Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO-Virgo Run O3b

We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC-2020 March 27 17:00 UTC). We conduct two independent searches: A generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate. © 2022. The Author(s). Published by the American Astronomical Society

Narrowband Searches for Continuous and Long-duration Transient Gravitational Waves from Known Pulsars in the LIGO-Virgo Third Observing Run

Isolated neutron stars that are asymmetric with respect to their spin axis are possible sources of detectable continuous gravitational waves. This paper presents a fully coherent search for such signals from eighteen pulsars in data from LIGO and Virgo's third observing run (O3). For known pulsars, efficient and sensitive matched-filter searches can be carried out if one assumes the gravitational radiation is phase-locked to the electromagnetic emission. In the search presented here, we relax this assumption and allow both the frequency and the time derivative of the frequency of the gravitational waves to vary in a small range around those inferred from electromagnetic observations. We find no evidence for continuous gravitational waves, and set upper limits on the strain amplitude for each target. These limits are more constraining for seven of the targets than the spin-down limit defined by ascribing all rotational energy loss to gravitational radiation. In an additional search, we look in O3 data for long-duration (hours-months) transient gravitational waves in the aftermath of pulsar glitches for six targets with a total of nine glitches. We report two marginal outliers from this search, but find no clear evidence for such emission either. The resulting duration-dependent strain upper limits do not surpass indirect energy constraints for any of these targets. © 2022. The Author(s). Published by the American Astronomical Society

GWTC-2.1: Deep extended catalog of compact binary coalescences observed by LIGO and Virgo during the first half of the third observing run

The second Gravitational-Wave Transient Catalog, GWTC-2, reported on 39 compact binary coalescences observed by the Advanced LIGO and Advanced Virgo detectors between 1 April 2019 15:00 UTC and 1 October 2019 15:00 UTC. Here, we present GWTC-2.1, which reports on a deeper list of candidate events observed over the same period. We analyze the final version of the strain data over this period with improved calibration and better subtraction of excess noise, which has been publicly released. We employ three matched-filter search pipelines for candidate identification, and estimate the probability of astrophysical origin for each candidate event. While GWTC-2 used a false alarm rate threshold of 2 per year, we include in GWTC-2.1, 1201 candidates that pass a false alarm rate threshold of 2 per day. We calculate the source properties of a subset of 44 high-significance candidates that have a probability of astrophysical origin greater than 0.5. Of these candidates, 36 have been reported in GWTC-2. We also calculate updated source properties for all binary block hole events previously reported in GWTC-1. If the 8 additional high-significance candidates presented here are astrophysical, the mass range of events that are unambiguously identified as binary black holes (both objects \geq 3M_\odot) is increased compared to GWTC-2, with total masses from \sim 14M_\odot for GW190924_021846 to \sim 182M_\odot for GW190426_190642. Source properties calculated using our default prior suggest that the primary components of two new candidate events (GW190403_051519 and GW190426_190642) fall in the mass gap predicted by pair-instability supernova theory. We also expand the population of binaries with significantly asymmetric mass ratios reported in GWTC-2 by an additional two events (the mass ratio is less than 0.65 and 0.44 at 90% probability for GW190403_051519 and GW190917_114630 respectively), and find that 2 of the 8 new events have effective inspiral spins \chi_\mathrm{eff} > 0 (at 90\% credibility), while no binary is consistent with \chi_\mathrm{eff} \lt 0 at the same significance. We provide updated estimates for rates of binary black hole and binary neutron star coalescence in the local Universe

Stakeholder roles for fostering ambidexterity in Sub-Saharan African agricultural netchains for the emergence of multi-stakeholder cooperatives

The Sub-Saharan African smallholder agricultural sector faces multiple and usually complex challenges, which can potentially be overcome by collective action. Smallholder farmers and other value chain stakeholders can tackle temporal, structural and contextual challenges by joining multi-level innovation networks to benefit collectively from shared information, knowledge, improved capacities and economies of scale in a process of innovation. Ambidexterity is a capability of innovation networks to balance exploration and exploitation dynamics in an innovation process, and is applicable at multiple levels: individuals, leaders, champions, teams and clusters. In the paradigm of open innovation, these levels become intertwined in hybrid social structures of innovation netchains. The objective of this paper is to describe the roles and identify the stakeholders that play those roles in an innovation process. We present case studies on farmer groups who participate in collective action and we compare multi-stakeholder platforms with other configurations of actors that tackle challenges in potato netchains in three Sub-Saharan African countries. We track and analyse innovation trajectories for six cases adapting netchain analysis techniques linking roles with the challenges faced at particular stages of each innovation trajectory. We find three management designs for fostering exploration and exploitation: (1) exploratory or exploitative management designs for small innovation networks; (2) exploitative management designs for larger networks; and (3) ambidextrous management designs for multi-stakeholder networks. Traditional roles played by managers are identified to manage exploration and exploitation in an ambidextrous way, but also evidence of roles of civil society actors facilitating collective action for the emergence of multi-stakeholder cooperatives. Since ambidexterity is about dynamism, we identified three types of mobility to be fostered when tackling challenges in an innovation process: (1) mobility-dynamism of the innovation process over time; (2) structural-knowledge mobility in innovation networks; and (3) boundary mobilit

Inflammation and neovascularization in hip impingement: not just wear and tear

Background: Femoroacetabular impingement (FAI) is a significant cause of osteoarthritis (OA) in young active patients, but the pathophysiology remains unclear. Increasingly, mechanistic studies point toward an inflammatory component in OA. Purpose: This study aimed to characterize inflammatory cell subtypes and neovascularization in FAI by exploring the phenotype and quantification of inflammatory cells and neovascularization in FAI versus OA samples. Study Design: Descriptive laboratory study. Methods: Ten samples of the labrum were obtained from patients with FAI (confirmed diagnosis) during open osteochondroplasty or hip arthroscopic surgery. Control samples of the labrum were collected from 10 patients with OA who were undergoing total hip arthroplasty. Labral biopsy specimens were evaluated immunohistochemically by quantifying the presence of macrophages (CD68, CD206, interleukin-13 [IL-13]), T cells (CD3), mast cells (mast cell tryptase), and vascular endothelium (CD34, vascular endothelial growth factor). Results: Labral biopsy specimens obtained from patients with FAI exhibited significantly greater macrophage, mast cell, and vascular endothelium expression compared with control OA labral samples (P < .05). The most significant difference was noted in macrophage (P < .01) and mast cell (P < .05) expression. Further subtyping of macrophages in FAI using the CD206 tissue marker and IL-13 revealed an M2 phenotype, suggesting that these cells are involved in a regenerate versus degenerate process. There was a modest but significant correlation between mast cells and CD34 expression (r = 0.4, P < .01) in FAI samples. Conclusion: This study provides evidence for an inflammatory cell infiltrate in FAI along with significant neovascularization. In particular, the significant infiltration of mast cells and macrophages was demonstrated, suggesting a role for innate immune pathways in the events that mediate hip impingement. Clinical Relevance: Further mechanistic studies to evaluate the net contribution and hence therapeutic utility of these cellular lineages and their downstream processes may reveal novel therapeutic approaches to the management of early hip impingement