76 TEMPORAL ORGANIZATION IN CELLS 



temperature of a cell, and its competence to respond to certain stimuli; or 

 between the size of 6 and the adaptive capacity of a cell. Such relations must 

 be introduced in association with the idea of thermodynamic force. Thus for 

 example in embryology, competent cells are ones with a certain potential for 

 response to particular stimuli. A change in an environmental parameter will 

 result in movement of the competent system in a manner determined by the 

 size and the direction of the "thermodynamic" force released or caused by 

 the stimulus, the result of which is the performance of a certain amount of 

 "work". These changes of epigenetic state are closely connected with changes 

 in the free energy function, as we will now see. 



The generalized force conjugate to the external parameter s^ is defined as 



in the case of the system without strong coupling between components. Thus 

 we see that the forces in the present theory enter through the quantities c, and Z?,, 

 which are taken to be functions of the external parameters. The canonical mean 

 of the force conjugate to s,. is 



(CO cxi ' 



_Zi [ + ^ 



^ 1 y (dcjl_dZ^^^dbjJi_ dZA 



_ ^ V / ^-' ^^^g ^p. 4. ^h ^'Qg^'/. 



= I 



+ 



(43) 



where P - _^^'-^^/" F - --'■^' 



where ^'"'- " 35, 3^. ' ^"-^ ~ ds^db, 



Now using the facts that 



