Self-Organization: A Common Principle of Information Processing by Distributed Dynamic Systems - Molecular Computing: Origins and Promises - page 181

Fig. 6.11 Change in the
stationary state of the
photosensitive Belousov-
Zhabotinsky medium as a
function of its illumination

condition of the reactor is created through a process of self-organization in the
Belousov-Zhabotinsky medium.
Of course this initial state of the reactor can be used for information processing,
i.e., for carrying out operations initiated by the vibrational mode of the medium.
They were discussed in detail in Chap. 5 . At the same time, the capabilities of the
processor can be significantly extended by switching the medium to the other
dynamic regimes that allow for performing information processing operations
different from those carried out in the vibrational mode.
It would seem that the most natural way to switch the regime is to change the
composition of the medium, which is determined by specifying the parameters of
the system for filling the reactor. However, this option has a significant drawback.
In this case, the switching time of the dynamic regimes turns out to be too large—
tens of seconds. The composition of the mixture is determined by the efficiency of
the pumps supplying individual components into the medium, and therefore the
system for filling the reactor has substantial inertia. A faster and more convenient
option to switch modes can be implemented by changing the illumination of the
light-sensitive Belousov-Zhabotinsky medium.
Let us return to the zero isoclines of this system (Fig. 6.11 ). The initial state of
the environment in the reactor in this figure corresponds to complete absence of
illumination. This is one of the stationary states corresponding to the vibrational
mode of the medium. Let us illuminate the medium with uniform light radiation in
the visible spectrum. Then a consistent increase in the intensity of the radiation will
cause the medium to pass through a sequence of stationary states. In this case, the
switching time is in the range of tenths of a second. After switching, the medium
can remain in each of the stationary states for any time as long as the chemical
composition, temperature, and intensity of the illuminating light are kept constant.
Various operations are performed by the medium in its various states, which greatly
increases

the information capabilities of the reaction-diffusion processor

(Fig. 6.12 ).
Along with the light radiation, controlled switching of the regimes of the
medium can be performed by local or global electric field. In this case, various
possibilities for exciting the dynamic regimes of the environment and for