Papers

Optical metasurfaces can shape the near fields of energetic electrons, enabling Smith-Purcell (SP) emission. We introduce a generalized SP effect relying on finite periodic arrays whose elements possess individually tunable polarizabilities, allowing us to explore higher-order SP radiation. By controlling the amplitude and phase of each of the elements, we show through rigorous theory the ability to create an SP steering device. In particular, we explore the active tuning capabilities of doped graphene, and thermally driven phase-change materials, which we compare with standard passive plasmonic structures made of gold and silver. Our results establish programmable electron-driven light sources and spectroscopic probes spanning the terahertz-to-visible range, advancing tunable metasurfaces for next-generation electron-photon technologies.

As a fundamental problem in network science, network dismantling focuses on identifying a set of critical nodes whose removal sharply reduces a network's connectivity and functionality. Potential applications include stopping rumor spread, blocking sentiment propagation, and controlling epidemics and pandemics. Previous studies have mainly focused on undirected networks, whereas many real-world networks are inherently directed, such as the World Wide Web and the global trade system. Moreover, the functionality of directed networks depends on the giant strongly connected component (GSCC), where nodes are mutually reachable. Considering both the directionality and heterogeneity of these networks, we propose a novel centrality measure, network incoherence (NI) centrality, and develop a trophic analysis-based dismantling (TAD) method, in which nodes are removed in descending order according to their NI centrality scores, aiming to efficiently dismantle directed networks by reducing the GSCC. When applied to a wide range of benchmark synthetic networks with varying degree heterogeneity and 15 real-world directed networks, our TAD method consistently outperforms existing state-of-the-art methods. Significantly, TAD also induces the largest maximum avalanches during the dismantling process, highlighting its ability to capture structurally critical nodes. These findings provide new insight into the structure-function relationship of directed networks and inform the design of more resilient systems against perturbations.

Early design decisions strongly influence environmental, economic and social outcomes, yet sustainability assessment tools rarely reveal trade-offs among these three pillars. This study presents a framework for Conflict Mapping and Resolution for Sustainability of Systems (CONFARM). CONFARM consists of four steps: lifecycle documentation, cause-effect mapping, conflict database construction and multi-criteria scoring. A conflict is recorded when a single decision produces positive and negative effects across pillars. Each effect is evaluated using impact magnitude and pillar weight to generate a sustainability ratio. CONFARM may be applied manually or through automated extraction using natural-language processing and large language models. The method is demonstrated in three sectors representing different data structures and system scales: agriculture (rice and corn), fashion (slow and fast fashion) and energy (nuclear and natural gas). Each system was analysed at increasing conflict densities. Results consistently showed that sustainability scores converged as more conflicts were mapped, indicating stable evaluation across methods. Slow fashion and nuclear systems exhibited relatively higher sustainability performance, while fast fashion and natural gas systems showed lower performance. CONFARM improves early-stage decision support by making trade-offs explicit and enabling comparative evaluation. It offers a structured approach for cleaner production and scalable sustainability assessment across domains.

In this work, we introduce a new approach for constructing a renormalized and regularized Fock matrix for self-consistent field calculations. The scheme relies on second-order perturbation theory and is conceptually related to quasiparticle self-consistent second-order Green's function theory (GF2). The regularization is derived within the framework of perturbative similarity renormalization group (SRG) theory. By optimizing both the regularization and spin-scaling parameters, we introduce three SRG-qsGF2 variants that enable accurate predictions of quasiparticle energies and dipole moments. Lastly, we demonstrate that formulating second-order perturbation theory for the total electronic energy using the renormalized SRG-qsGF2 Fock matrix as the unperturbed Hamiltonian mitigates divergence problems commonly observed in conventional Møller–Plesset perturbation theory.

We investigate the dynamics of nonlinear optical Thouless pumps in the presence of disorder, using optical waveguide arrays. It was previously known that the displacement of solitons in Thouless pumps is quantized and may exhibit integer and fractional transport over the course of the pump cycle. Here, we demonstrate that, in disordered nonlinear pumps, quantization may be maintained despite the presence of disorder, even though it would not be in the linear domain. Moreover, nonlinearity allows pumps to be executed more quickly (i.e., less adiabatically). This may serve as a design principle for integrated non-reciprocal devices based on temporal modulation.

