School accountability and student performance

Education

Does School Accountability Lead to Improved Student Performance?

The leading school reform policy in the United States revolves around strong accountability of schools with consequences for performance. The federal government's involvement through the No Child Left Behind Act of 2001 reinforces the prior movement of many states toward policies based on measured student achievement. Analysis of state achievement growth as measured by the National Assessment of Educational progress shows that accountability systems introduced during the 1990s had a clear positive impact on student achievement. This single policy instrument did not, however, also lead to any narrowing in the black-white achievement gap (though it did narrow the Hispanic-white achievement gap). Moreover, the balck-white gap appears to have been harmed over the decade by increasing minority concentrations in the schools. An additional issue surrounding stronger accountability has been a concern about unintended consequences related to such things as higher exclusion rates from testing, increased drop-out rates, and the like. Our analysis of special education placement rates, a frequently identified area of concern, does not show any responsiveness to the introduction of accountability systems.

Determining the implied volatility in the Dupire equation for vanilla European call options

The Black-Scholes model gives vanilla Europen call option prices as a function of the volatility. We prove Lipschitz stability in the inverse problem of determining the implied volatility, which is a function of the underlying asset, from a collection of quoted option prices with different strikes

Capabilities and constraints of NASA's ground-based reduced gravity facilities

The ground-based reduced gravity facilities of NASA have been utilized to support numerous investigations addressing various processes and phenomina in several disciplines for the past 30 years. These facilities, which include drop towers, drop tubes, aircraft, and sounding rockets are able to provide a low gravity environment (gravitational levels that range from 10(exp -2)g to 10(exp -6)g) by creating a free fall or semi-free fall condition where the force of gravity on an experiment is offset by its linear acceleration during the 'fall' (drop or parabola). The low gravity condition obtained on the ground is the same as that of an orbiting spacecraft which is in a state of perpetual free fall. The gravitational levels and associated duration times associated with the full spectrum of reduced gravity facilities including spaced-based facilities are summarized. Even though ground-based facilities offer a relatively short experiment time, this available test time has been found to be sufficient to advance the scientific understanding of many phenomena and to provide meaningful hardware tests during the flight experiment development process. Also, since experiments can be quickly repeated in these facilities, multistep phenomena that have longer characteristic times associated with them can sometimes be examined in a step-by-step process. There is a large body of literature which has reported the study results achieved through using reduced-gravity data obtained from the facilities

The effect of overloading on reliability of wheel loader structural components

This research attempts to provide a fundamental understanding into the relationship between the productivity of material handling equipment, specifically wheel loaders, and their ability to operate reliably when subjected to high overload conditions. The overall aim is to determine the effect of overloading the bucket on wheel loader reliability. The specific objectives of the research are to: 1) evaluate the effect of overloading the bucket on wheel loader productivity; 2) examine the effect of overloading the bucket on hydraulic pressures in the hoist cylinders (used as a proxy for forces on a wheel loader); and 3) investigate the effect of overloading the bucket on the reliability of structural components of a wheel loader. To achieve these objectives, the research used data from on-board equipment monitors from the global fleet of ultra-class wheel loaders for a specific original equipment manufacturer to test the various research hypotheses. The data included production data, failure and repair data, and hydraulic cylinder pressures, which were used as a proxy for stresses on structural components. ANOVA and Pearson and Spearman correlations tests were performed on data samples to test the hypotheses. Duty-cycle relationships were established using linear life stress relationships ratios for the wheel loaders structural components. The research showed that, while higher bucket loads increase productivity, there is evidence that they slow down the loading cycle, may be detrimental to productivity. The hoist cylinder pressure increased with increasing payload weight. The reliability of the structural components was similar in both the standard and duty-cycle cases; although, the accuracy of the reliability models increased when the models accounted for duty-cycles --Abstract, page iii

Large, long range tensile forces drive convergence during

Indirect evidence suggests that blastopore closure during gastrulation of anamniotes, including amphibians such as Xenopus laevis, depends on circumblastoporal convergence forces generated by the marginal zone (MZ), but direct evidence is lacking. We show that explanted MZs generate tensile convergence forces up to 1.5 mN during gastrulation and over 4 mN thereafter. These forces are generated by convergent thickening (CT) until the midgastrula and increasingly by convergent extension (CE) thereafter. Explants from ventralized embryos, which lack tissues expressing CE but close their blastopores, produce up to 2 mN of tensile force, showing that CT alone generates forces sufficient to close the blastopore. Uniaxial tensile stress relaxation assays show stiffening of mesodermal and ectodermal tissues around the onset of neurulation, potentially enhancing long-range transmission of convergence forces. These results illuminate the mechanobiology of early vertebrate morphogenic mechanisms, aid interpretation of phenotypes, and give insight into the evolution of blastopore closure mechanisms. © Shook et al