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Biomedical subjects

J O Ledbetter

Publications and source records attributed to J O Ledbetter.

5 recordsLinked to original sources
PubMed1979

Calibration testing of the jet filter as a respirable sampler.

This work was done to determine whether the jet filter can satisfactorily serve as a respirable sampler. Monodisperse polystyrene latex (PSL) spheres, crushed quartz particles, and hot-mix asphalt plant dust were used to calibrate the jet filter. The deposition characteristics for the sampler matched those specified by standards quite well for the PSL and the crushed quartz particles, i.e., those particles with optical and equivalent aerodynamic diameters near the same. The jet filter can meet its original design purpose - respirable sampling of radioactive aerosols. The sampler can also be used in gravimetric determinations by cutting the filter into two parts for weighing - the center portion with the non-respirable and the outer annulus with the respirable fraction.

Calibration↗
PubMed1978

Effects from past solid waste disposal practices.

This paper reviews documented environmental effects experience from the disposal of solid waste materials in the U.S. Selected case histories are discussed that illustrate waste migration and its actual or potential effects on human or environmental health. Principal conclusions resulting from this review were: solid waste materials do migrate beyond the geometric confines of the initial placement location; environmental effects have been experienced from disposal of municipal, agricultural, and toxic chemical wastes; and utilization of presently known science and engineering principles in sitting and operating solid waste disposal facilities would make a significant improvement in the containment capability of shallow land disposal facilities.

Environmental Pollution↗
PubMed1975

A drainage wind flow model.

A method of predetermining drainage wind velocities is derived in the form of an incremental velocity model. The model requires the topographical data and a general description of surface roughness. Using these fixed inputs with the model yields velocity factors. Velocity factors are determined as a function of height above the terrain and elapsed time since the occurrence of the maximum surface temperature. The velocity factors multiplied by a cooling factor give velocities. Time or space mean velocity may be found by summation techniques. By computing velocity factors for several points within an area of concern, one can determine drainage flow patterns and pollutant movements for any given night.

Air Movements↗
PubMed1975

Droplet size of cooling tower fog.

Fog from cooling towers causes problems of visibility and icing along roadways adjacent to the towers; moreover, the visible plume from the towers offers difficulty in that it is equated by much of the public with air pollution. It is desirable to know the size of the fog droplets in order to plan abatement procedures and to determine the airborne lifetimes of such fogs. The methodology involved capturing the droplets on slides coated with a vaseline-mineral oil mixture, making photomicrographs of the droplets, counting and sizing the droplets into eight droplet diameter increments; namely less than 5 mum, 5-10 mum, 10-20 mum, 20-40 mum, 40-60 mum, 60-80 mum, 80-100 mum, and greater than 100 mum. The resulting distribution was similar to that for natural fogs and clouds; i.e., it was bi-modal, the first mode at less than 5 mum containing the vast majority of the droplets, and the second at 20-40 mum. This study agrees with others that the size distribution of a fog in a saturated environment is continuously changing, with the smaller droplets tending to evaporate and the larger ones tending to grow, thus shifting the second mode toward larger sizes.

Air Pollution↗