Papers

In Part I of the companion paper [Ref Part I], we have extensively discussed about the creation of quasi-stationary ion scale (QSIS) inhomogeneity using a constant frequency external drive at ion-acoustic time scales, resulting in ion trapped particle instability (ITPI), wave-wave mode coupling interaction and energy cascading. QSIS thus formed is perturbed by applying small amplitude electron acoustic (EA) mode leading to the several key plasma response features. In this Part II, using electrostatic, unbounded, OpenMP Vlasov-Poisson solver i.e VPPM-OMP 1.0, we have investigated the formation of various phase space vortices (PSV) (generated using two step or one step time dependent downward frequency chirping drives) in the presence of background QSIS inhomogeneity obtained in Part I. In addition, we have also performed one to one comparison of individual cases with their homogeneous counterparts with exact simulation parameters. In presence of QSIS inhomogeneity, we have observed interesting phenomenon such as early onset of Langmuir (LAN) mode, suppression of PSV sizes, omission of PSVs when compared to the homogeneous cases. Also, for different two step or one step downward chirp perturbation cases, particle trapping or untrapping fractions and its response to the increasing chirp intervals are respectively reported.

We study thermal transport across copper-graphene-copper interfaces using Non-Equilibrium Molecular Dynamics (NEMD), focusing on the influence of finite domain length and domain configuration, including lattice initialisation and associated graphene wrinkling, on the predicted thermal conductivity and Kapitza resistance. In the literature, NEMD simulations identified trends in the Kapitza resistance of graphene-copper interfaces. However, the simulation outcomes and reliability may depend heavily on configuration choices that are underexplored in the literature. We identify a strong sensitivity of the Kapitza resistance to domain configuration choices that affect the lattice constants and atomic density. We show that two conventional lattice initialisation strategies yield a factor of two difference in the Kapitza resistance, despite differences of only a few per cent in the lattice parameters. This behaviour is accompanied by strain-dependent shifts in the graphene and copper phonon spectra, and by increased phonon overlap at lower strain. Counter to conventional expectations, greater phonon-mode overlap coincides with higher Kapitza resistance, showing that spectral overlap alone cannot capture the interfacial heat-transfer dynamics. We suggest that in lattices initialised with lower residual strain, a damping boundary layer develops near the interface, and increases thermal resistance, as indicated by increased local structural disorder and local spectral broadening over a wider interfacial region. Beyond strain- and density-related effects associated with the lattice constants, Kapitza resistance shows no significant dependence on domain length or boundary temperature enforcement in this study. By contrast, the copper lattice conductivity exhibits clear domain-size and temperature dependence, consistent with phonon mean-free-path limitations and supported by phonon spectral analysis.

Formation dynamics and stability starting from various phase space vortex (PSV) or Bernstein-Greene-Kruskal (BGK) structures i.e electron acoustic wave (EAW), Langmuir (LAN) waves is investigated in the presence of a quasi-stationary ion scale (QSIS) inhomogeneity using high resolution Vlasov-Poisson simulations with VPPM-OMP 1.0 solver. In a one dimensional, collisionless, periodic, unmagnetized plasma with kinetic ions and kinetic electrons, we first create a QSIS inhomogeneity using low amplitude electric field drive at ion acoustic (IA) frequency with k eq = mk min [where m = 2 is the mode number, k min corresponds to the longest scale in the system]. While creating QSIS inhomogeneity, we have demonstrated the existence of ion trapped particle instability (ITPI) which saturates as the amplitude of sideband modes become comparable to that of the primary nonlinear mode (quite analogous to the trapped particle instability in large amplitude electron plasma waves). Also, mode transition from m = 2 to m = 1 is observed during relaxation period due to the energy cascading process. Finally, an electron acoustic (EA) perturbation of scale k p = k min [m = 1] is applied on top of the QSIS inhomogeneity to determine its response in the presence of background ion scale inhomogeneity. Some key observations such as formation of transient PSV, wave-wave mode coupling interaction and various frequency generation alongwith comparative investigation with EA perturbation launched in the absence of ion scale inhomogeneity is also reported.

