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In the immediate vicinity of a source, there are strong gradients in the seismic wavefield that are tamed and modified in distributed acoustic sensing (DAS) recording due to combined effects of gauge-length averaging and local stacking on the local strain field. Close to a source broadside propagation effects are significant, and produce a characteristic impact on the local DAS channels. In the presence of topography, of surface or cable, additional effects are introduced that modify the expected signal. All these influences mean that the results of tap tests used to calibrate the channel positions along a DAS cable may give a distorted view of the actual geometry. Such effects can be important for detailed mapping of faulting processes and comparable features.

 

Advances in immersive virtual reality (IVR) are creating more computer-supported collaborative learning environments, but there is little research explicating how collaboration in IVR impacts learning. We ran a quasi-experimental study with 80 participants targeting ocean literacy learning, varying the manner in which participants interacted in IVR to investigate how the design of collaborative IVR experiences influences learning. Results are discussed through the lens of collaborative cognitive learning theory. Participants that collaborated to actively build a new environment in IVR scored higher for learning than participants who only watched an instructional guide’s avatar, or participants who watched the guide’s avatar and subsequently discussed what they learned while in IVR. Moreover, feeling negative emotions, feeling active in the environment, and feeling bonded to the group members negatively correlated with learning. Results shed light on the mechanisms behind how collaborative tasks in IVR can support learning. 

Dominant flow features in the near and intermediate wake of a horizontal-axis wind turbine are studied at near field-scale Reynolds numbers. Measurements of the axial velocity component were performed using a nano-scale hot-wire anemometer and analyzed using spectral methods to reveal the extent and evolution of the flow features. Experiments were conducted at a range of Reynolds numbers, of [Formula: see text], based on the rotor diameter and freestream velocity. Five different downstream locations were surveyed, between [Formula: see text], including the near wake, transition to the intermediate wake, and the intermediate wake. Three dominant wake features are identified and studied: the tip vortices, an annular shear layer in the wake core, and wake meandering. The tip vortices are shown to have a broadband influence in the flow in their vicinity, which locally alters the turbulence in that area. It is shown that shedding in the wake core and wake meandering are two distinct and independent low frequency features, and the wake meandering persists into the intermediate wake, whereas the signatures of the core shedding vanish early in the near wake. 

The ability of lotus leaves to repel water is desired in numerous applications, such as self-cleaning surfaces, biomedical devices, and naval vessels. Creating materials that mimic the hierarchical structure and surface chemistry of lotus leaves requires multistep processes that are impractical for the mass production of nonwettable products. Superhydrophobic surfaces have been created using graphene. However, graphene sheets obtained through graphite exfoliation or deposition on substrates are not superhydrophobic and require additional processes to achieve lotus-like water repellency. In this work, we show that graphene produced in the gas phase is inherently superhydrophobic. Gas-phase-synthesized graphene (GSG) and lotus leaves have fundamentally different structures, yet water droplets on both materials exhibit comparable contact angles, roll-off angles, and bouncing characteristics. Furthermore, hydrophilic surfaces become superhydrophobic when covered with GSG. The substrate-free synthesis of GSG is straightforward and sustainable, which could enable the manufacturing of a diverse range of water-repellent technologies. 

The next two decades are expected to open the door to the first coincident detections of electromagnetic (EM) and gravitational-wave (GW) signatures associated with massive black-hole (MBH) binaries heading for coalescence. These detections will launch a new era of multimessenger astrophysics by expanding this growing field to the low-frequency GW regime and will provide an unprecedented understanding of the evolution of MBHs and galaxies. They will also constitute fundamentally new probes of cosmology and would enable unique tests of gravity. The aim of this Living Review is to provide an introduction to this research topic by presenting a summary of key findings, physical processes and ideas pertaining to EM counterparts to MBH mergers as they are known at the time of this writing. We review current observational evidence for close MBH binaries, discuss relevant physical processes and timescales, and summarize the possible EM counterparts to GWs in the precursor, coalescence, and afterglow stages of a MBH merger. We also describe open questions and discuss future prospects in this dynamic and quick-paced research area.

 

Virtual professional development increases meaningful and diverse learning opportunities for in-service teachers (Darling-Hammond & McLaughlin, 2011). As part of virtual professional development the participants in this study engaged in doing math collaboratively and began thinking about mathematical and pedagogical decision making within their classrooms. Preliminary results suggest that participants valued the time to think flexibly about their own work and that of others and began to learn to recognize the hidden decisions they were making when solving a problem that it may benefit their students to know. 

