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Strict cell model

A consequence of a strict stochastic model is that not all B lymphocytes will exhibit allelic exclusion. If the rate of productive rearrangement is sufficiently high, there will be occasional double producers (see related discussion in Part I, Instruction and Selection). On the other hand, if the rate of productive rearrangement is low, there will be few doubles, but many cells will have only non-functional rearrangements. [Pg.36]

Sometimes called the "grandmother cell" model, in which a unit of learning or recognition (of your grandmother, for instance) was supposedly associated with a single brain cell or strictly local set of interconnections between cells, (back)... [Pg.163]

The invariant hole size and energy of hole formation in the Lacombe-Sanchez model implies a dependance of the internal energy on the density that is strictly of the van der Waals form, as in Flory s theory. Another, somewhat more complicated, model developed by Simha and his collaborators is similar to that of Sanchez and Lacombe in its use of a liquid lattice with vacant sites, but it also retains features of Prigogine s earlier cell model in the c parameter for external degrees of freedom and a lattice energy with a density dependence based on an effective (6-12) pair potential. Like the other theories, this one has been successful in correlating equation of state data both for neat polymer liquids and for nondilute solutions. [Pg.110]

Bearing in mind that phenomena occurring in nature are too complex to be completely described by mathematical equations, the required details to be described by the model must be goal-driven, i.e. the complexity of the model, and the related results, must be strictly connected to the main goal of the analysis itself. When, for example, the main purpose of the model is to provide the fuel cell performance, in order to analyze the whole system in which it is embedded, the spatial variation in the physical and chemical variables (such as gas concentration, temperature, pressure and current density, for example) are not relevant however the performances, in terms of efficiency, electrical and thermal power and input requirements are important [1-4],... [Pg.51]

Single-crystal X-ray results (9) point to strict alternation of Si and Al (the 4 0 ordering scheme) in accordance with Loewenstein s rules (10), but this model was recently challenged on the basis of 29si NMR measurements (1, 2) and our discovery that the sodium derivative can be rhombohedral (11,12). However, the controversy has now been resolved and the correctness of the X-ray model reaffirmed (13,14). A consequence of the Si, Al ordering is that the lattice parameter of the cubic cell is ca. 24.6 A, not 12.3 A as reported in earlier work, a feature reflected in weak superlattice reflections. The space group is Fm3c. [Pg.132]

Cell-type models are still in use (Adler, 1979 Russel and Benzing, 1981) because of their simplicity. Predicted results are often quite reasonable, exhibiting features intuitively anticipated. On the other hand, such models fail to provide definitive answers to many of the fundamental issues encountered in suspension rheology. Moreover, because of their strictly ad hoc geometric nature, no obvious way exists for their rational improvement. [Pg.21]

Chaotic behavior and synchronization in heterogeneous catalysis are closely related. Partial synchronization can lead to a complex time series, generated by superposition of several periodic oscillators, and can in some cases result in deterministically chaotic behavior. In addition to the fact that macroscopically observable oscillations exist (which demonstrates that synchronization occurs in these systems), a number of experiments show the influence of a synchronizing force on all the hierarchical levels mentioned earlier. Sheintuch (294) analyzed on a general level the problem of communication between two cells. He concluded that if the gas-phase concentration is the autocatalytic variable, then synchronization is attained in all cases. However, if the gas-phase concentration were the nonautocatalytic variable, then this would lead to symmetry breaking and the formation of spatial structures. When surface variables are the model variables, the existence of synchrony is dependent upon the size scale. Only two-variable models were analyzed, and no such strict analysis has been provided for models with two or more surface concentrations, mass balances, or heat balances. There are, however, several studies that focused on a certain system and a certain synchronization mechanism. [Pg.111]


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See also in sourсe #XX -- [ Pg.181 ]




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