Conventional photonic doping schemes predominantly employ circular or rectangular dielectric dopants with zero topological charge, where the effective permeability can only be tuned through material selection and geometric scaling, resulting in limited design flexibility. In this work, topological structures are introduced into dielectric dopants by embedding internal holes to generate nonzero topological charge. Based on this concept, a theoretical model is established to describe the effective permeability of photonic doping systems with nonzero topological charge, and the underlying mechanisms governing topological-charge-dependent transmission are systematically elucidated. The results demonstrate that engineering nonzero topological charge through the number, shape, size and position of internal holes within dielectric dopants enables flexible manipulation of the internal magnetic field distributions, thereby providing precisely control over the effective permeability, as well as the resonance frequency and spectral linewidth of the transmission spectrum. The proposed multi-dimensional photonic doping strategy, integrating topological-charge engineering with geometric design, substantially enriches the available degrees of freedom for dispersion engineering and provides a versatile platform for advanced functional photonic devices.

Mapping the dispersion of polaritons, hybrid quasiparticles arising from light-matter coupling, can provide key insights into the material dielectric response, coupling strength, and energy transfer pathways with other excitations. In this work, we present THz pump-Raman probe (TP-RP) as a versatile method for mapping the polariton dispersion in polar non-centrosymmetric materials, demonstrated here for the case of phonon-polaritons in LiNbO$_3$. By resonantly driving polaritonic modes with a broadband THz pump and probing them with a tunable NIR Raman pulse, TP-RP allows for the extraction of the momentum-dependence of both their frequency and damping rate with high accuracy. The spectral features observed in the pump-probe signal, including the polaritonic response as well as pulse artifacts, are reproduced within a many-body theoretical approach. Applying the technique to study the E(TO$_1$) phonon of LiNbO$_3$ enables the combined analysis of theory and experiments to uncover a nontrivial frequency dependence of the phonon intrinsic damping rate, revealing possible anharmonic couplings to other modes.

Reservoir computing has emerged as a powerful paradigm for harnessing the intrinsic dynamics of physical systems to perform complex information processing. Here, we theoretically and numerically investigate a reservoir computing system based on the two-dimensional discrete complex Ginzburg-Landau equation, a fundamental model describing driven-dissipative exciton-polariton lattices. We apply this framework to the challenging 52-class handwritten letter recognition task, decomposing temporal input signals to simulate word recognition. Our system achieves a high test accuracy, significantly outperforming a linear baseline. Through systematic parameter scans and nonlinear dynamics analysis, we establish a quantitative link between computational performance and the underlying physics: optimal classification occurs near the edge of stability, where the maximum Lyapunov exponent approaches zero. This principle holds universally across different control parameters, including nonlinear coupling and linear gain. Furthermore, we validate the practical feasibility of this approach by deploying the trained model on a Raspberry Pi 5 edge device. These results not only demonstrate the potential of polariton lattices for neuromorphic computing but also provide a general design principle for optimizing physical reservoir computing hardware.

Numerical simulation of droplet dynamics on complex surfaces with varying wettability is of great significance to both engineering applications and fundamental research. However, existing numerical methods still face challenges in accurately capturing interfacial interactions while preserving physical consistency and computational efficiency. In this work, a physically grounded and efficient smoothed particle hydrodynamics (SPH) model is developed for droplet dynamics simulation. To reduce computational cost, a single-phase droplet modeling strategy is employed. At the interface, long-range interactions are approximated using the SPH kernel function, whereas short-range interactions are represented through pressure. Based on this treatment, an explicit relationship between the intermolecular potential energy and the macroscopic surface tension coefficient is further established, thereby reducing reliance on empirical parameter calibration. The proposed method is first validated through static wetting simulations, where the equilibrium contact angles agree well with the Young–Dupré equation. Further simulations of wetting and droplet impact demonstrate that the method is capable of capturing complex dynamic wetting behaviors.

