Fundamental control of magnetic coupling through heterostructure morphology is a prerequisite for rational engineering of magnetic ground states. We report the tuning of magnetic interactions in ...superlattices composed of single and bilayers of SrIrO
inter-spaced with SrTiO
in analogy to the Ruddlesden-Popper series iridates. Magnetic scattering shows predominately c-axis antiferromagnetic orientation of the magnetic moments for the bilayer, as in Sr
Ir
O
. However, the magnetic excitation gap, measured by resonant inelastic x-ray scattering, is quite different between the two structures, evidencing a significant change in the stability of the competing magnetic phases. In contrast, the single layer iridate hosts a more bulk-like gap. We find these changes are driven by bending of the c-axis Ir-O-Ir bond, which is much weaker in the single layer, and subsequent local environment changes, evidenced through x-ray diffraction and magnetic excitation modeling. Our findings demonstrate how large changes in the magnetic interactions can be tailored and probed in spin-orbit coupled heterostructures by engineering subtle structural modulations.
This paper presents a mathematical model of oxidation and dissolution of supported platinum catalysts in polymer electrolyte membrane fuel cells (PEMFCs). Kinetic expressions for the oxidation and ...dissolution reactions are developed and compared to available experimental data. The model is used to investigate the influences of electrode potential and particle size on catalyst stability.
Abstract We present a framework for modeling astrophysical pulses from radio pulsars and fast radio bursts (FRBs). This framework, called fitburst , generates synthetic representations of dynamic ...spectra that are functions of several physical and heuristic parameters; the heuristic parameters can nonetheless accommodate a vast range of distributions in spectral energy. fitburst is designed to optimize the modeling of features induced by effects that are intrinsic and extrinsic to the emission mechanism, including the magnitude and frequency dependence of pulse dispersion and scatter broadening. fitburst removes intrachannel smearing through two-dimensional upsampling, and can account for phase-wrapping of “folded” signals that are typically acquired during pulsar-timing observations. We demonstrate the effectiveness of fitburst in modeling data containing pulsars and FRBs observed with the Canadian Hydrogen Intensity Mapping Experiment telescope.
Despite their sparse vegetation, dryland regions exert a huge influence over global biogeochemical cycles because they cover more than 40% of the world surface (Schimel 2010 Science 327 418–9). It is ...thought that drylands dominate the inter-annual variability (IAV) and long-term trend in the global carbon (C) cycle (Poulter et al 2014 Nature 509 600–3, Ahlstrom et al 2015 Science 348 895–9, Zhang et al 2018 Glob. Change Biol. 24 3954–68). Projections of the global land C sink therefore rely on accurate representation of dryland C cycle processes; however, the dynamic global vegetation models (DGVMs) used in future projections have rarely been evaluated against dryland C flux data. Here, we carried out an evaluation of 14 DGVMs (TRENDY v7) against net ecosystem exchange (NEE) data from 12 dryland flux sites in the southwestern US encompassing a range of ecosystem types (forests, shrub- and grasslands). We find that all the models underestimate both mean annual C uptake/release as well as the magnitude of NEE IAV, suggesting that improvements in representing dryland regions may improve global C cycle projections. Across all models, the sensitivity and timing of ecosystem C uptake to plant available moisture was at fault. Spring biases in gross primary production (GPP) dominate the underestimate of mean annual NEE, whereas models’ lack of GPP response to water availability in both spring and summer monsoon are responsible for inability to capture NEE IAV. Errors in GPP moisture sensitivity at high elevation forested sites were more prominent during the spring, while errors at the low elevation shrub and grass-dominated sites were more important during the monsoon. We propose a range of hypotheses for why model GPP does not respond sufficiently to changing water availability that can serve as a guide for future dryland DGVM developments. Our analysis suggests that improvements in modeling C cycle processes across more than a quarter of the Earth’s land surface could be achieved by addressing the moisture sensitivity of dryland C uptake.
