As shown before, the number of distinct networks which can be generated by substituting pairs of compounds does not merely depend on the reactions in the original network, as the number of possible substitutions may change after applying substitutions.
To illustrate this point, for a reaction r, if a substrate c is substituted by a compound x, we may subsequently substitute the pair of substrates (x, k), where k is any other substrate of r.
You will a thermometer for taking your dogs temperature, powdered milk substitute, a pair of sterilised scissors and some dental floss, a baby bottle, some examination gloves and some weighing scales for weighing the puppies.
Similarly, the possible substitutions for individual compounds may change after substituting a pair of compounds.
In the stockroom, Victoria had discovered that the store had sold out of those, so she'd substituted a pair in a lighter shade.
Mesut Özil stood out only in the briefest of flashes and Aaron Ramsey was overrun before Wenger substituted the pair just after the hour.
It immediately drew attention because it took charanga, a traditional Cuban style focused on violins and flute, and made it bold and brassy by substituting a pair of trombones for the strings.
As the TR-1 engines originally intended for the Su-9 were not yet ready for flight testing in late 1945, Pavel Sukhoi suggested substituting a pair of Jumo 004 engines and this was approved on 15 December.
He initiated the use of electromagnets in electric generators and invented the Playfair cipher, which is based on substituting different pairs of letters for paired letters in the message.
But as Ms. Lemercier (a popular French comedian) and Mr. Lindon (whose mature gravity has a vague resemblance to Jean Gabin) go through their poker-faced, tight-lipped paces, you may find yourself frustratedly substituting other pairs of actors in your mind for these two.
