Lewin has proved that if S is a ring and R a subring of finite index in S, then R contains an ideal of S which is also of finite index; and Feigelstock has recently shown that other classes of subrings must contain ideals belonging to the same class. We provide some extensions of these results, and apply them to prime rings. In the final section, we investigate finiteness of rings having only f...

The U.S. Geological Survey conducted an environmental assessment of 198 catchments in a 54,000-km area of central Colorado, much of which is on Federal land. The Colorado Mineral Belt, a northeast-trending zone of historical baseand precious-metal mining, cuts diagonally across the study area. The investigation was intended to test the hypothesis that degraded water and sediment quality are res...

Phosphorus (P) can be retained in mineral association with ferrous iron (Fe) as vivianite, Fe(II)3(PO4)2 ? 8 H2O, lake sediments. The is formed and remains stable under anoxic non-sulphidogenic conditions and, therefore, acts a long-term P sink. In laboratory experiments conditions, we investigated whether adsorbed to amorphous Fe(III)-hydroxide functioned precursor phase of vivianite when adde...