Abstract
The repeating FRB 20201124A was first discovered by CHIME/FRB in November of 2020, after which it was seen to repeat a few times over several months. It entered a period of high activity in ...April of 2021, at which time several observatories recorded tens to hundreds more bursts from the source. These follow-up observations enabled precise localization and host-galaxy identification. In this paper, we report on the CHIME/FRB-detected bursts from FRB 20201124A, including their best-fit morphologies, fluences, and arrival times. The large exposure time of the CHIME/FRB telescope toward the location of this source allows us to constrain its rates of activity. We analyze the repetition rates over different spans of time, constraining the rate prior to discovery to <3.4 day
−1
(at 3
σ
), and demonstrate a significant change in the event rate following initial detection. Lastly, we perform a maximum-likelihood estimation of a power-law luminosity function, finding a best-fit index
α
= −4.6 ± 1.3 ± 0.6, with a break at a fluence threshold of
F
min
∼
16.6
Jy ms, consistent with the fluence completeness limit of the observations. This index is consistent within uncertainties with those of other repeating FRBs for which it has been determined.
ABSTRACT
MicroRNA‐224 (miR‐224) is one of the most commonly up‐regulated microRNAs in hepatocellular carcinoma (HCC), which affects crucial cellular processes such as apoptosis and cell ...proliferation. In this study, we aim to elucidate the molecular mechanism that leads to the overexpression of miR‐224 in HCC. We examined the transcript expression of miR‐224 and neighboring miR‐452 and genes on chromosome Xq28 in tumor and paired adjacent nontumorous tissues from 100 patients with HCC and found that miR‐224 is coordinately up‐regulated with its neighboring microRNA (miRNA) and genes. This coordinated up‐regulation of miRNAs and genes at the Xq28 locus can be mimicked in nontransformed immortalized human liver cells by the introduction of histone deacetylase (HDAC) inhibitors, which resulted in a corresponding increase in histone H3 acetylation in this region. This miR‐224‐residing locus in Xq28 is reciprocally regulated by HDAC1, HDAC3, and histone acetylase protein, E1A binding protein p300 (EP300). Notably, in HCC tumors that significantly overexpress microRNA‐224, EP300 is also overexpressed and displays increased binding to the Xq28 locus. In transformed HCC cells, high miR‐224 expression can be attenuated through the inhibition of EP300, using either siRNA or the specific drug C646. In summary, overexpression of EP300 may account, in part, for the up‐regulation of miR‐224 expression in patients with HCC.—Wang, Y., Toh, H. C., Chow, P., Chung, A. Y. F., Meyers, D. J., Cole, P. A., Ooi, L. L. P. J., Lee, C. G. L. MicroRNA‐224 is up‐regulated in hepatocellular carcinoma through epigenetic mechanisms. FASEB J. 26, 3032–3041 (2012). www.fasebj.org
The high sensitivity and wide frequency coverage of the Murchison Widefield Array allow for the measurement of the spectral scaling of the pulsar scattering timescale, , from a single observation. ...Here we present three case studies targeted at bright, strongly scattered pulsars J0534+2200 (the Crab pulsar), J0835−4510 (the Vela pulsar), and J0742−2822. We measure the scattering spectral indices to be −3.8 0.2, −4.0 1.5, and −2.5 0.6 for the Crab, Vela, and J0742−2822, respectively. We find that the scattered profiles of both Vela and J0742−2822 are best described by a thin screen model where the Gum Nebula likely contributes most of the observed scattering delay. For the Crab pulsar we see characteristically different pulse shapes compared to higher frequencies, for which none of the scattering screen models we explore are found to be optimal. The presence of a finite inner scale to the turbulence can possibly explain some of the discrepancies.
