The purpose of this work is to explore learning and instruction within a project-based technology-rich fifth grade science classroom. Specifically, students worked in teams using three-dimensional (3-D) modeling software to construct 3-D models of the Earth-Moon-Sun system. For this study, naturalistic inquiry was used to build a holistic account of student activity. In particular, we examined students' difficulties, challenges, and successes as they constructed models of astronomical phenomena. Our findings are based on a synthesis of case studies of each student team as they constructed their models. Specifically, we characterize how students asked questions, planned, designed, constructed, evaluated and drew conclusions from their models. Our findings suggest that young students can build sophisticated models which in turn foster discussion and exploration of complex scientific concepts. Our findings also suggest that students traverse stages of model development initially simply following directions laid out by the instructor, but later as their model's complexity increase move to learning with their model rather than simply about their model. VSS: Modeling the Solar System 1

Social scientists rarely take full advantage of the information available in their statistical results. As a consequence, they miss opportunities to present quantities that are of greatest substantive interest for their research and express the appropriate degree of certainty about these quantities. In this article, we offer an approach, built on the technique of statistical simulation, to extract the currently overlooked information from any statistical method and to interpret and present it in a reader-friendly manner. Using this technique requires some expertise,

Information technology (IT) acceptance research has yielded many competing models, each with different sets of acceptance determinants. In this paper, we (1) review user acceptance literature and discuss eight prominent models, (2) empirically compare the eight models and their extensions, (3) formulate a unified model that integrates elements across the eight models, and (4) empirically validate the unified model. The eight models reviewed are the theory of reasoned action, the technology acceptance model, the motivational model, the theory of planned behavior, a model combining the technology acceptance model and the theory of planned behavior, the model of PC utilization, the innovation diffusion theory, and the social cognitive theory. Using data from four organizations over a six-month period with three points of measurement, the eight models explained between 17 percent and 53 percent of the variance in user intentions to use information technology. Next, a unified model, called the Unified Theory of Acceptance and Use of Technology (UTAUT), was formulated, with four core determinants of intention and usage, and up to four moderators of key relationships. UTAUT was then tested using the original data and found to outperform the eight individual models (adjusted R 2 of 69 percent). UTAUT was then confirmed with data from two new organizations with similar

The authors suggest that the most promising route to effective strategies for the prevention of adolescent alcohol and other drug problems is through a risk-focused approach. This approach requires the identification of risk factors for drug abuse, identification of methods by which risk factors have been effectively addressed, and application of these methods to appropriate high-risk and general population samples in controlled studies. The authors review risk and protective factors for drug abuse, assess a number of approaches for drug abuse prevention potential with high-risk groups, and make recommendations for research and practice. In spite of general decreases in the prevalence of the nonmed-ical use of most legal and illegal drugs in recent years, the abuse of alcohol and other drugs during adolescence and early adulthood remains a serious public health problem (Adams, Blanken, Ferguson, & Kopstein, 1990). The consequences of drug abuse are acute on both a personal and a societal level. For the developing young adult, drug and alcohol abuse under-mines motivation, interferes with cognitive processes, contrib-

This book presents a unified treatment of many different kinds of planning algorithms. The subject lies at the crossroads between robotics, control theory, artificial intelligence, algorithms, and computer graphics. The particular subjects covered include motion planning, discrete planning, planning under uncertainty, sensor-based planning, visibility, decision-theoretic planning, game theory, information spaces, reinforcement learning, nonlinear systems, trajectory planning, nonholonomic planning, and kinodynamic planning.

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Peer effects are potentially important for understanding the optimal organization of schools, jobs, and neighborhoods, but finding evidence is difficult because people are selected into peer groups based, in part, on their unobservable characteristics. I identify the effects of peers whom a child encounters in the classroom using sources of variation that are credibly idiosyncratic, such as changes in the gender and racial composition of a grade in a school in adjacent years. I use specification tests, including one based on randomizing the order of years, to confirm that the variation I use is not generated by time trends or other non-idiosyncratic forces. I find that students are affected by the achievement level of their peers: a credibly exogenous change of 1 point in peers’ reading scores raises a student’s own score between 0.15 and 0.4 points, depending on the specification. Although I find little evidence that peer effects are generally non-linear, I do find that peer effects are stronger intra-race and that some effects do not operate through peers’ achievement. For instance, both males and females perform better in math in classrooms that are more female despite the fact that females’ math performance is about the same as that of males.

Venture capital financing is widely believed to be influential for new innovative companies. We provide empirical evidence that venture capital financing is related to product market strategies and outcomes of start-ups. Using a unique hand-collected database of Silicon Valley high-tech start-ups we find that innovator firms are more likely to obtain venture capital than imitator firms. Venture capital is also associated with a significant reduction in the time to bring a product to market, especially for innovators. Our results suggest significant interrelations between investor types and product market dimensions, and a role of venture capital for innovative companies. 3 Venture capital is widely believed to contribute to the competitive strength of the U.S. economy by promoting the development of innovative start-ups. Yet little is known about what kind of companies are most likely to receive venture capital and what its impact is on

Research on dropping out of school has focused on characteristics of the individual or institution that correlate with the dropout decision. Many of these characteristics are nonmanipulable, and all are measured at one point in time, late in the youngster's school career. This paper describes two models for understanding dropping out as a developmental process that may begin in the earliest grades. The frustration-self-esteem model has been used for years in the study of juvenile delinquency; it identifies school failure as the starting point in a cycle that may culminate in the student's rejecting, or being rejected by, the school. The participa-tion-identification model focuses on students ' "involvement in schooling, “ with both behavioral and emotional components. According to this formulation, the likelihood that a youngster will successfully complete 12 years of schooling is maximized if he or she maintains multiple, expanding forms of participation in school-relevant activities. The failure of a youngster to participate in school and class activities, or to develop a sense of identification with school, may have significant deleterious consequences. The ability to manipulate modes of participation poses promising

is Eulerian. We prove that if the vertices of G are (improperly) coloured blue and red, such that the blue vertices cover the faces of G, there is no blue cycle, and every red cycle contains a vertex of degree at most 4, then G ∗ is Hamiltonian. This result implies the following special case of Barnette’s