A new extraction procedure is applied here to radioimmunoassay of serum estradiol. Small columns packed with porous, grainy kieselguhr are loaded with the samples. The kieselguhr material acts as support for the water phase, from which the lipophilic compound estradiol is eluted with diethyl ether. With use of a specially constructed rack, several columns can be handled simultaneously, which ma...

The effect of solar radiation on a natural bacterial population from the Chesapeake Bay was evaluated from measured changes in numbers of organisms engaged in amino acid uptake. From July through May, freshly collected water samples were exposed in quartz containers to 3.5 h of total sunlight both with and without UV-absorbing filters. Water samples were subsequently incubated with tritiated am...

Path integral simulations have been performed to determine the temperature of the maximum in density of water of the rigid, nonpolarizable TIP4PQ/2005 model treating long range Coulombic forces with the reaction field method. A maximum in density is found at 280 K, just 3 K above the experimental value. In tritiated water the maximum occurs at a temperature about 12 K higher than in water, in r...

Evaporative water losses (EWL) in arthropods have traditionally been measured by gravimetric methods (Loveridge, 1980), although electronic sensing of water has recently been employed (Hadley, Stuart & Quinlan, 1982; Hadley & Quinlan, 1982). Difficulties are encountered in separating the cuticular and respiratory components of total transpiration. Cuticular water loss has frequently been measur...

By EFSTRATIOS S. KURTIDES, WALTER A. RAMBACH AND HOWARD L. ALT T HE INCORPORATION of tritiated thymidine by the rat spleen is an accurate and reliable index of erythropoiesis under certain well-defined experimental conditions.1 Since tritiated thymidine uptake by various tissues reflects DNA synthesis, and therefore proliferative activity, changes in the latter will be reflected by parallel cha...