Coexistence of the antiferromagnetic and superconducting order and its effect on spin dynamics in electron-doped high-TcT_{c} cuprates

In the framework of the slave-boson approach to the $t-t'-t''-J$ model, it is found that for electron-doped high-$T_c$ cuprates, the staggered antiferromagnetic (AF) order coexists with superconducting (SC) order in a wide doping level ranged from underdoped to nearly optimal doping at the mean-field level. In the coexisting phase, it is revealed that the spin response is commensurate in a substantial frequency range below a crossover frequency $\omega_{c}$ for all dopings considered, and it switches to the incommensurate structure when the frequency is higher than $\omega_{c}$. This result is in agreement with the experimental measurements. Comparison of the spin response between the coexisting phase and the pure SC phase with a $d_{x^{2}-y^{2}}$-wave pairing plus a higher harmonics term (DP+HH) suggests that the inclusion of the two-band effect is important to consistently account for both the dispersion of the spin response and the non-monotonic gap behavior in the electron-doped cuprates.Comment: 6 pages, 5 figure

Suppressed star formation in circumnuclear regions in Seyfert galaxies

Feedback from black hole activity is widely believed to play a key role in regulating star formation and black hole growth. A long-standing issue is the relation between the star formation and fueling the supermassive black holes in active galactic nuclei (AGNs). We compile a sample of 57 Seyfert galaxies to tackle this issue. We estimate the surface densities of gas and star formation rates in circumnuclear regions (CNRs). Comparing with the well-known Kennicutt-Schmidt (K-S) law, we find that the star formation rates in CNRs of most Seyfert galaxies are suppressed in this sample. Feedback is suggested to explain the suppressed star formation rates.Comment: 1 color figure and 1 table. ApJ Letters in pres

A Systematic Analysis of Fe II Emission in Quasars: Evidence for Inflow to the Central Black Hole

Broad Fe II emission is a prominent feature of the optical and ultraviolet spectra of quasars. We report on a systematical investigation of optical Fe II emission in a large sample of 4037 z < 0.8 quasars selected from the Sloan Digital Sky Survey. We have developed and tested a detailed line-fitting technique, taking into account the complex continuum and narrow and broad emission-line spectrum. Our primary goal is to quantify the velocity broadening and velocity shift of the Fe II spectrum in order to constrain the location of the Fe II-emitting region and its relation to the broad-line region. We find that the majority of quasars show Fe II emission that is redshifted, typically by ~ 400 km/s but up to 2000 km/s, with respect to the systemic velocity of the narrow-line region or of the conventional broad-line region as traced by the Hbeta line. Moreover, the line width of Fe II is significantly narrower than that of the broad component of Hbeta. We show that the magnitude of the Fe II redshift correlates inversely with the Eddington ratio, and that there is a tendency for sources with redshifted Fe II emission to show red asymmetry in the Hbeta line. These characteristics strongly suggest that Fe II originates from a location different from, and most likely exterior to, the region that produces most of Hbeta. The Fe II-emitting zone traces a portion of the broad-line region of intermediate velocities whose dynamics may be dominated by infall.Comment: 20 pages, 14 figures, accepted for publication in Ap

Achieving strong coherency for a composite electrode via one-pot method with enhanced electrochemical performance in reversible solid oxide cells

We greatly appreciate the financial support from the National Key Research & Development Project (2020YFB1506304, 2017YFE0129300), National Natural Science Foundation of China (52072135), and China Scholarship Council (201806160178).The oxygen electrode with a fast oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and sufficient durability plays a pivotal role in reversible solid oxide cells (RSOCs). Here, we demonstrate a NdBa0.5Ca0.5Co1.5Fe0.5O5+δ@Gd0.1Ce0.9O2−δ (NBCCF@GDC) composite oxygen electrode via a one-pot method for exhibiting strong coherency, which result in boosting the electrochemical performance of RSOCs. The NBCCF@GDC electrode yields a very low polarization resistance (0.106 Ω-cm2 at 800 °C), high electrolysis current density (1.45 A cm–2 with 70 vol % absolute humidity at 1.3 V), and high power density (∼1.3 W cm–2 at 800 °C) and shows excellent reversibility and stability. Notably, strong coherency in these NBCCF@GDC composite materials was successfully revealed by HT-XRD, XPS, STEM, and EELS. The phase contiguity and interfacial coherence between NBCCF and GDC increase the Co oxidation state and the number of active sites, which enhanced the electrocatalytic activity for perovskites. Overall, this work demonstrates a highly desirable strategy for the production of functionalized electrodes for next-generation reversible solid oxide cells.PostprintPeer reviewe

A Systematic Study on Energy Dependence of Quasi-Periodic Oscillation Frequency in GRS 1915+105

Systematically studying all the RXTE/PCA observations for GRS 1915+105 before November 2010, we have discovered three additional patterns in the relation between Quasi-Periodic Oscillation (QPO) frequency and photon energy, extending earlier outcomes reported by Qu et al. (2010). We have confirmed that as QPO frequency increases, the relation evolves from the negative correlation to positive one. The newly discovered patterns provide new constraints on the QPO models

