Browse Articles

Investigation on the electroluminescence 2D microscopic localization intensity distribution of GaN-based flip-chip green mini-LEDs

Based on time-gated electroluminescence, a method to characterize the localized intensity distribution (LID) of flip-chip green mini-LEDs is proposed. Through the integration of RC circuit theory and carrier dynamics, the underlying physical mechanism of the double-exponential model is elucidated. Subsequent to analyzing the light emission behavior of LEDs during rising and falling edge phases, microscopic localized intensity is innovatively quantified and assessed via multi-metric joint analysis. The LID metrics align with radiative recombination efficiency, especially in the mesa region, validating its consistency with fundamental physical principles. Data reveal relatively high LID in the central mesa between the anode and the cathode, moderate LID in partial sidewalls, and low LID near the cathode and most sidewall regions. Correlating these microscopic features with process parameters offers insights for passivation optimization, homogeneous current injection, and low-damage etching, providing a 2D analytical framework to boost the performance and enhance the reliability of mini-LEDs.

EBV strain interacts with host HLA to drive nasopharyngeal carcinoma risk

Actinidia Deliciosa mediated synthesis of antimony oxide nanoparticles and their incorporation into chitosan matrix for enhanced antibacterial and photocatalytic activity

Phase-space sampling of propagated wavefunctions

We propose propagated Wigner sampling as a method for transitioning from quantum dynamics to more approximate mixed quantum–classical trajectories. The initial dynamics is propagated quantum mechanically until, at a suitable time, the Wigner function is calculated, sampled, and the remaining dynamics propagated by trajectory-based surface hopping. The approach exploits the Wigner phase-space representation and generalizes the Wigner sampling commonly used to generate initial conditions for trajectory dynamics to the more general case of arbitrary multi-state wavefunctions. The method is tested and evaluated on the one-dimensional Tully models. It is shown to afford an accurate representation of the dynamics, producing better results than standard surface hopping. We propose suitable strategies for generating trajectories from the quantum-derived Wigner function and discuss the scenarios in which this approach may prove useful in the context of non-adiabatic excited-state dynamics.

Diffraction ringing induced terahertz image edge enhancement

In traditional optics, diffraction ringing induced by a finite system aperture is often treated as an artifact requiring suppression. In this work, we experimentally demonstrate that diffraction ringing can directly enhance the edges of terahertz images. The experiment uses a terahertz time-domain spectroscopy system coupled to a 4f imaging system to image sharp-edged objects, including both square and hexagram, at 0.6, 0.8, and 1.0 THz. Under a limited aperture, clear edge enhancement is observed. This enhancement shows a negative correlation with frequency, meaning that lower frequencies produce stronger oscillations. This result is supported by good agreement among theory, simulation, and experiment. The research demonstrates that edge enhancement can be achieved directly during the imaging process, requiring neither additional optics nor complex digital processing. This approach improves processing efficiency and system integration, thereby holding promise for applications in object identification and classification.

Improving the elevated temperature behaviour of foamed concrete through nano titania addition and microstructure control

Nuclear-spin statistical weights from Young diagrams

Nuclear-spin statistical weights and selection rules in molecular spectroscopy are governed by the permutation symmetry of identical nuclei, although rigid and semi-rigid molecules typically realize only a proper subgroup of the full symmetric group. Building on the Schur–Weyl framework of Schmiedt, Jensen, and Schlemmer, we extend this approach to molecular geometries whose rovibrational motion realizes cyclic and dihedral permutation subgroups. By combining the Schur–Weyl decomposition of the n-spin Hilbert space with the Kraśkiewicz–Weyman–Adin–Roichman major-index branching rule for the restriction SN ↓ Cm, we obtain a fully combinatorial method for determining nuclear-spin symmetry species and statistical weights. Each standard Young tableau corresponds to a definite cyclic character determined by its major index, with reflections yielding the associated dihedral symmetry, so that nuclear-spin species follow directly from tableau data without projection operators or case-specific constructions. Applications to XeOF4, SF4, benzene, deuterated benzene, and the tropylium cation demonstrate that the method applies uniformly to realistic molecular point groups and reproduces established statistical weights while providing a transparent spin-resolved structure. The approach supplies the symmetry information required for rovibrational line-intensity modeling and provides a practical, automatable framework for nuclear-spin symmetry analysis in polyatomic molecules.