The response of Mack mode instabilities to a simple acoustic vibrating surface (AVS) is studied using the Direct Simulation Monte Carlo (DSMC) method to capture and analyze spontaneous second-mode instability growth. The DSMC simulations, analyzed with the Dynamic Mode Decomposition (DMD) method, model flow over a flat plate at an unseeded freestream Mach number of 6 and unit Reynolds number $Re_1\sim 1.18\times10^7$ m$^{-1}$. Power spectral density (PSD) analysis was found to identify the dominant frequencies of 200 to 500 kHz, in line with linear stability theory (LST) predictions. Closed-form kinetic-theory expressions were derived to predict the amplitude of the DSMC fluctuations in the window-averaged snapshots. It was observed that the DSMC-simulated flowfield naturally developed second Mack mode instabilities without any external seeding, i.e., arising spontaneously from the kinetic fluctuations of the simulated gas and of amplitude higher than the predicted DSMC fluctuations. Targeted interaction with these flow instabilities is demonstrated for an AVS, where forcing at the unstable frequency of 250 kHz results in amplified waves downstream, while at the stable frequency of 400 kHz AVS-induced disturbances are damped. The AVS thus excites only the waves at its forcing frequency, leaving the instability waves at other frequencies and the mean flow essentially unaltered. The ability of the kinetic simulations to capture and describe linear perturbations at Reynolds numbers corresponding to those of Mach 6 flight at altitudes of $\sim 20$ km suggests that DSMC provides a theoretical understanding of controlling laminar-turbulent transition through AVS materials in hypersonic boundary layers.

In an axisymmetric meniscus lifted from a free water surface and locally heated through near infrared radiation by an optical fiber, natural buoyancy and geometric constraints confine the hot liquid near the apex. This confinement enhances the thermal gradient along the meniscus surface and, above a critical optical power, drives the system into an unstable convection regime. By analyzing the water refractive index oscillations at the meniscus apex and the simultaneous advection of nearby floating particles, we demonstrate that the instability is characterized by periodic thermocapillary pulses with tunable frequency and directionality. By controlling these features, we modulate the hydrodynamic forces generated by the pulsed surface flow and actuate particles at the meniscus interface in sustained oscillations or stable orbital trajectories. With about 20 mW optical power and particles ranging from 0.1 to 0.5 mm, rotational velocities up to 600 rpm are achieved, the highest reported for continuous optothermal actuation. Our results establish a highly efficient propulsion mechanism at fluid interfaces with potential applications in light-powered micromotors, interfacial transport and soft microrobotics. More broadly, the optically heated meniscus configuration provides a simple and adaptable platform for generating, controlling and detecting large thermocapillary instabilities on fluid surfaces.

The structural organization of liquids near solid interfaces profoundly influences phenomena such as wettability, nanofluidic transport, and interfacial heat transfer. This study introduces the Interfacial Layering Oscillator Model (ILOM), a concise, semi-phenomenological framework that accurately captures the oscillatory density profiles of liquids adjacent to planar solid surfaces. By deriving a second-order differential equation rooted in classical statistical mechanics and calibrated with molecular dynamics simulations, ILOM predicts the amplitude, decay rate, and wavelength of interfacial density layering with exceptional computational efficiency. This versatile model applies to both hydrophilic and hydrophobic surfaces and extends to liquids beyond water, including methanol, providing valuable insights into critical interfacial properties that advance nanoscale fluid mechanics and material design.

