135 research outputs found
Hadron Structure on the Lattice
A few chosen nucleon properties are described from a lattice QCD perspective:
the nucleon sigma term and the scalar strangeness in the nucleon; the vector
form factors in the nucleon, including the vector strangeness contribution, as
well as parity breaking effects like the anapole and electric dipole moment;
and finally the axial and tensor charges of the nucleon. The status of the
lattice calculations is presented and their potential impact on phenomenology
is discussed.Comment: 17 pages, 9 figures; proceedings of the Conclusive Symposium of the
Collaborative Research Center 443 "Many-body structure of strongly
interacting systems", Mainz, February 23-25, 201
Atypical genomic cortical patterning in autism with poor early language outcome.
Cortical regionalization develops via genomic patterning along anterior-posterior (A-P) and dorsal-ventral (D-V) gradients. Here, we find that normative A-P and D-V genomic patterning of cortical surface area (SA) and thickness (CT), present in typically developing and autistic toddlers with good early language outcome, is absent in autistic toddlers with poor early language outcome. Autistic toddlers with poor early language outcome are instead specifically characterized by a secondary and independent genomic patterning effect on CT. Genes involved in these effects can be traced back to midgestational A-P and D-V gene expression gradients and different prenatal cell types (e.g., progenitor cells and excitatory neurons), are functionally important for vocal learning and human-specific evolution, and are prominent in prenatal coexpression networks enriched for high-penetrance autism risk genes. Autism with poor early language outcome may be explained by atypical genomic cortical patterning starting in prenatal development, which may detrimentally affect later regional functional specialization and circuit formation
Nuclear Physics from Lattice QCD
We review recent progress toward establishing lattice Quantum Chromodynamics
as a predictive calculational framework for nuclear physics. A survey of the
current techniques that are used to extract low-energy hadronic scattering
amplitudes and interactions is followed by a review of recent two-body and
few-body calculations by the NPLQCD collaboration and others. An outline of the
nuclear physics that is expected to be accomplished with Lattice QCD in the
next decade, along with estimates of the required computational resources, is
presented.Comment: 56 pages, 39 pdf figures. Final published versio
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Influence of young adult cognitive ability and additional education on later-life cognition
How and when education improves cognitive capacity is an issue of profound societal importance. Education and later-life education-related factors, such as occupational complexity and engagement in cognitive-intellectual activities, are frequently considered indices of cognitive reserve, but whether their effects are truly causal remains unclear. In this study, after accounting for general cognitive ability (GCA) at an average age of 20 y, additional education, occupational complexity, or engagement in cognitive-intellectual activities accounted for little variance in late midlife cognitive functioning in men age 56-66 (n = 1009). Age 20 GCA accounted for 40% of variance in the same measure in late midlife and approximately 10% of variance in each of seven cognitive domains. The other factors each accounted for <1% of the variance in cognitive outcomes. The impact of these other factors likely reflects reverse causation-namely, downstream effects of early adult GCA. Supporting that idea, age 20 GCA, but not education, was associated with late midlife cortical surface area (n = 367). In our view, the most parsimonious explanation of our results, a meta-analysis of the impact of education, and epidemiologic studies of the Flynn effect is that intellectual capacity gains due to education plateau in late adolescence/early adulthood. Longitudinal studies with multiple cognitive assessments before completion of education would be needed to confirm this speculation. If cognitive gains reach an asymptote by early adulthood, then strengthening cognitive reserve and reducing later-life cognitive decline and dementia risk may really begin with improving educational quality and access in childhood and adolescence.Peer reviewe
Quark transverse charge densities in the from lattice QCD
We extend the formalism relating electromagnetic form factors to transverse
quark charge densities in the light-front frame to the case of a spin-3/2
baryon and calculate these transverse densities for the isobar
using lattice QCD. The transverse charge densities for a transversely polarized
spin-3/2 particle are characterized by monopole, dipole, quadrupole, and
octupole patterns representing the structure beyond that of a pure point-like
spin-3/2 particle. We present lattice QCD results for the -isobar
electromagnetic form factors for pion masses down to approximatively 350 MeV
for three cases: quenched QCD, two-degenerate flavors of dynamical Wilson
quarks, and three flavors of quarks using a mixed action that combines domain
wall valence quarks and dynamical staggered sea quarks. We extract transverse
quark charge densities from these lattice results and find that the is
prolately deformed, as indicated by the fact that the quadrupole moment
