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Obsidian forms by slow cooling.
Get PDFObsidian is a natural glass that is a common product of silicic volcanic eruptions. It has been prized throughout human history for its glassy nature, finding use in tools, weapons and ornaments, and in ritual and spiritual practice. The absence of large crystals in obsidian has led to the widespread view that it is formed by rapid cooling of lava, preventing crystal nucleation and growth. Here we show that, on the contrary, the absence of vesicles in obsidian requires relatively slow cooling - on the order of 10 to 10 °C/s - to enable the resorption of remnant bubbles. Our bubble-resorption model for obsidian formation is supported by in-situ X-ray computed tomography at magmatic temperatures that reveals bubble shrinkage during resorption on cooling. We validate a numerical model for growth and resorption of bubbles against these results, then apply the model to explore the conditions under which obsidian can form in nature. Our findings revise the accepted thermal histories of obsidian-forming systems, overturning conventional wisdom for the formation of this culturally, archaeologically, and volcanologically important material. [Abstract copyright: © 2026. The Author(s).
A hybrid active galactic nucleus feedback model with spinning black holes, winds and jets
Get PDFWe present a hybrid active galactic nucleus (AGN) feedback model that features three accretion disc states (the thick, thin, and slim discs at low, moderate, and super-Eddington accretion rates, respectively), and two feedback modes: thermal isotropic and kinetic jets. The model includes black hole (BH) spin evolution due to gas accretion, BH mergers, jet spin-down, and Lense–Thirring torques. The BH spin determines the jet directions and affects the feedback efficiencies. The model is implemented in the swift code and coupled with the COLIBRE galaxy formation model. We present the first results from hybrid AGN feedback simulations run as part of the COLIBRE suite, focusing on the impact of new parameters and calibration efforts. Using the new hybrid AGN feedback model, we find that AGN feedback affects not just massive galaxies, but all galaxies down to M. BH spins are predicted to be near-maximal for intermediate-mass BHs ( M), and lower for other BH masses, which is in good agreement with observations. The intergalactic medium is hotter and impacted on larger scales in the hybrid AGN feedback simulations compared to those using purely thermal feedback. In the hybrid AGN simulations, we predict that half of the cumulative injected AGN energy is in thermal and the other half in jet form, broadly independent of BH mass and redshift. Jet feedback is important at all redshifts and dominates over thermal feedback at and , but only mildly
The Application of AI Chatbot System Based on CLIL Concept in the Teaching of Artificial Intelligence Courses
Get PDFThe interdisciplinary nature of artificial intelligence courses forces non-computer science majors to contend with the simultaneous challenges of terminology comprehension and language cognition. To increase the efficiency of terminology teaching, this project develops and deploys an OpenAI-based AI chatbot teaching system that incorporates the concept of content and language integrated learning (CLIL). The system creates a dual-track “terminology layer-cognition layer” framework that includes term recognition, multi-level explanation (contextual examples and conceptual associations), task-driven dialogues, and conversation memory bank (CMB) modules. It then guides students through natural language interactions to master the core AI terms in context. The system’s effectiveness was confirmed in a controlled experiment with 98 participants (including computer and non-computer majors) separated into two groups: experimental (chatbot teaching) and control (conventional PPT teaching). In terms of terminology mastery, the experimental group’s posttest score (86.0 ± 5.33) was considerably higher than that of the control group (66.98 ± 5.6). Non-computer science major students showed a more significant improvement effect (83.29 ± 4.5 vs. 63.62 ± 4.68 for the control group). Non-computing students evaluated the clarity of systematic terminology explanation (4.33 ± 0.76) and the effectiveness of contextual assistance (4.21 ± 0.88) as the most important aspects of their learning experience. These experimental results show that the fusion AI chatbot teaching system developed in this study can improve teaching efficiency while effectively reducing cognitive load, and that the task-guided and immediate feedback mechanism can significantly increase students’ learning engagement
Regular black hole formation in four-dimensional nonpolynomial gravities
