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In this work, we develop an open-source surgical simulation environment that includes a realistic model obtained by MRI-scanning a physical phantom, for the purpose of training and evaluating a Learning from Demonstration (LfD) algorithm for autonomous suturing. The LfD algorithm utilizes Dynamic Movement Primitives (DMP) and Locally Weighted Regression (LWR), but focuses on the needle trajectory, rather than the instruments, to obtain better generality with respect to needle grasps. We conduct a user study to collect multiple suturing demonstrations and perform a comprehensive analysis of the ability of the LfD algorithm to generalize from a demonstration at one location in one phantom to different locations in the same phantom and to a different phantom. Our results indicate good generalization, on the order of 91.5%, when learning from more experienced subjects, indicating the need to integrate skill assessment in the future. 

Abstract Valdivia Bank (VB) is an oceanic plateau in the South Atlantic that formed from hotspot‐ridge volcanism during the Late Cretaceous at the Mid‐Atlantic Ridge (MAR). It is part of Walvis Ridge (WR), a quasi‐linear seamount chain extending from offshore Namibia to Tristan da Cunha and Gough Islands. To understand Valdivia Bank evolution, we interpret the seismic stratigraphy from multichannel seismic data paired with coring results from International Ocean Discovery Program (IODP) Expedition 391, which recovered mostly pelagic nannofossil ooze and chalks. The seismic section can be divided into three seismic units (SU), a lower transparent interval which is faulted and conforms to basement, a middle, moderate to high amplitude interval which is thick in local depocenters such as rifts, and an upper, subparallel transparent interval. Notable features include regional unconformities, dipping clinoforms, mass transport and contourite deposits, and volcanic structures. Additionally, three infilled rifts are observed across the plateau. Our analysis implies that following a period of sedimentation in the Campanian, the edifice was faulted through the Paleocene, coinciding with a South Atlantic tectonic reorganization. Local depocenters formed as a result of rifting. Subsequently, the plateau experienced thermal rejuvenation and regional uplift during the Eocene. Volcanic mounds were emplaced atop Cretaceous sediments and intrusives were emplaced within the sediments. During the Cenozoic, sedimentation was punctuated, likely in response to changes in the carbonate compensation depth and bottom current intensification. VB sedimentation was complex and largely influenced by the paleoceanographic context of the plateau, as well as thermal rejuvenation and tectonism. 

Abstract Gamma-ray binaries are luminous in gamma rays, composed of a compact object orbiting a massive companion star. The interaction between these two objects can drive relativistic outflows, either jets or winds, in which particles can be accelerated to energies reaching hundreds of teraelectronvolts (TeV). However, it is still debated where and under which physical conditions particles are accelerated in these objects and ultimately whether protons can be accelerated up to PeV energies. Among the well-known gamma-ray binaries, LS 5039 is a high-mass X-ray binary with an orbital period of 3.9 days that has been observed up to TeV energies by the High Energy Stereoscopic System. We present new observations of LS 5039 obtained with the High Altitude Water Cherenkov (HAWC) observatory. Our data reveal that the gamma-ray spectrum of LS 5039 extends up to 200 TeV with no apparent spectral cutoff. Furthermore, we confirm, with a confidence level of 4.7σ, that the emission between 2 and 118 TeV is modulated by the orbital motion of the system, and find a 2.2σhint of variability above 100 TeV. This indicates that these photons are likely produced within or near the binary orbit, where they can undergo absorption by the stellar photons. In a leptonic scenario, the highest energy photons detected by HAWC can be emitted by ∼200 TeV electrons inverse Compton scattering stellar photons, which would require an extremely efficient acceleration mechanism operating within LS 5039. Alternatively, a hadronic scenario could explain the data through proton–proton or proton–gamma collisions of protons accelerated to petaelectronvolt energies. 

We describe an inertial rotation sensor with a 30-cm cylindrical proof-mass suspended from a pair of 14 μm thick BeCu flexures. The angle between the proof-mass and support structure is measured with a pair of homodyne interferometers, which achieve a noise level of ∼5prad/Hz. The sensor is entirely made of vacuum compatible materials, and the center of mass can be adjusted remotely. 

We constructed the magnetic field-temperature phase diagrams of new quasi-two-dimensional isosceles triangular lattice antiferromagnets (TLAF) Ca 3 MNb 2 O 9 (M=Co, Ni) from dc and ac magnetic susceptibilities, specific heat, dielectric constant, and electric polarization measurements on single crystalline samples. Ca 3 CoNb 2 O 9 with effective spin-1/2 Co 2+ ions undergoes a two-step antiferromagnetic phase transition at T N1 = 1.3 K and T N2 = 1.5 K and enters a stripe ordered state at zero magnetic field. With increasing field, successive magnetic phase transitions, reminiscent of the up-up-down ( uud ) and the oblique phases, are observed. The dielectric constant of Ca 3 CoNb 2 O 9 shows anomalies related to the magnetic phase transitions, but clear evidence of ferroelectricity is absent. Meanwhile, Ca 3 NiNb 2 O 9 with spin-1 Ni 2+ ions also shows a two-step antiferromagnetic transition at T N1 = 3.8 K and T N2 = 4.2 K at zero field. For Ca 3 NiNb 2 O 9 , the electric polarization in the magnetic ordered phases was clearly observed from the pyroelectric current measurements, which indicates its coexistence of magnetic ordering and ferroelectricity.