Single-cell model

PBM (Photochemical Box Model) is a simple stationary single-cell model with a variable height lid designed to provide volume-integrated hour averages of ozone and otlier photochemical smog pollutants for an urban area for a single day of simulation. 

Cardiac models are amongst the most advanced in silico tools for bio-med-icine, and the above scenario is bound to become reality rather sooner than later. Both cellular and whole organ models have aheady matured to a level where they have started to possess predictive power. We will now address some aspects of single cell model development (the cars ), and then look at how virtual cells interact to simulate the spreading wave of electrical excitation in anatomically representative, virtual hearts (the traffic ). 

Corapcioglu, M. Y. and Baehr, A. L., 1985, Immiscible Contaminant Transport in Soils and Groundwater with an Emphasis on Gasoline Hydrocarbons System of Differential Equations vs. Single Cell Model Water Science and Technology, Vol. 17, No. 9, pp. 23-37. 

One of the first models to examine transients in polymer-electrolyte fuel cells was a stack-level model by Amphlett et al. Their model is mainly empirical and examines temperature and gas flow rates. They showed that transient behavior lasts for a few minutes in a stack before a new steady state is reached. In a similar stack-level analysis, Yerramalla et al.2 9 used a slightly more complicated single-cell model and examined the shape of the transients. They noticed voltage behavior that had oscillations in it and some leakage current. Their overall analysis was geared to the development of a controller for the stack. 

When, on the other hand, the model is used as a tool for designing or improving a specific component of the fuel cell, it is important that the model is capable of providing very detailed information on the performance-related variables in that specific component. Examples of such analyses are copious in the literature (e.g. [4-8]), and most of them are developed at single cell level, with particular emphasis on one particular component or cell characteristic. Chan et al. [4], for example, applied an SOFC single cell model for analyzing the effect of the electrodes and... 

One of the pioneers of structured models in animal cell culture used a single-cell model (Batt and Kompala, 1989). Based on hybridoma metabolism (.Figure 8.6), the model was based on the formulation of four compartments amino acids (including the TCA precursors), the nucleotides (including DNA and RNA), the proteins, and lipids. The excreted byproducts (lactate and ammonia) and the excreted product (mAb) were also considered. However, although flexible for simulation of different... 

As highlighted in the reviews from Li et al. [71] and Hummon et al. [41], in addition to the mollusk single-cell models, MALDI-MS associated or not to nanoLC and on-line LC-ESI-MS/MS has been successfully applied to a wide variety of animal species from invertebrates to vertebrates. 

Corapcioglu MY, Baehr A. 1985. Immiscible contaminant transport in soils and groundwater with an emphasis on petroleum hydrocarbons System of differential equations vs single cell model. Water Science and Technology 17 23-37. 

A different approach has been investigated within the EU FP7 ESNATS project (www.esnats.eu FP7 2009-2013) that is the development of alternative tests based only on one single cell model, the embryonic stem cells (ES cells), taking advantage of their ability to mimic early embryo development and to differentiate in all three germ layers under specific differentiation protocols. The aim of the ESNATS project is to develop a novel all-in-one toxicity test platform, preferably based on human ES cells, to overcome interspecies variations. Several differentiation protocols have been optimized and adapted to the purpose of defining robust standard operation... 

J.A. Dusenberry (2000). Steady-state single cell model simulations of photoacclimation in a vertically mixed layer implications for biological tracer studies and primary productivity. J. Mar. Syst., 24, 201-220. 

Population Models. To understand why single-cell models are useful it is Important to review previous attempts at modeling populations. The history and philosophy of modeling as well as the virtues and faults Inherent in previous models has been well described in the literature. Among these articles are those by Tsuchiya, Fredrickson, Aris ( 1) Painter Marr ) ... 

These advantages make single-cell models particularly well-suited to testing the plausibility of hypotheses about metabolic mechanisms. 

Ideal Model. Having discussed why single-cell models may be useful, what characteristics should such models have The following features are Important ... 

Population Models From Single-Cell Models... 

The single-cell model Is limited In Its usefulness for engineering calculations unless a population model can be constructed from the Information In the single-cell model. It Is possible to build a population model using an ensemble of singlecell models to mimic the response of a large population of cells (24, 46, 68). Since computer capacity Is finite, the question Is really, "how few cell models can be Included In a population and still allow reasonable predictions of the behavior of a natural population of cells "... 

Figure 12 displays the steady-state stability of size-distributions generated with the structured single-cell model. Sixteen cell classes with fifteen cells per class were used. Random processes allowed were variation in "burst size of RP (20%) and in replication velocity (10%). Variation with respect to other criteria are currently being investigated. The stability displayed by the distributions will be acceptable in most potential applications. Clearly other types of distributions (e.g. RNA, DNA, protein, etc.) can be generated from such population runs. 

Single-cell models can be written that mimic very closely the responses of living cells. Such models are convenient tools for testing the plausibility of basic biochemical mechanisms. 

Figure 12. Computer simulation of a population using 240 structured cells (the Cornell single-cell model). There were 16 size classes and 15 cells per class in the simulation. The steady-state size distributions display a level of stability acceptable...

While clever experimental design may make it possible to test predictions of single-cell models without recourse to measurements of f, direct experimental access to the frequency function is often desirable and sometimes necessary in order to evaluate single-cell control and kinetic properties using the strategy just outlined. 

Atrial muscle The first detailed model of the excitation-contraction coupling mechanism in heart cells was constructed by Hilgemann and Noble [1987] and a single cell model was completed by Earm and Noble [1990]. A similarly detailed model of rabbit atrial cells was constructed by Lindblad et al. [1996] and modified to fit data from human atrial cells by Nygren et al. [1998]. Another model of human atrial cells based on the ventricular ceU model of Luo and Rudy [1994] but with improved calcium handling equations was formulated by Courtemanche et al. [1998]. The main differences between the Nygren and... 

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