We report observations of the optical counterpart of the long gamma-ray burst (GRB) GRB 230812B and its associated supernova (SN) SN 2023pel. The proximity (z= 0.36) and high energy (E_γ,iso∼ 10⁵³erg) make it an important event to study as a probe of the connection between massive star core collapse and relativistic jet formation. With a phenomenological power-law model for the optical afterglow, we find a late-time flattening consistent with the presence of an associated SN. SN 2023pel has an absolute peakr-band magnitude ofM_r= −19.46 ± 0.18 mag (about as bright as SN 1998bw) and evolves on quicker timescales. Using a radioactive heating model, we derive a nickel mass powering the SN ofM_Ni= 0.38 ± 0.01M_⊙and a peak bolometric luminosity ofL_bol∼ 1.3 × 10⁴³erg s⁻¹. We confirm SN 2023pel’s classification as a broad-line Type Ic SN with a spectrum taken 15.5 days after its peak in therband and derive a photospheric expansion velocity ofv_ph= 11,300 ± 1600 km s⁻¹at that phase. Extrapolating this velocity to the time of maximum light, we derive the ejecta massM_ej= 1.0 ± 0.6M_⊙and kinetic energy$E_{\mathrm{KE}}={1.3}_{-1.2}^{+3.3}\times {10}^{51}\mathrm{erg}$. We find that GRB 230812B/SN 2023pel has SN properties that are mostly consistent with the overall GRB-SN population. The lack of correlations found in the GRB-SN population between SN brightness andE_γ,isofor their associated GRBs across a broad range of 7 orders of magnitude provides further evidence that the central engine powering the relativistic ejecta is not coupled to the SN powering mechanism in GRB-SN systems.

 

Abstract Using ground-based gravitational-wave detectors, we probe the mass function of intermediate-mass black holes (IMBHs) wherein we also include BHs in the upper mass gap at ∼60–130 M ⊙ . Employing the projected sensitivity of the upcoming LIGO and Virgo fourth observing run (O4), we perform Bayesian analysis on quasi-circular nonprecessing, spinning IMBH binaries (IMBHBs) with total masses 50–500 M ⊙ , mass ratios 1.25, 4, and 10, and dimensionless spins up to 0.95, and estimate the precision with which the source-frame parameters can be measured. We find that, at 2 σ , the mass of the heavier component of IMBHBs can be constrained with an uncertainty of ∼10%–40% at a signal-to-noise ratio of 20. Focusing on the stellar-mass gap with new tabulations of the 12 C( α , γ ) 16 O reaction rate and its uncertainties, we evolve massive helium core stars using MESA to establish the lower and upper edges of the mass gap as ≃ 59 − 13 + 34 M ⊙ and ≃ 139 − 14 + 30 M ⊙ respectively, where the error bars give the mass range that follows from the ±3 σ uncertainty in the 12 C( α , γ ) 16 O nuclear reaction rate. We find that high resolution of the tabulated reaction rate and fine temporal resolution are necessary to resolve the peak of the BH mass spectrum. We then study IMBHBs with components lying in the mass gap and show that the O4 run will be able to robustly identify most such systems. Finally, we reanalyze GW190521 with a state-of-the-art aligned-spin waveform model, finding that the primary mass lies in the mass gap with 90% credibility. 

We report observations of the optical counterpart of the long gamma-ray burst GRB 221009A. Due to the extreme rarity of being both nearby (z= 0.151) and highly energetic (E_γ,iso≥ 10⁵⁴erg), GRB 221009A offers a unique opportunity to probe the connection between massive star core collapse and relativistic jet formation across a very broad range ofγ-ray properties. Adopting a phenomenological power-law model for the afterglow and host galaxy estimates from high-resolution Hubble Space Telescope imaging, we use Bayesian model comparison techniques to determine the likelihood of an associated supernova (SN) contributing excess flux to the optical light curve. Though not conclusive, we find moderate evidence (K_Bayes= 10^1.2) for the presence of an additional component arising from an associated SN, SN 2022xiw, and find that it must be substantially fainter (<67% as bright at the 99% confidence interval) than SN 1998bw. Given the large and uncertain line-of-sight extinction, we attempt to constrain the SN parameters (M_Ni,M_ej, andE_KE) under several different assumptions with respect to the host galaxy’s extinction. We find properties that are broadly consistent with previous GRB-associated SNe:M_Ni= 0.05–0.25M_⊙,M_ej= 3.5–11.1M_⊙, andE_KE= (1.6–5.2) × 10⁵²erg. We note that these properties are weakly constrained due to the faintness of the SN with respect to the afterglow and host emission, but we do find a robust upper limit onM_NiofM_Ni< 0.36M_⊙. Given the tremendous range in isotropic gamma-ray energy release exhibited by GRBs (seven orders of magnitude), the SN emission appears to be decoupled from the central engine in these systems.