Vernon N. Kerr

LIQUID SCINTILLATORS. III. THE QUENCHING OF LIQUID-SCINTILLATOR SOLUTIONS BY ORGANIC COMPOUNDS

Abstract A study has been made of the quenching characteristics of a large number of selected organic compounds in a few commonly encountered liquid scintillator solutions. From this it should be possible to anticipate the quenching difficulties associated with homogeneous liquid scintillation counting.

Synthesis of polydeoxynucleotides using chemically modified subunits

Abstract New approaches have been explored for enzymatic preparation of polydeoxynucleotides involving a variety of chemically synthesized 5′-triphosphates. Calf thymus terminal deoxynucleotidyltransferase utilized N4-acetyldeoxycytidine 5′-triphosphate, N6-isobutyryldeoxyadenosine 5′-triphosphate and deoxyuridine 5′-triphosphate to form polymers. Triphosphates found to be unreactive were arabinosylcytosine 5′-triphosphate and pp(dT)5; 3′-O-acetyldeoxyadenosine 5′-triphosphate failed to give the desired single terminal addition. When pp(dT)5 was used to initiate polymerization of deoxythymidine 5′-triphosphate, reaction occurred with retention of the 5′-terminal triphosphate group. This group was shown to be further retained during a successful replication reaction employing calf thymus DNA polymerase.

Parameters Affecting the Performance of Large Liquid Scintillation Counters

The performance of large liquid scintillation counters as a function of counter size, photocathode area, solution transparency, and inner wall reflectivity is treated mathematically in an empirically derived equation. The use of the equation allows a degree of quantitation of the light output of the counter, and figures show the effect of varying parameters upon this light output.

CONTEMPORARY CARBON-14 IN LEMONGRASS OIL

Liquid scintillation counting ofp- cymene, derived from lemongrass oil, has provided information on the world-wide increase in C14 since 1954. By June 1959, the activity in the tropospheric atmosphere and in the rapidly equilibrating biosphere is measured to have increased by 26·8 per cent in the northern hemisphere and 19·7 per cent in the southern hemisphere. The shape of the relationship between activity and time is essentially linear, with two sections of quite different slope.

RADIOCARBON IN PLANT PRODUCTS: GEOGRAPHY, SPECIES, AND TIME

Carbon14 measurements, on a global scale, have been made on a large number of essential oils obtained from various plants. The measurements allow conclusions to be drawn on the mixing of some compartments of the atmosphere and, in addition, metabolic differences between various species of plants are demonstrated. The course of C14 fallout, as recorded by the various plants, is charted.