Using three magnified Type Ia supernovae (SNe Ia) detected behind CLASH (Cluster Lensing and Supernovae with Hubble) clusters, we perform a first pilot study to see whether standardizable candles can ...be used to calibrate cluster mass maps created from strong lensing observations. Such calibrations will be crucial when next-generation Hubble Space Telescope cluster surveys (e.g. Frontier) provide magnification maps that will, in turn, form the basis for the exploration of the high-redshift Universe. We classify SNe using combined photometric and spectroscopic observations, finding two of the three to be clearly of Type Ia and the third probable. The SNe exhibit significant amplification, up to a factor of 1.7 at ... significance (SN-L2). We conducted this as a blind study to avoid fine-tuning of parameters, finding a mean amplification difference between SNe and the cluster lensing models of 0.09 ± 0.09stat ± 0.05sys mag. This impressive agreement suggests no tension between cluster mass models and high-redshift-standardized SNe Ia. However, the measured statistical dispersion of ... = 0.21 mag appeared large compared to the dispersion expected based on statistical uncertainties (0.14). Further work with the SN and cluster lensing models, post-unblinding, reduced the measured dispersion to ... = 0.12. An explicit choice should thus be made as to whether SNe are used unblinded to improve the model, or blinded to test the model. As the lensed SN samples grow larger, this technique will allow improved constraints on assumptions regarding e.g. the structure of the dark matter halo. (ProQuest: ... denotes formulae/symbols omitted.)
Abstract
The CHIME/FRB Project has recently released its first catalog of fast radio bursts (FRBs), containing 492 unique sources. We present results from angular cross-correlations of CHIME/FRB ...sources with galaxy catalogs. We find a statistically significant (
p
-value ∼ 10
−4
, accounting for look-elsewhere factors) cross-correlation between CHIME FRBs and galaxies in the redshift range 0.3 ≲
z
≲ 0.5, in three photometric galaxy surveys: WISE × SCOS, DESI-BGS, and DESI-LRG. The level of cross-correlation is consistent with an order-one fraction of the CHIME FRBs being in the same dark matter halos as survey galaxies in this redshift range. We find statistical evidence for a population of FRBs with large host dispersion measure (∼400 pc cm
−3
) and show that this can plausibly arise from gas in large halos (
M
∼ 10
14
M
⊙
), for FRBs near the halo center (
r
≲ 100 kpc). These results will improve in future CHIME/FRB catalogs, with more FRBs and better angular resolution.
The treatment effect of golimumab, a human monoclonal antibody against tumor necrosis factor (TNF)-alpha, in severe persistent asthma is unknown.
To assess the safety and efficacy of golimumab in a ...large population of patients with uncontrolled, severe persistent asthma.
From 2004 to 2006, 309 patients with severe and uncontrolled asthma, despite high-dose inhaled corticosteroids and long-acting beta(2) agonists, were randomized 1:1:1:1 to monthly subcutaneous injections of placebo or golimumab (50, 100, or 200 mg) through Week 52. Coprimary endpoints were the change from baseline through Week 24 in prebronchodilator percent-predicted FEV(1) and the number of severe asthma exacerbations through Week 24.
No significant differences were observed for the change in percent-predicted FEV1 (least squares mean: placebo, 2.44 95% confidence interval (CI) -0.574 to 5.461; combined 100-mg and 200-mg, 2.91 0.696-5.116) or severe exacerbations (mean +/- SD: placebo, 0.5 +/- 1.07 vs. combined 100-mg and 200-mg 0.5 +/- 0.97) through week 24. Through Week 24, 2.6% of patients treated with placebo vs. 19.5% of those treated with golimumab discontinued the study agent, and 1.3% and 7.8% discontinued study participation, respectively. An unfavorable risk-benefit profile led to early discontinuation of study-agent administration after the Week-24 database lock. Through Week 76, 20.5% of patients treated with placebo and 30.3% of patients treated with golimumab experienced serious adverse events, with serious infections occurring more frequently in golimumab-treated patients. One death and all eight malignancies occurred in the active groups.
Overall, treatment with golimumab did not demonstrate a favorable risk-benefit profile in this study population of patients with severe persistent asthma. Clinical trial registered with www.clinicaltrials.gov (NCT00207740).
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