Thermal coupling analysis of an embedded bismuth reservoir—C12A7 hollow cathode

The unique configuration of an embedded bismuth hollow cathode leads to a strong coupling between its discharge parameters and both internal temperatures and the mass flow rates. To elucidate this thermal coupling and achieve stable, self-sustaining operation without external heating, this study proposes an innovative cathode design that integrates an embedded bismuth reservoir with a low-work function C12A7 insert. The evolution of the temperature field during both the heating start-up and self-sustaining stages was systematically investigated through a combination of experiments and numerical simulations. The proposed design successfully demonstrated stable, self-sustaining discharge at currents from 2 to 5 A without external heat. The combined experimental and simulation results reveal the dominant role of discharge current: it directly governs the hollow cathode temperature, which, in turn, regulates the bismuth saturation vapor pressure and mass flow rate. The sensitivity of the cathode thermal state to power variations was quantified in different operating modes. The change in cathode-lid temperature per unit change in discharge power was approximately 6.35 °C/W in the keeper discharge mode and 4.15 °C/W in the anode discharge mode. These values are an order of magnitude higher than the 0.48 °C/W sensitivity observed from mass flow rate variations at a fixed current, underscoring the primary thermal influence of discharge current.

Structural energetics of cold sensitivity

Abstract Thermosensitive transient receptor potential (TRP) ion channels enable somatosensory nerve fibres to detect changes in our thermal environment over a wide physiologic range 1–3 . In mammals, the menthol receptor, TRPM8, is activated by temperatures below approximately 26 °C and is essential for the perception of cold or chemical cooling agents 4–6 . A fascinating, yet still unachieved goal is to elucidate mechanisms, both structural and thermodynamic, whereby TRPM8 or other thermosensitive channels are gated by changes in ambient temperature. Recent studies using cryogenic electron microscopy have attempted to address this challenging question but are limited by difficulties in visualizing temperature-evoked conformational sub-states or assessing the energetic landscape governing gating transitions 7,8 . Here we close this gap by combining cryogenic electron microscopy with hydrogen–deuterium exchange mass spectrometry to elucidate a mechanism for cold-evoked activation of TRPM8. First, we visualize TRPM8 channels in cellular membranes, where bona fide menthol- and cold-evoked open states are captured. We also identify a new ‘semi-swapped’ architecture in which interdigitation of channel sub-units is rearranged substantially following repositioning of the S6 transmembrane helix and elements of the pore region. We then use hydrogen–deuterium exchange mass spectrometry to pinpoint the pore and TRP helices as the regions exhibiting the greatest stimulus-evoked energetic changes that drive channel gating. Specifically, cold-evoked stabilization of the outer pore region repositions the pore lining S6 transmembrane helix while enabling binding of a regulatory lipid to stabilize the open channel. Structural mechanisms associated with activation are validated by comparison of human TRPM8 with the menthol-sensitive but relatively cold-insensitive avian orthologue. We propose a free energy landscape and conformational pathway whereby cold or cooling agents activate this thermosensory receptor.

