... a compiler framework designed to support transparent, lifelong program analysis and transformation for arbitrary programs, by providing high-level information to compiler transformations at compile-time, link-time, run-time, and in idle time between runs. LLVM defines a common, low-level code

for a minimum of 10 years. Analysis of expert performance provides unique evidence on the potential and limits of extreme environmental adaptation and learning. Our civilization has always recognized exceptional individuals, whose performance in sports, the arts, and science is vastly superior

A dual taxonomy is presented to reconcile 2 incongruous facts about antisocial behavior: (a) It shows impressive continuity over age, but (b) its prevalence changes dramatically over age, increasing almost 10-fold temporarily during adolescence. This article suggests that delinquency conceals 2 distinct categories of individuals, each with a unique natural history and etiology: A small group engages in antisocial behavior of 1 sort or another at every life stage, whereas a larger group is antisocial only during adolescence. According to the theory of life-course-persistent antisocial behavior, children's neuropsychological problems interact cumulatively with their criminogenic environments across development, culminating in a pathological personality. According to the theory of adolescence-limited antisocial behavior, a contemporary maturity gap encourages teens to mimic antisocial behavior in ways that are normative and adjustive. There are marked individual differences in the stability of antisocial behavior. Many people behave antisocially, but their antisocial behavior is temporary and situational. In contrast, the antisocial behavior of some people is very stable and persistent. Temporary, situational ' antisocial behavior is quite common in the population, especially among adolescents. Persistent, stable antisocial behavior is found among a relatively small number of males whose behavior problems are also quite extreme. The central tenet of this article is that temporary versus persistent antisocial persons constitute two qualitatively distinct types of persons. In particular, I suggest that juvenile delinquency conceals two qualitatively distinct categories of individuals, each in need of its own distinct theoretical explanation. Of course, systems for classifying types of antisocial persons have been introduced before (e. g.,

This paper uses a unique data set to measure peer effects among college roommates. Freshman year roommates and dormmates are randomly assigned at Dartmouth College. I find that peers have an impact on grade point average and on decisions to join social groups such as fraternities. Residential peer effects are markedly absent in other major life decisions such as choice of college major. Peer effects in GPA occur at the individual room level, whereas peer effects in fraternity membership occur both at the room level and the entire dorm level. Overall, the data provide strong evidence for the existence of peer effects in student outcomes.

Raising the standards of learning that are achieved through school education is an important national priority. Governments have been vigorous in the last ten years in making changes in pursuit of this aim. National curriculum testing, the development of the GCSE, league tables of school performance, initiatives to improve school planning and management, target setting, more frequent and thorough inspection; these are all means to the end. But the sum of all of these doesn’t add up to an effective policy because something is missing. Learning is driven by what teachers and pupils do in classrooms. Here, teachers have to manage complicated and demanding situations, channelling the personal, emotional and social pressures amongst a group of 30 or so youngsters in order to help them to learn now, and to become better learners in the future. Standards can only be raised if teachers can tackle this task more effectively—what is missing from the policies is any direct help with this task. In terms of systems engineering, present policy seems to treat the classroom as a bla k box. Certain inputs from the outside are fed in or make demands—pupils, teachers, other resources, management rules and requirements, parental anxieties, tests with pressures to

Human blastocyst-derived, pluripotent cell lines are described that have normal karyotypes, express high levels of telomerase activity, and express cell surface markers that characterize primate embryonic stem cells but do not characterize other early lineages. After undifferentiated proliferation in vitro for 4 to 5 months, these cells still maintained the developmental potential to form tro-phoblast and derivatives of all three embryonic germ layers, including gut epithelium (endoderm); cartilage, bone, smooth muscle, and striated muscle (mesoderm); and neural epithelium, embryonic ganglia, and stratiÞed squamous epithelium (ectoderm). These cell lines should be useful in human develop-mental biology, drug discovery, and transplantation medicine. Embryonic stem (ES) cells are derived from totipotent cells of the early mamma-lian embryo and are capable of unlimited, undifferentiated proliferation in vitro (1, 2). In chimeras with intact embryos, mouse ES

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Although narrative inquiry has a long intellectual history both in and out of education, it is increasingly used in studies of educational experience. One theory in educational research holds that humans are storytelling organisms who, individually and socially, lead storied lives. Thus, the study of narrative is the study of the ways humans experience the world. This general concept is refined into the view that education and educational research is the construc-tion and reconstruction of personal and social stories; learners, teachers, and researchers are storytellers and characters in their own and other's stories. In this paper we briefly survey forms of nar-rative inquiry in educational studies and outline certain criteria, methods, and writing forms, which we describe in terms of begin-ning the story, living the story, and selecting stories to construct and reconstruct narrative plots. Certain risks, dangers, and abuses possible in narrative studies are discussed. We conclude by describing

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One potentially useful feature of future computing environments is the ability to capture the live experiences of the occupants and to provide that record to users for later access and review. Over the last 3 years, we have designed and extensively used a particular instrumented environment, the classroom, designed to facilitate the easy capture of the traditional lecture experience. We will describe the history of the Classroom 2000 project at Georgia Tech, and provide results of extended evaluations of the impact of automated capture on the teaching and learning experience. In addition to understanding the impact of automated capture in this educational domain, there are many important lessons to take away from this long-term, largescale experiment with a living ubiquitous computing environment. The environment needs to address issues of scale and extensibility, and there needs to be a way to continuously evaluate the effectiveness of the environment and understand and react to the w...