A Guide to Global Population Projections

Interdisciplinary studies that draw on long-term, global population projections often make limited use of projection results, due at least in part to the historically opaque nature of the projection process. We present a guide to such projections aimed at researchers and educators who would benefit from putting them to greater use. Drawing on new practices and new thinking on uncertainty, methodology, and the likely future courses of fertility and life expectancy, we discuss who makes projections and how, and the key assumptions upon which they are based. We also compare methodology and recent results from prominent institutions and provide a guide to other sources of demographic information, pointers to projection results, and an entry point to key literature in the field.forecasting, population projections, projection methodology, uncertainty

Helping America's Dual Language Learners Succeed: A Research-based Agenda for Action

In the fall of 2014, the Heising-Simons and McKnight Foundations provided support for a National Research Summit on the Early Care and Education of Dual Language Learners (DLLs) in Washington, DC. The goal of the two day summit was to engage and extend the established knowledge base accrued by the Center for Early Care and Educational Research Dual Language Learners (CECER-DLL), while simultaneously informing the future potential efforts by the Heising-Simons and McKnight Foundations specific to the early care and education of dual language learners. Day two centered on the presentation of five McKnight-commissioned papers, the topics of which included: Research Based Models and Best Practices for DLLs across PreK - 3rd gradePerspectives on Assessment of DLLs Development & Learning, PreK - 3Human Resource Development and Support for Those Serving DLLsThe Critical Role of Leaderships in Programs Designed for DLLs, PreK - 3Policy Advances & Levers Related to DLLs in PreK - 3rd gradeThe report attempts to provide a short summary and synthesis of the topics covered in these papers and the discussion generated at the National Summit on Early Care and Education of Dual Language Learners. In addition, a set of recommendations are presented for each topic with regard to the implications drawn from these synthesis and of particular relevance to the supporting foundations' future investment considerations related to DLLs

Goal-oriented sensitivity analysis for lattice kinetic Monte Carlo simulations

In this paper we propose a new class of coupling methods for the sensitivity analysis of high dimensional stochastic systems and in particular for lattice Kinetic Monte Carlo. Sensitivity analysis for stochastic systems is typically based on approximating continuous derivatives with respect to model parameters by the mean value of samples from a finite difference scheme. Instead of using independent samples the proposed algorithm reduces the variance of the estimator by developing a strongly correlated-"coupled"- stochastic process for both the perturbed and unperturbed stochastic processes, defined in a common state space. The novelty of our construction is that the new coupled process depends on the targeted observables, e.g. coverage, Hamiltonian, spatial correlations, surface roughness, etc., hence we refer to the proposed method as em goal-oriented sensitivity analysis. In particular, the rates of the coupled Continuous Time Markov Chain are obtained as solutions to a goal-oriented optimization problem, depending on the observable of interest, by considering the minimization functional of the corresponding variance. We show that this functional can be used as a diagnostic tool for the design and evaluation of different classes of couplings. Furthermore the resulting KMC sensitivity algorithm has an easy implementation that is based on the Bortz-Kalos-Lebowitz algorithm's philosophy, where here events are divided in classes depending on level sets of the observable of interest. Finally, we demonstrate in several examples including adsorption, desorption and diffusion Kinetic Monte Carlo that for the same confidence interval and observable, the proposed goal-oriented algorithm can be two orders of magnitude faster than existing coupling algorithms for spatial KMC such as the Common Random Number approach

Protein detection by polymer optical fibers sensitized with overlayers of block or random copolymers

In this study a low cost and low complexity optical detection method of proteins is presented by employing a detection scheme based on electrostatic interactions, and implemented by sensitization of a polymer optical fiber (POF) surface by thin overlayer of properly designed sensitive copolymer materials with predesigned charges. This method enables the fast detection of proteins having opposite charge to the overlayer, and also the effective discrimination of differently charged proteins like lysozyme (LYS) and bovine serum albumin (BSA). More specifically, as sensitive materials here was used the block and the random copolymers of the same monomers, namely the block copolymer poly(styrene-b-2vinylpyridine) (PS-b-P2VP) and the corresponding random polymer poly(styrene-r-2-vinylpyridine) (PS-r-P2VP), of similar composition and roughly similar molecular weight. Moreover, this work focused on the comparison of the aforementioned sensitive materials regarding the way in which they can adapt on sensing optical platforms and constitute functional sensing bio-materials

Anisotropy and oblique total transmission at a planar negative-index interface

We show that a class of negative index (n) materials has interesting anisotropic optical properties, manifest in the effective refraction index that can be positive, negative, or purely imaginary under different incidence conditions. With dispersion taken into account, reflection at a planar negative-index interface exhibits frequency selective total oblique transmission that is distinct from the Brewster effect. Finite-difference-time-domain simulation of realistic negative-n structures confirms the analytic results based on effective indices.Comment: to appear in Phys. Rev.

Absolute negative refraction and imaging of unpolarized electromagnetic waves by two-dimensional photonic crystals

Absolute negative refraction regions for both polarizations of electromagnetic wave in two-dimensional photonic crystal have been found through both the analysis and the exact numerical simulation. Especially, absolute all-angle negative refraction for both polarizations has also been demonstrated. Thus, the focusing and image of unpolarized light can be realized by a microsuperlens consisting of the two-dimensional photonic crystals. The absorption and compensation for the losses by introducing optical gain in these systems have also been discussed

Optical Polarization and Spectral Variability in the M87 Jet

During the last decade, M87's jet has been the site of an extraordinary variability event, with one knot (HST-1) increasing by over a factor 100 in brightness. Variability was also seen on timescales of months in the nuclear flux. Here we discuss the optical-UV polarization and spectral variability of these components, which show vastly different behavior. HST-1 shows a highly significant correlation between flux and polarization, with P increasing from $\sim 20$ at minimum to >40% at maximum, while the orientation of its electric vector stayed constant. HST-1's optical-UV spectrum is very hard ($\alpha_{UV-O}\sim0.5$, $F_\nu\propto\nu^{-\alpha}$), and displays "hard lags" during epochs 2004.9-2005.5, including the peak of the flare, with soft lags at later epochs. We interpret the behavior of HST-1 as enhanced particle acceleration in a shock, with cooling from both particle aging and the relaxation of the compression. We set 2$\sigma$ upper limits of $0.5 \delta$ parsecs and 1.02$c$ on the size and advance speed of the flaring region. The slight deviation of the electric vector orientation from the jet PA, makes it likely that on smaller scales the flaring region has either a double or twisted structure. By contrast, the nucleus displays much more rapid variability, with a highly variable electric vector orientation and 'looping' in the $(I,P)$ plane. The nucleus has a much steeper spectrum ($\alpha_{UV-O} \sim 1.5$) but does not show UV-optical spectral variability. Its behavior can be interpreted as either a helical distortion to a steady jet or a shock propagating through a helical jet.Comment: 14 pages, 7 figures, ApJ, in pres

Effective medium theory of left-handed materials

We analyze the transmission and reflection data obtained through transfer matrix calculations on metamaterials of finite lengths, to determine their effective permittivity and permeability. Our study concerns metamaterial structures composed of periodic arrangements of wires, cut-wires, split ring resonators (SRRs), closed-SRRs, and both wires and SRRs. We find that the SRRs have a strong electric response, equivalent to that of cut-wires, which dominates the behavior of left-handed materials (LHM). Analytical expressions for the effective parameters of the different structures are given, which can be used to explain the transmission characteristics of LHMs. Of particular relevance is the criterion introduced by our studies to identify if an experimental transmission peak is left- or right-handed.Comment: to be published in Phys. Rev. Let