The impact of urbanization on construction minerals
Construction minerals (sand, gravel and crushed stone used in the production of concrete) are among our most plentiful mineral resources by volume. Increasing quantities of these materials are required for construction within urban areas. However, continuing and accelerating suburbanization is rapidly making unusable deposits of these minerals due to zoning and other restrictions. In addition, the low intrinsic value of mineral aggregates and their bulkiness make the economics of the industry extremely sensitive to location. Mathematical programming is used to investigate the economic impact of urbanization on the production and distribution of construction minerals.
Mining, planning, and the urban environment
As our populations grow and the processes of urbanization continue, new demands for minerals, space, and environmental quality will become increasingly important. Unfortunately, these demands as th...
Ultrastructural observations of the spermiogenesis in the Parotoplaninae (Plathelminthes, Proseriata) with special reference to a striated appendage of the intercentriolar body
SummaryThe spermiogenesis of three species of the Parotoplaninae (Otoplanidae, Proseriata) is described based on electron-microscopical observations. Special reference is given to organelles which do not persist in mature male gametes. One of these organelles is a striated appendage of the intercentriolar body. This differentiation has not been reported from any other plathelminth taxa up to now. The striated appendage, which may serve as a strengthening element, is hypothesized to be an autapomorphic feature of the Parotoplaninae.