School Choice Policies and Market Competition: Implications for the Public Education Sector

This dissertation studies the effect of school choice policies with a focus on charter schools and school vouchers. Exploiting the time-varying charter competition driven by the Michigan 2011 cap-lifting policy, the first chapter examines the effect of charter competition on traditional public school districts’ cost efficiency in two ways. The first part estimates the effect of the cap-lifting policy on districts’ resource allocation. The second part extends the policy analysis to disentangle the separate effects of potential competition and actual competition so that we can understand the dynamic effects of the policy. Results show that the cap-lifting policy on average pressures school districts to reduce non-instructional expenditure. The dynamic analysis indicates that such a change in resource allocation is the districts' attempt to deter future competition and extend sustainability. Further analysis also shows that actual charter competition changes districts’ student composition where the percentage of students in the English Language Learner program increases 2.5 percentage points. Little evidence shows that such student sorting results in a significant change in overall academic performance in the short term. The findings suggest that districts attempt to respond to the policy-driven charter competition by prioritizing instruction and reducing cost inefficiency. The second chapter investigates the effect of a Chilean targeted school voucher program. In 2008, Chile implemented a targeted voucher program that increased funding for disadvantaged students in public and participating private schools by approximately 50%. Evidence shows that disadvantaged students did make substantial fourth-grade test score gains exceeding 0.2 standard deviations. However, focused on contemporaneous changes in family background, as well as limited school input, market competition, and school switching responses, the analysis raises doubts that a program-induced improvement in school quality accounts for this convergence

Total Synthesis of Herbimycin A

Benzoquinone ansamycin antibiotic herbimycin A was synthesized in 19 linear steps and 4.2% yield. Highlighted is the design of a chiral γ-lactone as the C11–C15 synthon that enabled a facile catalytic asymmetric synthesis of the challenging C8–C20 fragment of the target molecule. The easy access to the stereogenic centers and high overall yield made the strategy applicable in the molecular editing of benzoquinone ansamycins

Substrate-Induced Liquid Layering: A New Insight into the Heterogeneous Nucleation of Liquid Metals

Liquid layering, which is a general phenomenon adjacent to the solid substrates, is less understood for its role in heterogeneous nucleation. In this work, the structural features and dynamics of the liquid Al layers induced by the (0001) sapphire and the (0001) TiB2 substrates, respectively, are quantitatively compared based on the ab initio molecular dynamics simulations. An almost fully ordered liquid Al layer is observed adjacent to the TiB2 substrate above the Al melting point, while the liquid layers near the sapphire substrate are weakly ordered with virtually no in-plane translational symmetry. Further liquid layering is facilitated by the ordered liquid layer near the TiB2 substrate, while impeded by the low in-plane ordering of the liquid layers near the sapphire substrate, resulting in different nucleation behaviors for the two systems. The difference in the liquid layering is caused, in part, by the lower adsorption strength at the sapphire–liquid Al interface than that at the TiB2–liquid Al interface. Additionally, the compressive stress imposed on the liquid layers seriously hinders the sapphire-induced liquid layering. We conclude from this work that the interfacial adsorption strength and mismatch alter the heterogeneous nucleation by influencing the features of the substrate-induced liquid layering

Suppressing stimulated Raman side-scattering by vector light

Recently, the verification of stimulated Raman side-scattering (SRSS) in different laser inertial confinement fusion ignition schemes poses an underlying risk of SRSS on ignition. In this paper, we propose a method to use the non-uniform polarization nature of vector light to suppress SRSS and give an additional threshold condition determined by the parameter of vector light. For SRSS at 90 degrees, where the scattered electromagnetic wave travels perpendicular to the density profile, the polarization variation of the pump will change the wave vector of scattered light, thereby reducing the growth length and preventing the scattered electromagnetic wave from growing. This suppressive scheme is verified through three-dimensional particle-in-cell simulations. Our illustrative simulation results demonstrate that for linearly polarized Gaussian light, the SRSS signal occurs in the 90-degree direction fiercely. At the same time, for the vector light, there is few SRSS signal even if the condition dramatically exceeds the threshold. Furthermore, we discuss the impact of vector light on stimulated Raman and Brillouin backscattering, and two-plasma decay

Table_1_Association of frailty with health service use among older Chinese adults: analysis of population-based panel data.docx

