Outer cove

Observation 5.1 A coronoid C with an outer cove or an outer fjord (on the outer perimeter of C) cannot be circumscribed. 

The presence of outer coves and fjords in C is a sufficient, but not necessary condition for the impossibility to circumscribe C. The below examples are adapted from a corresponding discussion for benzenoids by Brunvoll, Cyvin BN and Cyvin (1992b). The depicted single coronoids cannot be circumscribed. 

It is seen (Table 5.3 and Fig. 5.8) that X 6 C53H21 are the smallest h = 16) X isomers where coves possibly may occur. Then comes X C65H23 h = 21) and X C72H24 h = 24). These coronoid isomers are at the same time those where a phenalene hole, which implies inner coves, cannot be excluded. Indeed, such isomers with phenalene holes can be constructed, as is exemplified by Fig. 5.7. Naphthalenic single coronoid isomers with the same formulas and outer coves are also possible ... 

It has been recommended that the outer walls of the separation chamber be cove with black foil or that the work be carried out in a dark room under green or red light... 

The high bioavailability of Cd in the marine environment from Terra Nova Bay was ascribed to upwelling of deep nutrient rich water nearshore (70). Cadmiun has a nutrient-like concentration gradient in the water column, lower close to the surface and increasing with depth (75). In the water column, Cd would be absorbed by the phytoplankton, during the summer bloom, thus becoming available for benthic molluscs in which the Cd is bioaccumulated. Ecological studies undertaken in the inner and outer part of Potter Cove showed that after seasonal ice retreat no phytoplankton bloom occured (35). In spite of the low planktonic production, rich benthic animal comunities are found in the area (29). 

The situation for coves is different every cove (inner or outer) of C is evidently available for addition of a hexagon. A fjord of C is always available for addition except for the inner fjords of a naphthalene hole it is not allowed to immerse a hexagon into a fjord of a naphthalene hole of C when a new coronoid is supposed to be generated. 

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