where  𝑗f is the rate for the forward process of the j-th reaction and R is the gas constant. Equation (3d) indicates that  𝑗 is proportional to the thermodynamic force Aj /T when Aj /T  1; specifically, the j-th reaction is in the linear region under this condition. follows. The reaction rates at the initial stage are slightly higher than the rates of inflows of source substances in case (a), as previously mentioned. Therefore, reactions in an ORN are initially dominant and 2 starts at a high value and decreases because of decreases in Ci in the ORN. Then, inflows of source substances follow such reactions, accompanied by an increase in 1. The rates of inflow of source substances soon reach maxima and then decrease because the concentrations of source substances in the interior of an ORN increase and approach those in the exterior. Thus, 1 also reaches a peak and then decreases. Finally, increases in the concentrations of chemical substances in the ORN as a result of continuous inflows of source substances lead to an increase in the number of chemical reactions and, hence, to an increase in 2. The result in case (b) can be explained in a similar manner. Thus, the time courses of 1, 2, and  provide insight into how an ORN reaches a steady state.