Chemical Age

In addition, any chemical aging (Section 23.5.3) could affect these mechanisms for instance, if an elastomer surface is degraded by contact with hostile chemicals, access to the interior may be facilitated and its permeation characteristics would change accordingly. 

Bosch, Karl. Chemisches Zentralblatt 1913, 2, 195 German Patents 249,447, July 23, 1912 and 254,437, December 3, 1912 Chemical Age 1921, 29451-45 The Industrial Chemist 1934, 10, 90-94 "Nobel Lectures, Chemistry, 1922-1941" Elsevier Publish ing Company New York, 1966 pp 195-235 Mittasch, Alwin. 

Haynes, Williams. "This Chemical Age" Alfred A. Knopf New York, 1942 p. 75. 

Randomization If one is concerned about time-dependent effects (for example, analyzer response drift, or chemical aging effects in the calibration standards), then the order of preparation and analysis of calibration samples in the design should be randomized. 

Fig. 4. Chondrite-normalized mean REE patterns of uranium oxides from deposits located near the unconformity (McArthur River, Cigar Lake and Shea Creek) and from basement deposits (grey zone, this study). Fayek Kyser (1997) chemical age Bonhoure (2007) and Bonhoure et al. (2007) U/Pb isotopic age.

This section deals with chemical aging and related physical phenomena, such as diffusion and embrittlement. Apart from the chemical problem there is mechanical deterioration which is also related to long term environmental effects, but this was covered briefly in the preceding cumulative damage discussion. 

Pest Control in Germany, Schrader s work on Insecticides, The Chemical Age, 1951, p. 813—816. 

Kroger, M. and Weaver, J. C. (1979). Use of protein dye-binding values as indicators of the chemical age of conventionally made Cheddar cheese and hydrolyzed-lactose Cheddar cheese.. Food Sci. 44, 304-305. 

Chemical aging resulting from water absorption (i.e., hydrolysis) has not been as widely studied as physical aging. It is relatively well understood at the molecular scale (chemical mechanisms). But macromolecular (kinetics of decrease of the elastically active chain concentration) and mechanical aspects (effect of chain scissions on mechanical properties) are far from being elucidated. 

Once in the atmosphere, OAs can also undergo a wide range of physical and chemical aging processes under atmospheric conditions. OA components can react with atmospheric photooxidants (e.g., OH, NO3, and 03), acids (e.g., H2S04 and HN03), water, and UV radiation, forming for instance more polar and hygroscopic products than the precursor material. These atmospheric transformation processes can also occur at the surface layers of BC or EC (Poschl, 2005). 

More recently Braganca, Faulkner, and Quastel (B15) showed that this inhibition of acetylcholine synthesis in brain slices by ammonia is consistent only in the diminution of bound acetylcholine. They further showed that the addition of inhibitors of glutamine synthesis, such as methionine sulfoxide, ethionine sulfoxide, and methionine sulfoximine (the toxic product, causing convulsions, formed in flour chemically aged with nitrogen trichloride) would partially reverse the ammonium inhibition. These observations were confirmed and extended to a wide variety of ATP-requiring reactions by Weil-Malherbe. In support of this suggestion was the observation that ammonia is taken up by the brain in hepatic coma (B8). The observations are valid and have been confirmed, but the interpretation of the data and the hypothesis are questionable. A quantitative basis for the evaluation of this mechanism can... 

---