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Data on aerodynamic capture of particles are used to estimate efficiency of collection of pollen grains and spores by falling raindrops. Simple probability arguments then yield the fractional removal of airborne pollens and spores by rain. Pollen grains are generally large enough to be washed out by all but the lightest showers of large thunderstorm-type drops; smaller-sized spores experience lower removal rates. Various specialists concerned with pollen dissemination will find rain-scavenging a significant process.

Vitamin D(3)-(3)H has been administered intravenously to seven normal subjects, three patients with biliary fistulas, and four patients with cirrhosis. Plasma D(3)-(3)H half-times normally ranged from 20 to 30 hours. in vivo evidence that a metabolic transformation of vitamin D occurs was obtained, and a polar biologically active vitamin D metabolite was isolated from plasma. Urinary radioactivity averaged 2.4% of the administered dose for the 48-hour period after infusion, and all the excreted radioactivity represented chemically altered metabolites of vitamin D. The metabolites in urine were mainly water-soluble, with 26% in conjugated form. From 3 to 6% of the injected radioactivity was excreted in the bile of subjects with T-tube drainage and 5% in the feces of patients having no T-tube. The pattern of fecal and biliary radioactivity suggested that the passage of vitamin D and its metabolites from bile into the intestine represents an essential stage for the fecal excretion of vitamin D metabolites in man. Abnormally slow plasma disappearance of vitamin D(3)-(3)H in patients with cirrhosis was associated with a significant decrease in the quantity and rate of glucuronide metabolite excretion in the urine.

Easily wettable pollen particles (contact angle theta < 90(o)) can be distinguished from poorly wettable particles (theta > 90(o)) by a simple laboratory test. Although some differences in degree of wettability were observed among the 15 pollens tested, all were wettable and most were strongly wettable. Grain wettability is not likely to suppress rain-scavenging efficiencies.