Particles Of Different Densities Research Articles

Scavenging of Aerosol Particles by a Failing Water Drop and Calculation of Washout Coefficients

Abstract Collection efficiencies of falling water drops ranging from 0.094 to.O.254 cm in radius for silver chloride aerosol particles in nitrogen ranging from 0.15 to 0.6 μm in radius have been measured. The drops accelerated for distances ranging from 30 to 515 cm prior to entrance into the scavenging chamber. Results were extrapolated to terminal velocity. The results for the slower moving drops (30 cm acceleration distance) agreed roughly with the predictions of a theory based upon collection by Brownian diffusion. However, near terminal velocity, Brownian diffusion theory did not account for the results. Instead, for each value of particle radius a, the collection efficiency was a sharply increasing function of the impaction parameter P. Results by other workers for particles of different density agreed approximately with our values, provided comparisons were made at the same values of aρ½ where ρ is the particle density. Calculations of washout coefficient indicated that the half-life of 0.1-μm aero...

Subcellular localization of serotonin in an identified serotonin-containing neurone.

KNOWLEDGE of the subcellular localization of serotonin (5-hydroxytryptamine) in neurones is important for an understanding of the precise physiological role of this amine in nervous tissue. Some of the most pertinent pharmacological and electrophysiological data on the neuronal role of serotonin have been obtained from work with molluscs1,2. In particular there is strong evidence that the amine acts as a transmitter on one particular type of neurone in the gastropod brain2. Fractionation studies with homogenates of bivalve ganglia, which are extremely rich in serotonin, have shown that the amine is bound to particles, but associated with particles of different density from those binding acetylcholine3. The precise type of particle or particles associated with serotonin, however, is not definitely known4.

Studies on DNA from low-density particles of SV40: II. Noninfectious virions associated with a large-plaque variant

The purified virions of a large-plaque variant of SV40 consist of two classes of particles of different densities, 1.33 and 1.34 g/cm 3. The lighter virions (1.33) are noninfectious but are immunologically and morphologically indistinguishable from infectious virions (1.34). DNA from noniufectious virions is also defective. The light particles have been shown to contain circular DNA about 12% shorter than that from infectious virions. The difference in density and the defectiveness of light virions are believed to be due to the alteration in the amount of DNA contained in the virions.

Second-Order Fields near a Pulsating Source

An approximately spherical sound field of finite extent is produced in a liquid by a pulsating gas bubble. Observations of tracer particles near the bubble indicate an absence of acoustic streaming (as befits a spherical field) but the presence of radiation pressure. By the use of spherical tracer particles of different densities and compressibilities, comparisons with radiation-pressure theory can be made. At higher sonic amplitudes surface waves appear on the bubble accompanied by acoustic streaming in the nearby liquid. Measurements of the critical amplitude for the onset of these surface waves permit comparison with theory and with Eisenmenger's experimental results for parametrically excited plane surface waves. [This work was supported in part by a grant from the National Institutes of Health, Department of Health, Education, and Welfare.]