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PREFACE 



The recent very rapid developments in nuclear physics and the parallel 

 progress in tracer techniques have made it imperative to compile from the 

 vast accumulation of data and experimental procedures some of the material 

 that appears to be most essential to applications of isotopic tracers and 

 nuclear radiations. For the most part, such information is to be found at 

 the present time only in widely scattered literature. Nuclear physicists, 

 to be sure, have access to this information by virtue of their familiarity with 

 the technical literature in the field, but even for the nuclear physicist it is 

 often necessary to refer to many different sources for much of the explicit 

 data he requires. The situation is very much worse for those who are less 

 familiar with nuclear physics but who plan to employ isotopic tracers and 

 high-energy radiations in their research. For such persons, Seaborg and 

 Perlman's "Table of Isotopes" has been literally the only comprehensive 

 source for some of the essential information. 



Until recently the compilation of a volume of this kind would have been 

 somewhat futile, since there was too little data that was firmly established 

 and a compilation, once made, would have had to be completely revised and 

 considerably extended six months later. Now, however, it is felt that at 

 least an effort can be made in this direction with the accumulated information 

 derived from the extensive research during and since the war. While it is 

 impossible to present in a single volume the vast amount of material that 

 biologists and physicists in this field would like to have immediately avail- 

 able, it is hoped that the present book, despite its obvious limitations, may 

 find some justification in attempting to provide some of the information for 

 which there seems a pressing demand. 



Based on the experience of our laboratory, it was felt that an urgent need 

 could be satisfied if the present volume were prepared in the form of a ready 

 reference in which fundamental data and descriptions of processes and instru- 

 ments were available in compact form. On the other hand the book was 

 expanded beyond a simple compilation of data and formulas in order to 

 make it more intelligible to those who are less conversant with the terminology 

 and details of nuclear physics and tracer methods. In general, descriptions 

 of processes and instruments have been made rather elementary and with 

 the intention of noting only the essential principles and those data which are 

 important in practice. 



The biological and medical aspects of tracer methods, presented by 