Cities in the United States and worldwide concentrate populations with diverse incomes, demographics and health risks, making access to healthcare facilities and emergency services critical. Urban flooding amplifies congestion and further degrades healthcare accessibility, but its impacts are uneven within and across cities, often burdening underserved populations and underplanned areas. These risks are intensifying as rapid development, aging infrastructure and climate change increase urban flood exposure. Across 30 of the most populous US cities, we show that peak-hour congestion alone reduces accessibility by 4% to 29%, while flooding further reduces it by 2% to more than 90%. These losses depend on flood type, transportation design, infrastructure planning, health vulnerability and spatial inequality. Flooding also increases spatial inequality in healthcare access, but the social burden varies by city and flood type, with urban coastal flooding disproportionately affecting less socially vulnerable populations in the United States. Our findings suggest that targeted approaches for embedding flood resilience in transportation and healthcare systems will be more effective than universal strategies, while allowing cities to learn from diverse urban regions facing similar accessibility risks.

We present a combined experimental and numerical investigation of the preferential alignment of Kolmogorov-size, high-aspect-ratio fibers in turbulent channel flow at friction Reynolds numbers $\mathit{Re}_{\tau}=300$ and $550$. Time-resolved volumetric measurements in the TU Wien Turbulent Water Channel are used to simultaneously track fibers and surrounding tracer particles, enabling the reconstruction of fiber trajectories together with a coarse-grained estimate of the local velocity-gradient tensor (VGT). Complementary direct numerical simulations (DNS) of channel flow laden with prolate ellipsoids provide a reference point-particle description. The analysis focuses on the channel core, where the experimental data recover the canonical alignment of vorticity with the intermediate strain-rate eigenvector, thereby supporting the reliability of the reconstructed VGT. We show that fibers preferentially align with the local vorticity direction, while weaker but still non-random alignments are observed with the strain eigenvectors. By measuring finite-time deformation along fiber trajectories through the left Cauchy–Green tensor, we further show that the strongest alignment occurs with the leading principal direction of Lagrangian stretching. The comparison with DNS shows overall good agreement, while deviations at higher Reynolds number suggest increasing finite-size filtering effects.

Biological systems across scales, along with many engineering problems, must control noisy systems with limited information. Here we study information-limited feedback control of stochastic systems to achieve target steady states, and derive a lower bound on the information rate from controlled system to controller. This framework allows us to obtain performance-information Pareto frontiers for wide-ranging control problems with limited information. For systems with state-independent passive dynamics, the bound is saturated by an explicit optimal control protocol which probabilistically time-reverses the passive dynamics. We showcase these results through applications to nonlinear particle localization, microbial navigation, and experimentally realized information engines.

Oscillator-based Ising machines, in which the phases of coupled self-sustaining oscillators evolve toward decreasing an Ising Hamiltonian, are commonly interpreted as physical realizations of the Ising model. This interpretation, however, requires the phase dynamics generated by the physical oscillator network to match a prescribed Ising dynamics. Here we show that this correspondence is generally not guaranteed. For arbitrary self-sustaining oscillators under weak coupling, we derive the physical phase interaction from the harmonic overlap between the injected waveform and the perturbation projection vector (also referred to as impulse sensitivity function). We find that uncompensated harmonic phase mismatches between these two quantities generate even components in the physical coupling function, causing a network with the correct coupling topology to implement a non-Ising dynamics. We further show that delayed coupling provides a universal phase-compensation mechanism. For a fixed delay, we derive a condition on the delay under which the even components is minimized in the sense of L2-norm, and oscillator examples confirm that the predicted delay substantially suppresses the even components and brings the realized coupling function closer to the prescribed odd interaction. We then show that a periodically modulated delay can, under suitable moment conditions, eliminate the even components in the phase dynamics. These results establish a general design principle for implementing prescribed energy-based dynamics in physical oscillator networks.

