How has the Louisiana Scholarship Program Affected Students? A Comprehensive Summary of Effects after Four Years

School choice has long been a subject of robust debate. Private school vouchers—programs providing public funds for students to attend K-12 private schools—tend to be the most contentious form of school choice. Over the past three years, our research team has released a series of reports examining how the LSP has affected key student and community conditions

Area laws in quantum systems: mutual information and correlations

The holographic principle states that on a fundamental level the information content of a region should depend on its surface area rather than on its volume. This counterintuitive idea which has its roots in the nonextensive nature of black-hole entropy serves as a guiding principle in the search for the fundamental laws of Planck-scale physics. In this paper we show that a similar phenomenon emerges from the established laws of classical and quantum physics: the information contained in part of a system in thermal equilibrium obeys an area law. While the maximal information per unit area depends classically only on the number of microscopic degrees of freedom, it may diverge as the inverse temperature in quantum systems. A rigorous relation between area laws and correlations is established and their explicit behavior is revealed for a large class of quantum many-body states beyond equilibrium systems.Comment: 5 pages, 2 figures, published version with appendi

3D-to-2D Transition of Anion Vacancy Mobility in CsPbBr₃under Hydrostatic Pressure

We study the effects of hydrostatic pressure in the range 0.0--2.0 GPa on anion mobility in the orthorhombic $Pnma$ phase of CsPbBr$_{3}$. Using density functional theory and the climbing nudged elastic band method, we calculate the transition states and activation energies for anions to migrate both within and between neighbouring PbBr$_{3}$ octahedra. The results of those calculations are used as input to a kinetic model for anion migration, which we solve in the steady state to determine the anion mobility tensor as a function of applied pressure. We find that the response of the mobility tensor to increasing pressure is highly anisotropic, being strongly enhanced in the $(010)$ lattice plane and strongly reduced in the direction normal to it at elevated pressure. These results demonstrate the potentially significant influence of pressure and strain on the magnitude and direction of anion migration in lead--halide perovskites.Comment: 25 pages, 3 figure

Non-innocent role of fluorine as an electron donor in oxides

Engineering of reducible oxides is generally focused on the cation sites. As such, anion doping remains an underutilized tool despite its unique potential in altering the defect chemistry and steering redox processes. In this contribution, we explore the possibilities offered by substitution on the anion site on the case of a prototypical reducible oxide, namely cerium oxide, doped with fluorine. The choice of fluorine is motivated by the general stability of fluorine in oxide lattices and the fact that it can be readily incorporated in these up to very high concentration with minimal structural distortion [1]. Utilizing photoemission spectroscopy in combination with density functional theory [2], we show that the general notion of fluorine acting as a straightforward ionic donor fails to capture the intricacies of electronic interactions at play. Specifically, we provide evidence for covalent hybridization in the nominally ionic fluorine-cerium interaction that allows for altering the anion derived electron density in cerium oxide beyond the oxygen 2p band (see Figure 1), contrary to the simplified picture of solely introducing a deeper-laying fluorine 2p band [3]. The emergent electronic configuration can be further coupled to standard valence band engineering methods, such as strain manipulation, to provide an unprecedented playground for designing the oxide properties. Our results also demonstrate the practicality of interatomic resonant photoemission spectroscopy as a gauge of non-trivial electronic effects of ligand origin, allowing to efficiently probe the above-mentioned effects. We note that fluorine doping represents a complement to oxygen vacancy engineering and highlight the fact that, unlike oxygen vacancies, the electronic effects generated by fluorine can persist in an oxidizing environment. The latter represents an important contribution the electronic modification of mixed-anion oxides can provide to a breadth of fields, ranging from superoxide stabilization to resistive switching. Please click Additional Files below to see the full abstract

Slit Mask Integral Field Units for the Southern African Large Telescope

Two fibre integral field units (IFU) are being built in the SAAO fibre-lab for the Robert Stobie Spectrograph's visible arm and the future red arm. Each IFU sits in its own slit-mask cassette and is referred to as a slit-mask IFU (SMI). They will be available some time in 2022. The smaller, 200 micron fibre IFU has 309 X 0.9 arcsec diameter spatial elements covering an elongated hexagonal footprint of 18 X 23 arcsec. The larger, 400 micron fibre IFU has 178 X 1.8 arcsec diameter spatial elements covering an on-sky area of 21 X 44 arcsec. In both cases there are two groups of 13 fibres offset by roughly 50 arcsec on either side of the primary array to sample sky. The 1.8 and 0.9 arcsec spatial resolution SMIs provide median spectral resolution of 1200 and 2400 respectively at H alpha wavelengths in the low resolution mode covering 320 to 740 nm bandpass. At a higher grating angle the SMI will deliver spectral resolution up to 5000 and 10000 with 400 and 200 micron core fibre respectively. A future red-arm will extend the simultaneous wavelength coverage up to 900 nm at a median resolution of 3000/6000 for the same flavors of IFUs. SMIs are inserted in the same fashion as the existing longslit cassettes at the SALT focal plane. Prismatic fold mirrors direct the focal plane into the fibre IFU and then back into the RSS collimator after the fibres are routed 180 deg within the cassette and formatted into a pseudo-slit. Fold prisms ensure that the spectrograph collimator continues to see the same focal plane. In this paper we describe the design, fabrication, assembly and characterization of Slit Mask IFUs

Education Freedom and Student Achievement: Is More School Choice Associated with Higher State-Level Performance on the NAEP?

