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An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Planning at a higher level of abstraction instead of low level torques improves the sample efficiency in reinforcement learning, and computational efficiency in classical planning. We propose a method to learn such hierarchical abstractions, or subroutines from egocentric video data of experts performing tasks. We learn a self-supervised inverse model on small amounts of random interaction data to pseudo-label the expert egocentric videos with agent actions. Visuomotor subroutines are acquired from these pseudo-labeled videos by learning a latent intent-conditioned policy that predicts the inferred pseudo-actions from the corresponding image observations. We demonstrate our proposed approach in context of navigation, and show that we can successfully learn consistent and diverse visuomotor subroutines from passive egocentric videos. We demonstrate the utility of our acquired visuomotor subroutines by using them as is for exploration, and as sub-policies in a hierarchical RL framework for reaching point goals and semantic goals. We also demonstrate behavior of our subroutines in the real world, by deploying them on a real robotic platform. Project website: this https URL.
Optical spectra of the Type II supernova 1987F, obtained shortly after discovery and at late times, are atypical of SNe II. When first observed, broad Hα was superposed on a nearly featureless continuum, but its profile did not have the characteristic P Cygni shape, and its centroid was blueshifted by >~1500 km s^-1^ with respect to the systemic velocity. Many months later, the object was dominated by broad permitted emission lines of hydrogen, with Fe II and Ca II emission detected as well; forbidden lines, normally quite strong at this phase, were very weak. The derived electron density in the ejected envelope at this time was >~10^9^ cm^-3^. Together with the observed expansion velocities, this leads to an estimate of M>~5-30 M_sun_ for the envelope, implying that the progenitor was very massive. The light curve, which declined very slowly at both early and late times, supports this conclusion. With a few small but possibly significant exceptions, the overall optical spectroscopic properties of SN 1987F closely resemble those of Type I Seyfert nuclei and QSOs; in particular, a comparison is made with the spectrum of 3C 48. The same can be said for the much less extensively observed Type II SN 1988I, although in this object there is no direct evidence for Fe II emission. Even the optical luminosities of the SNe are comparable to those of moderately active galactic nuclei. Had either of these SNe occurred in the nucleus of a normal galaxy, the nucleus would probably have been classified as a Type I Seyfert the only data available were low-resolution optical spectra. It is possible that certain environment conditions, such as the presence of a dense interstellar medium, may increase the rate at which object such as SN 1987F and SN 1988I are produced. Following the work of Terlevich and Melnick, I suggest that the observed properties of some low-luminosity active galaxies might actually be due to violent bursts of star formation rather than accretion onto a supermassive black hole.
This paper gives a new sufficient condition for complete stability of a nonsymmetric cellular neural network (CNN). The convergence theorem of the Gauss-Seidel method, which is an iterative technique for solving a linear algebraic equation, plays an important role in our proof. It is also shown that the existence of a stable equilibrium point does not imply complete stability of a nonsymmetric CNN.
Summary The Legendre–Hadamard necessary condition for energy minimizers is derived in the framework of Cosserat elasticity theory.
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As cyclic fatigue is considered to be a major cause of clinical tooth fractures, achieving a comprehensive understanding of the fatigue behavior of dentin is of importance. In this note, the fatigue behavior of human dentin is examined in the context of the Kitagawa‐Takahashi diagram to define the limiting conditions for fatigue failure. Specifically, this approach incorporates two limiting threshold criteria for fatigue: (i) a threshold stress for fatigue failure, specifically the smooth‐bar (unnotched) fatigue endurance strength, at small crack sizes and (ii) a threshold stress‐intensity range for fatigue‐crack growth at larger crack sizes. The approach provides a “bridge” between the traditional fatigue life and fracture mechanics based damage‐tolerant approaches to fatigue‐life estimation, and as such defines a “failure envelope” of applied stresses and flaw sizes where fatigue failure is likely in dentin This approach may also be applied to fatigue failure in human cortical bone (i.e. clinical “stress fractures”), which exhibits similar fatigue behavior characteristics, and in principle may aid clinicians in making quantitative evaluations of the risk of fractures in mineralized tissues. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
A growing number of observations reveal a subset of Type Ia supernovae undergoing circumstellar interaction (SNe Ia-CSM). We present unpublished archival Spitzer Space Telescope data on SNe Ia-CSM 2002ic and 2005gj obtained > 1300 and 500 days post-discovery, respectively. Both SNe show evidence for late-time mid-infrared (mid-IR) emission from warm dust. The dust parameters are most consistent with a pre-existing dust shell that lies beyond the forward-shock radius, most likely radiatively heated by optical and X-ray emission continuously generated by late-time CSM interaction. In the case of SN 2005gj, the mid-IR luminosity more than doubles after 1 year post-discovery. While we are not aware of any late-time optical-wavelength observations at these epochs, we attribute this rebrightening to renewed shock interaction with a dense circumstellar shell.