) is larger than the value -3 characterizing a point particle and the
fact that the transverse charge density in a of maximal transverse
spin projection is elongated along the axis of the spin.Comment: 35 pages, 10 figure
Broad-line region in NGC 4151 monitored by two decades of reverberation mapping campaigns. I. Evolution of structure and kinematics
We report the results of long-term reverberation mapping (RM) campaigns of
the nearby active galactic nuclei (AGN) NGC 4151, spanning from 1994 to 2022,
based on archived observations of the FAST Spectrograph Publicly Archived
Programs and our new observations with the 2.3m telescope at the Wyoming
Infrared Observatory. We reduce and calibrate all the spectra in a consistent
way, and derive light curves of the broad H line and 5100\,{\AA}
continuum. Continuum light curves are also constructed using public archival
photometric data to increase sampling cadences. We subtract the host galaxy
contamination using {\it HST} imaging to correct fluxes of the calibrated light
curves. Utilizing the long-term archival photometric data, we complete the
absolute flux-calibration of the AGN continuum. We find that the H time
delays are correlated with the 5100\,{\AA} luminosities as . This is remarkably consistent with
Bentz et al. (2013)'s global size-luminosity relationship of AGNs. Moreover,
the data sets for five of the seasons allow us to obtain the velocity-resolved
delays of the H line, showing diverse structures (outflows, inflows and
disks). Combining our results with previous independent measurements, we find
the measured dynamics of the H broad-line region (BLR) are possibly
related to the long-term trend of the luminosity. There is also a possible
additional 1.86 years time lag between the variation in BLR radius and
luminosity. These results suggest that dynamical changes in the BLR may be
driven by the effects of radiation pressure.Comment: Accepted for publication in MNRAS; comments welcome
Bt Crop Effects on Functional Guilds of Non-Target Arthropods: A Meta-Analysis
Background: Uncertainty persists over the environmental effects of genetically-engineered crops that produce the insecticidal Cry proteins of Bacillus thuringiensis (Bt). We performed meta-analyses on a modified public database to synthesize current knowledge about the effects of Bt cotton, maize and potato on the abundance and interactions of arthropod non-target functional guilds. Methodology/Principal Findings: We compared the abundance of predators, parasitoids, omnivores, detritivores and herbivores under scenarios in which neither, only the non-Bt crops, or both Bt and non-Bt crops received insecticide treatments. Predators were less abundant in Bt cotton compared to unsprayed non-Bt controls. As expected, fewer specialist parasitoids of the target pest occurred in Bt maize fields compared to unsprayed non-Bt controls, but no significant reduction was detected for other parasitoids. Numbers of predators and herbivores were higher in Bt crops compared to sprayed non-Bt controls, and type of insecticide influenced the magnitude of the difference. Omnivores and detritivores were more abundant in insecticide-treated controls and for the latter guild this was associated with reductions of their predators in sprayed non-Bt maize. No differences in abundance were found when both Bt and non-Bt crops were sprayed. Predator-to-prey ratios were unchanged by either Bt crops or the use of insecticides; ratios were higher in Bt maize relative to the sprayed non-Bt control
Characterization of Mechanical and Magnetic Properties of Ni-Mn-Ga Shape Memory Thin Films Deposited onto Silicon and Alumina Substrates
The mechanical and magnetic properties of off-stoichiometric Ni2MnGa shape memory thin films deposited onto silicon and alumina substrates at different thicknesses are examined. Two sets of films were deposited onto silicon(100) substrates and one set of films were deposited onto polycrystalline alumina. The films deposited onto silicon had a composition of Ni49.5Mn28.0Ga22.5 and Ni51.4Mn28.3Ga20.3. The films deposited onto the alumina substrates had a composition of Ni51.4Mn28.3Ga20.3. Substrate curvature measurements were performed to characterize the martensitic phase transformation temperature, the in-plane film stress change during the phase transformation, and the biaxial modulus of each film. Vibrating sample magnetometry was performed to characterize the Curie temperature and the magnetic anisotropy of each film. The crystallographic texture was characterized for a set of films deposited onto silicon using x-ray diffraction techniques. The martensitic transformation temperature increased with increasing film thickness on the Ni51.4Mn28.3Ga20.3 and decreased with increasing film thickness for the Ni49.5Mn28.0Ga22.5 films. The magnitude of the in-plane stress change during the phase transformation showed an increasing trend with increasing film thickness for the Ni51.4Mn28.3Ga20.3 films and a decreasing trend for the Ni49.5Mn28.0Ga22.5 films. For each set of films, there was a thickness dependence of the biaxial modulus for the films. The Curie temperature was not effected by film thickness. For the films deposited onto alumina substrates, a thickness dependence of the magnetic anisotropy was observed. The mechanical and magnetic properties of the Ni-Mn-Ga films showed both a compositional and thickness dependence
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