Solid oxide fuel cells enable efficient conversion of hydrogen into electricity. However, the limited availability of materials for their cathode, anode, and electrolyte remains a concern. This study introduces three high-entropy oxide perovskites as novel electrolyte materials for fuel cells (Ba0.50Sr0.50)(Ti0.33Zr0.33Hf0.33)O3 with s0/d0 cations, (Ba0.50Sr0.50)(Ga0.33In0.33Sn0.33)O3 with s0/d10 cations, and (Ba0.50Sr0.50)(Ti0.33Zr0.33Sn0.33)O3 with mixed s0/d0/d10 cations. Through sequential sintering by high-pressure torsion processing and calcination, these perovskites were synthesized and then printed with a thickness of about 6-10 microns on a Ni-SrZr0.5Ce0.4Y0.1O3 substrate as an anode and then coated with Ba0.5La0.5CoO3 as a cathode. Electrochemical analysis and impedance spectroscopy show that (Ba0.50Sr0.50)(Ti0.33Zr0.33Sn0.33)O3 with s0/d0/d10 cations exhibits the best performance with negligible current leakage and lowest ohmic resistance, while its maximum power density reaches 0.53 W.cm-2 at 973 K. Complementary synchrotron X-ray absorption and photoelectron spectroscopy analyses indicate that the superior performance of (Ba0.50Sr0.50)(Ti0.33Zr0.33Sn0.33)O3 correlates with its heterogeneous electronic structure characterized by tailored unoccupied d-orbital states, and favorable local metal-oxygen bond lengths and extrinsic oxygen vacancies. This investigation demonstrates the significance of high-entropy perovskites with mixed s0/d0/d10 cations as new rare-earth metal-free ion-conducting electrolytes, particularly for protonic solid oxide fuel cells.

Chirality in a discrete $Z_q$ spin interaction distinguishes clockwise from counterclockwise phase differences, but its manifestation in continuous nonlinear dynamics is unclear. We show that any pairwise $Z_q$ Hamiltonian admits a unique equilibrium-preserving embedding into a continuous phase-energy landscape that matches the discrete energy on the $q$-state phase grid, where every grid point is stationary. This embedding reveals that a $Z_q$ kernel is nonchiral if and only if the sine components of the relaxation vanish. Chirality of the discrete $Z_q$ model is therefore exactly the odd part of the continuous phase interaction. In the induced nonlinear phase dynamics, this odd part becomes an orientation-dependent phase shift in the multi-harmonic coupling, and chiral reversal flips this shift while preserving the coupling magnitudes. In self-sustaining oscillator networks, the shift is further realized as a direction-dependent delay. Transistor-level ring-oscillator simulations validate the predicted phase locking and reversal of directed phase bias. These results show that algebraic handedness in a discrete spin Hamiltonian can be represented as tunable time-domain asymmetry in continuous nonlinear dynamics.

We develop a quantum model for the rotational dynamics of a freely floating levitated ferromagnetic gyroscope (LFG), emphasizing the interplay between intrinsic spin $\boldsymbol{S}$, mechanical angular momentum $\boldsymbol{L}$, and magnetic torque. The conserved total angular momentum projection along the $z$-directed magnetic field $\boldsymbol{B}$, $J_z=S_z+L_z$, is quantized, leading in the small-libration-amplitude limit to discrete precessional states $|m\rangle$ (eigenstates of $J_z$ with eigenvalues $J_z = m\hbar$) and librational harmonic oscillator states $|n\rangle$ ($n=0,1,2,\ldots$). The discreteness of the energies and dynamical variables is governed by the quantum precession scale $\Omega_Q=\hbar/I$, where $I$ is the moment of inertia of the LFG. We find that the phenomenon of LFG precession persists into high-field regimes where the magnitude of the rotational angular momentum associated with precession exceeds the total intrinsic spin. We analyze the complementary quantum limits of localized semiclassical LFG orientation wave packets and exact $J_z$-eigenstates $|m\rangle$, clarifying the relation between classical precession signals and the underlying quantized spin-rotor dynamics. We further show that radio-frequency fields can drive $\Delta m = \pm 1$ and $\Delta n = \pm 1$ transitions, enabling ladder spectroscopy, tilt-angle control, and sideband-like coupling between precession and libration. The coupled dynamics also exhibit branch-point magnetic resonances where precession and librational motion become strongly coupled. These results establish a framework for using LFGs not only as ultrasensitive torque and magnetic-field sensors, but also as controllable mesoscopic quantum systems. The techniques developed here may be applied to searches for exotic, beyond-the-standard model spin-dependent interactions, ultralight dark matter, and spin-gravity couplings.

As a fundamental arena for the development of his dynamics, Newton postulated the existence of absolute space, in which bodies innately possess absolute velocity. Despite this, Newton argued that, although real, absolute properties cannot be detected. Since then, the claim that absolute velocity would be undetectable in such a Newtonian universe has been generally accepted. Here, we show that standard arguments for such a claim, beginning with the one offered by Newton himself, beg the question. We conclude that there are no formal reasons to believe that absolute velocity would be undetectable in a Newtonian universe.

