Economic inequality and the provision of schooling

This paper was presented at the conference "Unequal incomes, unequal outcomes? Economic inequality and measures of well-being" as part of session 3, "Education and crime in urban neighborhoods." The conference was held at the Federal Reserve Bank of New York on May 7, 1999. The authors examine the empirical evidence on the relationship between school finance reform and student outcomes, review the economic literature in the field, and present new evidence of the effects of reform on community and school composition. They argue that if one's goal is to reduce income inequality substantially, one should not look to school finance reform as a particularly effective policy instrument. Even the most optimistic estimates of the impact of school finance reform on the distribution of student performance indicate that these effects are relatively small. Furthermore, the authors note that these small gains may come at a cost - the movement of higher income families into private sector schools, a development that would lead to less diversity within the public schools.Income distribution ; Income ; Education

Evidence for a Single Ureilite Parent Asteroid from a Petrologic Study of Polymict Ureilites

Ureilites are ultramafic achondrites composed of olivine and pyroxene, with minor elemental C, mostly as graphite [1]. The silicate composition indicates loss of a basaltic component through igneous processing, yet the suite is very heterogeneous in O isotopic composition inherited from nebular processes [2]. Because of this, it has not yet been established whether ureilites were derived from a single parent asteroid or from multiple parents. Most researchers tacitly assume a single parent asteroid, but the wide variation in mineral and oxygen isotope compositions could be readily explained by an origin in multiple parent asteroids that had experienced a similar evolution. Numerous ureilite meteorites have been found in Antarctica, among them several that are clearly paired (Fig. 1) and two that are strongly brecciated (EET 83309, EET 87720). We have begun a detailed petrologic study of these latter two samples in order to characterize the range of materials in them. One goal is to attempt to determine whether ureilites were derived from a single parent asteroid

Processes in Early Planetesimals: Evidence from Ureilite Meteorites

Ureilites are primitive ultramafic achondrites composed largely of olivine and pigeonite, with minor augite, carbon, sulphide and metal. They represent very early material in the history of the Solar System and form a bridge between undifferentiated chondrites and fully differentiated asteroids. They show a mixture of chemical characteristics, some of which are considered to be nebula-derived (e.g. a negative correlation between Mg/Fe and Delta O-17 that resembles that of the ordinary chondrites but at lower Delta O-17 values) whereas others have been imposed by asteroidal differentiation. Carbon isotope data show a striking negative correlation of delta C-13 values with mg# in olivine. delta C-13 also correlates positively with Delta O-17, and therefore this isotopic variation was probably also nebula-derived. Thus, oxygen and carbon isotope compositions and Fe-Mg systematics of each monomict ureilite were established before differentiation processes began. Heated by decay of short-lived radioactive isotopes, the ureilite asteroid started to melt. Metal and sulphide would have melted first, forming a Fe-S eutectic liquid, which removed chalcophile elements and incompatible siderophile elements, and basaltic melts that removed Al, Ca and the LREE. Several elements show different abundances and/or correlations with Fo content in olivine, e.g. carbon shows a positive correlation in ferroan ureilites, and a weak or even negative correlation in more magnesian compositions. HSE such as Os and Ir also show different distributions, i.e. ureilites with Fo 82 tend to have much less scattered and overall lower Os and Ir abundances. A similar change in elemental behaviour is shown by the Fe-Mn relations in ureilitic olivines: those with Fo contents 85 show much greater scatter. This suggests that a major change affected the parent body at a time when melting had reached relatively magnesian bulk compositions. We consider that this event may have been a hit and run collision in which the ureilite parent body collided with a larger object. During the collision, the ureilite mantle broke up catastrophically but re-accreted in a jumbled state around the still-intact core. Mg-rich basaltic melts that were in the process of being formed at the time of break-up were retained in part as melt clasts that re-accreted to the regolith and are found in polymict ureilites

Curved Gratings as Plasmonic Lenses for Linearly Polarised Light

The ability of curved gratings as sectors of concentric circular gratings to couple linearly polarized light into focused surface plasmons is investigated by theory, simulation and experiment. Curved gratings, as sectors of concentric circular gratings with four different sector angles, are etched into a 30-nm thick gold layer on a glass coverslip and used to couple linearly-polarised free space light at nm into surface plasmons. The experimental and simulation results show that increasing the sector angle of the curved gratings decreases the lateral spotsize of the excited surface plasmons, resulting in focussing of surface plasmons which is analogous to the behaviour of classical optical lenses. We also show that two faced curved gratings, with their groove radius mismatched by half of the plasmon wavelength (asymmetric configuration), can couple linearly-polarised light into a single focal spot of concentrated surface plasmons with smaller depth of focus and higher intensity in comparison to single-sided curved gratings. The major advantage of these structures is the coupling of linearly-polarised light into focused surface plasmons with access to and control of the plasmon focal spot, which facilitates potential applications in sensing, detection and nonlinear plasmonics.Comment: 15 pages and 12 figure

