Various algorithms for evaluating nonbonded interactions in molecular dynamics (MD) simulations of macromolecular systems are considered, and a combination of two techniques using a space grid for finding neighbor atoms is proposed. The application of grid search techniques to nonrectangular periodic systems is discussed. Finally, the computing time required by different algorithms is compared on a Cray-1 vector processing computer as well as on a CDC Cyber 170/760 sequential computer. Neighbor list techniques turn out to be faster than the grid search techniques for the systems considered here. However, storage requirements may exclude the use of neighbor list techniques for large systems. Finally, MD of complex macromolecular systems turned out to be about 4-14 times faster on a Cray-1 than on a Cyber 170/760.

Despite various interoperability recommendations, heterogeneity of Geographic Information Systems (GIS) is still an issue. This led to an increasing need for a data integration system that allows transparent and uniform access to spatial data disseminated over a network. In this paper, we describe the internals of query processing in the VirGIS mediation system. Recall that a data mediation system provides users with a uniform access to a multitude of (local/remote) data sources, without duplicating the data. The user poses his query against a virtual (global) schema, the query is in turn rewritten into queries sent to the local sources. VirGIS complies with Open GIS Consortium recommendations in using the Geography Markup Language (GML) for the encoding and the transport of geographic information, and the Web Feature Server (WFS) interfaces to perform communications with clients and data sources.

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