Nanophotonic platforms have multiple properties and features desirable for producing correlated photon pairs. In these platforms, spontaneous parametric down-conversion (SPDC) and spontaneous four-wave-mixing (SFWM) have been used to achieve photon pair production. By placing the nonlinear region in a resonant cavity, the source obtains an enhanced nonlinear interaction and naturally filters out photons by frequency according to the cavity linewidth. Among various platforms, X-cut thin-film lithium niobate (TFLN) stands out for its strong second-order optical nonlinearity ($\chi^{(2)}$) and access to a strong platform for modulating light. Although previously demonstrated, present sources are limited in their photon pair channel availability, limiting the potential of quantum applications in quantum information processing, communication, and sensing that can scale in robustness by having access to multiple photon pair channels. To this end, we demonstrate a photon pair source on X-cut TFLN with 80 measured photon pair channels spanning the C and L optical bands with a frequency spacing of 49.5 GHz between photons. We characterize the second-order correlation function and pair generation rate (PGR) of 80 channels, the highest number of channels demonstrated to date, and achieve a pair generation of 125.7 kHz / {\mu}W after accounting for the cavity's escape efficiency. We also demonstrate heralded single photon operation by calculating a heralded auto-correlation dip of 0.0544 $\pm$ 0.0054 with 2.2 mW of on-chip pump power. These findings demonstrate the promise of X-cut TFLN as a strong platform for quantum optical applications.

Single-photon emission in two-dimensional single-layer WSe2 is attractive for the on-demand generation of quantum states of light. The electronic states that are responsible for single-photon generation preferentially form in regions of localized tensile strain, enabling deterministic positioning and strain engineering. Nanoindentation of single-layer WSe2 yields controlled and reproducible deformations that generate the localized strain needed to activate the single-photon-emitting states. However, using nanoindentation both for investigating structure-property relationships and for manufacturing quantum light sources based on WSe2 is hindered by key questions on the structural integrity of the indented 2D material, the resulting strain generated, and the sub-micron location of the emitters. In this work, we study the structure of indented single-layer WSe2 using a fabrication process that inverts the indents into protruding pillars that can be probed using electron microscopy. We explicitly identify strain relaxation of the indented single-layer WSe2 due to tearing and confirm that single-photon-emitting states still form in these systems, likely at the extremities of the tear. For indents that are confirmed to be intact (i.e., not torn), we assess the ability to strain engineer the single-photon emitters. While strain does not strongly affect the emission energy or the brightness, we find that increased strain reduces the spatial density of emitters. This trend indicates that an optimal amount of strain is needed for emitter formation and/or the emitters preferentially form on the periphery of the indent. Our investigation provides insight into the most relevant structure-property relationships for using strain to engineer quantum light sources in single-layer WSe2 and other 2D semiconductors.

We present a message passing formalism to study the age-targeted robustness of networks that have evolved under the addition and deletion of vertices. We show that in the growing regime removing the oldest vertices fragments the network far sooner than random failure, while the oldest core is far more robust under targeted removal of the young. At a balanced turnover of vertices the attack value vanishes identically and we prove that the giant component is invariant under arbitrary age-targeting.

An alternative explanation is presented for recent reports that attribute sustained chemiluminescence (CL) and electrochemiluminescence (ECL) from electrogenerated microbubbles on steel or copper electrodes in aqueous luminol solutions (over 2-30 V range) to the spontaneous formation of hydroxyl radicals at the gas-water interface. Our experiments with a broad set of electrodes, viz., steel, copper, aluminium, and platinum, reveal that while microbubbles can be electrogenerated on all electrodes, CL is exhibited by steel and Cu only and not by Al and Pt. These observations establish that the gas-water interface of microbubbles is not the site for hydroxyl radical generation (else CL would be recorded in all cases). Complementary quantification of H2O2 in these experiments reveals its electrode dependence as follows: Al > Cu > Steel > Pt. This establishes that depending on the electrode, H2O2 forms first, and in some cases, hydroxyl radicals are observed (i.e., where CL/ECL is seen). Experiments with NMR and EPR spectroscopy revealed that: (i) H2O2 formation occurs only when O2 is present in water; and (ii) while steel and copper generate hydroxyl radicals through 1-electron reduction of H2O2, Al does not promote one-electron reduction of H2O2 to generate hydroxyl radicals, and Pt preferentially promotes disproportionation of H2O2 to H2O and O2. In fact, we demonstrate that H2O2 and hydroxyl radicals can be observed at specific metal-water interfaces even without microbubbles, confirming that the solid surface is the reactive site. Therefore, this work affords electrode-based predictions of whether or not electrogenerated microbubbles would yield CL in luminol solutions and calls into question the notion of spontaneous formation of hydroxyl radicals at gas-water interfaces.

