Particle Counts in the Ultramicroscope

Badger, E. H. M.

doi:10.1038/157480b0

Cited by 3 publications

(3 citation statements)

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“…This investigation sets aside the lack of uniformity over longer spatial scales and focuses on finer structure-the domain where one might be more tempted to apply the results of, e.g., Scrase (1935), Badger (1946), Herdan (1960). We are testing the hypothesis that, when the background concentration is "constant", the aerosol particles are distributed perfectly randomly (i.e.…”

Section: Basic Trendsmentioning

confidence: 99%

“…There is a fair amount of literature supporting the Poisson formulation. Herdan (1960) and the sources cited therein (Badger, 1946;Fairs, 1943;Scrase, 1935) argue that Poisson statistics are appropriate for suspended particles in a fluid. Additional evidence for Poisson statistics (which can be physically interpreted as perfect spatial randomness) can be found in Green (1927) and Chapman and Ruhf (1955) (the latter of which cites the conclusions from Student, 1907).…”

Section: Introductionmentioning

confidence: 99%

“…Two of the studies (Green, 1927;Scrase, 1935) rely on particle activation prior to measurement and result in the measurements being dominated by the small particles present. One of the studies (Badger, 1946) assumes all deviations from Poisson statistics must be due to experimental error without physical justification.…”

Section: Introductionmentioning

confidence: 99%

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Spatial distributions of aerosol particles: Investigation of the Poisson assumption

Larsen

2007

Journal of Aerosol Science

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Atmospheric particulates are known to be distributed non-uniformly in space due to spatially localized sources and incomplete mixing. Many studies have extensively examined the variability of aerosol particle concentrations on diurnal, seasonal, and annual timescales. Receiving much less attention, however, are aerosol particle spatial distributions on shorter ( 5 min) temporal scales. Knowledge regarding the spatial distribution on these temporal scales is vital to fully understand and predict the properties of microphysical processes like activation, coagulation, and collision/coalescence, as well as some large-scale phenomena like radiation attenuation through a thick yet dilute layer of particles. Traditional treatments of microphysical phenomena often implicitly assume that particles are perfectly randomly distributed (obey Poisson statistics) on short temporal scales, even though this assumption may be inconsistent with observations made on longer scales. This study seeks to explicitly resolve the statistics of particle positions on a variety of temporal scales (over five orders of magnitude) to determine if and when the assumption of perfect spatial randomness can be justified in nature. Some implications of the results are discussed. ᭧

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Section: Basic Trendsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatial distributions of aerosol particles: Investigation of the Poisson assumption

Larsen

2007

Journal of Aerosol Science

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Experiments on the Accuracy of Surface Drop Bacterial Counts

Badger¹,

Pankhurst²

1960

Journal of Applied Bacteriology

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SUMMARY: A statistical experiment has shown that no significant proportion of the errors of determination of bacterial populations by the surface drop method could be attributed to the dropping technique employed. With both pure and mixed cultures the numbers of colonies/drop followed a Poisson distribution very closely. It is suggested that in order to determine bacterial populations at a consistent level of accuracy a constant number of colonies should be counted rather than a constant number of drops. Whenever it is justified, the confidence limits for the results of counts should be quoted.

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