissipation rate. In homogeneous turbulence, the covari-... 

Pichavant M, Montel J-M, Richard LR (1992) Apatite solubility in peraluminous liquids experimental data and an extension of the Harrison-Watson model. Geoehim Cosmoehim Acta 56 3855-3861 Poitrasson F, Chenery SR, Bland DJ (1996) Contrasted monazite hydrothermal alteration mechanisms and their geochemical implications. Earth Planet Sci Lett 145 79-96 Poitrasson F, Chenery SR, Shepherd TJ (2000) Electron microprobe and LA-ICP-MS study of monazite hydrothermal alteration implications for U-Th-Pb geochronology and nuclear ceramics. Geoehim Cosmoehim Acta 64 3283-3297... 

In the bioinformatics realm, SRS (Sequence Retrieval System) [2] is a popular system, which uses a centralized collection of data resources primarily in flat text file form and, more recently, handles XML (Extensible Markup Language) files as well. Data resources are treated in a federated manner since each is maintained in its original form. However, SRS contains a large number of cross-references between corresponding fields in various data sources, so that keyword searches can be done across them. SRS thus performs more structured searches across the information than what a simple text search provides (such as web indexes perform, for example). Even though the data model implicit in the cross-reference tables is not very deep, SRS provides a useful way for users to browse and do simple queries across a large number of data sources as well as to integrate results from some computational methods. 

Although this picture was found to be in a satisfying agreement with SR-SW calculations, further extension of these studies appears quite pointless now because more accurate DV-Xa modelling of this topic has been carried out in the mean time (e.g., see [29]). The application of the latter method could lead to a ftnal decision as to the extent of cooperation between polarization (pvai) and core reorganisation (3p) in shifting the ratio R, and as to whether the interpretation of these variations as pure valency effects [27] is on safe groimds. 

Extensions beyond the data base of (2) are largely untested and include additions to PITZER.DATA for (1) the calculation of the thermodynamic properties of aqueous solutions containing Fe(II), Mn(II), Sr +, Ba2+, Li+, and Br (2) the estimation of the temperature dependence of many of the single-salt parameters from selected literature data and (3) the calculation of the thermodynamic properties of NaCl solutions to approximately 300 °C along the vapor pressure curve of water beyond 100 C (18)-Except for the NaCl-H20 system, the PHRQPITZ aqueous model should not be used outside the temperature range 0 to 60 C. Several recent evaluations of the temperature dependence of Pitzer interaction parameters to relatively high temperatures (19-21) have not yet been incorporated in the PHRQPITZ data base. 

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