Hypothesis: Surrounding fluids affect critically drop wetting dynamics in many applications involving viscous environments. Although macroscopic effects of outer fluid viscosity on contact line motion have been documented, the extent to which the outer fluid modulates internal flow pattern is still not well understood, largely due to experimental challenges. It is hypothesized that the external fluid exerts a dominant effect on the internal flow fields and energy dissipation, thereby altering dynamic contact angle evolution and overall wetting behavior. Elucidating this coupling mechanism is essential for advancing our understanding of multiphase spreading in complex fluid systems. Experiments: We investigate the spreading of Newtonian and non-Newtonian shear-thinning aqueous drops in air versus in oil, using high-speed imaging and custom-built micro-PIV. Internal velocity and viscosity fields are measured to quantitatively relate internal flow evolution to contact line motion. Dynamic contact angle was measured and analyzed using composite model incorporating hysteresis and pinning. Scaling laws were derived to compare spreading dynamics under different outer fluid viscosities and substrate wettabilities. Findings: In air, capillary waves trigger Laplace pressure gradients that drive rapid, outward internal flow as well as fast contact line motion. In contrast, viscous oils suppress wave formation and generate recirculating vortices, resulting in a significantly slower spreading process dominated by viscous drag. Despite power-law spreading in both cases, the governing timescales reflect fundamentally different mechanisms: inertial forces within the drop dominate in air, whereas external fluid viscosity controls the spreading dynamics in oil. A unified scaling incorporating outer-fluid viscosity and equilibrium contact angle gathers diverse data onto a master curve. These results underscore the central role played by outer-fluid induced internal flow in governing wetting dynamics.

In this paper we examine how porosity fluctuations affect the hydrodynamic permeability of a porous matrix or membrane. We introduce a fluctuating Darcy model, which couples the Navier-Stokes equation to the space- and time-dependent porosity fluctuations via a Darcy friction term. Using a perturbative approach, a Dyson equation for hydrodynamic fluctuations is derived and solved to express the permeability in terms of the matrix fluctuation spectrum. Surprisingly, the model reveals strong modifications of the fluid permeability in fluctuating matrices compared to static ones. Applications to various matrix excitation models - breathing matrix, phonons, active forcing - highlight the significant influence of matrix fluctuations on fluid transport, offering insights for optimizing membrane design for separation applications.

We present a new algorithm for numerical magnetohydrodynamics on staggered meshes preserving $\nabla \cdot B = 0$. Our algorithm is based on the constrained transport method and supports both cell-based adaptive mesh refinement and temporal substepping. We handle resolution changes directly on the logically Cartesian grid without needing interpolation or projection between nested or neighboring grids, nor coupling the solution between refinement levels.

We report validation tests of a calcium atomic-beam source fabricated via Laser Powder Bed Fusion (L-PBF). The surface quality and elemental composition of the printed component were quantitatively assessed, allowing us to establish reference parameters for reliable operation in an ultra-high-vacuum environment. Safe operating conditions of the atomic oven were determined through a combination of simulations and experimental measurements. The ability of the device to deliver an atomic beam to the main experimental region – the electron/ion trap – was verified using atomic fluorescence imaging. Fluorescence spectroscopy was further employed to characterize the beam divergence, yielding an emission-cone half-angle of approximately 19 degrees for atoms near the beam axis. A current of atoms on the order of $10^8$ s$^{-1}$ was estimated in the electron-trapping region, which is more than sufficient for anticipated electron-trapping and ion-trapping experiments.

Defect engineering can improve the linked charge, spin, and lattice behavior of thermoelectric topological insulators. Using density functional theory with spin orbit coupling, we study structural, electronic, optical, thermoelectric, piezoelectric, and charge density features of pristine and Cu doped Bi2Te3. Cu substitution slightly expands the lattice and lowers the total energy minimum, which stabilizes the structure. The density of states shows that Cu d and Te p hybridization creates sharp states near the Fermi level, raising the carrier concentration and supporting higher Seebeck coefficient and power factor. Transport calculations show an increase in the Seebeck coefficient from about 180 microvolts per kelvin in pristine Bi2Te3 to about 220 microvolts per kelvin at 300 K while keeping the electrical conductivity nearly unchanged. Optical spectra reveal strong low energy absorption and very large static dielectric constants (greater than 600), indicating tunable light matter coupling. The piezoelectric coefficient e33 rises from 0.19 C/m2 in pristine Bi2Te3 to 0.38 C/m2 at 5 percent Cu and 0.51 C/m2 at 10 percent Cu, reflecting symmetry breaking and strain driven polarization. Charge density difference maps show anisotropic redistribution, with Cu donating about 0.8 electrons mainly to Te sites, which enhances p type behavior and phonon scattering. Overall, Cu doping reshapes Bi2Te3 into a multifunctional material with coupled thermoelectric, piezoelectric, and optical responses suitable for hybrid energy harvesting, infrared detection, and spin based devices.