Acemoglu and Robinson (2024 Nobel laureates in Economics) trace national histories in The Narrow Corridor as paths through a two-dimensional (state power, society power) space but plot none: quantifying the two axes at each moment is the labor-intensive, judgment-laden task that has kept the framework qualitative. We ask whether large language models (LLMs) can operationalize it. We introduce a reproducible, provider-agnostic pipeline that scores a country period by period using chain-of-thought (events first, then score) and in-context anchoring on prior periods, against an explicit rubric with schema-validated output. As a proof of concept we produce a twelve-country trajectory atlas (Iran, France, the United Kingdom, the United States, China, Chile, Colombia, the Democratic Republic of the Congo, Lebanon, Zambia, Somalia, and India), chosen to place at least two countries in each of the book's four Leviathan types, and compare four models. We assess the scores for consistency with an expert index (V-Dem) and for inter-model agreement, reading agreement as concurrent consistency rather than accuracy, since such indices likely appear in the models' training data, and discuss conceptually how the biases of an LLM annotator and a human expert differ. Code, prompts, runs, and an interactive gallery of the animated trajectories are released.

After geomagnetic storms erode the plasmasphere, cold ionospheric plasma flows along magnetic field lines to refill the depleted flux tubes. Previous studies have suggested that refilling undergoes two stages characterized by their distinct refilling rates; however, not all observations or models exhibit this feature, and a recent analysis indicates that only a subset of refilling events display two clear stages. In this study, we show that the magnitude of the field-aligned electron temperature gradient and initial/boundary temperature regulate the durations of both the early and late stages. Performing multivariate regressions from the results of simulating early and late-time refilling demonstrated that the length of each stage uniquely depends on the temperature gradient and initial/boundary temperature. These results suggest that variations in the temperature profile may explain why some refilling events appear single-staged in observations.

We introduce a novel discretization of the incompressible Euler equations based on their interpretation as geodesic equations on the Lie group of volume-preserving diffeomorphisms. It is well known that encoding diffeomorphisms and their infinitesimal generators through a discretized Koopman representation places a nonholonomic constraint on discrete velocities, for which there is no consensus on a variational treatment. We show that taking the vakonomic perspective, as opposed to the usual perspective of Lagrange–d'Alembert, yields discrete fluid trajectories that remain geodesics on a (sub-)Riemannian manifold. In particular, the resulting vakonomic dynamics are Lie–Poisson and their solutions admit a discrete relabeling symmetry, leading to machine-precision satisfaction of Casimir invariants along with a discrete analogue of Kelvin's Circulation Theorem. Using an efficient momentum map representation based on low-rank Clebsch variables, we show that these vakonomic fluids behave stably and consistently even at low grid resolutions, leading to increased robustness and physical realism in the long term.

Synthetic-population tools increasingly run every individual as an independent large language model (LLM) agent. Using real survey microdata, we show that this paradigm has a basic failure mode, and we set a distribution-first corrective against it, all measured with a deterministic, construct-validated verifier on non-WEIRD (Turkey-first) data. First, N independent LLM agents grounded on 2,414 real World Values Survey respondents fail to reproduce the population's response distribution: they pile onto a modal default (four scenarios x five seeds: concentration 0.36->0.69, entropy 1.46->0.77, 85% collapse, TVD=0.44), and the collapse is a predictable function of scenario structure (r=0.55 with a single-answer structure). Second, Verbalized Sampling (VS) fixes the field's chronic under-dispersion without training in three model families (fidelity +7 to +10; significant on Qwen, p=0.002, d=6.2), yet the same move universally overshoots into over-dispersion (SD-ratio 0.4-0.56 -> 1.26-1.37), a structural property of VS. Third, survey fidelity transfers only weakly to agentic behavior: in a single-model, single-domain booking task, a persona is dominated by a cheapest-default (~80%) that income modulates but does not override (comfort choice 0%->7%->32% across income bands). Fourth, a placebo-controlled memorization attack and an election backtest show VS keeps aggregate strength while subgroup and individual claims are contaminated by recall and underdetermination. We close with the corrective: model the distribution once (VS) and assign it to grounded characters at O(1) cost, with a budget-aware router whose honest AUC is 0.805, not the tautological 1.0 of a code-derived oracle. The central contribution needs no realism claim: it measures the internal inconsistency of the independent-agent route and the conditions under which the distribution-first route calibrates.

