Quantitative Analysis by the Point-Centered Quarter Method

This document is an introduction to the use of the point-centered quarter method. It briefly outlines its history, its methodology, and some of the practical issues (and modifications) that inevitably arise with its use in the field. Additionally this paper shows how data collected using point-centered quarter method sampling may be used to determine importance values of different species of trees and describes and derives several methods of estimating plant density and corresponding confidence intervals. New to this revision is an appendix of R functions to carry out these calculations.Comment: 56 pages, 12 figures, 16 tables. Corrected typos. Expanded Appendix B on Angle-Order Methods. Added Appendix D containing R functions to carry out all calculations. Added references. Original version: 34 pages, 6 figures, 16 table

Understanding insertion and integration in a study abroad context: the case of English-speaking sojourners in France

This paper draws on a recent study of British students of languages undertaking a year abroad in France, in a variety of placements (as language teaching assistants, as exchange students, and as workplace interns). The data were gathered in the context of the 2011-2013 LANGSNAP project, a larger study undertaken which investigated both the language learning and social integration of British students spending an academic year abroad in France, Spain or Mexico Having made a positive choice to specialise in languages at university, and having already reached a relatively advanced level in French during their secondary school education, it could be assumed that these students were positively motivated to further develop their language skills, to deepen their intercultural understanding, and to integrate socially within the local society. Indeed, in pre-departure interviews (in French), the participating students unanimously expressed the wish to integrate and in particular to make French same-aged friends. The paper first of all presents an overview of the range of tools used to gather both quantitative and qualitative data on participants’ social integration. The paper then goes on to evaluate the degree of success of even such highly motivated participants in achieving this declared goal, and to consider social, sociolinguistic and personal factors which appear to influence the degree of social integration achieved by individual participants

Finite-time barriers to front propagation in two-dimensional fluid flows

Recent theoretical and experimental investigations have demonstrated the role of certain invariant manifolds, termed burning invariant manifolds (BIMs), as one-way dynamical barriers to reaction fronts propagating within a flowing fluid. These barriers form one-dimensional curves in a two-dimensional fluid flow. In prior studies, the fluid velocity field was required to be either time-independent or time-periodic. In the present study, we develop an approach to identify prominent one-way barriers based only on fluid velocity data over a finite time interval, which may have arbitrary time-dependence. We call such a barrier a burning Lagrangian coherent structure (bLCS) in analogy to Lagrangian coherent structures (LCSs) commonly used in passive advection. Our approach is based on the variational formulation of LCSs using curves of stationary "Lagrangian shear", introduced by Farazmand, Blazevski, and Haller [Physica D 278-279, 44 (2014)] in the context of passive advection. We numerically validate our technique by demonstrating that the bLCS closely tracks the BIM for a time-independent, double-vortex channel flow with an opposing "wind".Comment: 11 pages, 6 figure

Lessons From India in Organizational Innovation: A Tale of Two Heart Hospitals

Recent discussions in health reform circles have pinned great hopes on the prospect of innovation as the solution to the high-cost, inadequate-quality U.S. health system. But U.S. health care institutions--insurers, providers and specialists--have ceded leadership in innovation to Indian hospitals such as Care Hospital in Hyderabad and the Fortis Hospitals around New Delhi, which have U.S.-trained doctors and can perform open heart surgery for $6000 (compared to$100,000 in the United States). The Indian success is a window into America\u27s stalemate with inflating costs and stagnant innovation

Unbalanced Nested Component Error Model and the Value of Soil Insecticide and Bt Corn for Controlling Western Corn Rootworm

We describe four recently developed panel data estimators for unbalanced and nested data, a common problem for economic and experimental data. We estimate a western corn rootworm damage function with each estimator, including separate parameters for random effects from year, location, and experimental errors. We then use each estimator to assess the cost of the western corn rootworm soybean variant and the net benefit of soil insecticide and Bt corn for controlling this pest. At current prices, we find that soil insecticide generates a net loss ranging about $0.50-$3.25/ac, while Bt corn generates a net benefit ranging $2.50-$7.00/ac.

Frozen reaction fronts in steady flows: a burning-invariant-manifold perspective

The dynamics of fronts, such as chemical reaction fronts, propagating in two-dimensional fluid flows can be remarkably rich and varied. For time-invariant flows, the front dynamics may simplify, settling in to a steady state in which the reacted domain is static, and the front appears "frozen". Our central result is that these frozen fronts in the two-dimensional fluid are composed of segments of burning invariant manifolds---invariant manifolds of front-element dynamics in $xy\theta$-space, where $\theta$ is the front orientation. Burning invariant manifolds (BIMs) have been identified previously as important local barriers to front propagation in fluid flows. The relevance of BIMs for frozen fronts rests in their ability, under appropriate conditions, to form global barriers, separating reacted domains from nonreacted domains for all time. The second main result of this paper is an understanding of bifurcations that lead from a nonfrozen state to a frozen state, as well as bifurcations that change the topological structure of the frozen front. Though the primary results of this study apply to general fluid flows, our analysis focuses on a chain of vortices in a channel flow with an imposed wind. For this system, we present both experimental and numerical studies that support the theoretical analysis developed here.Comment: 21 pages, 30 figure