5,473 research outputs found
The Public Education Tax Credit
Public education is an end, not a means. For a democratic nation to thrive, its schools must prepare children not only for success in private life but for participation in public life. It must foster harmonious social relations among the disparate groups in our pluralistic society and ensure universal access to a quality education. Unfortunately, the American school system has long fallen short as a means of fulfilling these purposes. This paper offers a more effective way of delivering on the promise of public education, by ensuring that all families have the means to choose their children's schools from a diverse market of education providers. All education providers -- government, religious, and secular -- can contribute to public education because all can serve the public by educating children. Educational freedom can most effectively be realized through nonrefundable education tax credits -- for both parents' education costs for their own children and taxpayer donations to nonprofit scholarship funds. This paper argues that tax credits enjoy practical, legal, and political advantages over school vouchers. These advantages are even more important for choice programs that target low-income children, as tax credits mitigate some disadvantages inherent to targeted programs. It also contends that broad-based programs are superior to narrowly targeted ones, even when the goal is specifically to serve disadvantaged students. Targeted programs are fundamentally inferior -- in both practical and strategic terms -- to broad-based programs that include the voting middle class. Finally, accountability in education means accountability to parents and taxpayers. Education tax credits afford this accountability without the need for intrusive government regulations that create political and market liabilities for school choice policies. To date, school choice policy has spread and grown only slowly, in part because of inadequate legislation. Existing school choice laws fall short in terms of both market principles and political considerations. Pursuing a policy that follows more closely what works economically and politically should increase the likelihood of long-term legislative success, program success, program survival, and program expansion
Integrability of graph combinatorics via random walks and heaps of dimers
We investigate the integrability of the discrete non-linear equation
governing the dependence on geodesic distance of planar graphs with inner
vertices of even valences. This equation follows from a bijection between
graphs and blossom trees and is expressed in terms of generating functions for
random walks. We construct explicitly an infinite set of conserved quantities
for this equation, also involving suitable combinations of random walk
generating functions. The proof of their conservation, i.e. their eventual
independence on the geodesic distance, relies on the connection between random
walks and heaps of dimers. The values of the conserved quantities are
identified with generating functions for graphs with fixed numbers of external
legs. Alternative equivalent choices for the set of conserved quantities are
also discussed and some applications are presented.Comment: 38 pages, 15 figures, uses epsf, lanlmac and hyperbasic
Nebraska Art Today: A Centennial Invitational Exhibition
Anniversaries make suitable opportunities for summing up - appraising past progress and looking forward to a better future. Hence, in Nebraska\u27s 100th year as one of the United States of America, it is appropriate that we trace activity in the arts during pioneer days and the period of expansion, pausing perhaps to offer congratulations for past accomplishments or to wish that achievement had been higher.
Middle Western culture is a transplant and a product of the times. The newly-opened territory offered opportunities for material advancement, and settlers either brought with them an acquaintance with genteel living or a desire for a better life. Practical matters and the demands of everyday living had to come first. But when the first days of prosperity arrived, the successful could indulge themselves in comfort and luxuries which naturally reflected the tastes of the decade. The decorative arts were patterned on plush Victorian parlors adapted from royal palaces. Paintings fitted the decor, being usually copies of old masters or derivatives of European Salon paintings which featured pleasing landscapes, romanticized peasants, or story-telling scenes. It is not to be expected to find a collector who would explore the work of the painters experimenting in such unproved techniques as impressionism, even though examples by painters now world-famous were exhibited in the state. In general the work of local artists followed the national taste. As might be expected, most art activity centered in the larger towns of lincoln and Omaha, both for creative artists and for patrons of the arts.
The illustrations in the first part of this booklet show paintings from the early exhibitions in Nebraska which can still be seen today, or other works by the same artists. These pictures represent only a sampling of the collections and are intended to show the variety of painting types and the changing pattern of styles. Many of the paintings may seem dated to us now, but they represent not only the taste of their patrons, but reflect attitudes of each period, just as painting in 1967 expresses the new forces with which we are confronted - electronics, mechanization, splitting atoms and exploring outer space. Once the artist knows how the earth is flattened and patterned by a view from 30,000 feet in the sky, he can no longer present a landscape from the view-point of a rural shepherd without ignoring the realities of his own existence. Paintings of today should be different from those of yesterday. The work of representative Nebraska artists of today illustrated in this catalog gives a sampling of the varied and individual work being done now. While this work shows the influence of contemporary trends, all art evolves from the past. The earliest artists who painted in Nebraska cannot be claimed as Nebraskans. They were artists-explorers who passed through during the first half of the 19th Century as expedition members, or in the latter half of the Century as professional artists who were inspired by the glorious vistas of the plains and the mountains and whose paintings found a ready market among those fascinated by the new West. However, they are a part of our heritage and should be mentioned
Random tensor models in the large N limit: Uncoloring the colored tensor models
Tensor models generalize random matrix models in yielding a theory of
dynamical triangulations in arbitrary dimensions. Colored tensor models have
been shown to admit a 1/N expansion and a continuum limit accessible
analytically. In this paper we prove that these results extend to the most
general tensor model for a single generic, i.e. non-symmetric, complex tensor.