Unsteady aerodynamic phenomena, such as gusts, turbulence, and fluid-structure interactions affect an aircraft during flight. For design, optimisation and certification, it is indispensable to quantify such unsteady aerodynamic effects. Industry-standard computational fluid dynamics methods, such as solving the unsteady Reynolds-averaged Navier-Stokes equations or the linearized frequency domain method, are either computationally expensive or restricted by assumptions like linearity. Once trained, machine learning methods are capable of computing non-linear relationships very fast, making them suitable as surrogate models. By autoregressively applying graph neural networks (GNNs), operating on a discretised spatial domain, spatio-temporal predictions can be made. However, autoregressive GNNs suffer from error accumulation leading to unstable rollouts over time. Here we show that combining GNNs with augmented Neural Ordinary Differential Equations yields temporally stable predictions of the surface forces on a pitching airfoil. We found that our approach, called GNODE, based on Graph Neural Ordinary Differential Equations, provides temporally more stable, spatially smoother, and overall more accurate results than an autoregressive GNN baseline. Tests are conducted on a dataset consisting of a simulations of a pitching airfoil, including transonic shocks, transient behaviour and dynamic non-linearities. Augmenting GNODEs with additional latent dimensions improves the expressivity and accuracy by capturing underlying history effects. The developed method demonstrates an approach that is suitable to model non-linear spatio-temporal systems with exogenous inputs.

Internal coordinates are the natural language of molecular structure, but automatic non-redundant constructions remain difficult for fused rings, high coordination, molecular symmetry, and weakly bound fragments. We present SONIC (Symmetry-Oriented Non-redundant Internal Coordinates), implemented in SMITH, as a deterministic construction of localized, symmetry-adapted generalized internal coordinates. SMITH accepts a frozen molecular state, supplied topology or primitives, or Cartesian input through a revision-pinned standalone perception kernel. It classifies ordinary primitives, adds chemically typed special and composite families, protects ring and fragment coordinates, and performs block-local rank reduction using analytic Wilson B rows. Local pseudosymmetry orders center, ring, and bond domains, while exact molecular point-group projection is applied within homogeneous blocks. The output is a frozen coordinate contract with human-readable decompositions, symmetry and rank diagnostics, analytic first derivatives, and optional Gaussian 16 serialization. Optimization, internal-to-Cartesian realization, force fields, and higher-order Hessian transformations remain downstream responsibilities. Validation covers acyclic, fused, bridged, high-coordinate, non-covalent, and eta3 metal-complex cases, including rotation/permutation invariance, Python/Fortran checks, and independent GIC evaluation.

The Amateur Radio on the International Space Station (ARISS) program is recognized by its great Science, Technology, Engineering, and Mathematics (STEM) impact: it brings space science to education and outreach initiatives by enabling direct contact with astronauts in orbit and other space savvy professionals. Strategic partnerships between ARISS and digital platforms for citizen science act as a powerful real-world STEM motivator and can overcome logistical barriers, demonstrating a scalable model for inclusive outreach, sparking curiosity in space exploration and STEM careers among underrepresented communities. As a case study, this article focus on the impact of an historic milestone: on April 18$^{th}$ 2025 the Pan-African Citizen Science e-Laboratory (PACS e-Lab) orchestrated the first Africa-wide ARISS contact experiment and connected 300 students, educators, and STEM enthusiasts from 38 African nations and beyond with NASA astronaut Nichole Ayers aboard the ISS Expedition 72. Within the African context, this initiative not only inspired a new generation of African scientists, but it also set a precedent for wider collaboration on space science education across the continent. Strategic partnership between ARISS and PACs e-LAB promotes capacity building through international and regional cooperation on space science and adds a new "New Space" narrative that emphasizes the interconnectedness of space with our daily lives and the possibility that everyone has to be a part of it.

