Charter Schools and the Road to College Readiness: The Effects on College Preparation, Attendance and Choice

The analysis here focuses on Boston's charter high schools. For the purpose of this report, an analysis of high schools is both a necessity and a virtue. It is necessary to study high schools because most students applying to charters in earlier grades are not yet old enough to generate data on postsecondary outcomes. Charter high schools are also of substantial policy interest: a growing body of research argues that high school may be too late for cost-effective human capital interventions. Indeed, impact analyses of interventions for urban youth have mostly generated disappointing results.This report is interested in ascertaining whether charter schools, which in Massachusetts are largely budget-neutral, can have a substantial impact on the life course of affected students. The set of schools studied here comes from an earlier investigation of the effects of charter attendance in Boston on test scores.The high schools from the earlier study, which enroll the bulk of charter high school students in Boston, generate statistically and socially significant gains on state assessments in the 10th grade. This report questions whether these gains are sustained

Explaining Charter School Effectiveness

Estimates using admissions lotteries suggest that urban charter schools boost student achievement, while charter schools in other settings do not. We explore student-level and school-level explanations for these differences using a large sample of Massachusetts charter schools. Our results show that urban charter schools boost achievement well beyond ambient non-charter levels (that is, the average achievement level for urban non-charter students), and beyond non-urban achievement in math. Student demographics explain some of these gains since urban charters are most effective for non-whites and low-baseline achievers. At the same time, non-urban charter schools are uniformly ineffective. Our estimates also reveal important school-level heterogeneity in the urban charter sample. A non-lottery analysis suggests that urban schools with binding, well-documented admissions lotteries generate larger score gains than under-subscribed urban charter schools with poor lottery records. We link the magnitude of charter impacts to distinctive pedagogical features of urban charters such as the length of the school day and school philosophy. The relative effectiveness of urban lottery-sample charters is accounted for by over-subscribed urban schools' embrace of the No Excuses approach to education.

Mixed-precision arithmetic in the ENDGame dynamical core of the Unified model, a numerical weather prediction and climate model code

The Met Office's weather and climate simulation code the Unified Model is used for both operational Numerical Weather Prediction and Climate modelling. The computational performance of the model running on parallel supercomputers is a key consideration. A Krylov sub-space solver is employed to solve the equations of the dynamical core of the model, known as ENDGame. These describe the evolution of the Earth's atmosphere. Typically, 64-bit precision is used throughout weather and climate applications. This work presents a mixed-precision implementation of the solver, the beneficial effect on run-time and the impact on solver convergence. The complex interplay of errors arising from accumulated round-off in floating-point arithmetic and other numerical effects is discussed. A careful analysis is required. The mixed-precision solver is now employed in the operational forecast to satisfy run-time constraints without compromising the accuracy of the solution

The role of the cloud radiative effect in the sensitivity of the Intertropical Convergence Zone to convective mixing

Studies have shown that the location and structure of the simulated Intertropical Convergence Zone (ITCZ) is sensitive to the treatment of sub-gridscale convection and cloud-radiation interactions. This sensitivity remains in idealised aquaplanet experiments with fixed surface temperatures. However, studies have not considered the role of cloud-radiative effects (CRE, atmospheric heating due to cloud-radiation interactions) in the sensitivity of the ITCZ to the treatment of convection. We use an atmospheric energy input (AEI) framework to explore how the CRE modulates the sensitivity of the ITCZ to convective mixing in aquaplanet simulations. Simulations show a sensitivity of the ITCZ to convective mixing, with stronger convective mixing favoring a single ITCZ. For simulations with a single ITCZ, the CRE maintains the positive, equatorial AEI. To explore the role of the CRE further, we prescribe the CRE as either zero or a meridionally and diurnally varying climatology. Removing the CRE is associated with a reduced equatorial AEI and an increase in the range of convective mixing rates that produce a double ITCZ. Prescribing the CRE reduces the sensitivity of the ITCZ to convective mixing by 50%. In prescribed CRE simulations, other AEIcomponents, in particular the surface latent heat flux, modulate the sensitivity of the AEI to convective mixing. Analysis of the meridional moist static energy transport shows that a shallower Hadley circulation can produce an equatorward energy transport at low latitudes even with equatorial ascent