While magnetic fluids are well known for their rich ferrohydrodynamic behaviors, prior researches on dynamic droplet morphologies have largely been confined to the nonconducting matters. From an alternative, the electrically conductive magnetic liquid metals offer ever larger space for explorations meanwhile also incubate intriguing mysteries that had not been understood before. Here, we disclosed a group of rather profound fluidic phenomena happening on the magnetic liquid metals with sizes spanning from millimeter to centimeter scales when subject to the impact of a rotating magnet pair. We conceived that the identified flow patterns highly resemble that of the Chinese Taiji diagrams widely known as a classical theory to describe all things genesis and transformation, indicating the kaleidoscopic variations and intrinsic clues between modern magnetic liquid metal physics and the nature rules lying behind the ancient Eastern philosophy. Through systematically tuning the droplet volume, magnetic field strength, and magnet rotational speed, we achieved precise control over the liquid metal fluidic morphologies such as ellipses, dumbbells, toroidal rings, and Yin-Yang symbols, and quantified their dependence on the prescribed experimental conditions. Following the routes to construct the Taiji eight diagrams and their derivatives, we classified the disclosed flow patterns into eight representative schemes and three phase diagrams were plotted to characterize the fluidic patterns of the magnetic droplets correspondingly. The underlying mechanisms of magnetic liquid metal flow separation and coalescence were further interpreted from an energy perspective. These findings suggest enormous experimental insights and a theoretical framework for advancing fundamental magnetohydrodynamics and related engineering practices.

This study investigates the effect of the ion-to-electron temperature ratio ($T_i/T_e$) on microturbulence driven transport in Quiescent H-mode (QH-mode) plasmas in the DIII-D tokamak. Utilizing the Gyrokinetic Toroidal Code (GTC) and the QH-mode equilibrium, we perform linear and nonlinear simulations to analyze transport properties and instability dynamics under variations of $T_i$ and $T_e$. Our results demonstrate that decreasing $T_i/T_e$ leads to a relative destabilization of trapped electron modes (TEM) over ion temperature gradient (ITG) modes, with the transition between these regimes dictated by $T_i/T_e$. When the electron temperature is increased at fixed ion temperature, we observe an increase in transport saturation levels. In contrast, decreasing the ion temperature at fixed electron temperature results in more modest transport enhancement. The radial correlation length, which characterizes eddy size, increases with rising $T_e$ and decreases with falling $T_i$, consistent with the observed trends in turbulent transport. Additionally, we examine the impact of impurity addition on turbulence and growth rates, finding that impurity presence does not significantly alter transport quantities compared to the impurity-free case. Finally, investigating helium as an alternative main ion species, we find that helium plasmas exhibit higher linear growth rates but result in lower transport saturation levels than deuterium plasmas, suggesting potential confinement benefits. These findings provide quantitative insights into the temperature ratio dependence in QH-mode plasmas and highlight the role of temperature profiles and zonal flows in influencing plasma confinement.

Integrating focal mechanism solutions with rupture directivity analysis enables high-resolution characterization of subsurface fault geometry and earthquake rupture processes. However, resolving these parameters for small-magnitude earthquakes remains challenging due to small rupture sizes, short durations, and low signal-to-noise ratio (SNR). Here, we utilized a dense array of nodal seismometers in the Changning region, Sichuan Basin, China, to study the focal mechanism and rupture directivity of aftershocks following the 2019 Ms 6.0 induced earthquake. Using PhaseNet+ and SKHASH, we first enhance the focal mechanism catalog (1<M<4). Then, applying the spectral ratio method with empirical Green's functions (EGF), we observe azimuth-dependent corner frequencies of two M3 aftershocks, by spectral fitting to the Brune's model, which are consistent with unilateral rupture. Our results reveal that the two earthquakes occurred at an unidentified conjugate fault and ruptured towards N60{\deg}E unilaterally, which significantly differs from the northwestward rupture of the MS 6.0 mainshock. Furthermore, we obtain a rupture speed of approximately 0.6 times the shear wave velocity. We also apply the spectral decomposition method to compute stress drops (M>1), and their spatial variability reflects a long-term interplay between fluid injection and faults in the salt-mining area. These findings illuminate a complex fault system beneath the Changning anticline and highlight the importance of high-resolution seismic arrays in resolving rupture processes of small-magnitude events.

