ost Americans believe that if a chemical is in their cosmetics, their coat, or their couch, someone is making sure it’s safe for their health. In reality, little toxicity information or regulation is required for 80,000 industrial chemicals used in commerce in the United States. To address this, legislation to update the inef ective 1976 Toxic Substance Control Act (TSCA) is currently moving th...

THE CEREBRAL CIRCULATION IS REGULATED TO MATCH CEREBRAL BLOOD FLOW (CBF) TO THE VARYING METABOLIC NEEDS OF THE TISSUE PERFUSED, DESPITE POSSIBLE CHANGES IN SYSTEMIC ARTERIAL PRESSURE (AP). The CBF is determined by the ratio between cerebral perfusion pressure (CPP) and vascular resistance. The CPP may be computed as the difference between AP and intracranial pressure (ICP) because blood pressur...

Consensus trees are used in phylogenetics as summaries or representations of sets of source trees. Here we ask ‘How good are consensus trees?’ in the sense of how well do individual consensus trees represent the set of source trees for which they stand? There are many different consensus methods and various contexts in which they may be used (Swofford, 1991; Wilkinson, 1994; Leclerc, 1998). Con...

ICSI was ®rst applied in cases of severe male factor infertility in which conventional IVF would be expected to fail or to give poor outcomes (Van Steirteghem et al., 1993). More recently, however, ICSI has been increasingly used in cases in which conventional IVF would not necessarily be inef®cient. In such cases, ICSI is often preferred because of its reliability in terms of achieving high fe...

We examine two factors that explain air traffic congestion: network benefits due to hubbing and congestion externalities. While both factors impact congestion, we find that the hubbing effect dominates empirically. Hub carriers incur most of the additional travel time from hubbing, primarily because they cluster their flights in short time spans to provide passengers as many potential connectio...

Hybrid architectures have been used in several recent knowledge representation systems. This paper explores some distinctions between various hybrid representation architectures, focusing in particular on systems built around restricted representation languages This restricted language architecture is illustrated by describing KL-TWO, a hybrid reasoner based on the restricted representation fac...