Charter School Demand and Effectiveness: A Boston Update

This report begins with a focus on applications to charter schools. While much attention has been focused on charter school waitlists, waitlist data can be misleading. It includes duplicates, but also includes waitlists that have been rolled over from year to year and might be an unrealistic measure of demand. Instead, the authors investigate three factors related to demand: the yearly percentage of each middle school and high school class that applies to a charter in our lottery sample; the percentage of applicants that receive an offer from a charter school; and where students ultimately attend. This report also examines the demographic makeup of charter school enrollees and compare it to BPS. The next section follows the path of charter school students and report their performance in charters using the evidence from the lotteries. The lottery sample now covers many more charter schools. The 2009 report included findings from eight schools. This report includes MCAS results through 2012 from 12 schools and many more cohorts from the original schools, with additional newly opened schools contributing to the demand analysis. In addition to updating the test score results from the 2009 report, this report breaks down the test score effects by student subgroups. Trends are investigated over time in charter performance and by school groups. Finally, this report gives results using statistical controls, which allow the authros to estimate effects for attending charter schools that do not have sufficient lottery records for the more rigorous lottery based analysis. The lottery sample now contains almost all Boston charter schools with entry grades at middle or high school

Who Benefits from KIPP?

Charter schools affiliated with the Knowledge is Power Program (KIPP) are emblematic of the No Excuses approach to public education. These schools feature a long school day, an extended school year, selective teacher hiring, strict behavior norms and a focus on traditional reading and math skills. We use applicant lotteries to evaluate the impact of KIPP Academy Lynn, a KIPP charter school that is mostly Hispanic and has a high concentration of limited English proficiency (LEP) and special-need students, groups that charter critics have argued are typically under-served. The results show overall gains of 0.35 standard deviations in math and 0.12 standard deviations in reading for each year spent at KIPP Lynn. LEP students, special education students, and those with low baseline scores benefit more from time spent at KIPP than do other students, with reading gains coming almost entirely from the LEP group.

Solar-electric-propulsion cargo vehicles for split/sprint Mars mission

In support of the proposed exploration of Mars, an unmanned cargo ferry SEMM1 (Solar Electric Mars Mission) was designed. The vehicle is based on solar electric propulsion, and required to transport a cargo of 61,000 kg. The trajectory is a combination of spirals; first, out from LEO, then around the sun, then spiral down to low Mars orbit. The spacecraft produces 3.03 MWe power using photovoltaic flexible blanket arrays. Ion thrusters using argon as a propellant were selected to drive the ship, providing about 60 Newtons of thrust in low Earth orbit. The configuration is based on two long truss beams to which the 24 individual, self-deployable, solar arrays are attached. The main body module supports the two beams and houses the computers, electrical, and control equipment. The thruster module is attached to the rear of the main body, and the cargo to the front

Describing and prescribing the constitutive response of yield stress fluids using large amplitude oscillatory shear stress (LAOStress)

Large amplitude oscillatory shear (LAOS) is used as a tool to probe the nonlinear rheological response of a model elasto-viscoplastic material (a Carbopol microgel). In contrast to most recent studies, these large amplitude measurements are carried out in a stress-controlled manner. We outline a descriptive framework of characterization measures for nonlinear rheology under stress-controlled LAOS, and this is contrasted experimentally to the strain-controlled framework that is more commonly used. We show that this stress-controlled methodology allows for a physically intuitive interpretation of the yielding behavior of elasto-viscoplastic materials. The insight gained into the material behavior through these nonlinear measures is then used to develop two constitutive models that prescribe the rheological response of the Carbopol microgel. We show that these two successively more sophisticated constitutive models, which are based on the idea of strain decomposition, capture in a compact manner the important features of the nonlinear rheology of the microgel. The second constitutive model, which incorporates the concept of kinematic hardening, embodies all of the essential behaviors exhibited by Carbopol. These include elasto-viscoplastic creep and time-dependent viscosity plateaus below a critical stress, a viscosity bifurcation at the critical stress, and Herschel–Bulkley flow behavior at large stresses

Challenges facing gap-based silviculture and possible solutions for mesic northern forests in North America

Gap-based silvicultural systems were developed under the assumption that richness, and diversity of tree species and other biota positively respond to variation in size of harvest-created canopy gaps. However, varying gap size alone often does not meet diversity objectives and broader goals to address contemporary forest conditions. Recent research highlights the need to consider site factors and history, natural disturbance models, within-gap structure and recruitment requirements in addition to light resources for desired tree diversity. This synthesis brings together silvicultural developments and ecological literature on gap-based management, highlighting interactions with other factors such as microsite conditions, non-tree vegetation and more. We pose a revised concept for managers and researchers to use in prescriptions and studies focused on integrated overstory and understory manipulations that increase structural complexity within and around canopy openings