Natural ageing data

Extrapolated unaged and 40 years natural ageing data Compound A (natural rubber - standard)... 

Of note are the values for °Th and as the revised values postdate the development of mass spectrometric techniques for measurement of U and Th in natural materials. Data published prior to Cheng et al. (2000b) does use not use the revised values whereas data published subsequently may or may not use the new values. The revised half-lives do have a small, but significant effect on calculated °Th ages, particularly ages older than about 100 ka. Furthermore, the new value for the half-life changes values as these are calculated from measured atomic ratios using... 

Whatever mathematical model is assumed for the dose-incidence relationship, it is noteworthy that susceptibility can vary markedly with age, so that the radiation-induced cancer excess at various times after irradiation may more nearly approximate a constant percentage of the natural age-specific incidence than a constant number of additional cases, depending on the neoplasm in question. For some individual neoplasms, but not the leukemias, the data do in fact suggest that the "relative risk model is more appropriate than the absolute risk model (see Section 6.1.7). For all neoplasms combined, also, the excess of radiation-induced cases at different times after irradiation approximates more nearly a constant percentage of the age-specific incidence. 

W. J. Barrow Research Laboratory Test Data of Naturally Aged Papers ... 

Fig. 5.32 Hardness data for friction stir welded 7050-T7551 Al alloys naturally aged for >6 years. HAZ, heat-affected zone TMAZ, thermomechanically affected zone.

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