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ELEMENTARY CHEMICAL PROCESSES 



1. If a spherical target have radiosensitive dimensions corresponding 

 to its geometric dimensions and if each hit be lethal, the probability 

 that a hit at any distance x from the center would produce a lethal effect 

 would be unity within the radius r and zero outside. Figure 2 illustrates 



^0 



-r r 



Distance from center of target 



Fig. 2. Lethality of a hit as a function of distance from center of target on basis of 



simple target theory. 



this situation. On the same model, geometric dimensions and dimension 

 computed from radiobiological effect would be identical for all sizes of 

 biological particle. The "ideal" line 1 of Fig. 3 shows this effect. 



Geometric "radius" 



Fig. 3. Effect of various factors on biologically computed "radius" of target. 1, 



Ideal; 2, ideal + contribution from region D; 3, C/(A + B) = constant > 0; 



4, CI {A + B) increases with size. 



