Cell model validation

These may be produced by grouping together multiple cell models to form virtual tissue segments, or even the whole organ. The validity of such multi-cellular constructs crucially depends on whether or not they take into account the heart s fine architecture, as cardiac structure and function are tightly interrelated. 

With the work still in the infant stages, there is no accepted method of modeling electrode reactions with DFT. A few recent studies have attempted to include both electrostatic and solvent effects in DFT models of electrochemical reactions using different approaches.84-89 However, the lack of surface techniques available for in situ study of electrochemical cells hinders validation of models by experimental data. Results can only offer qualitative information at best. Despite the challenges, DFT modeling of electrochemical reactions offers promise as a method for providing insights into the electrochemical interface in cases where experiments are difficult. 

Fig. 10.11 Schematic diagram of a drug screening concept. Disease-associated genes are identified using different display technologies. Probes for disease-associated genes are designed and are spotted onto the porous chip. Libraries of pharmaceutical compounds are screened against a validated cell model...

Nguyen L, Dautrey S, Vo C, Sexton R, Morin PE, Ducharme, R. Proudlock (2001) Validation of a Caco-2 cell model for a higher throughput permeability assays. AAPS PharmSci 3(3) abstract. 

As noted in the Introduction, one of the defining characteristics of any fuel-cell model is how it treats transport. Thus, these equations vary depending on the model and are discussed in the appropriate subsections below. Similarly, the auxiliary equations and equilibrium relationships depend on the modeling approach and equations and are introduced and discussed where appropriate. The reactions for a fuel cell are well-known and were introduced in section 3.2.2. Of course, models modify the reaction expressions by including such effects as mass transfer and porous electrodes, as discussed later. Finally, unlike the other equations, the conservation equations are uniformly valid for all models. These equations are summarized below and not really discussed further. 

Almost all of the models assume local thermal equilibrium between the various phases. The exceptions are the models of Beming et al., ° who use a heat-transfer coefficient to relate the gas temperature to the solid temperature. While this approach may be slightly more accurate, assuming a valid heat-transfer coefficient is known, it is not necessarily needed. Because of the intimate contact between the gas, liquid, and solid phases within the small pores of the various fuel-cell sandwich layers, assuming that all of the phases have the same temperature as each other at each point in the fuel cell is valid. Doing this eliminates the phase dependences in the above equations and allows for a single thermal energy equation to be written. 

Model validation phase consists in establishing the range of validity and the accuracy of the code in describing fuel cell behaviour under different operating con-... 

In the light of the above, we recommend that while verification is applied, validation of the cell and stack calculations in comparison to carefully designed experiments must take priority in the fuel cell modeling community. Only by proper validation of the 3 -D calculations using, at least, the spatial distribution of temperature and current measurements, the computer simulations can take its proper role in design analysis and improvement with relevance to industrial application. Needless to say, the computation time must be reduced for practicality purposes. 

Franke H, Galla H, Beuckmann CT (2000) Primary cultures of brain microvessel endothelial cells a valid and flexible model to study drug transport through the blood-brain barrier in vitro. Brain Res Brain Res Protoc 5 248-256... 

Ju H, Wang CY (2004) Experimental validation of a PEM fuel cell model by current distribution data. J Electrochem Soc 151(11 ) A1954—60... 

Mohler, J. L., Partin, and Coffey, D. S. (1987b) Prediction of metastatic potential by a new grading system of cell motility validation in the Dunning R-3327 prostatic adenocarcinoma model. J. Urol. 138, 168-170. 

For investigating endocrine disruption of estrogenic compounds, in vitro models are well established and some are well validated. For other tissues, such as adrenal and thyroid, there is less concurrence about test systems and models, but a number of useful cell models are available. In vitro assays provide results that are sometimes limited in scope or impact, but such results can synergize... 

To parameterize the new quantities occurring in these equations a few semi-empirical relations from the literature were adopted. The asymptotic value of bubble induced turbulent kinetic energy, fesia, is estimated based on the work of [3]. By use of the so-called cell model assumed valid for dilute dispersions, an average relation for the pseudo-turbulent stresses around a group of spheres in potential flow has been formulated. Prom this relation an expression for the turbulent normal stresses determining the asymptotic value for bubble Induced turbulent energy was derived ... 

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