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Today, exponential growth in network content makes it difficult to build and maintain a complete document index to support efficient search. Centralized search services must actively and repeatedly probe the network for new or changed content. The scope and rapid evolution of the Internet means that even the best pull-based search services will always be(More)
Bugs in distributed systems are often hard to find. Many bugs reflect discrepancies between a system's behavior and the programmer's assumptions about that behavior. We present Pip 1 , an infrastructure for comparing actual behavior and expected behavior to expose structural errors and performance problems in distributed systems. Pip allows programmers to(More)
Device drivers typically execute in supervisor mode and thus must be fully trusted. This paper describes how to move them out of the trusted computing base, by running them without supervisor privileges and constraining their interactions with hardware devices. An implementation of this approach in the Nexus operating system executes drivers in user space,(More)
Many interesting large-scale systems are distributed systems of multiple communicating components. Such systems can be very hard to debug, especially when they exhibit poor performance. The problem becomes much harder when systems are composed of "black-box" components: software from many different (perhaps competing) vendors, usually without source code(More)
1. In the present study we have taken advantage of the unique anatomy of visceral sensory neurons that enabled us to isolate and examine the role of calcium channel subtypes at the soma, central synaptic terminals, and peripheral sensory endings. 2. N-type calcium channels dominated somatic currents (60%), with lesser (16% and 12%) contributions from P- and(More)
Wide-area distributed applications are challenging to debug, optimize, and maintain. We present Wide-Area Project 5 (WAP5), which aims to make these tasks easier by exposing the causal structure of communication within an application and by exposing delays that imply bottlenecks. These bottlenecks might not otherwise be obvious, with or without the(More)
BACKGROUND Cullin-dependent E3 ubiquitin ligases (CDL) are key regulators of protein destruction that participate in a wide range of cell biological processes. The Roc subunit of CDL contains an evolutionarily conserved RING domain that binds ubiquitin charged E2 and is essential for ubiquitylation. Drosophila melanogaster contains three highly related Roc(More)
This paper describes the design and implementation of a new operating system authorization architecture to support trustworthy computing. Called <i>logical attestation</i>, this architecture provides a sound framework for reasoning about run time behavior of applications. Logical attestation is based on attributable, unforgeable statements about program(More)
Dynamic cardiovascular regulation depends on baroreflexes and the processing of sensory information. We evaluated the influence of choice of anesthetic on the frequency-response characteristics of the baroreflex of rats by electrical stimulation of two major baroreceptor-containing nerves, the carotid sinus (CSN) and aortic depressor nerves (ADN). The ADN(More)
The key principles behind current peer-to-peer research include fully distributing service functionality among all nodes participating in the system and routing individual requests based on a small amount of locally maintained state. The goals extend much further than just improving raw system performance: such systems must survive massive concurrent(More)