This paper presents the design and status of Accumulator Ring (AR) RF Equipment Protection System (EPS) of Advanced Light Source Upgrade project at LBNL. The key components of AR RF EPS include a Master Interlock PLC subsystem handling supervisory control and slow interlocks in \SI{}{\milli\second} scale, an FPGA-based LLRF Controller managing fast interlocks in \SI{}{\micro\second} scale, a 60 kW high-power amplifier with standalone PLC-based slow (\SI{}{\milli\second} scale) and FPGA-based fast (\SI{}{\micro\second} scale) protection systems, and an RF Drive Control Chassis acting as primary RF mitigation device. The design of AR RF EPS is presented along with internal RF and external AR subsystems interfaces.

This Letter uncovers five distinct charge transport modes and their transitions in dual-energy electron beam diodes. We via first-principle particle-in-cell (PIC) simulations establish that the specific mode (e.g., space charge oscillations) and the current transport characteristics are essentially governed by the interplay between the electron beam energy and injected current density. A generalized analysis is conducted for n-component electron beams, and a theoretical piecewise function is for the transmitted current density proposed, which agrees well with the PIC results under designed conditions. The discovery provides a mechanistic picture of multiple electron beam transport in diodes, paving the way for novel designs of high-performance modern vacuum electronic devices.

Elastic metasurfaces offer precise control over elastic waves for applications such as vibration isolation, sensing, and imaging. However, achieving high-efficiency and scattering-free performance with complex functionalities remains a fundamental challenge. While conventional Generalized Snell's Law (GSL) designs suffer from inherent inefficiencies and parasitic scattering, recent alternatives–including impedance-matching methods and diffraction-grating-based metagratings–have sought to overcome these drawbacks. While efficiency improvement has been demonstrated, both methods are limited in generating complex wavefields such as focusing. Here, we propose a direct wave-shaping (DWS) topology optimization framework that bypasses these intermediate concepts and automates the design of high-performance, monolithic elastic metasurfaces. To mitigate the high computational expense, we parameterize the geometry with movable, deformable and interactable elliptical voids, thereby drastically reducing the design variables while enabling holistic optimization that inherently accounts for nonlocal inter-cell couplings. We demonstrate the framework by designing metasurfaces for challenging tasks including high-efficiency longitudinal-to-transverse wave conversion with large-angle beam steering, wavelength-multiplexed beam steering, and both reflective and transmissive metalenses with numerical apertures exceeding 0.99. Compared to state-of-the-art gradient-index, impedance-based, and hybrid designs, our metasurfaces consistently exhibit superior efficiency, significantly reduced spurious scattering, and enhanced focusing capability, with the most demanding transmissive metalens validated experimentally. This work establishes a scalable and computationally efficient pathway to realizing practical, high-performance elastic metasurfaces for advanced wave manipulation.

Meso-scale structures in signed networks have been studied under the limiting assumption of the validity of social balance theory, which predicts positive connections within groups and negative connections between groups. Here, we propose and apply a methodology that overcomes this limitation and is able to find and characterize also the different possible unbalanced structures in signed networks. Applying our methodology to 24 empirical networks, from social-political, financial, and biological domains, we find that unbalanced meso-scale structures are prevalent in real-world networks, including cases with substantial balance at the micro-scale of triangles. In particular, we find that assortativity often prevails regardless of the interaction sign and that core-periphery structures are typical in online social networks. Our findings highlight the complexity of meso-scale relational structures, the importance of using computational methods that are a priori agnostic to specific patterns, and the importance of independently evaluating micro- and meso-scale predictions of social balance theory.

