Secondary maximum phenomenon

The shortcoming of such descriptions of exchange is that diffusion is not a local phenomenon, as implied by these formulations, and eddy sizes most important to exchange within the canopy can be many times larger than scales associated with the distribution of sources and sinks of heat, water vapour, etc. As an obvious example, gradient diffusion would not permit a secondary maximum in the wind profile in an extensive canopy, because such a profile would require a counter-gradient flux of momentum. 

An enhanced dielectric loss maximum was observed at -85°C when a polysulfone sample which contained 0.76 wt. % unassociated water and no detectable level of clustered water (<0.01 wt. %) was run (Fig. 6, curve A). An apparent low temperature broadening of the dielectric loss dispersion was noted for another polysulfone specimen with 0.76 wt. % unassociated water and an additional 0.04 wt. % clustered water (Fig. 6, curve B). However, when a polysulfone sample which contained the same amount of unassociated water as the two prior samples but had 0.16 wt. % clustered water was analyzed, it had a significantly more intense loss peak centered near -105°C (Fig. 6, curve C). We believe that this shift in loss maximum and increase in loss intensity is caused by the development of an additional secondary loss peak about 20° below the 3-transition (Figure 6). In earlier work we had observed the same phenomenon in polycarbonate where the new loss peak occurred about 40 below its 3-transition as a separate loss peak. 

The end-product repression involves probably the blockage of formation of specific synthases, at the time of a maximum rate of secondary biosynthesis. This results in a gradual decline in the level of the enzyme and a retardation of the product formation. The phenomenon was observed in gramicidin S synthases by Bacillus brevis (30), bacitracin synthase in Bacillus licheniformis (31), anhydrotetracycline hydratase by treptomyces aureofaci-ens (4), novobiocic acid synthase in Streptomyces niveus (35) or dimethylallyltryptophan synthase by ciaviceps (33). 

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