Binary-black-hole initial data with nearly-extremal spins

There is a significant possibility that astrophysical black holes with nearly-extremal spins exist. Numerical simulations of such systems require suitable initial data. In this paper, we examine three methods of constructing binary-black-hole initial data, focusing on their ability to generate black holes with nearly-extremal spins: (i) Bowen-York initial data, including standard puncture data (based on conformal flatness and Bowen-York extrinsic curvature), (ii) standard quasi-equilibrium initial data (based on the extended-conformal-thin-sandwich equations, conformal flatness, and maximal slicing), and (iii) quasi-equilibrium data based on the superposition of Kerr-Schild metrics. We find that the two conformally-flat methods (i) and (ii) perform similarly, with spins up to about 0.99 obtainable at the initial time. However, in an evolution, we expect the spin to quickly relax to a significantly smaller value around 0.93 as the initial geometry relaxes. For quasi-equilibrium superposed Kerr-Schild (SKS) data [method (iii)], we construct initial data with \emph{initial} spins as large as 0.9997. We evolve SKS data sets with spins of 0.93 and 0.97 and find that the spin drops by only a few parts in 10^4 during the initial relaxation; therefore, we expect that SKS initial data will allow evolutions of binary black holes with relaxed spins above 0.99. [Abstract abbreviated; full abstract also mentions several secondary results.

Stable Model Counting and Its Application in Probabilistic Logic Programming

Model counting is the problem of computing the number of models that satisfy a given propositional theory. It has recently been applied to solving inference tasks in probabilistic logic programming, where the goal is to compute the probability of given queries being true provided a set of mutually independent random variables, a model (a logic program) and some evidence. The core of solving this inference task involves translating the logic program to a propositional theory and using a model counter. In this paper, we show that for some problems that involve inductive definitions like reachability in a graph, the translation of logic programs to SAT can be expensive for the purpose of solving inference tasks. For such problems, direct implementation of stable model semantics allows for more efficient solving. We present two implementation techniques, based on unfounded set detection, that extend a propositional model counter to a stable model counter. Our experiments show that for particular problems, our approach can outperform a state-of-the-art probabilistic logic programming solver by several orders of magnitude in terms of running time and space requirements, and can solve instances of significantly larger sizes on which the current solver runs out of time or memory.Comment: Accepted in AAAI, 201

Dusty Disks Around Central Stars of Planetary Nebulae

Only a few percent of cool, old white dwarfs (WDs) have infrared excesses interpreted as originating in small hot disks due to the infall and destruction of single asteroids that come within the star's Roche limit. Infrared excesses at 24 micron were also found to derive from the immediate vicinity of younger, hot WDs, most of which are still central stars of planetary nebulae (CSPN). The incidence of CSPN with this excess is 18%. The Helix CSPN, with a 24 micron excess, has been suggested to have a disk formed from collisions of Kuiper belt-like objects (KBOs). In this paper, we have analyzed an additional sample of CSPN to look for similar infrared excesses. These CSPN are all members of the PG 1159 class and were chosen because their immediate progenitors are known to often have dusty environments consistent with large dusty disks. We find that, overall, PG 1159 stars do not present such disks more often than other CSPN, although the statistics (5 objects) are poor. We then consider the entire sample of CSPN with infrared excesses, and compare it to the infrared properties of old WDs, as well as cooler post-AGB stars. We conclude with the suggestion that the infrared properties of CSPN more plausibly derive from AGB-formed disks rather than disks formed via the collision of KBOs, although the latter scenario cannot be ruled out. We finally remark that there seems to be an association between CSPN with a 24 micron excess and confirmed or possible binarity of the central star.Comment: 11 pages, 5 figures, AJ, in pres

Comparison of trigger point injections versus traditional therapies in the management of post-surgical pain in patients who had anterior cervical surgery: A Retrospective Study