The Laser Interferometer Lunar Antenna (LILA) presents a novel concept for observing gravitational waves from astrophysical sources at sub-Hertz frequencies. Compared to the Earth, the seismic environment of the moon, while uncertain, is known to be orders of magnitude lower, opening the possibility for achieving this sub-Hz band. This band fills the gap between space-based detectors (mHz) and Earth-based detectors (10 Hz to a few kHz). The initial version of LILA, known as LILA Pioneer, calls for non-suspended optics, relying on the moon's resonant modes to respond to gravitational waves. However, the follow-on design, LILA Horizon, requires suspensions to realize in-band free floating test masses and to filter the residual seismic background. This paper will establish baseline designs for these suspensions for different assumptions of the seismic background.

Inversion of Rayleigh-wave dispersion data is particularly challenging at sites with strong impedance contrasts, where modal energy often transitions smoothly from the fundamental to higher modes at low frequencies. Analysts may misinterpret this transition as a continuation of the fundamental mode, leading to an overestimation of shear-wave velocity (Vs) in deeper layers and/or a misinterpretation of bedrock depth. Although effective-mode inversion can theoretically account for such behavior, it requires precise source-receiver geometry and cannot be applied when target dispersion data are formed by combining multiple active shots with passive-array recordings that have unknown source locations. This study introduces a predominant-mode inversion framework that addresses low-frequency mode jumps by automatically identifying, at each frequency, the Rayleigh-wave mode with the maximum vertical surface amplitude. This enables inversion without explicit mode indexing or assumptions about fundamental-mode dominance. The predominant-mode forward model is derived and implemented using the thin-layer method. The forward model is integrated into a particle-swarm-optimization global search algorithm and applied to invert three synthetic models exhibiting low-frequency mode jumps, using multiple layering parameterizations. Across all cases, the predominant-mode method accurately recovers major velocity contrasts and interface depths, whereas fundamental-mode inversions consistently overestimate Vs and mislocate deeper boundaries. The method is further validated using real field data from active and passive surface-wave measurements at the I15 Downhole Array Site. Inverted Vs profiles show strong agreement with downhole PS logs and with empirical transfer functions. Overall, the predominant-mode framework provides a robust approach for surface-wave inversion at sites with strong impedance contrasts.

This work reports the electrical characteristics comparison study between Cr2O3 and NiOx based heterojunction diodes (HJD) on halide vapor phase epitaxy (HVPE) grown e̱ta}-Ga2O3 epitaxial layers. Both as-fabricated Cr2O3 and NiOx HJDs exhibited forward current density in a range of 130-150 A/cm^2 at 5 V with rectifying ratios >10^10 and a reverse leakage current density at 10^-8 A/cm^2 at -5 V. The differential specific on-resistance of Cr2O3 and NiOx HJDs was 12.01 m{\Omega}*cm^2 and 12.05 m{\Omega}*cm^2, respectively. Breakdown voltages of Cr2O3 HJDs ranged from 1.4-1.9 kV and 1.5-2.3 kV for NiOx HJDs. Theoretical band alignment between Cr2O3 and e̱ta}-Ga2O3 was calculated from first principles. The ambient exposed NiOx/HVPE e̱ta}-Ga2O3 HJDs forward current density degraded after 10 days while that of Cr2O3/HVPE e̱ta}-Ga2O3 HJDs remained nearly unchanged after the same amount of time. It was later confirmed that the ambient exposed sputtered NiOx sheet resistance (Rsh) degradation gave rise to the reduction of the forward current density of the NiOx based HJDs, and water (H2O) was qualitatively determined to be the agent attributed to the forward conduction degradation by measuring the Rsh of NiOx-on-sapphire reference wafer after exposing it to different environments. The Cr2O3/HVPE e̱ta}-Ga2O3 HJD also exhibited enhanced thermal stability compared to the NiOx/e̱ta}-Ga2O3 heterostructures at elevated temperatures. Interfacial nickel gallate (Ga2NiO4) phase formation expected from phase diagrams can explain the reduced thermal stability of NiOx/e̱ta}-Ga2O3 HJDs. This study indicates that Cr2O3 is a stable p-type oxide for the realization of robust multi-kV e̱ta}-Ga2O3 HJDs.

