487 research outputs found

    High-Stakes Testing and Student Achievement: Problems for the No Child Left Behind Act

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    Under the federal No Child Left Behind Act of 2001 (NCLB), standardized test scores are the indicator used to hold schools and school districts accountable for student achievement. Each state is responsible for constructing an accountability system, attaching consequences -- or stakes -- for student performance. The theory of action implied by this accountability program is that the pressure of high-stakes testing will increase student achievement. But this study finds that pressure created by high-stakes testing has had almost no important influence on student academic performance

    High-Stakes Testing and Student Achievement: Does Accountability Pressure Increase Student Learning?

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    This study examined the relationship between high-stakes testing pressure and student achievement across 25 states. Standardized portfolios were created for each study state. Each portfolio contained a range of documents that told the “story” of accountability implementation and impact in that state. Using the “law of comparative judgments,” over 300 graduate-level education students reviewed one pair of portfolios and made independent evaluations as to which of the two states’ portfolios reflected a greater degree of accountability pressure. Participants’ judgments yielded a matrix that was converted into a single rating system that arranged all 25 states on a continuum of accountability “pressure” from high to low. Using this accountability pressure rating we conducted a series of regression and correlation analyses. We found no relationship between earlier pressure and later cohort achievement for math at the fourth- and eighth-grade levels on the National Assessment of Educational Progress tests. Further, no relationship was found between testing pressure and reading achievement on the National Assessment of Education Progress tests at any grade level or for any ethnic student subgroup. Data do suggest, however, that a case could be made for a causal relationship between high-stakes testing pressure and subsequent achievement on the national assessment tests—but only for fourth grade, non-cohort achievement and for some ethnic subgroups. Implications and directions for future studies are discussed

    Honeycomb Core Permeability Under Mechanical Loads

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    A method for characterizing the air permeability of sandwich core materials as a function of applied shear stress was developed. The core material for the test specimens was either Hexcel HRP-3/16-8.0 and or DuPont Korex-1/8-4.5 and was nominally one-half inch thick and six inches square. The facesheets where made of Hercules' AS4/8552 graphite/epoxy (Gr/Ep) composites and were nominally 0.059-in. thick. Cytec's Metalbond 1515-3M epoxy film adhesive was used for co-curing the facesheets to the core. The permeability of the specimens during both static (tension) and dynamic (reversed and non-reversed) shear loads were measured. The permeability was measured as the rate of air flow through the core from a circular 1-in2 area of the core exposed to an air pressure of 10.0 psig. In both the static and dynamic testing, the Korex core experienced sudden increases in core permeability corresponding to a core catastrophic failure, while the URP core experienced a gradual increase in the permeability prior to core failure. The Korex core failed at lower loads than the HRP core both in the transverse and ribbon directions

    Restricted feedback control of one-dimensional maps

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    Dynamical control of biological systems is often restricted by the practical constraint of unidirectional parameter perturbations. We show that such a restriction introduces surprising complexity to the stability of one-dimensional map systems and can actually improve controllability. We present experimental cardiac control results that support these analyses. Finally, we develop new control algorithms that exploit the structure of the restricted-control stability zones to automatically adapt the control feedback parameter and thereby achieve improved robustness to noise and drifting system parameters.Comment: 29 pages, 9 embedded figure

    Genetic and neuronal regulation of sleep by neuropeptide VF

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    Sleep is an essential and phylogenetically conserved behavioral state, but it remains unclear to what extent genes identified in invertebrates also regulate vertebrate sleep. RFamide-related neuropeptides have been shown to promote invertebrate sleep, and here we report that the vertebrate hypothalamic RFamide neuropeptide VF (NPVF) regulates sleep in the zebrafish, a diurnal vertebrate. We found that NPVF signaling and npvf-expressing neurons are both necessary and sufficient to promote sleep, that mature peptides derived from the NPVF preproprotein promote sleep in a synergistic manner, and that stimulation of npvf-expressing neurons induces neuronal activity levels consistent with normal sleep. These results identify NPVF signaling and npvf-expressing neurons as a novel vertebrate sleep-promoting system and suggest that RFamide neuropeptides participate in an ancient and central aspect of sleep control

    Piecewise Linear Models for the Quasiperiodic Transition to Chaos

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    We formulate and study analytically and computationally two families of piecewise linear degree one circle maps. These families offer the rare advantage of being non-trivial but essentially solvable models for the phenomenon of mode-locking and the quasi-periodic transition to chaos. For instance, for these families, we obtain complete solutions to several questions still largely unanswered for families of smooth circle maps. Our main results describe (1) the sets of maps in these families having some prescribed rotation interval; (2) the boundaries between zero and positive topological entropy and between zero length and non-zero length rotation interval; and (3) the structure and bifurcations of the attractors in one of these families. We discuss the interpretation of these maps as low-order spline approximations to the classic ``sine-circle'' map and examine more generally the implications of our results for the case of smooth circle maps. We also mention a possible connection to recent experiments on models of a driven Josephson junction.Comment: 75 pages, plain TeX, 47 figures (available on request

    Nuclear receptors in vascular biology

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    Nuclear receptors sense a wide range of steroids and hormones (estrogens, progesterone, androgens, glucocorticoid, and mineralocorticoid), vitamins (A and D), lipid metabolites, carbohydrates, and xenobiotics. In response to these diverse but critically important mediators, nuclear receptors regulate the homeostatic control of lipids, carbohydrate, cholesterol, and xenobiotic drug metabolism, inflammation, cell differentiation and development, including vascular development. The nuclear receptor family is one of the most important groups of signaling molecules in the body and as such represent some of the most important established and emerging clinical and therapeutic targets. This review will highlight some of the recent trends in nuclear receptor biology related to vascular biology
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