Identifying New Pari-Mutuel iGaming Offerings in the United States

Purpose: The purpose of this paper is to develop a competitive landscape of current offerings in the online fantasy sports and online pari-mutuel wagering market in the US and to determine potential differentiated pari-mutuel sports iGaming offerings based on that landscape

Friction modelling requirements and implementation in railway freight vehicle dynamic simulations

The highly nonlinear characteristics of dry friction damped suspension components used in railway freight vehicles increases the modelling challenges in Multibody Simulations (MBS) software packages such as VAMPIRE, SIMPACK and ADAMS VI-RAIL. These system nonlinearities then lead to lower confidence levels in modelling methodologies and therefore, more uncertainty in the simulation results produced by these models. The main reasons for the low confidence levels associated with friction modelling methodologies in the context of railway freight vehicles, are due to the lack of reliable test data to validate the friction models used in the primary/secondary suspension. Therefore, there is an industry requirement to better understand the in service/maintenance requirements of these components, first from a testing perspective and then from a modelling one. Once this current gap in knowledge and understanding is bridged, the results generated from the simulation models could then be used in the future to replace on-track/laboratory testing, which would bring significant cost benefits to the rail freight industry. The work presented in this thesis reviews the current friction testing and modelling methodologies as well as the simplifying assumptions that are implemented in commercial MBS software packages. The most common friction model that is used in railway vehicle MBS for example, is the Coulomb model of dry friction. This model however, is not capable of describing stick-slip behaviour, pre-sliding displacements or the viscoelastic effects of friction surfaces when they start to yield under extreme loading conditions. The Coulomb friction model also has a discontinuity in the vicinity of zero velocity, which can cause numerical issues in MBS as the friction force in this region, is non-differentiable. To handle the discontinuity, a variety of regularisation methods are generally implemented in the Coulomb model which are further discussed in the literature review. The impact of these regularisation methods on the validity of MBS results however are currently not fully understood or justified, as these tend to be mathematical smoothing functions that are not actually related to the mechanical properties of the friction surfaces. Therefore, to better understand the limitations of the Coulomb friction model and its application, as well as the different regularisation methods that are implemented in freight vehicle secondary suspension friction models, several scale model benchmark tests have been carried out on a variety of rail industry standard secondary suspension wear liner components. The critical modelling parameters that are required to develop a comprehensive/optimised freight vehicle secondary suspension friction model were then calculated from the benchmark test data. These parameters include the torsional stiffness and damping properties of the centre plate/wear liner components, as well as the Coefficient of Friction (COF) values and frequency signatures of the secondary suspension system. From this research, three novel secondary suspension friction models are proposed that have been developed to work in conjunction with the SIMPACK software package via the co-simulation functionality. These models include the novel local/global friction models, which are used together in MBS to describe the hysteresis and frequency responses of the centre plate/wear liner components as well as increases in these parameters as a function of time and the number of running cycles

Evidence from Polymict Ureilite Meteorites for a Single "Rubble-Pile" Ureilite Parent Asteroid Gardened by Several Distinct Impactors

Ureilites are ultramafic achondrite meteorites that have experienced igneous processing whilst retaining heterogeneity in mg# and oxygen isotope ratios. Polymict ureilites represent material derived from the surface of the ureilite parent asteroid(s). Electron microprobe analysis of more than 500 olivine and pyroxene clasts in six polymict ureilites reveals that they cover a statistically identical range of compositions to that shown by all known monomict ureilites. This is considered to be convincing evidence for derivation from a single parent asteroid. Many of the polymict ureilites also contain clasts that have identical compositions to the anomalously high Mn/Mg olivines and pyroxenes from the Hughes 009 monomict ureilite (here termed the Hughes cluster ). Four of the six samples also contain distinctive ferroan lithic clasts that have been derived from oxidized impactors. The presence of several common distinctive lithologies within the polymict ureilites is additional evidence that the ureilites were derived from a single parent asteroid. Olivine in a large lithic clast of augite-bearing ureilitic has an mg# of 97, extending the compositional range of known ureilite material. Our study confirms that ureilitic olivine clasts with mg#s 85, which also show more variable Mn contents, including the melt-inclusion bearing "Hughes cluster" ureilites. We interpret this to indicate that the parent ureilite asteroid was disrupted by a major impact at a time when melt was still present in regions with a bulk mg# > 85, giving rise to the two types of ureilites: common ferroan ones that were already residual after melting and less common magnesian ones that were still partially molten when disruption occurred, some of which are the result of interaction of melts with residual mantle during disruption. A single daughter asteroid re-accreted from the disrupted remnants of the mantle of the proto-ureilite asteroid, giving rise to a "rubble-pile" body that had material of a wide variety of compositions and shock states present on its surface. The analysed polymict ureilite meteorites represent regolith that subsequently formed on this asteroidal surface, including impact-derived material from at least six different meteoritic sources