Parametric resonance provides a versatile mechanism to manipulate wave signals in time-modulated metamaterials, but typically operates within narrow wavelength or frequency ranges. Here, we show that one-dimensional arrays of coupled resonators can generically exhibit parametric amplification across an entire band under standing-wave parametric modulation. We develop a general physical framework to describe the parametric resonance of isolated bands, derive modulation conditions needed to achieve full-band amplification for a given band, and demonstrate their validity in a model of active mechanical metamaterials based on tunable membrane resonator arrays. We numerically demonstrate applications of the proposed strategy in distortion-free amplification and temporal splitting of wave packets, with results in quantitative agreement with our theoretical calculations. Our strategies for broadband amplification can be generalized to other active wave media with nearly flat or cosine-like dispersion relations, with potential applications in loss-mitigation, noise squeezing, and programmable wave manipulation.

This study investigates the spatiotemporal thermal response of human hands during controlled contact cooling using short wave infrared (SWIR), mid wave infrared (MWIR), and long wave infrared (LWIR) thermography. Three participants simultaneously placed one hand on a cooling metal plate and the contralateral hand on a reference plate maintained near room temperature. Temperature evolution was analyzed in five anatomical regions, including the distal finger, proximal finger, vessel associated region, non vessel region, and forearm. Quantitative metrics, including temperature variation, bilateral temperature difference, initial cooling rate, and frequency-domain amplitude, were extracted from the thermal image sequences. The results showed that the finger regions exhibited the largest temperature reductions and highest cooling rates, indicating greater sensitivity to thermal stimulation than the dorsal hand and forearm. MWIR and LWIR measurements revealed highly consistent cooling dynamics, while LWIR imaging provided enhanced thermal contrast and sensitivity. Frequency-domain analysis demonstrated that the dominant thermal response was concentrated in the low frequency range below 0.05 Hz. Furthermore, pixel-wise cooling rate maps highlighted substantial spatial heterogeneity across the hand surface. Numerical bioheat simulations confirmed that blood perfusion and skin plate contact conductance are key factors governing the cooling response. These findings demonstrate the potential of dynamic infrared thermography as a non-contact tool for assessing peripheral thermoregulation and vascular function during controlled cooling experiments.

Many dynamical systems exhibit diverse modes of behavior. In biology, such modes can represent individual or cell fates. While the emergence of multimodality is commonly studied, transient bimodality is much less well understood. Under transient bimodality, a system moving from a well-defined initial to a final state transiently undergoes a bifurcation into multiple probability modes. This noise-driven phenomenon can significantly impact processes such as cell differentiation and speciation in the presence of changing environmental conditions. We detail a theoretical approach for understanding transient bimodality connecting results from ecology, optics, chemical reaction networks and cell biology, propose a “minimal model” of transient bimodality and derive a general criterion for its presence. We show that fast-to-slow dynamics can lead to transient bimodality in addition to the well-known case of slow-to-fast dynamics. Finally, we discuss the role of transient bimodality across the scientific literature, with emphasis on biochemical kinetics and gene regulation.

We report robust Fano-like spectral profiles in substrate-supported Au-coated Ag nanoislands fabricated by solid-state dewetting followed by Au overgrowth. Combining electrostatic modal analysis, full-wave simulations, and linear transmission spectroscopy, we investigate the origin of these profiles, their tunability, and their robustness against morphological disorder. Increasing the Au coating thickness progressively red-shifts the low-energy resonance and transfers spectral weight to it from the high-energy resonance, whereas the Fano-like antiresonant dip undergoes a limited spectral displacement. The electrostatic modal analysis identifies this dip as the signature of destructive interference between superradiant and subradiant hybridized modes, and its weak spectral evolution is consistently reproduced by theory, simulations, and experiments. These results establish Au-coated Ag nanoislands as a scalable, lithography-free platform for engineering robust yet tunable Fano-like optical responses accessible through standard far-field spectroscopy.