The Effect of the Uruguay round on the Intensive and Extensive Margins of Trade

Do tariffs inhibit trade flows by limiting the entry of exporting firms (extensive margin') or by restricting the average volume exported by each firm (intensive margin')? Using a gravity equation approach, we analyze how the decrease in tariffs promoted during the 1990s by the Uruguay Round multilateral trade agreement affected the trade margins of French firms across 57 sectors and in 147 countries, from 1993 to 2002. Our main contribution is to estimate the elasticity of trade for both margins, controlling for the unobserved heterogeneity of trade flows thanks to a three-dimensional panel and to time-varying tariffs as a measure of variable trade costs. Our results show that the number of firms exporting in a given sector to a given destination is related to the level of tariffs. But they also show that the decrease in tariffs determined by the implementation of the Uruguay Round did not lead more firms to export and instead, only encouraged incumbent exporters to increase their shipments. We control for two problems that may affect our basic specification: tariffs changes may be endogenous and zero flows are not included. Our results are confirmed - even when the extensive margin is significant, its contribution is very small.Tariffs, Trade margins, Uruguay Round

Versal unfoldings for linear retarded functional differential equations

We consider parametrized families of linear retarded functional differential equations (RFDEs) projected onto finite-dimensional invariant manifolds, and address the question of versality of the resulting parametrized family of linear ordinary differential equations. A sufficient criterion for versality is given in terms of readily computable quantities. In the case where the unfolding is not versal, we show how to construct a perturbation of the original linear RFDE (in terms of delay differential operators) whose finite-dimensional projection generates a versal unfolding. We illustrate the theory with several examples, and comment on the applicability of these results to bifurcation analyses of nonlinear RFDEs

Lesson Study: Restructuring Teacher Professional Development in the United States

This study reports how teachers at one suburban elementary school in the United States launched, organized, and structured lesson study, as well as how participants interpreted and perceived the lesson study experience. Additionally, it examines how lesson study supports teachers’ professional learning and the development of collaborative teacher teams. In doing so, it attempts to answer the following research questions: What does the lesson study experience look like at one elementary school in the United States? How does lesson study support and influence school based professional learning teams? How does and to what extent does the lesson study experience impact individual teacher’s perceptions about teaching, learning, and working collaboratively? A case study methodology was utilized in conducting research that involved exploring a bounded system through in-depth data collection, using multiple sources of information in an effort to develop a triangulation of data. Ultimately, through the collection and analysis of multiple data points, I attempted to construct an in depth understanding of lesson study and how it impacts the individual and collective development of teachers

Experimental pre-assessing entanglement in Gaussian states mixing

We suggest and demonstrate a method to assess entanglement generation schemes based on mixing of Gaussian states at a beam splitter (BS). Our method is based on the fidelity criterion and represents a tool to analyze the effect of losses and noise before the BS in both symmetric and asymmetric channels with and without thermal effects. More generally, our scheme allows one to pre-assess entanglement resources and to optimize the design of BS-based schemes for the generation of continuous variable entanglement.Comment: 10 pages, 15 figure