Prescribed Diffusion Treatment

In an early attempt, Mozumder (1968) used a prescribed diffusion approach to obtain the e-ion geminate recombination kinetics in the pure solvent. At any time t, the electron distribution function was assumed to be a gaussian corresponding to free diffusion, weighted by another function of t only. The latter function was found by substituting the entire distribution function in the Smoluchowski equation, for which an analytical solution was possible. The result may be expressed by 

In the general case, whether the e-ion pair is isolated or not, the probability density P(r, t) that an electron will remain extant at time t is given by the Smoluchowski equation 

Equation (7.30) shows that the fundamental information on recombination kinetics is contained in the solution of the scavenger-free case, from which the recombination kinetics with a scavenger may be obtained via an exponential transformation. The scavenger reaction probability is now given by 

Mozumder (1971) calculated F(t) by the prescribed diffusion method. For the isolated ion-pair case, the solution appears in (7.28) for the multiple ion-pair case, further approximation was introduced in the nature of mean force acting on an electron, by which the problem was reduced to that of a collection of isolated 

Chapter 7 Spur Theory of Radiation Chemical Yields 

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Of the drug that is administered in eye-drops, 80% diffuses into the general circulation and can have systemic effects, even when low concentrations are used (1). The lacrimal pump is the essential route of diffusion from eye-drops into the systemic circulation, through active cellular absorption in the lacrimal secretory pathways. The active ingredient avoids first-pass metabohsm and reaches its site of action directly, resulting in increased systemic availability. All the same, this form of treatment is generally very well tolerated, when one bears in mind the immense volume of eye-drops prescribed by ophthalmologists each day. 

To make a transformer steel with the proper hysteresis characteristics, it has to be loaded with silicon up to a certain prescribed content. This is accomplished by exposing a steel sheet that is low in silicon content and of 2 mm thickness to an atmosphere of SiQ4 that dissociates to Si(g) and Cl2(g). The silicon gas dissolves in the steel up to 3 wt% at equilibrium. The treatment is to be carried out at 1255 K. Silicon diffusivity in steel at this temperature is 8.2 X 10 m /s. 

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