Sedimentation in centrifuge

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%. ... 

Sedimentation in centrifugal field 0.5 pm -10 pm Eritsch Analysette 21 (Anderson Pipette centrifuge)... 

Sedimentation in Centrifuges In a cylindrical vessel with a diameter d<-yi that rotates with a rotational frequency n (rotations per unit time), the centrifugal acceleration acentrifugai to which the particles are subjected is ... 

Packed red cells are prepared from whole blood. These are collected ia blood coUectioa units having integrally attached transfer packs. The red cells are sedimented by centrifugation, and the plasma and huffy coat are expressed from the bag. Further processiag of the packed red cells may be needed for a number of clinical indications. To reduce the white blood cell (WBC) contamination in a red cell product, two separation techniques are used. 

Sedimentation Equipment. Centrifugal sedimentation equipment is usually characterized by limiting flow rates and theoretical settling capabihties. Feed rates in industrial appHcations may be dictated by Hquid handling capacities, separating capacities, or physical characteristics of the soHds. Sedimentation equipment performance is illustrated in Figure 8 on the basis of nominal clarified effluent flow rates and the appHcable values. The... 

FIG. 18-138 Principl es of centrifugal separation and filtration (a) sedimentation in rotating imperforate bowl (h) Bltration in rotating perforate basket. 

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. 

White blood cells, red blood cells and cultured fibroblasts are commonly used to measure enzyme activities, especially for the diagnosis of inherited enzyme abnormalities. Leukocytes may be collected by sedimentation in viscous media such as Fycol. The collection of red cells presents no problem following centrifugation of anticoagulated blood. The assay of enzymes and fibroblasts requires appropriate tissue culture facilities and extensive experience in dealing with cultured human cells. 

Carrots (Boleo) were peeled by 2% NaOH at 88-96°C for 4 minutes, minced by a meat mincer (2 mm) and homogenised for 2 minutes by an ULTRA-TURRAX T25 homogenizer (from Jahne Kunkel). The carrot mash was preheated to 45°C (20 minutes) before the enzyme preparations, 25 mg enzyme protein/kg mash, were added. The enzymes were dissolved in water to give a dilution of 5% (v/v) of the carrot mash. The mash was incubated at 45°C under stirring (60 rpm) for 2 hours, before the enzymes were inactivated at 86°C for 5 minutes in a microwave oven. Finally the purees were homogenised for 1 minute by ULTRA TURRAX. The viscosity of the puree was measured by a BROOKFIELD viscosimeter Model DV-n + with spindle A from HELIPATH SPINDLE SET at 2.5 rpm thermosta-ted at 50°C. The stability of the puree was measured as the sediment (in %) after centrifugation in 10 ml tube a 1660 x g for 10 minutes. 

If the motion of the molecule is one of translation, as it is during sedimentation in a centrifugal field, the velocity of every bead is the same, and in the free-draining case the difference in velocity Aw, for each bead relative to the solvent is the same as the (relative) translational velocity u of the molecule as a whole. Fig. 138 is illustrative of this case. The total force on the molecule is then... 

Urine, for Trichomoniasis Prepare two films from sediment. Fix in Schaudinn or PVA fixative. Preserve the remainder of sediment in 10% Formalin. Centrifuge. Cover the sediment with sterile saline and send it on ice (not frozen) for direct mounts and culture. 

Sputum, for Nematode larvae or Paragonimus eggs Break up mechanically or digest 1 part sputum plus 5 parts 3% NaOH for 1 h. Centrifuge, and preserve the sediment in an equal volume of 10% buffered Formalin. 

Cytocentrifugation is used to prepare additional non-gynecologic specimens containing little or nonvisible sediment after centrifugation. This method is used in addition to the monolayer concentration technique for immunohisto-chemistry staining. 

The pyrogenic flame hydrolyzed silica Aerosil 200, a commercial product from Degussa, was used as a dispersion in doubly distilled water (1). The precipitated silica was prepared by hydrolysis of orthosilicic acid tetraethylester in ammoniacal solution according to the method of Stober, Fink and Bohn (11). The prepared suspension was purified by repeated centrifugation, separation from solvent and redispersion of the sediment in fresh water. Finally, the water was evaporated and the wet silica dried at 150°C for about half an hour. 

Figure 7.7. Expression of CR3 in neutrophils in unfractionated blood and after isolation. The expression of CD1 lb was measured in neutrophils in (i) unfractionated whole blood, (ii) after isolation using Mono-Poly resolving medium and (iii) after isolation using dextran sedimentation and centrifugation in Ficoll-Hypaque. Further experimental details may be found in Watson, Robinson Edwards, 1992.

Figure 3.38 Centrifugal effects. The path of a particle unimpeded by frictional effects is at a tangent (A) to the circle described by the rotation of the centrifuge tube. When impeded by friction, its path (B) more closely resembles circular movement with a reduced rate of sedimentation in the tube.

Another technique consists of submitting the emulsion to centrifugation and determining the droplet volume fraction < / at the top (bottom) of the cream (sediment). The centrifugation typically takes several hours until the equilibrium volume fraction is achieved. After equilibration, if the droplets occupy a distance much less than that of the centrifuge lever arm, the spatial gradient in the acceleration can be neglected, and the osmotic pressure can be determined (see Fig. 4.1) ... 

Suspend the sediment in 10 ml of Soln. C and centrifuge at 4 °C with 1500 rpm for 5 min. Repeat this step until the lymphocytes are free from thrombocytes. Dilute the lymphocyte concentrate with about 20 ml Soln. D for further experiments. 

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