Active networks are a novel approach to network architecture in which the switches (or routers) of the network perform customized computations on the messages flowing through them. This approach is motivated by both lead user applications, which perform user-driven computation at nodes within the network today, and the emergence of mobile code technologies that make dynamic network service innovation attainable. The authors discuss two approaches to the realization of active networks and provide a snapshot of the current research issues and activities. They illustrate how the routers of an IP network could be augmented to perform such customized processing on the datagrams flowing through them. These active routers could also interoperate with legacy routers, which transparently forward datagrams in the traditional manner.

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A survey of active network research

This paper gives a systematic introduction to HMM, the heterogeneous multiscale methods, including the fundamental design principles behind the HMM philosophy and the main obstacles that have to be ...

Heterogeneous multiscale methods: A review

The field of systematic biology has been revitalized and transformed during the last few decades by the confluence of phylogenetic thinking with ready access to the tools of molecular biology. Indeed, the title of this volume and the fact that it is already in its second edition offers ample testimony to the impact that molecular approaches have had on efforts to reconstruct the phylogenetic history of plants. Concomitant with the proliferation of molecular tools has been a growing awareness that reliance on a single data set may often result in insufficient phylogenetic resolution or misleading inferences. Accordingly, it is an increasingly widespread practice to apply multiple data sets to a common group of taxa. One of the consequences of analyzing multiple data sets is that the phylogenies inferred may differ from each other in one or more details. This phylogenetic incongruence is not rare; to the contrary, it is almost the rule rather than the exception, being evident to varying degrees.

Phylogenetic Incongruence: Window into Genome History and Molecular Evolution

A consistent two-step estimation procedure is proposed for a system of equations with limited dependent variables. Monte Carlo simulation results suggest the procedure outperforms an existing two-step method.

Two-Step Estimation of a Censored System of Equations

A venerable supposition of American survey research is that the vast majority of voters have incoherent and unstable preferences about political issues, which in turn have little impact on vote choice. We demonstrate that these findings are manifestations of measurement error associated with individual survey items. First, we show that averaging a large number of survey items on the same broadly defined issue area—for example, government involvement in the economy, or moral issues—eliminates a large amount of measurement error and reveals issue preferences that are well structured and stable. This stability increases steadily as the number of survey items increases and can approach that of party identification. Second, we show that once measurement error has been reduced through the use of multiple measures, issue preferences have much greater explanatory power in models of presidential vote choice, again approaching that of party identification.

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M. R. Spiegel

Papers

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