Purine is not common, but the purine structure occurs in many natural substances.
This structure occurs in many reptiles and in a few birds, including ducks.
This kind of structure occurs in craters on the Moon and other solid bodies, and occurs when material deep within the surface is uplifted as a whole during the impact.
This ring structure occurs in such important biologically active natural products as thiamine (vitamin B1), bacitracin, and the penicillins, and in numerous synthetic drugs, dyes, and industrial chemicals.
A diversity of mouth and jaw structure occurs in the perciforms; most of it is brought about by the various types of feeding behaviour.
In stage I, disordering of the crystalline structure occurs.
This kind of structure occurs owing to the successive layers of deposition.
During the calcination treatment, the surfactant F127 decomposes, and the contraction of the mesoporous structure occurs.
The progressive collapse of the structure occurs only in the bay where the removal side column is located.
The local directional structure occurs in non-directional aromatic layers, and then the directional structure extends to the entire area.
Due to sliding motion between asperities of the contacting surfaces in the bearing, polishing of the raceway honing structure occurs.
