. Adventures in radioisotope research;. Radioactive tracers; Radiobiology. ARTIFICIAL ACTIVITY Oi' JIAIWII'M AM) SOMK OTllKK ELEMENTS 69 paraffin block, 1 Ik^ second one in a paraffin l)iock but Avil h 1 he preparation surrounded by a shield of cadmium, which al)Sorbed nearly 100% of the C-neutrons, and th(> 1hird one with fast neutrons. The result of the activation of the first named sample is seen from Fi^. 3b. The investig- ation of the second sample led to the result thai in the presence of. ~i I 1 1 r 20 40 60 80 100 200 days Fii^. 3. Dot-ny Curve of .Scandium InadiatL-d in a Paraffin
. Adventures in radioisotope research;. Radioactive tracers; Radiobiology. ARTIFICIAL ACTIVITY Oi' JIAIWII'M AM) SOMK OTllKK ELEMENTS 69 paraffin block, 1 Ik^ second one in a paraffin l)iock but Avil h 1 he preparation surrounded by a shield of cadmium, which al)Sorbed nearly 100% of the C-neutrons, and th(> 1hird one with fast neutrons. The result of the activation of the first named sample is seen from Fi^. 3b. The investig- ation of the second sample led to the result thai in the presence of. ~i I 1 1 r 20 40 60 80 100 200 days Fii^. 3. Dot-ny Curve of .Scandium InadiatL-d in a Paraffin Block for a) 24 h) .'>() Davs. cadmium the artificial radioactivity of scandium is reduced to 2% of the value obtained in the absence of cadmium. From Fig. 3 there follows for the half-life period of scandium the value 90 zb 5 days. Quite recently Walke (11), by making use of Lawrence's powerful cyclo- tron, bombarded scandium with deuterons and obtained a period of 85 i 2 days. We want furlhermorci to mention an early experim(>nt in which we bombarded scandium with fast neutrons emitted by a mixture ol 600 millicuries emanation and beryllium powder ; we observed a period of decay of about 50 hours. As shown by Pool, Cork, and Thornton (8).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hevesy, Georg von, 1885-1966. New York, Pergamon Press
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