Aerosols centrifuges

For determination of the aerodynamic diameters of particles, the most commonly apphcable methods for particle-size analysis are those based on inertia aerosol centrifuges, cyclones, and inertial impactors (Lundgren et al.. Aerosol Measurement, University of Florida, Gainesville, 1979 and Liu, Fine Paiiicles—Aerosol Generation, Measurement, Sampling, and Analysis, Academic, New York, 1976). Impactors are the most commonly used. Nevertheless, impactor measurements are subject to numerous errors [Rao and Whitby, Am. Ind. Hyg. A.s.soc.]., 38, 174 (1977) Marple and WiUeke, "Inertial Impactors, in Lundgren et al.. Aerosol Measurement and Fuchs, "Aerosol Impactors, in Shaw, Fundamentals of Aerosol Sci-... 

Menon, V.B., P. Kotrappa and D.P. Bhanti, A Study of the Attachment of Thoron Decay Products to Aerosols using an Aerosol Centrifuge,... 

In an aerosol centrifuge, particles are made to follow circular paths until they strike the outer wall of the unit. The distance from the inlet that a particle is deposited is indicative of particle size. This can be shown as follows ... 

Aerosol centrifuges are useful in the laboratory but have little application in air cleaning. When care is taken so that the aerosol enters the rotating annulus at a single point, the units are often called aerosol spectrometers. A discussion of the calibration and operation of the popular Stober spectrometer design (Stober and Flachsbart, 1969) is given by Martonen (1989). 

Concentrations and size distributions can also be determined by centrifuging. In the aerosol centrifuge, an aerosol is introduced into a rotating chamber and centrifugal force is used to move particles to the outer wall where they are deposited and collected. The deposit location, in terms of distance from the entrance slit, is related to the particle size. Aerosol centrifuges have been used to determine particle size distributions of aerosols having particle sizes ranging from about 0.05 to 3.0pm [131]. 

All elutriation devices that act as spectrometers have two gas streams an aerosol stream and a clean carrier gas stream. Consequently, they are susceptible to cloud settling and instability effects. Aerosol centrifuges (see Section 3.9) are particularly susceptible because of the high centrifugal acceleration they exert on the particles and gas streams. 

Asgharian, B. and Godo, M.N. (1999). Size separation of spherical particles and fibers in an aerosol centrifuge. Aerosol Sci Tech 30 383-400. 

Equipment PCR machine, scintillation counter, tabletop centrifuge, temperature-controlled water baths, equipment for horizontal and vertical electrophoresis, UV-illuminator, phosphor imager, automatic DNA sequencer, vacuum dot-blot manifold (Schleicher and Schuell). PCR 0.5 ml hot-start mbes, aerosol resistant pipette rips, autoclaved Eppendorf tubes (all from Fischer Scientific, Brightwaters, NY) and glassware, diethyl pyrocarbonate (DEPC, Sigma)-treated solutions. 

Centrifugation and blending of products can lead to aerosol formation and containment of such activities to prevent transfer of live microorganisms is necessary. 

Tests with Aerosol Sprays. One of the chief means of applying concentrated oil sprays is in aerosol form. An aerosol generally remains suspended in the air for some time and is carried by normal wind or air currents. Aerosols are probably best adapted to interior applications but have been used with some success outdoors. They may be produced by liquefied-gas formulations released through capillary nozzles, by steam and air atomization, by centrifugal disks and rotors, by extremely high pressure, and by heat vaporization. 

The theoretical basis of the cylindrical centrifuge is a straightforward application of force balance on particles in the annulus. If the centrifugal force acting on the particle is constant, the length from the entrance where a particle of given size is deposited is proportional to the aerosol flow rate, but inversely proportional to rotation speed and the square of the particle radius. These relationships are borne out by deposition experiments using particles of known radius and density. 

The SISAK (Short-lived Isotopes Studied by the AKUFVE-technique, where AKUFVE is s Swedish acronym for an arrangement of continuous investigations of distribution ratios in liquid extraction) system performs continuous liquid-liquid extractions using small-volume separator centrifuges [66]. Activities are delivered to the apparatus with an aerosol... 

A He(KCl)-jet transportation system was used for the transfer of the activities. The KC1 aerosol with the reaction products was collected by impaction on a Pt or Teflon slip for 60 or 90 s, was picked up with lOpL of the aqueous phase and was transferred to a 1 mL centrifuge cone containing 20 iL of the organic phase. The phases were mixed ultrasonically for 5 s and were centrifuged for 10 s for phase separation. The organic phase was transferred to a glass cover slip, was evaporated to dryness on a hot plate, and was placed over a passivated ion-implanted planar silicon detector (PIPS). This procedure took about 1 min. 

Both cyclones and centrifugal rotor devices remove particles of larger aerodynamic diameter by impaction induced by abrupt changes in aerodynamic flow lines, followed by collection of the liquid water out of the flow stream. Coarse aerosol particle (> 2.5 pm diameter) distributions usually overlap the lower end of cloud droplet distributions, hence are removed to a substantial extent in the... 

One way to remove these particles from air is to subject them to high centrifugal forces. If an aerosol particle is caused to move in a circular path, it will have a radial acceleration given by Eq. 7.1. This radial acceleration can be likened to the acceleration due to gravity in a gravitational field. By rotating the aerosol, accelerations many times that of gravity can be achieved. 

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