Controlled concentration change during

When the active centre concentrations change during propagation, the whole polymerization is non-stationary. Kinetically the process becomes more complicated and often even experimental control of the process becomes more difficult. On the other hand, a non-stationary condition can be utilized in studies of the elementary polymerization steps. To this end, the non-stationary phases of radical polymerizations are suitable, where outside these phases the process is essentially stationary [23-25]. Hayes and Pepper [26] called attention to the existence and solution of a simple non-stationary case caused by slower decay of rapidly generated cationic centres. In more complicated cases, exact analysis of the causes of a non-stationary condition is often beyond present possibilities. Information from the process kinetics is often not conclusive. It should be mentioned that, even when the condition d[Ac]/dt = 0 is strictly valid, polymerizations may be non-stationary, particularly in those cases when during propagation the more active form of the centres is slowly transformed to the less active form or vice versa. 

The fate of toxic substances within an animal is monitored in two ways first, by measuring the concentration changes during uptake from a controlled environment, and second by following the decline in concentration after exposure has ceased. The latter process is termed clearance, elimination, or depuration. 

The largest division of interfacial electrochemical methods is the group of dynamic methods, in which current flows and concentrations change as the result of a redox reaction. Dynamic methods are further subdivided by whether we choose to control the current or the potential. In controlled-current coulometry, which is covered in Section IIC, we completely oxidize or reduce the analyte by passing a fixed current through the analytical solution. Controlled-potential methods are subdivided further into controlled-potential coulometry and amperometry, in which a constant potential is applied during the analysis, and voltammetry, in which the potential is systematically varied. Controlled-potential coulometry is discussed in Section IIC, and amperometry and voltammetry are discussed in Section IID. 

Control fluid quality during use, involving checks on correct dilution and make-up, concentration and freedom from contamination in service, regular cleaning and fluid changing Provide and use appropriate personal protective equipment A high standard of personal hygiene... 

We must control concentration during these measurements of E°, since the voltage of a cell changes as concentrations change. For example, in the laboratory we studied a cell based on reaction (38) ... 

Influence of polymerization conditions upon incorporation of flavin-containing polyanion. The amount of polyanion (1) incorporated as dopant in a PPy film during electropolymerization can easily be controlled by changing the ionic strength (low molar mass salt) and/or the pH of the monomer solution. The correlation between the amount of polymer-bound flavin incorporated in the film and the concentration of the added low molar mass salt, sodium-p-toluenesulphonate (NaOTs), at pH=7 is shown... 

In general, not only the effective activation energy but also the effective order of reaction is changed during the transition from kinetic to diffusion control. According to Fick s first law, the rate of diffusion (in-terphase and intraparticlc) is proportional to the concentration gradient, i.c. it is first order. The effective reaction order observed under severe intraparticlc diffusion control approaches a value of (n + l)/2, where n is the intrinsic order of reaction. In the case that... 

Typical applications for exhaust air purification are characterized by rapid concentration changes An efficient control strategy must prevent the reaction from extinction during times of low concentrations and the catalyst from overheating and sintering during times of... 

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