The Scintillating Bubble Chamber collaboration is searching for Weakly Interacting Massive Particles using a novel bubble chamber with intended thresholds as low as 100eV. Existing molecular dynamics simulations of bubble formation in bubble chambers were conducted with non-scintillating target materials and therefore do not account for the energy transfer to photons or time-delayed releases that occur in atomic de-excitation. In this study, we use the HOOMD-blue molecular dynamics framework to simulate bubble formation in liquid argon, including photon creation, ionization, and direct nuclear recoils. A multi-stage bubble growth process similar to that reported in the literature was observed. When comparing simulated thresholds with and without scintillation effects, we found that scintillation raises the average energy required to form a bubble by a factor of 2.16. This is larger than the fraction of energy lost to photon creation, and demonstrates that energy stored in excited molecular states with lifetimes longer than the rapid growth phase of nucleation (~250 ps) does not contribute significantly to bubble formation. This conclusion was further supported by simulations showing increased bubble nucleation thresholds when the excited molecular state lifetimes were increased, even under identical thermodynamic conditions.

We designed a gallium nitride hexagonal hollow nanowire whispering gallery mode cavity that generates an |m|=6 topological light with orbital angular momentum (OAM). OAM is generated by breaking the cross-sectional mirror symmetry of the nanowire, which creates a non-Hermitian system. This is achieved by replacing the central airhole of the hollow nanowire with a cluster of 6 overlapping circular air holes with rotational offset relative to the hexagonal cross-sectional profile of the nanowire. The design parameters were then further optimized in Finite Element Method using an inverse design method to maximize the normalized OAM order |l|. We were able to realize of a cavity mode with |l| = 5.7, a mode purity of about 97%, and a Q-factor of ~250. This marks the first OAM generating active photonic device design falling within a sub-micron footprint, with additional novelties of being single component and materialistically homogeneous.

Development of machine learned interatomic potentials (MLIP) is critical for performing reliable simulations of materials at length and time scales that are comparable to those in the laboratory. We present here a MLIP suitable for simulations of the temperature dependent structure and dynamics of single layer hexagonal boron nitride (h-BN) with defects and grain boundaries, developed using a strictly local equivariant deep neural network as formulated in the Allegro code. The training dataset consisted of about 30,000 images of h-BN with and without point defects generated with ab-initio molecular dynamics simulations, based on density functional theory (DFT), at 500, 1000, and 1500K. The developed MLIP predicts potential energies and forces with a mean absolute error (MAE) of 4 meV/atom and 60 meV/Angstrom , respectively. It also reproduces phonon dispersion curves and density of vibrational states of pristine bulk h-BN that are comparable with that obtained from density functional theory-based calculations. Molecular dynamics simulations of the motion of the 4|8 grain boundary unit in h-BN shows the first step to have an activation barrier ~2.2 eV, indicating immobility of the grain boundary. Moving the grain boundary units past the first shows much lower activation barriers of ~0.42eV, suggesting a facile motion of the grain boundary once the first movement is stimulated. These simulations yield a scaled mobility of 1.739*10^(-11) m^3/Js for a temperature of 1500K which, given the inherent differences in the set-ups, is not too far from the experimental value of 1.36*10^(-9) m^3/Js. The ability to predict grain boundary mobility within reasonable agreement with experiment demonstrates the robustness of the MLIP and its suitability for reliable simulations of defect structures and dynamics in single layer h-BN.

We present a numerical study of three-dimensional gravity-capillary standing waves by using cubic and quintic truncated Hamiltonian formulations and the Craig-Sulem expansion of the Dirichlet-Neumann operator (DNO). The resulting models are treated as triply periodic boundary-value problems and solved via a spatio-temporal collocation method without executing initial-value calculations. This approach avoids the numerical stiffness associated with surface tension and numerical instabilities arising from time integration. We reduce the number of unknowns significantly by exploiting the spatio-temporal symmetries for three types of symmetric standing waves. Comparisons with existing asymptotic and numerical results illustrate excellent agreement between the models and the full potential-flow formulation. We investigate typical bifurcations and standing waves that feature square, hexagonal, and more complex flower-like patterns under the three-wave resonance. These solutions are generalisations of the classical Wilton ripples. Temporal simulations of the computed three-dimensional standing waves exhibit perfect periodicity and reveal an instability mechanism based on the reported oblique instability in two-dimensional standing waves.

