Centrifugation methods

Another method of separating petrolatum from residua is by centrifuge dewaxing. In this process, the reduced cmde oil is dissolved in naphtha and chilled to —18° C or lower, which causes the wax to separate. The mixture is then fed to a battery of centrifuges where the wax is separated from the Hquid. However, the centrifuge method has been largely displaced by solvent dewaxing methods as well as more modem methods of wax removal. Similar use is... 

In conventional chemical pulping systems, micronized talc is used for pitch control. The mechanism is not well understood, but talc does adsorb on the pitch and detackify it, preventing it from agglomerating and attaching on equipment. In de-inking talc is used both to enhance ink removal in conventional screening/centrifugation methods and as a carrier in flotation systems. 

Centrifugation methods separate macromolecules on the basis of their characteristic densities. Particles tend to fail through a solution if the density of the solution is less than the density of the particle. The velocity of the particle through the medium is proportional to the difference in density between the particle and the solution. The tendency of any particle to move through a solution under centrifugal force is given by the sedimentation coefficient, S ... 

Temperature 20°C, equilibrium dialysis, small unilamellar vesicles (DOPC), 0.1 M KC1 [382]. Centrifugation method (15 min, 150,000 g), brush-border membrane vesicles [433]. 

For fine suspended solids with particles that are too small to be separated from the liquid by gravitational or centrifugal methods, a barrier method such as a filter may be used. The liquid is passed through a filter medium (usually a cloth or screen) that provides a support for the solid particles removed from the slurry. In actuality, the pores in the filter medium are frequently larger than the particles, which penetrate some distance into the medium before being trapped. The layer of solids that builds up on the surface of the medium is called the cake, and it is the cake that provides the actual filtration. The pressure-flow characteristics of the porous cake primarily determine the performance of the filter. 

CNTs can conjugate with nucleic acids via non-covalent bond. ssDNA, short double-stranded DNA and total RNA molecules can attach to the surface of CNTs and can disperse CNTs in aqueous environment. The poly(30T) has the highest dispersion efficiency (Zheng et al., 2003). For example, 1 mg DNA molecules mix with lmg CNTs in 1ml water, yield at most 4mg/ml CNT solution. DNA-CNT complexes can be purified or isolated by electronic properties such as agarose gel electrophoresis and centrifuge method (Cui et al., 2004a Karajanagi et al., 2004). 

Isolation of Cells for Transport Studies Use of nonequilibrium thermodynamics in the analysis of transport general flow-force relationships and the linear domain, 171, 397 cell isolation techniques use of enzymes and chelators, 171, 444 cell separation by gradient centrifugation methods, 171, 462 cell separation by elutriation major and minor cell types from complex tissues,... 

BS W Bottoms, Sediment, and Water. This centrifuge method is used to measure the approximate amount of suspended solids and water in crude oil and petroleum products. 

Twenty-five years ago the dewaxing processes available to the refiner of lubricating oils were the cold pressing method applicable only to low viscosity distillates and the cold settling and centrifuge methods applicable to certain residual oils. A vast amount of... 

The nitration is performed without stirring, and hence with a more concentrated nitric acid than in the centrifugal method, so that the process proceeds more rapidly. The temperature of the acid is 24-25°C. A charge of 14-18 kg of cotton is immersed in the acid so that it is spread uniformly throughout the vessel. The proportion of cotton to acid varies within the range 1 30 to 1 38. 

CA 47, 4781(1953)(Rapi(i analysis by centrifugal method) l6)Riegel, ChemMach... 

Jaurequi, C.A., Regenstein, J.M., and Baker, R.C. 1981. A simple centrifugal method for measuring expressible moisture A water-binding property of muscle foods. J. Food Sci. 46 1271 -1273. 

Hogeboom, Schneider, and Palade refined the differential centrifugation method for fractionation of cell parts. 

Some of the disadvantages were overcome by the use of the colloidal probe technique to measure adhesion forces (review Ref. [216]). The colloidal probe technique offers the advantage that the same particle can be used for a series of experiments and its surface can be examined afterwards. The accessible range of particle size is typically limited to a range between 1 /zm and 50 pm. The tedious sample preparation, limits the number of different particles used within one study, for practical reasons. Therefore the colloidal probe and centrifugal methods complement each other. 

Figure 6.20 Schematic of the centrifuge method to determine adhesion forces of particles on surfaces. Friction forces can also be analyzed when the particles are placed on at a horizontal surface.

We wish to report data on a series of whole coals and coal macerals using conventional CP/MAS, dipolar dephasing, and 2-D dipolar dephasing techniques. These data provide a wealth of new structural information and demonstrate that multiple pulse and 2-D spectroscopic techniques can be utilized on complex carbonaceous materials. We also report data obtained on maceral samples separated by the density gradient centrifugation method which separates coal maceral groups according to density. 

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