BackgroundFrailty is a common syndrome characterized by rapid growth in the aging population that has an impact on healthcare systems. This study aimed to investigate the impact of frailty on health service use and whether this effect varies with chronic diseases and socioeconomic status among older individuals in China.MethodsA balanced panel data analysis was conducted on 3,306 older individuals who completed follow-ups for the three waves of the China Health and Retirement Longitudinal Study (CHARLS) in 2011, 2013, and 2015. The Physical Frailty Phenotype (PFP) Scale was used to assess frailty status. Negative binomial regression was used to test the associations between frailty status, outpatient visits in the past 4 weeks, and annual inpatient hospital days.ResultsCompared with robust individuals, individuals with pre-frail or frail status were likely to report a higher number of outpatient visits [pre-frail: incidence rate ratio (IRR) = 1.28, 95% CI = 1.16–1.41; frail: IRR = 1.45, 95% CI = 1.23–1.71], and inpatient hospital days (pre-frail: IRR = 1.40, 95% CI = 1.24–1.58; frail: IRR = 2.17, 95% CI = 1.81–2.60) after controlling for all covariates. All five frailty components (weight loss, exhaustion, low physical activity, slowness, and weakness) were associated with a higher number of inpatient hospital days, and two components (weight loss and exhaustion) were associated with a higher number of outpatient visits. The effect of frailty on inpatient hospital stays persisted in different socioeconomic groups, across all health insurance programmes and physical comorbidities.ConclusionFrailty is associated with greater health service use among older individuals. Effective screening, prevention, intervention, and management of frailty may be important to reduce health service use.</p

Substrate-Induced Liquid Layering: A New Insight into the Heterogeneous Nucleation of Liquid Metals

Liquid layering, which is a general phenomenon adjacent to the solid substrates, is less understood for its role in heterogeneous nucleation. In this work, the structural features and dynamics of the liquid Al layers induced by the (0001) sapphire and the (0001) TiB2 substrates, respectively, are quantitatively compared based on the ab initio molecular dynamics simulations. An almost fully ordered liquid Al layer is observed adjacent to the TiB2 substrate above the Al melting point, while the liquid layers near the sapphire substrate are weakly ordered with virtually no in-plane translational symmetry. Further liquid layering is facilitated by the ordered liquid layer near the TiB2 substrate, while impeded by the low in-plane ordering of the liquid layers near the sapphire substrate, resulting in different nucleation behaviors for the two systems. The difference in the liquid layering is caused, in part, by the lower adsorption strength at the sapphire–liquid Al interface than that at the TiB2–liquid Al interface. Additionally, the compressive stress imposed on the liquid layers seriously hinders the sapphire-induced liquid layering. We conclude from this work that the interfacial adsorption strength and mismatch alter the heterogeneous nucleation by influencing the features of the substrate-induced liquid layering

The In-Plane Structure and Dynamic Property of the Homogeneous Al-Al Solid-Liquid Interface

Using molecular dynamics simulation and a newly developed COMB3 potential, the in-plane ordering and diffusion constant profiles at the homogeneous (100), (110), and (111) interfaces between solid and liquid Al have been examined. We found that the in-plane ordering characterized by 2-D density maps and 2-D structure factors existed in the first 6, 10, and 3 out-of-plane layers at the (100), (110), and (111) interfaces, respectively, showing a strong dependence on substrate orientation. In layers with in-plane ordering, the diffusion constant is greatly reduced relative to its value in the bulk liquid, while the influence of layers without in-plane ordering is negligible. The three diffusivity components turn out to be isotropic at the homogeneous interfaces. The Al-Al interfaces studied here will serve as an important reference in comparisons of the structure and properties of different solid-liquid interfaces, which will greatly support the design of grain refiners

The In-Plane Structure and Dynamic Property of the Homogeneous Al-Al Solid-Liquid Interface

Using molecular dynamics simulation and a newly developed COMB3 potential, the in-plane ordering and diffusion constant profiles at the homogeneous (100), (110), and (111) interfaces between solid and liquid Al have been examined. We found that the in-plane ordering characterized by 2-D density maps and 2-D structure factors existed in the first 6, 10, and 3 out-of-plane layers at the (100), (110), and (111) interfaces, respectively, showing a strong dependence on substrate orientation. In layers with in-plane ordering, the diffusion constant is greatly reduced relative to its value in the bulk liquid, while the influence of layers without in-plane ordering is negligible. The three diffusivity components turn out to be isotropic at the homogeneous interfaces. The Al-Al interfaces studied here will serve as an important reference in comparisons of the structure and properties of different solid-liquid interfaces, which will greatly support the design of grain refiners

Reinforcement learning for human-robot shared control

This paper aims at proposing a general framework of shared control for human-robot interaction. Human dynamics are considered in analysis of the coupled human-robot system. Motion intentions of both human and robot are taken into account in the control objective of the robot. Reinforcement learning is developed to achieve the control objective subject to unknown dynamics of human and robot. The closed-loop system performance is discussed through a rigorous proof. Simulations are conducted to demonstrate the learning capability of the proposed method and its feasibility in handling various situations. Compared to existing works, the proposed framework combines motion intentions of both human and robot in a human-robot shared control system, without the requirement of the knowledge of humans and robots dynamics

A framework of human–robot coordination based on game theory and policy iteration

In this paper, we propose a framework to analyze the interactive behaviors of human and robot in physical interactions. Game theory is employed to describe the system under study, and policy iteration is adopted to provide a solution of Nash equilibrium. The human’s control objective is estimated based on the measured interaction force, and it is used to adapt the robot’s objective such that human-robot coordination can be achieved. The validity of the proposed method is verified through a rigorous proof and experimental studies