Civilization first stage

Figure 3.43 Thermomechanical cycle in the tension direction for a specimen of T25C25 (step 1 —> pretension to 25% strain at temperatures above Tg, step 2 —> cooling down to room temperature while holding the pre-strain constant, step 3 —> unloading, which completes the first stage of programming. The Poisson effect is due to the second programming in the transverse direction by compression. Step 4 —> free shape recovery). Source [59] Reproduced with permission from the American Society of Civil Engineers...

The first indication of an increase in the flux of each of the trace metals begins simultaneously in Fig. 19. This corresponds to the final stage of deposition of the lower clay band, at about the time of the U.S. Civil War (1860-1865), when industrialization in this area greatly intensified. The rate of increase since then has been generally sustained to the present. The increase is nearly linear in the case of Cu and Zn, but deviates considerably from a smooth rise in the case of Pb, and there is no obvious acceleration due to the introduction of leaded gasoline in the 1920s. 

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