School choice is on the rise in many states. Since the start of the new millennium, many states have launched or expanded private school choice options, permitted and expanded independently operated public charter schools, eased restrictions on homeschooling, and enacted policies that allow and encourage various forms of public school choice. One thing that is not on the rise, unfortunately, is average student scores on the National Assessment of Education Progress (NAEP). Student performance on the assessments, typically called “The Nation’s Report Card,” were flat from 2001 until 2015 and have dropped slightly in both 2017 and 2019

HexPak and GradPak: variable-pitch dual-head IFUs for the WIYN 3.5m Telescope Bench Spectrograph

We describe the design, construction, and expected performance of two new fiber integral field units (IFUs) --- HexPak and GradPak --- for the WIYN 3.5m Telescope Nasmyth focus and Bench Spectrograph. These are the first IFUs to provide formatted fiber integral field spectroscopy with simultaneous sampling of varying angular scales. HexPak and GradPak are in a single cable with a dual-head design, permitting easy switching between the two different IFU heads on the telescope without changing the spectrograph feed: the two heads feed a variable-width double-slit. Each IFU head is comprised of a fixed arrangement of fibers with a range of fiber diameters. The layout and diameters of the fibers within each array are scientifically-driven for observations of galaxies: HexPak is designed to observe face-on spiral or spheroidal galaxies while GradPak is optimized for edge-on studies of galaxy disks. HexPak is a hexagonal array of 2.9 arcsec fibers subtending a 40.9 arcsec diameter, with a high-resolution circular core of 0.94 arcsec fibers subtending 6 arcsec diameter. GradPak is a 39 by 55 arcsec rectangular array with rows of fibers of increasing diameter from angular scales of 1.9 arcsec to 5.6 arcsec across the array. The variable pitch of these IFU heads allows for adequate sampling of light profile gradients while maintaining the photon limit at different scales.Comment: 10 pages, 4 figures, presented at SPIE, Astronomical Telescopes and Instrumentation, 1 - 6 July 2012, Amsterdam, Netherland

Induction Mapping of the 3D-Modulated Spin Texture of Skyrmions in Thin Helimagnets

Envisaged applications of skyrmions in magnetic memory and logic devices crucially depend on the stability and mobility of these topologically non-trivial magnetic textures in thin films. We present for the first time quantitative maps of the magnetic induction that provide evidence for a 3D modulation of the skyrmionic spin texture. The projected in-plane magnetic induction maps as determined from in-line and off-axis electron holography carry the clear signature of Bloch skyrmions. However, the magnitude of this induction is much smaller than the values expected for homogeneous Bloch skyrmions that extend throughout the thickness of the film. This finding can only be understood, if the underlying spin textures are modulated along the out-of-plane z direction. The projection of (the in-plane magnetic induction of) helices is further found to exhibit thickness-dependent lateral shifts, which show that this z modulation is accompanied by an (in-plane) modulation along the x and y directions

Long-term potentiation requires activation of calcium-independent phospholipase A2

AbstractThe predominant phospholipase activity present in rat hippocampus is a calcium-independent phospholipase A2 (302.9 ± 19.8 pmol/mg·min for calcium-independent phospholipase A2 activity vs. 14.6 ± 1.0 pmol/mg·min for calcium-dependent phospholipase A2 activity). This calcium-independent phospholipase A2 is exquisitely sensitive to inhibition by the mechanism-based inhibitor, (E)-6-(bromomethylene)-tetrahydro-3-(1-naphthalenyl)-2H-pyran -2-one (BEL). Moreover, treatment of hippocampal slices with BEL prior to tetanic stimulation prevents the induction of LTP (40.8 ± 5.6% increase in excitatory postsynaptic potential (EPSP) slope for control slices (n = 6) vs. 5.8 ± 8.5% increase in EPSP slope for BEL-treated slices (n = 8)). Importantly, LTP can be induced following mechanism-based inhibition of phospholipase A2 by providing the end product of the phospholipase A2 reaction, arachidonic acid, during the application of tetanic stimulation. Furthermore, the induction of LTP after treatment with BEL is dependent on the stereoelectronic configuration of the fatty acid provided since eicosa-5,8,11-trienoic acid, but not eicosa-8,11,14-trienoic acid, rescues LTP after BEL treatment (37.6 ± 16.1% increase in EPSP slope for eicosa-5,8,11-trienoic acid vs. −3.7 ± 5.2% increase in EPSP slope for eicosa-8,11,14-trienoic acid). Collectively, these results provide the first demonstration of the essential role of calcium-independent phospholipase A2 in synaptic plasticity