The Unified Model of Active Galactic Nuclei: II. Evolutionary Connection

(Abbreviated) We assemble a sample composed of 243 nearby Seyfert galaxies with redshifts $z\le 0.05$ to test the unification scheme. The sample contains 94 BLS1s, 44 NLS1s, 36 X-ray absorbed HBLR S2s, 42 X-ray absorbed non-HBLR S2s and 27 X-ray unabsorbed Seyfert 2s (unabsorbed non-HBLR S2s and HBLR S2s). We find that: 1) NLS1s have less massive black hole masses than BLS1s; 2) HBLRS2s have the same mass distribution of the black holes with BLS1s; 3) the absorbed non-HBLR S2s have less massive black holes than HBLR S2s; 4) unabsorbed non-HBLR S2s have the most massive black holes. We thus have a queue of black hole masses from small to large: narrow to broad line Seyfert galaxies, providing new evidence for the evolutionary sequence of Seyfert galaxies. We find that the opening angles of the torus in NLS1s and absorbed non-HBLR S2s are significantly smaller than that in BLS1s and HBLR S2s. The growth of the black holes and increases of the opening angles of the tori determine the various appearances of Seyfert galaxies. We also find that the unabsorbed Seyfert 2 galaxies could be caused by low gas-to-dust ratios in the present sample. This indicates that the star formation histories could be different in the unabsorbed from in absorbed Seyfert 2 galaxies, showing evidence for suppressed star formation by black hole activities. We outline a new unification scheme based on the orientation hypothesis: Seyfert galaxies can be unified by including growth of black holes, Eddington ratios, changing opening angles of tori and gas-to-dust ratios in the tori. Seyfert galaxies are tending to finally evolve to unabsorbed non-HBLR Seyfert 2 galaxies, in which the black holes are accreting with low accretion rates and both the broad line region and dusty torus disappear.Comment: ApJ, vol 661 (2007), in pres

Bayesian Hierarchical Models for High-Dimensional Mediation Analysis with Coordinated Selection of Correlated Mediators

We consider Bayesian high-dimensional mediation analysis to identify among a large set of correlated potential mediators the active ones that mediate the effect from an exposure variable to an outcome of interest. Correlations among mediators are commonly observed in modern data analysis; examples include the activated voxels within connected regions in brain image data, regulatory signals driven by gene networks in genome data and correlated exposure data from the same source. When correlations are present among active mediators, mediation analysis that fails to account for such correlation can be sub-optimal and may lead to a loss of power in identifying active mediators. Building upon a recent high-dimensional mediation analysis framework, we propose two Bayesian hierarchical models, one with a Gaussian mixture prior that enables correlated mediator selection and the other with a Potts mixture prior that accounts for the correlation among active mediators in mediation analysis. We develop efficient sampling algorithms for both methods. Various simulations demonstrate that our methods enable effective identification of correlated active mediators, which could be missed by using existing methods that assume prior independence among active mediators. The proposed methods are applied to the LIFECODES birth cohort and the Multi-Ethnic Study of Atherosclerosis (MESA) and identified new active mediators with important biological implications

Bayesian Sparse Mediation Analysis with Targeted Penalization of Natural Indirect Effects

Causal mediation analysis aims to characterize an exposure's effect on an outcome and quantify the indirect effect that acts through a given mediator or a group of mediators of interest. With the increasing availability of measurements on a large number of potential mediators, like the epigenome or the microbiome, new statistical methods are needed to simultaneously accommodate high-dimensional mediators while directly target penalization of the natural indirect effect (NIE) for active mediator identification. Here, we develop two novel prior models for identification of active mediators in high-dimensional mediation analysis through penalizing NIEs in a Bayesian paradigm. Both methods specify a joint prior distribution on the exposure-mediator effect and mediator-outcome effect with either (a) a four-component Gaussian mixture prior or (b) a product threshold Gaussian prior. By jointly modeling the two parameters that contribute to the NIE, the proposed methods enable penalization on their product in a targeted way. Resultant inference can take into account the four-component composite structure underlying the NIE. We show through simulations that the proposed methods improve both selection and estimation accuracy compared to other competing methods. We applied our methods for an in-depth analysis of two ongoing epidemiologic studies: the Multi-Ethnic Study of Atherosclerosis (MESA) and the LIFECODES birth cohort. The identified active mediators in both studies reveal important biological pathways for understanding disease mechanisms

Critical Role of Activating Transcription Factor 4 in the Anabolic Actions of Parathyroid Hormone in Bone

Parathyroid hormone (PTH) is a potent anabolic agent for the treatment of osteoporosis. However, its mechanism of action in osteoblast and bone is not well understood. In this study, we show that the anabolic actions of PTH in bone are severely impaired in both growing and adult ovariectomized mice lacking bone-related activating transcription factor 4 (ATF4). Our study demonstrates that ATF4 deficiency suppresses PTH-stimulated osteoblast proliferation and survival and abolishes PTH-induced osteoblast differentiation, which, together, compromise the anabolic response. We further demonstrate that the PTH-dependent increase in osteoblast differentiation is correlated with ATF4-dependent up-regulation of Osterix. This regulation involves interactions of ATF4 with a specific enhancer sequence in the Osterix promoter. Furthermore, actions of PTH on Osterix require this same element and are associated with increased binding of ATF4 to chromatin. Taken together these experiments establish a fundamental role for ATF4 in the anabolic actions of PTH on the skeleton