Parker Solar Probe (PSP) observes abundant circularly polarized ion-scale waves throughout the inner heliosphere. These waves are a signature of the interplay between plasma microinstabilities and turbulent dissipation. We perform a mission-wide statistical survey of ion-scale waves observed by PSP, investigating if the waves correspond to specific free energy sources in the measured proton velocity distributions. We find that left-handed waves (LHWs) are frequently observed, with the fraction of time they are observed increasing closer to the Sun, reaching $\sim$30%. Right-handed waves (RHWs) are less frequently observed, with the associated time fraction decreasing closer to the Sun. The observed LHWs are generally consistent with parallel propagating ion cyclotron wave (ICW) storms that occur continuously for extended periods of time. Turbulent energy spectra are consistently steeper when LHW storms are observed; these wave storms mediate the spatial transport of the free energy associated with temperature anisotropy. The observed RHWs are generally consistent with oblique and parallel fast magnetosonic waves (FMWs), and their observation is well correlated with enhanced proton parallel heat flux, which quantifies the presence of secondary proton populations. Using observations and the SAVIC machine learning instability identification algorithm, we identify a threshold on the proton heat flux beyond which FMWs are likely to be driven unstable by the proton beams. We are thus able to associate trends in the observed ion-scale waves with known sources of free energy for Encounters 3 through 24 of the PSP's prime science phase.

URANOS is a newly developed 3D neutron transport Monte-Carlo code from thermal to fast energy domains. It was originally developed for the CASCADE detector. The purpose of this simulation program is to provide a fast computational workflow and an intuitive graphical user interface (GUI) for small to medium-sized projects. It features a ray-casting algorithm based on a voxel engine. The simulation domain is defined layerwise, whereas the geometry is extruded from a pixel matrix of materials, identified by specific numbers. Input files are a stack of pictures, all other settings, including the configuration of predefined sources, can be adjusted via the GUI. The scattering kernel features the treatment of elastic and inelastic collisions, absorption and absorption-like processes like evaporation. Cross sections, energy distributions and angular distributions are taken from evaluated data bases. In order to simulate boron-lined detectors it also models the charged particle transport following the conversion by computing the energy loss in the boron and its consecutive layer. The electron track is then projected onto a readout unit by longitudinal and transversal diffusion. URANOS is freely available and can be used to simulate the response function of boron-lined or epithermal neutron detectors, small-scale laboratory setups and especially transport studies of cosmic-ray induced environmental neutrons. It offers an easy accessibility and comparably simple interface capable of handling complex geometries. URANOS therefore offers possibilities to understand and simulate the neutron environment at instruments, which would otherwise require extensive modeling and training on dedicated packages.

In this paper, we propose a novel secure wireless transmission architecture that enables the co-existence of spatial field modulation (SFM) and digital bandpass modulation (DBM), utilizing multi-mode vortex waves and programmable meta-surfaces (PMS). Distinct from conventional joint modulation schemes, our approach establishes two logically independent transmission channels–SFM and DBM–thereby eliminating the need for joint signal design or time synchronization. Specifically, the orthogonality of vortex wave modes is exploited to construct a high-capacity multi-mode DBM channel, in which each mode carries modulated symbols independently. As the composite waveform passes through the PMS, energy from different vortex modes is spatially focused onto distinct positions, dynamically determined by the PMS configuration. This spatial mapping forms a unique lookup table that encodes additional information in the electro-magnetic (EM) field distribution, effectively enabling a second, concurrent SFM channel. To enhance physical-layer security, the DBM channel transmits encrypted symbols transformed via dynamic symbol-domain mapping, while the corresponding mapping relations–or key information–are carried by the SFM channel. This lightweight dual-channel encryption strategy provides strong confidentiality without requiring complex joint decoding. To validate the feasibility of the proposed architecture, we design and implement a proof-of-concept prototype system, and conduct experimental demonstrations under real-world wireless communication conditions. The experimental results confirm the effectiveness of the co-existent DBM-SFM design in achieving reliable and secure transmission. The proposed architecture offers a scalable, low-complexity, and secure transmission solution for future IoT networks, especially in scenarios demanding both spectral efficiency and physical-layer confidentiality.