A system for optical navigation includes an optical navigation sensor integrated circuit configured to generate image information for use in navigation sensing and a collapsible structure which sets the distance between the optical navigation sensor IC and a navigation surface and which can be expanded or collapsed as needed. The composition is free of SiO2 or substantially free of SiO2, and is useful as a mortar or coating for molten aluminum or steel contact refractories. Such toxicants are frequently present as contaminants in aquatic and terrestrial environments. The glycerol-rich portion can be reacted with at least one of an oxidant and a catalyst at conditions sufficient to produce the partially oxidized reaction product. The first layer extends to a first height in the trench and the second layer extends to a second height in the trench; the second height is greater than the first height.