Colors appear in this setting as a canonical book-keeping device and not as a
fundamental feature. In the large N limit, we exhibit a set of Virasoro
constraints satisfied by the free energy and an infinite family of
multicritical behaviors with entropy exponents \gamma_m=1-1/m.Comment: 15 page
Quantum Phase Slips in one-dimensional Josephson Junction Chains
We have studied quantum phase-slip (QPS) phenomena in long one-dimensional
Josephson junction series arrays with tunable Josephson coupling. These chains
were fabricated with as many as 2888 junctions, where one sample had a tunable
weak link in the middle. Measurements were made of the zero-bias resistance,
, as well as current-voltage characteristics (IVC). The finite is
explained by QPS and shows an exponential dependence on with a
distinct change in the exponent at . When the IVC
clearly shows a remnant of the Coulomb blockade, which evolves to a
zero-current state with a sharp critical voltage as is tuned to a smaller
value. The zero-current state below the critical voltage is due to coherent QPS
and we show that these are enhanced at the central weak link. Above the
critical voltage a negative differential resistance is observed which nearly
restores the zero-current state
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Health benefits and control costs of tightening particulate matter emissions standards for coal power plants - The case of Northeast Brazil.
Exposure to ambient particulate matter (PM) caused an estimated 4.2 million deaths worldwide in 2015. However, PM emission standards for power plants vary widely. To explore if the current levels of these standards are sufficiently stringent in a simple cost-benefit framework, we compared the health benefits (avoided monetized health costs) with the control costs of tightening PM emission standards for coal-fired power plants in Northeast (NE) Brazil, where ambient PM concentrations are below World Health Organization (WHO) guidelines. We considered three Brazilian PM10 (PMx refers to PM with a diameter under x micrometers) emission standards and a stricter U.S. EPA standard for recent power plants. Our integrated methodology simulates hourly electricity grid dispatch from utility-scale power plants, disperses the resulting PM2.5, and estimates selected human health impacts from PM2.5 exposure using the latest integrated exposure-response model. Since the emissions inventories required to model secondary PM are not available in our study area, we modeled only primary PM so our benefit estimates are conservative. We found that tightening existing PM10 emission standards yields health benefits that are over 60 times greater than emissions control costs in all the scenarios we considered. The monetary value of avoided hospital admissions alone is at least four times as large as the corresponding control costs. These results provide strong arguments for considering tightening PM emission standards for coal-fired power plants worldwide, including in regions that meet WHO guidelines and in developing countries
Proton deflectometry analysis in magnetized plasmas: magnetic field reconstruction in one dimension
Proton deflectometry is increasingly used in magnetized high-energy-density
plasmas to observe electromagnetic fields. We describe a reconstruction
algorithm to recover the electromagnetic fields from proton fluence data in
1-D. The algorithm is verified against analytic solutions and applied to
example data. The virtue of a 1-D algorithm is that it is fast and can be
incorporated into higher-level analysis routines and workflows, for example to
scan parameters and conduct uncertainty analysis. Furthermore, working through
the 1-D algorithm exposes the fundamental importance of boundary conditions and
the initial proton fluence profile for an accurate reconstruction. From these
considerations we propose a hybrid mesh-fluence reconstruction technique where
fields are reconstructed from fluence data in an interior region with boundary
conditions supplied by direct mesh measurements at the boundary.Comment: 10 pages, 6 figures. For code library, see:
https://github.com/wrfox/PRADICAMEN
Confluence of geodesic paths and separating loops in large planar quadrangulations
We consider planar quadrangulations with three marked vertices and discuss
the geometry of triangles made of three geodesic paths joining them. We also
study the geometry of minimal separating loops, i.e. paths of minimal length
among all closed paths passing by one of the three vertices and separating the
two others in the quadrangulation. We concentrate on the universal scaling
limit of large quadrangulations, also known as the Brownian map, where pairs of
geodesic paths or minimal separating loops have common parts of non-zero
macroscopic length. This is the phenomenon of confluence, which distinguishes
the geometry of random quadrangulations from that of smooth surfaces. We
characterize the universal probability distribution for the lengths of these
common parts.Comment: 48 pages, 33 color figures. Final version, with one concluding
paragraph and one reference added, and several other small correction
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