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Most papers that employ Differences-in-Differences estimation (DD) use many years of data and focus on serially correlated outcomes but ignore that the resulting standard errors are incon-sistent. To illustrate the severity of this issue, we randomly generate placebo laws in state-level data

-secting, hypersurface flowing along its gradient field with con-stant speed or a speed that depends on the curvature. It is moved by solving a “Hamilton-Jacob? ’ type equation written for a func-tion in which the interface is a particular level set. A speed term synthesizpd from the image is used to stop the interface

significantly limited the performance, flexibility, and functionality of applications. The exokernel architecture removes these limitations by allowing untrusted software to implement traditional operating system abstractions entirely at application-level. We have implemented a prototype exokernel-based system

detailed �rm-level data, we �nd evidence of complementarities among all three of these innovations in factor demand and productivity regressions. In addition, �rms that adopt these innovations tend to use more skilled labor. The effects of IT on labor demand are greater when IT is combined

Many versions of Unix provide facilities for user-level packet capture, making possible the use of general purpose workstations for network monitoring. Because network monitors run as user-level processes, packets must be copied across the kernel/user-space protection boundary. This copying can

This paper presents Scribe, a scalable application-level multicast infrastructure. Scribe supports large numbers of groups, with a potentially large number of members per group. Scribe is built on top of Pastry, a generic peer-to-peer object location and routing substrate overlayed on the Internet

the communication path, while still providing full protection. The model presented by U-Net allows for the construction of protocols at user level whose performance is only limited by the capabilities of network. The architecture is extremely flexible in the sense that traditional protocols like TCP and UDP

This paper anal yzes the causes of packetl oss in a 38-node urban mul ti-hop 802.11b network. The patterns and causes oflv# are important in the design of routing and errorcorrection proto colv as wel as in networkplqq"(v The paper makes the fol l owing observations. The distribution of inter-nodel oss rates is rel'RfivD' uniform over the wh ol range oflv$ rates; there is no clq$ threshol separating "in range" and "out of range." Mostls ks have relj tivel stabl el oss rates from one second to the next, though a smal l minority have very burstyl osses at that time scal e. Sign al to-noise ratio and distance have lv tl e predictive val e forl oss rate. Thel arge number of lv ks with intermediate l oss rates is probabl y due to mul ti-path fading rather than attenuation or interference. The phenomena discussed here are al l wel l -known. The contributions of this paper are an understanding of their rel ative importance, of how they interact, and of the impl ications for MAC and routing protocol design.

Power dissipation and thermal issues are increasingly significant in modern processors. As a result, it is crucial that power/performance tradeoffs be made more visible to chip architects and even compiler writers, in addition to circuit designers. Most existing power analysis tools achieve high accuracy by calculating power estimates for designs only after layout or floorplanning are complete In addition to being available only late in the design process, such tools are often quite slow, which compounds the difficulty of running them for a large space of design possibilities.