Forced diffusion

Kdhler, W and Schdfer, R, Polymer Analysis by Thermal-Diffusion Forced Rayleigh Scattering. Vol. 151, pp. 1-59. 

TDFRS Thermal diffusion forced Rayleigh scattering... 

Finally, we have the diffusion force,1 which tends to be opposed to the existing gradient by thermal motion ... 

A cloud is essentially an aerosol with mobile boundaries. The stability of a cloud involves two distinct aspects. Because of Coulomb, image, and diffusion forces, particles in a given volume will flocculate. This will result... 

Schmitz et al (31) have proposed that the discrepancy between QLS and tracer diffusion measurements can be reconciled by considering the effects of small ions on the dynamics and scattering power of the polyelectrolyte. In this model, the slow mode arises from the formation of "temporal aggregates . These arise as the result of a balance between attractive fluctuating dipole forces coming from the sharing of small ions by several polyions, and repulsive electrostatic and Brownian diffusion forces. This concept is attractive, but needs to be formulated quantitatively before it can be adequately tested. 

Since N and Wj are constants for the same surfe.ce we may write this expression as (1 — di) n, where is a constant. In comparison with the enormous electrostatic field the diffusive force is negligible. Under these conditions the rate of collision is given by... 

In the absence of pressure diffusion, forced diffusion, and thermal... 

The basic expressions for the mass fluxes and the equations of continuity for multi-component mixtures are given in Sec. II,B. For a -component mixture of ideal gases in a system in which there is no pressure diffusion, forced diffusion, or thermal diffusion, the fluxes are given by... 

It is evident that the contributions due to angular movements are caused by diffusion forces corresponding to the state of orientation, whereas the radial component is a hydrodynamic contribution. The radial force, as exerted by the flowing solvent, is balanced by the rigidity of the rod and has no consequences for the birefringence of orientation. According to eqs. (5.15), one obtains for rigid dumb-bells ... 

To determine the concentration at the "crossover" point (where stable and unstable regions of the front intersect), the method of Leavitt (4) can be used, provided the carrier gas is essentially unadsorbed, and axial diffusion forces and thermal conductivities are negligible (see the aforementioned reference for the corrections for these latter effects). For such a case, an energy balance across the stable and unstable portions of the front, along with relations to describe the equilibrium loadings at the extrema of these fronts (for example, the LRC model) can be combined to solve for the crossover concentration. The energy balance across each front takes the form ... 

Polymer Analysis by Thermal-Diffusion Forced Rayleigh Scattering... 

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