Prekindergarten Teachers\u27 Experiences Teaching Preliteracy to English Language Learners

Pre-K teachers in Metro Georgia have little to no training in working with English language learner/dual language learner (ELL/DLL) students, nor do they know how to instruct these students to meet Pre-K preliteracy criteria. As Pre-K classrooms contain increasing numbers of ELL/DLL students, the purpose of this qualitative case study was to explore teachers\u27 need to support emergent literacy for ELL/DLL students in the Pre-K setting. The theoretical foundations for this study included Vygotsky\u27s sociocultural theory and Kreshan\u27s theory of language acquisition. Thirteen teachers participated in the study. Selection criteria was (1) having 2 years of teaching experience and (2) having ELL/DLL students in their classrooms. Interview and observational data were analyzed using a priori, emergent, and thematic coding. The themes emerging from the study addressed teacher needs in four areas: professional development focused on the needs of ELL/DLL students and on providing sheltered instruction, time to collaborate with others in their ELL/DLL instructional practices, and technology as a source of materials and ideas. The project study is a proposed professional development course to help teachers teach emergent literacy skills to ELL/DLL students. The findings may lead to improved practices for teachers offering ELL/DLL preliteracy instruction and increased literacy development for ELL/DLL preschool students. Positive social change will occur as local school and community members recognize the increased contributions by well-educated ELL/DLL students whose road to success started in preschool

Effect of glass aggregates upon abrasiveness of asphaltic mixtures

The utilization of glass as an aggregate in asphaltic concrete pavements has been suggested as a means for reusing the increasing amounts of waste glass generated each year in the United States. Recent studies have shown that asphaltic mixtures containing glass aggregates can be designed to meet Marshall requirements for stability, flow and void content but the abrasiveness of mixtures containing glass aggregates had not been investigated. The objectives of this study were to develop a laboratory wear testing apparatus and compare the abrasiveness of asphaltic concrete mixtures using glass aggregates with the abrasiveness of mixtures using several different conventional aggregates. Equipment and procedures were developed to assess the relative abrasiveness of laboratory prepared specimens and field specimens containing glass and conventional aggregates by spinning a rubber wheel on the specimen surface and measuring the resulting weight loss of the wheel. Based upon the results of the tests conducted, it was concluded that coarse glass particles cause more wear than limestone or gravel coarse aggregates while no difference in wear results when traprock coarse aggregates are replaced by coarse glass. Replacement of either limestone or traprock fine aggregate by fine glass in mixtures containing limestone coarse aggregate increased wear while no difference in wear results when fine glass substituted for river sand. However, in mixtures containing gravel coarse aggregate, fine glass causes more wear than river sand. Since the effects of skid resistance and aggregate angularity upon wear were found to differ from effects reported in a previously published study of tire wear, it was concluded that the testing method developed might not accurately reflect differences in tire wear resulting from surfaces of varying composition. Modifications in the testing method to minimize abrasion of the specimen surface during testing are suggested --Abstract, pages ii-iii

A matrix-free parallel two-level deflation preconditioner for the two-dimensional Helmholtz problems

We propose a matrix-free parallel two-level-deflation preconditioner combined with the Complex Shifted Laplacian preconditioner(CSLP) for the two-dimensional Helmholtz problems. The Helmholtz equation is widely studied in seismic exploration, antennas, and medical imaging. It is one of the hardest problems to solve both in terms of accuracy and convergence, due to scalability issues of the numerical solvers. Motivated by the observation that for large wavenumbers, the eigenvalues of the CSLP-preconditioned system shift towards zero, deflation with multigrid vectors, and further high-order vectors were incorporated to obtain wave-number-independent convergence. For large-scale applications, high-performance parallel scalable methods are also indispensable. In our method, we consider the preconditioned Krylov subspace methods for solving the linear system obtained from finite-difference discretization. The CSLP preconditioner is approximated by one parallel geometric multigrid V-cycle. For the two-level deflation, the matrix-free Galerkin coarsening as well as high-order re-discretization approaches on the coarse grid are studied. The results of matrix-vector multiplications in Krylov subspace methods and the interpolation/restriction operators are implemented based on the finite-difference grids without constructing any coefficient matrix. These adjustments lead to direct improvements in terms of memory consumption. Numerical experiments of model problems show that wavenumber independence has been obtained for medium wavenumbers. The matrix-free parallel framework shows satisfactory weak and strong parallel scalability.Comment: 36 pages, 18 figures, a manuscript to be submitted as a journal pape

