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Improvements to the 529 platform could increase the number of low- and moderate-income families saving in 529s and make it easier for these families to build assets for education. These reforms include large initiatives, such as coordinating existing higher education tax credits and financial aid with 529s, as well as small initiatives to increase savings. This document contains several low-cost, simple reforms for 529s at the federal level. These would be important first steps for enabling more low- and moderate-income students to complete higher education

Reconstruction of deglacial sea surface temperatures in the tropical Pacific from selective analysis of a fossil coral

The Sr/Ca of coral skeletons demonstrates potential as an indicator of sea surface temperatures (SSTs). However, the glacial-interglacial SST ranges predicted from Sr/Ca of fossil corals are usually higher than from other marine proxies. We observed infilling of secondary aragonite, characterised by high Sr/Ca ratios, along intraskeletal pores of a fossil coral from Papua New Guinea that grew during the penultimate deglaciation (130 +/- 2 ka). Selective microanalysis of unaltered areas of the fossil coral indicates that SSTs at similar to 130 ka were &lt;= 1 degrees C cooler than at present in contrast with bulk measurements ( combining infilled and unaltered areas) which indicate a difference of 6-7 degrees C. The analysis of unaltered areas of fossil skeletons by microprobe techniques may offer a route to more accurate reconstruction of past SSTs.</p

Local Atomic Structure of Martensitic Ni2+x_{2+x}Mn1−x_{1-x}Ga: An EXAFS Study

The local atomic structure of Ni$_{2+x}$Mn$_{1-x}$Ga with 0 $\le$ $x$ $\le$ 0.16 alloys was explored using Mn and Ga K-edge Extended X-ray Absorption Fine Structure (EXAFS) measurement. Inorder to study the atomic re-arrangements that occur upon martensitic transformation, room temperature and low temperature EXAFS were recorded. The changes occurring in the L2$_1$ unit cell and the bond lengths obtained from the analysis enables us to determine the modulation amplitudes over which the constituent atoms move giving rise to shuffling of the atomic planes in the modulated structure. The EXAFS analysis also suggests the changes in hybridization of Ga-$p$ and Ni-$d$ orbitals associated with the local symmetry breaking upon undergoing martensitic transition.Comment: Accepted for publication in Physical Review

Structural precursor to the metal-insulator transition in V_2O_3

The temperature dependence of the local structure of V_2O_3 in the vicinity of the metal to insulator transition (MIT) has been investigated using hard X-ray absorption spectroscopy. It is shown that the vanadium pair distance along the hexagonal c-axis changes abruptly at the MIT as expected. However, a continuous increase of the tilt of these pairs sets in already at higher temperatures and reaches its maximum value at the onset of the electronic and magnetic transition. These findings confirm recent theoretical results which claim that electron-lattice coupling is important for the MIT in V_2O_3. Our results suggest that interactions in the basal plane play a decisive role for the MIT and orbital degrees of freedom drive the MIT via changes in hybridization.Comment: 6 pages, 5 figures, 2 table

XAFS spectroscopy. I. Extracting the fine structure from the absorption spectra

Three independent techniques are used to separate fine structure from the absorption spectra, the background function in which is approximated by (i) smoothing spline. We propose a new reliable criterion for determination of smoothing parameter and the method for raising of stability with respect to k_min variation; (ii) interpolation spline with the varied knots; (iii) the line obtained from bayesian smoothing. This methods considers various prior information and includes a natural way to determine the errors of XAFS extraction. Particular attention has been given to the estimation of uncertainties in XAFS data. Experimental noise is shown to be essentially smaller than the errors of the background approximation, and it is the latter that determines the variances of structural parameters in subsequent fitting.Comment: 16 pages, 7 figures, for freeware XAFS analysis program, see http://www.crosswinds.net/~klmn/viper.htm

L-Edge Xanes Measurements of the Oxidation State of Tungsten in Iron Bearing and Iron Free Silicate Glasses

Tungsten is important in constraining core formation of the Earth because this element is a moderately siderophile element (depleted ~ 10 relative to chondrites) and, as a member of the Hf-W isotopic system, it is useful in constraining the timing of core formation. A number of previous experimental studies have been carried out to determine the silicate solubility and metal-silicate partitioning behavior of W, including its concomitant oxidation state. However, results of previous studies are inconsistent on whether W occurs as W(4+) or W(6+). It is assumed that W(4+) is the cation valence relevant to core formation. Given the sensitivity to silicate composition of high valence cations, knowledge of the oxidation state of W over a wide range of fO2 is critical to understanding the oxidation state of the mantle and core formation processes. This study seeks to measure the W valence and change in valence state over the range of fO2 most relevant to core formation, around IW-2

Iron Redox Systematics of Shergottites and Martian Magmas

Martian meteorites record a range of oxygen fugacities from near the IW buffer to above FMQ buffer [1]. In terrestrial magmas, Fe(3+)/ SigmaFe for this fO2 range are between 0 and 0.25 [2]. Such variation will affect the stability of oxides, pyroxenes, and how the melt equilibrates with volatile species. An understanding of the variation of Fe(3+)/SigmaFe for martian magmas is lacking, and previous work has been on FeO-poor and Al2O3-rich terrestrial basalts. We have initiated a study of the iron redox systematics of martian magmas to better understand FeO and Fe2O3 stability, the stability of magnetite, and the low Ca/high Ca pyroxene [3] ratios observed at the surface

Platinum Partitioning at Low Oxygen Fugacity: Implications for Core Formation Processes

Highly siderophile elements (HSE = Au, Re, and the Pt-group elements) are tracers of silicate / metal interactions during planetary processes. Since most core-formation models involve some state of equilibrium between liquid silicate and liquid metal, understanding the partioning of highly siderophile elements (HSE) between silicate and metallic melts is a key issue for models of core / mantle equilibria and for core formation scenarios. However, partitioning models for HSE are still inaccurate due to the lack of sufficient experimental constraints to describe the variations of partitioning with key variable like temperature, pressure, and oxygen fugacity. In this abstract, we describe a self-consistent set of experiments aimed at determining the valence of platinum, one of the HSE, in silicate melts. This is a key information required to parameterize the evolution of platinum partitioning with oxygen fugacity

Deconvolution problems in x-ray absorption fine structure

A Bayesian method application to the deconvolution of EXAFS spectra is considered. It is shown that for purposes of EXAFS spectroscopy, from the infinitely large number of Bayesian solutions it is possible to determine an optimal range of solutions, any one from which is appropriate. Since this removes the requirement for the uniqueness of solution, it becomes possible to exclude the instrumental broadening and the lifetime broadening from EXAFS spectra. In addition, we propose several approaches to the determination of optimal Bayesian regularization parameter. The Bayesian deconvolution is compared with the deconvolution which uses the Fourier transform and optimal Wiener filtering. It is shown that XPS spectra could be in principle used for extraction of a one-electron absorptance. The amplitude correction factors obtained after deconvolution are considered and discussed.Comment: 6 two-column pages, 5 eps figures; submitted to J. Phys.: Appl. Phy

Iron redox systematics of martian magmas.

第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月18日（金） 国立国語研究所 2階講