440 research outputs found
The (d,6-Li) Reaction Studies
Supported by the National Science Foundation and Indiana Universit
Stochastic volatility and leverage effect
We prove that a wide class of correlated stochastic volatility models exactly
measure an empirical fact in which past returns are anticorrelated with future
volatilities: the so-called ``leverage effect''. This quantitative measure
allows us to fully estimate all parameters involved and it will entail a deeper
study on correlated stochastic volatility models with practical applications on
option pricing and risk management.Comment: 4 pages, 2 figure
Presupernova Structure of Massive Stars
Issues concerning the structure and evolution of core collapse progenitor
stars are discussed with an emphasis on interior evolution. We describe a
program designed to investigate the transport and mixing processes associated
with stellar turbulence, arguably the greatest source of uncertainty in
progenitor structure, besides mass loss, at the time of core collapse. An
effort to use precision observations of stellar parameters to constrain
theoretical modeling is also described.Comment: Proceedings for invited talk at High Energy Density Laboratory
Astrophysics conference, Caltech, March 2010. Special issue of Astrophysics
and Space Science, submitted for peer review: 7 pages, 3 figure
On the valence-bond solid phase of the crossed-chain quantum spin model
Using a series expansion based on the flow-equation method we study the
ground state energy and the elementary triplet excitations of a generalized
model of crossed spin-1/2 chains starting from the limit of decoupled
quadrumers. The triplet dispersion is shown to be very sensitive to the
inter-quadrumer frustration, exhibiting a line of almost complete localization
as well as lines of quantum phase transitions limiting the stability of the
valence-bond solid phase. In the vicinity of the checkerboard-point a finite
window of exchange couplings is found with a non-zero spin-gap, consistent with
known results from exact diagonalization. The ground state energy is lower than
that of the bare quadrumer case for all exchange couplings investigated. In the
limiting situation of the fully frustrated checkerboard magnet our results
agree with earlier series expansion studies.Comment: 8 pages, 7 figure
Measurement of the Proton and Deuteron Spin Structure Functions g2 and Asymmetry A2
We have measured the spin structure functions g2p and g2d and the virtual
photon asymmetries A2p and A2d over the kinematic range 0.02 < x < 0.8 and 1.0
< Q^2 < 30(GeV/c)^2 by scattering 38.8 GeV longitudinally polarized electrons
from transversely polarized NH3 and 6LiD targets.The absolute value of A2 is
significantly smaller than the sqrt{R} positivity limit over the measured
range, while g2 is consistent with the twist-2 Wandzura-Wilczek calculation. We
obtain results for the twist-3 reduced matrix elements d2p, d2d and d2n. The
Burkhardt-Cottingham sum rule integral - int(g2(x)dx) is reported for the range
0.02 < x < 0.8.Comment: 12 pages, 4 figures, 1 tabl
Maternal plasma folate impacts differential DNA methylation in an epigenome-wide meta-analysis of newborns
Folate is vital for fetal development. Periconceptional folic acid supplementation and food fortification are recommended to prevent neural tube defects. Mechanisms whereby periconceptional folate influences normal development and disease are poorly understood: epigenetics may be involved. We examine the association between maternal plasma folate during pregnancy and epigenome-wide DNA methylation using Illumina" s HumanMethyl450 Beadchip in 1,988 newborns from two European cohorts. Here we report the combined covariate-adjusted results using meta-analysis and employ pathway and gene expression analyses. Four-hundred forty-three CpGs (320 genes) are significantly associated with maternal plasma folate levels during pregnancy (false discovery rate 5%); 48 are significant after Bonferroni correction. Most genes are not known for folate biology, including APC2, GRM8, SLC16A12, OPCML, PRPH, LHX1, KLK4 and PRSS21. Some relate to birth defects other than neural tube defects, neurological functions or varied aspects of embryonic development. These findings may inform how maternal folate impacts the developing epigenome and health outcomes in offspring
Precision Measurement of the Proton and Deuteron Spin Structure Functions g2 and Asymmetries A2
We have measured the spin structure functions g2p and g2d and the virtual
photon asymmetries A2p and A2d over the kinematic range 0.02 < x < 0.8 and 0.7
< Q^2 < 20 GeV^2 by scattering 29.1 and 32.3 GeV longitudinally polarized
electrons from transversely polarized NH3 and 6LiD targets. Our measured g2
approximately follows the twist-2 Wandzura-Wilczek calculation. The twist-3
reduced matrix elements d2p and d2n are less than two standard deviations from
zero. The data are inconsistent with the Burkhardt-Cottingham sum rule if there
is no pathological behavior as x->0. The Efremov-Leader-Teryaev integral is
consistent with zero within our measured kinematic range. The absolute value of
A2 is significantly smaller than the sqrt[R(1+A1)/2] limit.Comment: 12 pages, 4 figures, 2 table
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