Get PDFWe construct four-dimensional gravity theories that resolve the Schwarzschild singularity and enable dynamical studies of nonsingular gravitational collapse. The construction employs a class of nonpolynomial curvature invariants that produce actions with (i) second-order equations of motion in spherical symmetry and (ii) a Birkhoff theorem, ensuring uniqueness of the spherically symmetric solution. Upon spherical reduction to two dimensions, these theories map to a particular subclass of Horndeski scalar-tensor models, which we use to explicitly verify the formation of regular black holes as the by-product of the collapse of pressureless stars and thin shells. We also show that linear perturbations on top of maximally symmetric backgrounds are governed by second-order equations
Economy and society: labor costs for temple construction on late Archaic / early Classical Paros
No full textWomen Football Fans in China: A Call to Action for Expanding Global Understandings of Gender, Football and Fandom
No full textIn recent years, women’s participation in football fandom has attracted growing scholarly attention, reflecting broader debates about gender, cultural change and the transformation of contemporary sport. Yet these discussions continue to overlook the experiences of women in non-Western contexts, where football cultures operate within different historical trajectories, value systems and social structures. China offers a particularly important case study at this moment, as football has grown in popularity and an increasing number of women have become engaged as fans, while their experiences remain largely absent from existing research. Examining these experiences therefore addresses a clear gap in the literature, responds to the need for more inclusive accounts of fandom, and offers an opportunity to reconsider dominant frameworks in gender and sport, including how the “feminization” of fandom unfolds beyond the contexts in which it has traditionally been studied
THE NAME OF THE ORGANON
No full textThis article discusses the question whether the use of ὄργανον as a title to designate Aristotle’s logical treatises as a unitary bibliographical entity can be traced back to the ancient commentators or emerged as late as in the Renaissance. A review of the ancient and medieval evidence locates the earliest certain traces of this use in the eleventh or twelfth century
Understanding luminescence of metal-containing thermally activated delayed fluorescence (TADF) luminophores
No full textMetal TADF (thermally activated delayed fluorescence) emitters, here understood as those containing a d-block metal, are an important and ever-growing group of luminophores. Although they often seem to belong more in the transition metal complex world, they are rightful contenders of not only phosphorescent transition metal compounds, but also conventional, metal-free TADF emitters. Their unique properties include extremely short TADF lifetimes, often in the range 0.1–10 µs, fast intersystem crossing (ISC) and reverse ISC (RISC), minimal prompt fluorescence or lack thereof, small Stokes shifts, and temperature-dependent behaviour, including dual TADF/phosphorescence emission – but not every metal TADF emitter displays all of them at once! In this review, we discuss the general photophysical properties of metal TADF emitters and the relevant photophysical approaches applicable to studies of them. We make a brief overview of the most recent examples of computational works on metal TADF luminophores that shed some light on the up-conversion mechanism. Finally, we review some recent examples of Cu(i), Ag(i), Au(i)/Au(iii) as well as Zn(ii) TADF emitters, and discuss possibly all relevant works on Pd(ii), Pt(ii), Ir(iii), and Zr(iv) TADF complexes. We identify that metal TADF complexes form two principal groups: (I) those analogous to donor–acceptor or charge-transfer TADF emitters and (II) those analogous to multiresonance TADF emitters
An extension of C++ with memory-centric specifications for HPC to reduce memory footprints and streamline MPI development
No full textC++ leans towards a memory-inefficient storage of structs:The compiler inserts padding bits, while it is not able to exploit knowledge about the range of integers, enums or bitsets.Furthermore, the language provides no support for arbitrary floating-point precisions.We propose a language extension based upon attributes through whichdevelopers can guide the compiler what memory arrangements would be beneficial:Can multiple booleans or integers with limited range be squeezed into one bit field, do floating-point numbers hold fewer significant bits than in the IEEE standard, and is a programmer willing to trade attribute ordering guarantees for a more compact object representation?The extension offers the opportunity tofall back to normal alignment and native C++ floating point representations via plain C++ assignments,no dependencies upon external libraries are introduced, and the resulting coderemains (syntactically) standard C++.As MPI remains the de-facto standard for distributed memory calculations in C++,we furthermore propose additional attributes which streamline the MPI datatype modelling in combination with our memory optimisation extensions.Our work implements the language annotations within LLVM and demonstrates their potential impact through smoothed particle hydrodynamics benchmarks.They uncover the potential gains in terms of performance and development productivity
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