Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Evaluating Therapies to Prevent Future Stroke in Patients with Patent Foramen Ovale-Related Strokes : The SCOPE Study

Note: The material presented in this section previously appeared in the following peer-reviewed publication: Kent DM, Saver JL, Kasner SE, et al. .. Heterogeneity of treatment effects in an analysis of pooled individual patient data from randomized trials of device closure of patent foramen ovale after stroke. JAMA. 2021;326(22):2277-2286. doi:10.1001/jama.2021.20956 Background: Patent foramen ovale (PFO)-associated strokes comprise approximately 10% of ischemic strokes in adults aged 18 to 60 years. Despite the overall beneficial effects of closure device placement in patients with a first PFO-associated cerebral ischemic event, the best treatment option for any individual patient encountered in routine clinical practice is often quite unclear. Objective: The objective of this study was to evaluate the heterogeneity of treatment effect of PFO closure on stroke recurrence based on previously developed scoring systems. Methods: Individual patient data were pooled from 6 randomized clinical trials that compared PFO closure plus medical therapy vs medical therapy alone in patients with PFO-associated stroke, which involved a total of 3740 participants. The trials were conducted worldwide from 2000 to 2017. Comparisons were made between PFO closure plus medical therapy vs medical therapy alone. Subgroup analyses used the Risk of Paradoxical Embolism (RoPE) score (a 10-point score in which higher scores reflect younger age and the absence of vascular risk factors) and the PFO-Associated Stroke Causal Likelihood (PASCAL) algorithm, which combines the RoPE score with high-risk PFO features (either an atrial septal aneurysm or a large shunt) to classify patients into 3 categories of causal relatedness: “unlikely,” “possible,” and “probable.” The main outcome was ischemic stroke. Results: Over a median follow-up of 57 months (interquartile range, 24-64 months), 121 outcomes occurred in 3740 patients. The annualized incidence of stroke with medical therapy was 1.09% (95% CI, 0.88%-1.36%) and with device closure was 0.47% (95% CI, 0.35%-0.65%); the adjusted hazard ratio (HR) was 0.41 (95% CI, 0.27-0.60). Subgroup analyses showed statistically significant interaction effects. Patients with low vs high RoPE score had HRs of 0.61 (95% CI, 0.37-1.00) and 0.21 (95% CI, 0.11-0.42), respectively (P for interaction = .02). Patients classified under PASCAL as unlikely, possible, and probable had HRs of 1.14 (95% CI, 0.53-2.46), 0.38 (95% CI, 0.22-0.65), and 0.10 (95% CI, 0.03-0.35), respectively (P for interaction = .003). The 2-year absolute risk reduction was −0.7% (95% CI, −4.0% to 2.6%), 2.1% (95% CI, 0.6%-3.6%), and 2.1% (95% CI, 0.9%-3.4%) in the unlikely, possible, and probable PASCAL categories, respectively. Device-associated adverse events were generally higher among patients classified as unlikely; the absolute risk increases in atrial fibrillation beyond day 45 postrandomization with device were 4.41% (95% CI, 1.02%-7.80%), 1.53% (95% CI, 0.33%-2.72%), 0.65% (95% CI, −0.41% to 1.71%) in the unlikely, possible, and probable PASCAL categories, respectively. Conclusions: Among patients aged 18 to 60 years with PFO-associated stroke, risk reduction for recurrent stroke with device closure varied across groups classified by their probabilities that the stroke was causally related to the PFO. Application of these classification systems has the potential to guide individualized decisions regarding the selection of device closure vs medical therapy, supporting patient-centered decision-making for patients with PFO-associated cerebral ischemic events. Limitations: Some limitations of the study were the following: data were missing with respect to functional outcomes with recurrent stroke; trials had heterogenous definitions of key variables; the original PASCAL classification could not be evaluated; and several questions remain unaddressed, such as the best type of antithrombotic therapy, the role of new PFO devices, and the role of closure for patients older than 60 years

Extreme Enhancement of Carbon Hydrogasification via Mechanochemistry

Carbon hydrogasification is the slowest reaction among all carbon-involved small-molecule transformations. Here, we demonstrate a mechanochemical method that results in both a faster reaction rate and a new synthesis route. The reaction rate was dramatically enhanced by up to 4 orders of magnitude compared to the traditional thermal method. Simultaneously, the reaction exhibited very high selectivity (99.8 % CH4, versus 80 % under thermal conditions) with a cobalt catalyst. Our study demonstrated that this extreme increase in reaction rate originates from the continuous activation of reactive carbon species via mechanochemistry. The high selectivity is intimately related to the activation at low temperature, at which higher hydrocarbons are difficult to form. This work is expected to advance studies of carbon hydrogasification, and other solid-gas reactions.clos

Influence of Cation Substitutions Based on ABO₃ Perovskite Materials, Sr_1–<i>x</i>Y_<i>x</i>Ti_1–<i>y</i>Ru_<i>y</i>O_3−δ, on Ammonia Dehydrogenation

In order to screen potential catalytic materials for synthesis and decomposition of ammonia, a series of ABO₃ perovskite materials, Sr_1–<i>x</i>Y_<i>x</i>Ti_1–<i>y</i>Ru_<i>y</i>O_3−δ (<i>x</i> = 0, 0.08, and 0.16; <i>y</i> = 0, 0.04, 0.07, 0.12, 0.17, and 0.26) were synthesized and tested for ammonia dehydrogenation. The influence of A or B site substitution on the catalytic ammonia dehydrogenation activity was determined by varying the quantity of either A or B site cation, producing <b>Sr</b>_{<b>1</b>–<b><i>x</i></b>}<b>Y</b>_{<b><i>x</i></b>}Ti_0.92Ru_0.08O_3−δ and Sr_0.92Y_0.08<b>Ti</b>_{<b>1</b>–<i><b>y</b></i>}<b>Ru</b>_{<b><i>y</i></b>}O_3−δ, respectively. Characterizations of the as-synthesized materials using different analytical techniques indicated that a new perovskite phase of SrRuO₃ was produced upon addition of large amounts of Ru (≥12 mol %), and the surface Ru⁰ species were formed simultaneously to ultimately yield <b>Ru</b>_{<b><i>z</i></b>}(surface)/Sr_0.92Y_0.08<b>Ti</b>_{<b>1</b>–<b><i>y</i></b>}<b>Ru</b>_{<i><b>y</b></i>–<b><i>z</i></b>}O_3−δ and/or <b>Ru</b>_{<b><i>z</i></b>–<b><i>w</i></b>}(surface)/Sr_<i>w</i>Ru_<i>w</i>O₃/Sr_{0.92–<i>w</i>}Y_0.08<b>Ti</b>_{<b>1</b>–<b><i>y</i></b>}<b>Ru</b>_{<b><i>y</i></b>–<b><i>z</i></b>}O_3−δ. The newly generated surface Ru⁰ species at the perovskite surfaces accelerated ammonia dehydrogenation under different conditions, and Sr_0.84Y_0.16Ti_0.92Ru_0.08O_3−δ exhibited a NH₃ conversion of ca. 96% at 500 °C with a gas hourly space velocity (GHSV) of 10 000 mL g_cat^–1 h^–1. In addition, Sr_0.84Y_0.16Ti_0.92Ru_0.08O_3−δ further proved to be highly active and stable toward ammonia decomposition at different reaction temperatures and GHSVs for >275 h