Chemistry Reference
In-Depth Information
Fig. 5.12
Formation of spi-
rals in oscillator networks.
To p
A spiral can be seen clearly in
the oscillator population.
Bot-
tom
Image of the network at
higher magnification reaveal-
ing the lack of perfect local
connectivity for each droplet.
Scale bar is 150
ยต
reveals that the local network of each oscillator is not complete according to the
2-dimensional hexagonal packing. The lack of local connections creates a refractory
effect on the excitatory wave due to the different speeds it travels at, in the different
directions. This causes the wave to turn and eventually forms a spiral or other rotary
patterns depending on the exact topology of the network.
Finally, we note that the effect of the bilayer membrane is not just to easily pass
the various species of the BZ reaction from one oscillator to another, such that a dis-
crimination of the 'individual oscillator' is simply lost. In such a case, the behaviour
of the oscillator network can be considered to be the same as that of the BZ reac-
tion in bulk. However, more complex relationships between neighbouring oscillators
connected by a bilayer are seen. As we mentioned before, both the excitatory and
inhibitory components of the BZ reaction can traverse through the bilayer. The for-
mation of the target patterns as described before indicated that the BZ mixture used
in our experiments is excitatory i.e. the excitatory coupling wins over the inhibitory
coupling in determining the state of the coupled oscillators, leading to wave like
patterns as we have seen so far. However, it has been reported in literature [
6
,
7
]
that due to inhibitory coupling between BZ oscillators, it is possible to generate pat-
terns that strongly differ from wave-like patterns. We increased the concentration
of malonic acid to 700 mM compared to the 500 mM used for the previous experi-
ments. It is expected that increasing the concentration of the malonic acid results in a
greater production of the inhibitor, bromine, as shown in the BZ reaction schematic
in Fig.
5.1
, thus possibly leading to an inhibitory coupling effect. When the coupling
is inhibitory i.e. non-excitatory, we expect that wave like patterns will not result.