Introduction: The opioid epidemic has launched the United States into a public health crisis, resulting in a greater emphasis on non-opioid multimodal pain control methods. At our institution, postoperative posterior neck stiffness and myofascial pain is a common concern after anterior cervical discectomy and fusion or anterior cervical corpectomy with fusion surgery (hereinafter ACS), likely due to prolonged intraoperative positioning in neck extension. Studies have shown successful analgesic outcomes of trigger point injections with local anesthetic for generalized myofascial pain.1-2 This retrospective pilot study aimed to evaluate whether trigger point injections with bupivacaine decreases postsurgical pain compared with traditional therapies in patients undergoing ACS and thereby decrease the amount of opioid medication used. Methods: After IRB approval, we retrospectively reviewed medical records of all patients who received ACS from January 2019 to March 2020 at a single university hospital. We identified patients who received trigger point injections (TP) versus standard care (SC). We excluded patients if TP was performed \u3e3hr from surgery, in recovery for opioid use disorder, underwent a posterior approach, staged surgery, or sustained cervical trauma. The primary outcomes were pain control through the Visual Analog Scale (VAS) and calculated oral morphine equivalents (OME) taken at 6, 12, and 24 hours post-operatively. Secondary outcomes included length of stay (LOS). Results: 137 patients received anterior cervical surgery (100 SC, 37 TP), 62 were excluded. A total of 75 (47 SC, 28 TP) patients were included in this study. The average OME at 6 hours significantly decreased when comparing SC vs TP (32 vs 22, p=0.025). There was no significant difference in average VAS at all time points and average OME at 12 and 24 hours (Table 1). 50% of patients were discharged by 18 hours. Discussion: Our results suggest that TP with bupivacaine significantly reduce opioid consumption within 6 hours of the postoperative period, without increasing overall pain level. There is an opportunity for TP to be included in non-opioid multimodal pain regimens for postoperative myofascial neck pain, especially during the opioid crisis. Limitations of this retrospective study were the small number of study participants, that many patients were discharged before 18 hours and some may have been on chronic pain therapy. The identified limitations will help inform our future investigations and design a prospective randomized control study

Prototype effective-one-body model for nonprecessing spinning inspiral-merger-ringdown waveforms

We first use five non-spinning and two mildly spinning (chi_i \simeq -0.44, +0.44) numerical-relativity waveforms of black-hole binaries and calibrate an effective-one-body (EOB) model for non-precessing spinning binaries, notably its dynamics and the dominant (2,2) gravitational-wave mode. Then, we combine the above results with recent outcomes of small-mass-ratio simulations produced by the Teukolsky equation and build a prototype EOB model for detection purposes, which is capable of generating inspiral-merger-ringdown waveforms for non-precessing spinning black-hole binaries with any mass ratio and individual black-hole spins -1 \leq chi_i \lesssim 0.7. We compare the prototype EOB model to two equal-mass highly spinning numerical-relativity waveforms of black holes with spins chi_i = -0.95, +0.97, which were not available at the time the EOB model was calibrated. In the case of Advanced LIGO we find that the mismatch between prototype-EOB and numerical-relativity waveforms is always smaller than 0.003 for total mass 20-200 M_\odot, the mismatch being computed by maximizing only over the initial phase and time. To successfully generate merger waveforms for individual black-hole spins chi_i \gtrsim 0.7, the prototype-EOB model needs to be improved by (i) better modeling the plunge dynamics and (ii) including higher-order PN spin terms in the gravitational-wave modes and radiation-reaction force.Comment: 20 pages, 8 figures. Minor changes to match version accepted for publication in PR

Collectivization of Vascular Smooth Muscle Cells via TGF-β-Cadherin-11-Dependent Adhesive Switching.

OBJECTIVE: Smooth muscle cells (SMCs) in healthy arteries are arranged as a collective. However, in diseased arteries, SMCs commonly exist as individual cells, unconnected to each other. The purpose of this study was to elucidate the events that enable individualized SMCs to enter into a stable and interacting cell collective. APPROACH AND RESULTS: Human SMCs stimulated to undergo programmed collectivization were tracked by time-lapse microscopy. We uncovered a switch in the behavior of contacting SMCs from semiautonomous motility to cell-cell adherence. Central to the cell-adherent phenotype was the formation of uniquely elongated adherens junctions, ≤60 μm in length, which appeared to strap adjacent SMCs to each other. Remarkably, these junctions contained both N-cadherin and cadherin-11. Ground-state depletion super-resolution microscopy revealed that these hybrid assemblies were comprised of 2 parallel nanotracks of each cadherin, separated by 50 nm. Blocking either N-cadherin or cadherin-11 inhibited collectivization. Cell-cell adhesion and adherens junction elongation were associated with reduced transforming growth factor-β signaling, and exogenous transforming growth factor-β1 suppressed junction elongation via the noncanonical p38 pathway. Imaging of fura-2-loaded SMCs revealed that SMC assemblies displayed coordinated calcium oscillations and cell-cell transmission of calcium waves which, together with increased connexin 43-containing junctions, depended on cadherin-11 and N-cadherin function. CONCLUSIONS: SMCs can self-organize, structurally and functionally, via transforming growth factor-β-p38-dependent adhesive switching and a novel adherens junction architecture comprised of hybrid nanotracks of cadherin-11 and N-cadherin. The findings define a mechanism for the assembly of SMCs into networks, a process that may be relevant to the stability and function of blood vessels