Rate of passage

In membrane separations, the product S Dj is referred to as the per-meabihty, p (kmoL/m s Pa). The rate of passage of material through a membrane is referred to as flux, with symbol J . Jj is equal to Ni in the equations given above. Generally Jj has the dimensions of velocity, m/s (more conveniently, Im/s), or conventionally as /m hr, gal/ft day, or ftVft day. For most apphcations, throughput is expressed in volumes instead of moles or mass. 

A enters element 1 by eonveetion and dispersion. The output term is the rate of passage of A through the eross-seetion at 1 -i- 61. The disappearanee by reaetion is the volumetrie rate of disappearanee (-r ) times the volume of the differential element 27ir6r6l. 

Considering now the case where there is a temperature gradient in the T-direction, the rate of passage of molecules through the unit plane a-a = (2 ,N (where r 2 is some fraction of the order of unity). If the temperature difference between two planes situated a distance jX apart is (0 — O ), the net heat transferred as one molecule passes in one direction and another molecule passes in the opposite direction is c,n(0 — ff), where cm is the heat capacity per molecule. 

Considering the diffusion, in the T-direction, of one constituent A of a mixture across the plane a-a, if the numerical concentration is on one side of the plane and on the other side at a distance of jk, the net rate of passage of molecules per unit area... 

At high cuprous ion concentrations the reaction becomes zero-order in reduc-and is determined by the rate of passage of O2 from the gaseous to... 

Classically, the rate of electron transfer is determined by the rate of passage of the system over the barrier defined by the surfaces. In the semiclassical model (13) a nuclear tunneling factor that measures the increase in rate arising from... 

The efficiency of screening is defined as the ratio of the mass of material which passes the screen to that which is capable of passing. This will differ according to the size of the material. It may be assumed that the rate of passage of particles of a given size through the screen is proportional to the number or mass of particles of that size on the screen at any... 

Permeability is a measure of the rate of passage of gas or liquid through a material. Diffusion is the movement of material from one chemical potential to another. Thus, these two terms... 

The rate of passage through the gastrointestinal tract exerts an important influence on the intake and digestibility (Poppi ef a/., 2000). Thus, digestibility is... 

Morrow, H.J. (1998) Fermentation kinetics and in vivo apparent digestibilities and rates of passage of two chop lengths of big bale silage and hay in ponies. MSc. thesis. University of Wales, Aberystwyth, 131 pp. 

Rate of passage of drugs through the liver and into the systemic circulation. 

Most substances, lipid soluble or not, cross the capillary wall at rates that are extremely rapid in comparison with their rates of passage across other body membranes. In fact, the supply of most drugs to the various tissues is limited by blood flow rather than by restraint imposed by the capillary wall. This bulk flow of liquid occurs through intercellular pores and is the major mechanism of passage of drugs across most capillary endothelial membranes, with the exception of those in the CNS. 

The quantity Aand like quantities, is the standard free energy of activation, which governs the rate of passage of a representative point in the system from A to B. It is not Gj - but Ga - Ga° (see Fig. 7.72). 

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