2,910 research outputs found

    The Influence of Accelerated Reader on the Affective Literacy Orientations of Intermediate Grade Students

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    Although the highly popular Accelerated Reader (AR) book reading incentive program claims to motivate children of all reading ability levels, very little independent empirical research has examined this assertion. To help fill this void, we used two related three-factor mixed designs with Method (AR vs. Control), Gender, and either Grade Level(fourth vs. fifth) or Reading Ability (high vs. low) to explore AR’s influence on the reading attitudes and self-perceptions of children in two comparable school districts. The analyses indicate that AR positively influenced academic reading attitudes, but not recreational ones, and that it negatively influenced two types of self-perceptions in low achieving male readers. These findings and others of consequence are discussed along with implications for future research

    Dynamical Screening and Superconducting State in Intercalated Layered Metallochloronitrides

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    An essential property of layered systems is the dynamical nature of the screened Coulomb interaction. Low energy collective modes appear as a consequence of the layering and provide for a superconducting-pairing channel in addition to the electron-phonon induced attractive interaction. We show that taking into account this feature allows to explain the high critical temperatures (Tc~26K) observed in recently discovered intercalated metallochloronitrides. The exchange of acoustic plasmons between carriers leads to a significant enhancement of the superconducting critical temperature that is in agreement with the experimental observations

    Large isotope effect on TcT_c in cuprates despite of a small electron-phonon coupling

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    We calculate the isotope coefficients α\alpha and α∗\alpha^\ast for the superconducting critical temperature TcT_c and the pseudogap temperature T∗T^\ast in a mean-field treatment of the t-J model including phonons. The pseudogap phase is identified with the dd-charge-density wave (dd-CDW) phase in this model. Using the small electron-phonon coupling constant λd∼0.02\lambda_d \sim 0.02 obtained previously in LDA calculations in YBa2_2Cu3_3O7_7, α∗\alpha^{\ast} is negative but negligible small whereas α\alpha increases from about 0.03 at optimal doping to values around 1 at small dopings in agreement with the general trend observed in many cuprates. Using a simple phase fluctuation model where the dd-CDW has only short-range correlations it is shown that the large increase of α\alpha at low dopings is rather universal and does not depend on the existence of sharp peaks in the density of states in the pseudogap state or on specific values of the phonon cutoff. It rather is caused by the large depletion of spectral weight at low frequencies by the dd-CDW and thus should also occur in other realizations of the pseudogap.Comment: 8 pages, 5 figures, to be publ. in PR

    The Writing Observation Framework: A Guide for Refining and Validating Writing Instruction

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    The Writing Observation Framework (WOF) is a new tool for enhancing writing instruction in schools. The WOF organizes principles of writing instruction In a way that improves the evaluation of teachers\u27 writing practices, encourages a shared philosophy of the writing process and its instruction, and assists schools in demonstrating the integrity of their writing programs

    Influence of higher d-wave gap harmonics on the dynamical magnetic susceptibility of high-temperature superconductors

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    Using a fermiology approach to the computation of the magnetic susceptibility measured by neutron scattering in hole-doped high-Tc superconductors, we estimate the effects on the incommensurate peaks caused by higher d-wave harmonics of the superconducting order parameter induced by underdoping. The input parameters for the Fermi surface and d-wave gap are taken directly from angle resolved photoemission (ARPES) experiments on Bi{2}Sr{2}CaCu{2}O{8+x} (Bi2212). We find that higher d-wave harmonics lower the momentum dependent spin gap at the incommensurate peaks as measured by the lowest spectral edge of the imaginary part in the frequency dependence of the magnetic susceptibility of Bi2212. This effect is robust whenever the fermiology approach captures the physics of high-Tc superconductors. At energies above the resonance we observe diagonal incommensurate peaks. We show that the crossover from parallel incommensuration below the resonance energy to diagonal incommensuration above it is connected to the values and the degeneracies of the minima of the 2-particle energy continuum.Comment: 13 pages, 7 figure

    A Whole-Class Support Model for Early Literacy: The Anna Plan

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    The Anna Plan is a unique delivery model for enhancing schoolwide literacy instruction in the primary grades. Based on the principles of Reading Recovery and Four Blocks literacy instruction, it provides supplementary reading instruction through the distinctive use of teaching staff. Over six years, it has resulted in sweeping changes in the way literacy instruction occurs as well as noteworthy increases in children\u27s reading abilities. This article gives a brief history of the authors\u27 work within the Anna Plan, explains each of the model\u27s seven tenets, and describes the research base that drives it. The focal point of the article is the detailed description of the organization and components of the five-day framework used to augment classroom reading and writing instruction. Finally, the authors recount how the Anna Plan has been embraced by two elementary schools and offer some conclusions about what contributes to the success of whole-class support models for early literacy

    Performance Indices for Multivariate Ice Hockey Statistics

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    A Review of the Use of Performance Indices in Ice Hocke

    WHO WON THE 1996 NHL PLUS-MINUS AWARD?

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    Point total, goals plus assists, is an NHL player’s most important individual statistic; it is the best predictor of salary. However, an individual player\u27s goals and assists are only indirectly important to his team because the team objective is to win games and not necessarily to watch individual players run up their point totals. Unfortunately, sometimes opposition teams score easy goals against a team\u27s best goal scorers because these players do not always play well defensively.vAs a result of this conflict, hockey uses a statistic called the plus/minus, (P/M), which purports to measure a player\u27s offensive versus defensive ability

    Electronic Collective Modes and Superconductivity in Layered Conductors

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    A distinctive feature of layered conductors is the presence of low-energy electronic collective modes of the conduction electrons. This affects the dynamic screening properties of the Coulomb interaction in a layered material. We study the consequences of the existence of these collective modes for superconductivity. General equations for the superconducting order parameter are derived within the strong-coupling phonon-plasmon scheme that account for the screened Coulomb interaction. Specifically, we calculate the superconducting critical temperature Tc taking into account the full temperature, frequency and wave-vector dependence of the dielectric function. We show that low-energy plasmons may contribute constructively to superconductivity. Three classes of layered superconductors are discussed within our model: metal-intercalated halide nitrides, layered organic materials and high-Tc oxides. In particular, we demonstrate that the plasmon contribution (electronic mechanism) is dominant in the first class of layered materials. The theory shows that the description of so-called ``quasi-two-dimensional superconductors'' cannot be reduced to a purely 2D model, as commonly assumed. While the transport properties are strongly anisotropic, it remains essential to take into account the screened interlayer Coulomb interaction to describe the superconducting state of layered materials.Comment: Final version (minor changes) 14 pages, 6 figure

    A universal high energy anomaly in angle resolved photoemission spectra of high temperature superconductors - possible evidence of spinon and holon branches

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    A universal high energy anomaly in the single particle spectral function is reported in three different families of high temperature superconductors by using angle-resolved photoemission spectroscopy. As we follow the dispersing peak of the spectral function from the Fermi energy to the valence band complex, we find dispersion anomalies marked by two distinctive high energy scales, E_1=~ 0.38 eV and E_2=~0.8 eV. E_1 marks the energy above which the dispersion splits into two branches. One is a continuation of the near parabolic dispersion, albeit with reduced spectral weight, and reaches the bottom of the band at the gamma point at ~0.5 eV. The other is given by a peak in the momentum space, nearly independent of energy between E_1 and E_2. Above E_2, a band-like dispersion re-emerges. We conjecture that these two energies mark the disintegration of the low energy quasiparticles into a spinon and holon branch in the high T_c cuprates.Comment: accepted for publication in Phys. Rev. Let
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