Injectivity models

The active back-arc extension in the Okinawa Trough and the Taupo Depression in New Zealand can be explained by the injection model. 

Xu H, Eddinsaas NC, Suslick KS (2009) Spatial separation of cavitatin bubble populations The nanodroplet injection model. J Am Chem Soc 131 6060-6061... 

Two mechanisms are possible for dye sensitization. In one, direct electron injection from the excited dye level into the conduction band of the silver halide occurs. An extensive series of experiments varying the relative positions of the dye HOMO and LUMO levels with respect to the silver halide valence and conduction band positions has established the validity of the direct electron injection model [11], In this mechanism (Fig. 4), the dye molecular orbital levels (HOMO and... 

The flow through the reservoir begins with Darcy s law, which is described in detail in many books on reservoir engineering (such as Craft and Hawkins, 1959). Clearly the results presented in this section are simplified, but they provide insights into the injection modeling for acid gas injection projects. 

Figure 11.9 Normalised comparison of electron absorption dynamics of N3-sensitised Ti02 films in ethylene/propylene carbonates (1 1) following excitation at different wavelengths. Inset the same data plotted on a shorter time scale. The solid lines are fits using the two-state injection model. The fast component is well described by a <100 fs rise and the slow component is fitted by a stretched exponential function with a 50 ps time constant. Reproduced with permission from J. Phys. Chem. B 107, 7376 (2003) (Asbury et al, 2003). Copyright 2003 American Chemical Society.

The one-compartment bolus IV injection model is mathematically the simplest of aU PK models. Drug is delivered directly into the systemic circulation by a rapid injection over a very short period of time. Thus the bolus rV injection offers a near perfect example of an instantaneous absorption process. Representation of the body as a single compartment implies that the distribution process is essentially instantaneous as well. The exact meaning of the assumptions inherent in this model are described in the next section. Model equations are then introduced that allow the prediction of plasma concentrations for drugs with known PK parameters, or the estimation of PK parameters from measured plasma concentrations. Situations in which the one-compartment instantaneous absorption model can be used to reasonably approximate other types of drug delivery are described later in Section 10.7.5. 

The two-compartment bolus IV injection model is somewhat more mathematically complex than the one-compartment bolus IV injection model. As in the one-compartment model, drug is delivered directly into the systemic circulation by a rapid injection over a very short period of time. However, the body is now represented by two compartments, called compartment 1 and compartment 2. The systemic circulation is always included in compartment 1, commonly called the central compartment, which additionally contains any tissues that come to instantaneous (or rapid) equilibrium with the systemic circulation. The tissues in compartment 2, commonly called the tissue compartment, take substantially more time to reach equilibrium with the circulation. Two-compartment models also have an additional complexity that two different types of rate constants must be defined. Micro rate... 

Figure 10.56 Graphical representation of the amount of drug in compartment 1 (/4i) versus time (f) and ln(/4i) versus f for a two-compartment bolus IV injection model.

The two-compartment zero-order absorption model is more complex and harder to work with than the one-compartment zero-order absorption model. Thus the one-compartment model is often used when it provides a reasonable approximation to the two-compartment values. In fact, the one-compartment model is often used even when a drug is known to significantly deviate from single compartment kinetics. Just as in the case of the two-compartment bolus IV injection model in Section 10.10.5.3, as a general rule of thumb the one-compartment model can be employed with reasonable accuracy as long as < 2 82- When this simplification is used, the one-compartment IV infusion equations in Section 10.8 can be used without modification for an IV infusion, or with the modifications listed in Section 10.11.5.1 for steady extravascular delivery. 

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