A matrix-free parallel solution method for the three-dimensional heterogeneous Helmholtz equation

The Helmholtz equation is related to seismic exploration, sonar, antennas, and medical imaging applications. It is one of the most challenging problems to solve in terms of accuracy and convergence due to the scalability issues of the numerical solvers. For 3D large-scale applications, high-performance parallel solvers are also needed. In this paper, a matrix-free parallel iterative solver is presented for the three-dimensional (3D) heterogeneous Helmholtz equation. We consider the preconditioned Krylov subspace methods for solving the linear system obtained from finite-difference discretization. The Complex Shifted Laplace Preconditioner (CSLP) is employed since it results in a linear increase in the number of iterations as a function of the wavenumber. The preconditioner is approximately inverted using one parallel 3D multigrid cycle. For parallel computing, the global domain is partitioned blockwise. The matrix-vector multiplication and preconditioning operator are implemented in a matrix-free way instead of constructing large, memory-consuming coefficient matrices. Numerical experiments of 3D model problems demonstrate the robustness and outstanding strong scaling of our matrix-free parallel solution method. Moreover, the weak parallel scalability indicates our approach is suitable for realistic 3D heterogeneous Helmholtz problems with minimized pollution error.Comment: 25 pages, 15 figures, manuscript submitted to a special issue of conference NMLSP202

Pest categorisation of Arceuthobium spp. (non-EU)

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of Arceuthobium spp. (non-EU), a well-defined and distinguishable group of parasitic plant species of the family Viscaceae, also known as dwarf mistletoes. These are flowering plants parasitising a wide range of conifers of the families Pinaceae and Cupressaceae. Arceuthobium species (non-EU) are regulated in Council Directive 2000/29/EC (Annex IAI) as harmful organisms whose introduction into the EU is banned. Many Arceuthobium species are recognised, with most dwarf mistletoes native in the New World, and north-western Mexico and the western USA as the centre of diversity for the genus. Only two Arceuthobium species are native (and reported to be present) in the EU (Arceuthobium azoricum and Arceuthobium oxycedrum), which are thus not part of this pest categorisation. Hosts of non-EU dwarf mistletoes include species of the genera Abies, Cupressus, Juniperus, Larix, Picea, Pinus, Pseudotsuga and Tsuga. Most Arceuthobium spp. can parasitise more than one species of conifer host. Dwarf mistletoes could enter the EU via host plants for planting and cut branches, but these pathways are closed. They could establish in the EU, as hosts are widespread and climatic conditions are favourable. They would be able to spread following establishment by human movement of host plants for planting and cut branches, as well as natural spread. Should non-EU dwarf mistletoes be introduced in the EU, impacts can be expected on coniferous woodlands, plantations, ornamental trees and nurseries. The main uncertainties concern (i) the precise distribution and host range of the individual Arceuthobium spp. and (ii) the level of susceptibility of conifers native to Europe. For Arceuthobium spp. (non-EU) as a group of organisms, the criteria assessed by the Panel for consideration as a potential quarantine pest are met, while, for regulated non-quarantine pests, the criterion on the pest presence in the EU is not met

Towards Accuracy and Scalability: Combining Isogeometric Analysis with Deflation to Obtain Scalable Convergence for the Helmholtz Equation

Finding fast yet accurate numerical solutions to the Helmholtz equation remains a challenging task. The pollution error (i.e. the discrepancy between the numerical and analytical wave number k) requires the mesh resolution to be kept fine enough to obtain accurate solutions. A recent study showed that the use of Isogeometric Analysis (IgA) for the spatial discretization significantly reduces the pollution error. However, solving the resulting linear systems by means of a direct solver remains computationally expensive when large wave numbers or multiple dimensions are considered. An alternative lies in the use of (preconditioned) Krylov subspace methods. Recently, the use of the exact Complex Shifted Laplacian Preconditioner (CSLP) with a small complex shift has shown to lead to wave number independent convergence while obtaining more accurate numerical solutions using IgA. In this paper, we propose the use of deflation techniques combined with an approximated inverse of the CSLP using a geometric multigrid method. Numerical results obtained for both one- and two-dimensional model problems, including constant and non-constant wave numbers, show scalable convergence with respect to the wave number and approximation order p of the spatial discretization. Furthermore, when kh is kept constant, the proposed approach leads to a significant reduction of the computational time compared to the use of the exact inverse of the CSLP with a small shift