Centrifugal force field

Every method, with the exception of imaging technologies, provides the measurement of an equivalent spherical diameter in one form or another. The spherical diameter information can be deduced indirectiy from the behavior of the particles passing through restricted volumes or channels under the influence of gravity or centrifugal force fields, and from interaction with many forms of radiation. 

Differences in mobilities of ions, molecules, or particles in an electric field can be exploited to perform useful separations. Primary emphasis is placed on electrophoresis and dielec trophoresis. Analogous separation processes involving magnetic and centrifugal force fields are widely apphed in the process industiy (see Secs. 18 and 19). 

Sedimentation coefficients are a measure of the velocity witli which a particle sediments in a centrifugal force field. Sedimentation coefficients are typically expressed in Svedbergs (.symbolized S), named to honor The Svedberg, developer of the ultracentrifuge. One S equals 10 . sec. 

The objective of this paper is to illustrate the efficacy of inferring the interdroplet forces in a concentrated protein stabilized oil-in-water emulsion from the knowledge of the equilibrium profile of continuous phase liquid holdup (or, dispersed phase faction) when the emulsion is subjected to a centrifugal force field. This is accomplished by demonstrating the sensitivity of continuous phase liquid holdup profile for concentrated oil-in-water emulsions of different interdroplet forces. A Mef discussion of the structure of concentrated oil-in-water emulsion is presented in the next section. A model for centrifugal stability of concentrated emulsion is presented in the subsequent section. This is followed by the simulation of continuous phase liquid holdup profiles for concentrated oil-in-water emulsions for different centrifugal accelerations, protein concentrations, droplet sizes, pH, ionic strengths and the nature of protein-solvent interactions. 

An Improved disc centrifuge photosedimentometer (DCP) was developed for use in the determination of the particle size and size distribution of latices, pigments and other particulates. Separation is based on Stokes Law for the sedimentation of particles in a centrifugal force field and does not rely on the use of particle size calibrants or standards. The DCP Instrument provides accurate stable particle size analyses over a wide range of conditions while at the same time is rugged enough for heavy use in both a research and quality control environment. A stand-alone data collection, analysis and management system was developed both for routine quality control operation and for research use of the instrument. 

Tiscareno-Lechuga F, Tellez C, Menendez M, and Santamaria J. A novel device for preparing zeolite—a membranes under a centrifugal force field. J Membr Sci 2003 212(1-2) 135-146. 

C f, C o, and are the solute concentrations in the mobile phase at a moment t, before equilibrium and after equilibrium, respectively), A depends on Sp, B on the physical properties of the solvent system, and b on solutes and solvent system. This variation is very interesting, because it shows that a high mobile-phase flow rate decreases the retention time without decreasing efficiency. However, it was observed that Sp decreases with the flow rate and the resolution R, also decreases as described in the following section. The flow rate of the mobile phase may be increased to decrease the separation time, but, at the condition that Sp remain satisfactory to maintain a sufficient R, [2]. Finally, it has been shown that N increases with the centrifugal force field [2]. 

Fig. 5 Analysis of centrifugal force field for type-J planetary motion, (a) Planetary motion (b) planetary motion in an x-y coordinate system for the analysis of centrifugal force (c) distribution of the eentrifugal vectors on the column holder. (From Ref. [12].)...

The design of the cross-axis CPC is based on the hybrid between type-L and type-X planetary motions, which results in an extremely complex centrifugal force field with a three-dimensional fluctuation of force vectors during each revolution cycle of the holder. The pattern of this centrifugal force field produced by the cross-axis CPC somewhat resembles that produced by the type-J planetary motion (Fig. 5c), but it is superimposed by a force component acting in parallel to the axis of the coil holder. This additional force component acts to improve the retention of the stationary phase. This beneficial effect is greatest in type-L planetary motion and becomes smallest in the type-X planetary motion. A detailed mathematical analysis on this planetary motion is described elsewhere. 

In all cases, countercurrent chromatography (CCC) utilizes a hydrodynamic behavior of two immiscible liquid phases through a tubular column space which is free of a solid support matrix. The most versatile form of CCC, called the hydrodynamic equilibrium system, applies a rotating coil in an acceleration field (either in the unit gravity or in the centrifuge force field). Two immiscible liquid phases confined in such a coil distribute themselves along the length of the coil to form various patterns of hydrodynamic equilibrium [1],... 

It should be noted that the centrifuge force field acts on the fluid in the rotated coil in parallel with other forces of different nature [5] ... 

Fi, inertial force caused by coil motion, comprises components of centrifugal force field viscosity force due to the overflow of the stationary phase along the coil tube walls... 

The performance of the hydrodynamic CCC system is remarkably improved by rotating the coil in the centrifugal force field, but this requires a planetary mo-... 

Sedimentation [22] of the disperse phase usually takes place under the force of gravity. (It may be caused also by an imposed centrifugal force field). A sphere of diameter D and density d under the influence of gravitational force Fg will have a terminal settling velocity Vts in the laminar region governed by Stake s law ... 

For analytical purposes counter-current sifting in gravitational and centrifugal force fields is normally used. The cross-current principle is also sometimes applied more often this variation is combined with counter-current sifting. The terms counter- and cross-current describe the movement of coarse particles in relation to fluid flow in the separation zone. 

From Robison, the sedimentary velocity of particles with concentration C in centrifugal force field... 

The difference schemes for particles sedimentation in centrifugal force field are shown in equation (8), (11), (12), and the direct difference format of equation (13). At a certain interval of time, the particlesconcentration and temperature and the solid fraction of every element are calculated, and then the condition under which the particles stop sedimenting is judged. The sedimentation of particles terminates when (a) the fraction of solid reach to 100% due to the solidification procedure, and (b) the volume fraction of reinforcement particles reach beyond a critical value 0.74 or 74%. ... 

In centrifugal force field, the mathematical model of reinforcement particle distribution is... 

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