Secondary gravitational field

As a real case, the primary electric field can be applied, for example, to generate the density gradient in a suspension of charged colloidal particles and can be coupled with a secondary gravitational field to focus the components of the separated sample that practically are not affected by the primary electric field. 

In the previous chapters our attention was paid mainly to the study of the figure of the earth and with this purpose in mind we represented the total field as a sum of the normal and secondary fields. In this chapter, we will discuss a completely different application of the gravity method, related to exploration geophysics, in which the gravitational field is measured in order to study lateral changes of the density near the earth s surface. By analogy, we also represent the gravitational field as a superposition of two fields ... 

An important conclusion can be drawn from this computer simulation. The operational variables of focusing FFF experiments using a coupling of two effective field forces can be chosen in such a way that in many practically important cases, the natural gravitation can be exploited as a secondary field to focus the components of the separated sample. The apparatus and the experimental procedure to perform such a separation is very simple and inexpensive compared with classical centrifugation. The condition necessary to realize such a separation is that... 

---