By far the most troubling aspect of the results discussed above is that they are not consistent with the experimental results originally presented by Varela et al. .
In particular, a careful examination of those original results suggests that the model must have had some, unspecified, mechanism to overcome or preempt the class of failure now described here. However, given that the work was done over 25 years ago, it seemed that it would be extremely difficult to gain much further insight into this problem. The current author who was involved in the original work (Varela), no longer had any clear recollection of what additional mechanism was present in the model to account for this discrepancy.
Fortunately, a printout of an early version of the original simulation program, coded in FORTRAN-IV, has recently been rediscovered, and has now been incorporated in a published technical report . As discussed in more detail in that report, this program has been rekeyed, and it has been possible to execute it again. This did not reproduce the precise results of the original publication; most likely it was not exactly the same version, and, in any case, the original pseudo-random number source is no longer available, so the precise execution trajectory is bound to be different. However, this did suffice to show that the program did, indeed, exhibit some mechanism whereby free links, confined within the membrane, tended not to spontaneously bond to each other. This motivated a detailed reanalysis of the program code, which finally resulted in the identification of a previously un-reported interaction--chain-based bond inhibition.
This is an interaction whereby bonding is inhibited to any free L particle which is in the immediate vicinity of another L particle which is doubly bonded. In effect then, a free L particle cannot form a bond as long as it is alongside (as opposed to at the end of) an existing chain of L particles; but it can form bond(s) when it is at the end of a chain; and, especially, when it is positioned at a site where a chain has broken (i.e. a rupture site).<Note 7>
The next section reviews experimental results from SCL when the chain-based bond inhibition reaction is enabled.
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Timestamp: Tue Apr 22 22:10:03 GMT 1997