Centrifugation relative centrifugal force

Serum separator tubes are available (Table 2-2) that contain an inert, thixotropic, polymer gel material with a specific gravity of approximately 1.04. Aspiration of blood into the tube and subsequent centrifugation displace the gel, which settles like a disk between cells and supernatant when the tube is centrifuged. Relative centrifugal force (RCF) must be at least 1100 Xg for gel release and barrier formation. Release of intracellular components into the supernatant is prevented by the barrier for several hours or, in some cases, for a few days. These separator tubes may be used as primary containers from which serum can be directly aspirated by a number of analytical instruments. 

The centrifugal force produced increases the impeller static pressure [the first term of the right-hand side of Eq. (9.79)] and reduces the relative velocity U2 To increase the static pressure by a change in the relative velocity, the following relationship is necessary ... 

A cyclone separator is an economical device for removing particulate solids from a fluid system. The induced centrifugal force (see Figure 7-6) is tangentially imparted on the wall of the cyclone cylinder. This force, with the density difference between the fluid and solid, increases the relative settling velocity. 

The first pseudo force, Fi, is called the Coriolis force, and its magnitude is directly proportional to the angular velocity of the rotating frame of reference and the linear velocity of the particle in this frame. By definition, this force is perpendicular to the plane where vectors Vi and o are located, Fig. 2.3a, and depends on the mutual position of these vectors. The second fictitious force, F2, is called the centrifugal force. Its magnitude is directly proportional to the square of the angular velocity and the distance from the particle to the center of rotation. It is directed outward from the center and this explains the name of the force. It is obvious that with an increase of the angular velocity the relative contribution of this force... 

As follows from these formulas, at a finite distance from the earth the potential of the centrifugal force, as well as its first derivatives, have finite values and are continuous. The fact that Uc and grad Uc increase unlimitedly with an increase of x and y should not confuse us because our study takes place either on the earth s surface or relatively close to it. Besides, as we know, the value of co is very small. In this light it is proper to notice that the earth s figure is mainly defined by the force of attraction because the influence of rotation is very small. As concerns the Lapla-cian, that is, a sum of second derivatives, it is constant outside the earth. 

An unknown event disturbed the equilibrium of the interstellar cloud, and it collapsed. This process may have been caused by shock waves from a supernova explosion, or by a density wave of a spiral arm of the galaxy. The gas molecules and the particles were compressed, and with increasing compression, both temperature and pressure increased. It is possible that the centrifugal forces due to the rotation of the system prevented a spherical contraction. The result was a relatively flat, rotating disc of matter, in the centre of which was the primeval sun. Analogues of the early solar system, i.e., protoplanetary discs, have been identified from the radiation emitted by T Tauri stars (Koerner, 1997). 

The particles are subject to centrifugal, inertial, and drag forces as they are carried in the spriraling flow, and it is assumed that the particles that strike the outer wall before the fluid reaches the vortex finder will be collected. It is assumed that the tangential velocity of the particle is the same as that of the fluid (Vp0 = Ve) but that the radial velocity is not (Fpr Vr), because the particles move radially toward the wall relative to the fluid. The centrifugal force acting on the particle is... 

Relative centrifugal force is a measure or the intensity of centrifugal force compared with that due to gravity. 

The effect of centrifugation is therefore dependent upon the mass of the particle and the convenience of using the relative centrifugal force is that the value for the mass of the particle is eliminated from the equation, permitting more general comparisons of centrifuge performance ... 

In comparing the relative centrifugal force developed by different centrifuges it is important to appreciate that the value varies considerably from the top to the bottom of a centrifuge tube (Figure 3.39). 

Figure 3.39 Relative centrifugal force. The relative centrifugal force developed by any rotor can be calculated but will vary depending upon the distance from the centre of rotation.

During ultracentrifugation, when the frictional force equals the centrifugal force and the particle achieves maximum velocity, the relative molecular mass... 

The position of the liquid interface is determined by balancing centrifugal forces as in Figure 9.3. The lip, of radius rw, over which the denser liquid leaves the bowl is part of a removable ring. Various sizes maybe fitted to provide for the separation of liquids of various relative densities. 

It is the aim of this section to offer but a brief introduction to this relatively new field of endeavour that will surely have a not inconsiderable role in shaping the whole future of both physical and chemical processing. It may be noted at the outset, however, that it is not the use of centrifugal forces which is a relatively new development, but rather their application in spinning discs and indeed, centrifugal devices are already widely used in processing, as indicated by the following examples ... 

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