William Walker is professor of international relations at the University of St. Andrews in Scotland. He is the co-author with David Albright and Frans Berkhout of SIPRI’s Plutonium and Highly Enriched Uranium: World Inventories, Capabilities and Policies (forthcoming, 1996). There have been many recent cases of states reversing course. Russia has embraced capitalism and democracy, China has thr...

Human activities have begun to transform northern peatlands into global sources of dissolved organic carbon (DOC). In Estonia, there are 10,091 km of peatlands, constituting 22.3% of the country’s total area. The increasing number of drought days during the last 50 years, which constitutes a threat of an increased flux of dissolved carbon, has also been observed in Estonia. The aim of the curre...

A simplified sewer nework modelling approach based on the hybrid linear systems framework is discussed. It involives both continuous and discrete variables to include a novel approximation of the overflow and flow over weirs phenomena. The model is validated against data provided by a simulator based on a physical model and is shown to be easily adapted to an optimal/predictive control setting ...