High reactive regime

Figure 3 Dynamic recrossmgs m the low and high friction regimes. Recrossmgs back to the reactive state lead to a lowering of the rate constant below the transition state theory value.

Polymerization reactions of multifunctional monomers such as those used in dental restorations occur in the high crosslinking regime where anomalous behavior is often observed, especially with respect to reaction kinetics. This behavior includes auto acceleration and autodeceleration [108-112], incomplete functional group conversion [108,109,113-116], a delay in volume shrinkage with respect to equilibrium [108, 117,118], and unequal functional group reactivity [119-121]. Figures 3 and 4 show a typical rate of polymerization for a multifunctional monomer as a function of time and conversion, respectively. Several distinctive features of the polymerization are apparent in the rate profiles. 

In general, the concepts of bistability and hysteresis are related not only to the reaction kinetics but also to the time scale of the experiment. For this reason, the lattice size corresponding to the boundary between small and large lattices depends on the time scale of the experiment as well. MC simulations [66] indicate that often the boundary size is about 5x5. For somewhat larger lattices, one can observe the fluctuation-driven transitions between the high- and low-reactive regimes [42]. 

The first-generation MAO inhibitors phenelzine (19)and tranylcypromine (23) act as substrates for MAOA and MAOB but are converted by the enzyme to highly reactive intermediates that then react irreversibly with the enzyme to cause an irreversible inhibition. of activity. Recovery of MAO activity after exposure to these MAO inhibitors requires the synthesis of new enzyme protein, a process that takes some weeks to completely restore activity (173, 174). A clinical antidepressant response is associated with an inhibition of platelet MAO activity of approximately 80%, and measurement of platelet MAO activity can be used to monitor treatment dose regimes (175). 

In isodesmic polymerizations, the individual monomers associate with an association constant that is independent of the polymer size. This is comparable to the simplest description of a step-growth polycondensation given by Flory s principle of equal reactivity [10]. The mechanism gives rise to a PDI of 2 in the high-concentration regime. 

There is evidence [74—77] that gas-dynamic processes behind the pressure perturbation penetrating into curved ducts or reflecting from non-planar end elements affect explosion phenomena. For these observations some highly reactive stoichiometric mixtures (characteristic time of their chemical reactions and the reaction zones are much less than for gas-dynamic processes) have been used. It reduces the complete pattern of probable interaction regimes and does not allow... 

Deflagration-to-detonation transition (DDT) The flame acceleration to great velocity (in special cases the velocity exceeds 1,0(X) m/s) followed by sudden transition to the detonation regime. DDT conditions are characteristic for mixtures of high reactivity in a geometric space contributing to the flame acceleration, for example in an obstructed volume. The reactivity is characterized by the detonation cell size, the flame velocity and the expansion ratio. 

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