How enterprise social media use affects employee well-being

Starting from the amorphous ground state: Linking landscape thermodynamics to slow dynamics and crossover

A microscopic understanding of low-temperature thermodynamics and its relation to dynamical features, such as a fragile-to-strong crossover (FSC) remains a central challenge in glass physics. Using swap Monte Carlo combined with a full potential-energy-landscape (PEL) analysis of a non-network-forming model, we obtain equilibrium data deep into the glassy regime and identify a finite system size that simultaneously reproduces bulk behavior for T ≳ Tg/2 and allows complete sampling of the PEL down to its lowest-energy amorphous states. This enables the direct computation of the configurational entropy over the full temperature range of the finite system without relying on liquid-state thermodynamic integration. We find a pronounced depletion of low-energy states relative to the Gaussian regime of the PEL, which governs the low-temperature curvature of the configurational entropy. Numerically, the apparent activation energy of the diffusivity closely follows the temperature dependence of the mean inherent structure energy and exhibits a gradual crossover toward Arrhenius-like behavior. This correlation is consistent with a trap-model description of the PEL, in which the FSC emerges naturally as a consequence of the depletion of low-energy states and, thus, of the lower bound of the PEL. We further argue, as illustrated analytically for a simple binomial model of the PEL, that the observability of a FSC depends on whether the depletion regime is reached within the accessible temperature window.

Special topic: Transformative frontiers in additive manufacturing

Carbonyl swapping converts cyclic ketones to saturated heterocycles

Vimentin molecular linkages with nesprin-3 enhance nuclear deformations by cell geometric constraints

Salt-independent counterion kinetics and sub-Poisson number fluctuations in B-DNA from microsecond molecular dynamics

Manning’s counterion condensation theory predicts a salt-independent condensed fraction for polyelectrolytes with charge density parameter ξ>1. While the thermodynamic aspects of this prediction have been examined, atomistic tests of whether condensed-ion kinetics are likewise weakly salt-dependent have remained limited. We address this question using 29 independent 1 μs all-atom trajectories of three B-DNA duplexes spanning ionic strengths from 0 to 521 mM. For d(CGCGAATTCGCG)2 (1BNA, x-ray; 16 simulations at six ionic strengths), the Na+ mean residence time in the major groove from Kohlrausch–Williams–Watts stretched-exponential analysis is 511±33 ps with no significant salt dependence (CV = 6.5%, Spearman ρ=−0.15, p=0.77). Similar behavior is observed for the same sequence started from a nuclear magnetic resonance structure (1NAJ, 514±31 ps, CV = 5.9%). A second sequence, d(CCAACGTTGG)2 (5DNB), gives a shorter mean residence time (368±27 ps) and provides supportive but more limited evidence for near-salt-invariance because replicate simulations are not available; independent mean first-passage-time analysis gives 385±13 ps and the same qualitative pattern. While residence times vary little, major-groove occupancy increases 2.4-fold with ionic strength, consistent with increased association but nearly unchanged dissociation kinetics. Ion-number fluctuations are sub-Poisson for all well-sampled conditions, with the grand mean Fano factor F=0.872±0.036, and are less sensitive to salt than occupancy. Together, these results provide atomistic evidence that condensed counterion kinetics in B-DNA depend only weakly on salt, while sequence-dependent differences in absolute residence time lie outside the line-charge approximation of Manning theory.

Auxetic effect and magnetocrystalline anisotropy of square-lattice transition metal dihalide monolayers

The structural, mechanical, and magnetic properties of square-lattice 3d transition metal dihalide monolayers MX2 have been systematically investigated via crystal structure analysis by particle swarm optimization and density functional theory calculations. We identified 17 stable monolayers (MX2 for M=Mn, Fe, Co, Cu, Zn with X=Cl, Br, I, plus NiBr2 and NiI2). Among these stable systems, 13 monolayers (MnCl2, MnBr2, FeX2, CoCl2, CoBr2, NiBr2, NiI2, CuCl2, and ZnX2) exhibit in-plane auxetic effects, with CuCl2, NiI2, ZnCl2, and ZnBr2, showing superior auxetic performance compared to many typical 2D auxetic materials. FeI2 displays a near-zero Poisson's ratio, making it suitable for high geometric stability applications. All these monolayers also feature strong elastic anisotropy and low Young's moduli, favorable for strain engineering in flexible devices. Our spin-polarized calculations demonstrate that the ground magnetic state of MX2 monolayers can be effectively tuned by the Hubbard U, the halogen species, and the 3d electron count of M atom. The magnetocrystalline anisotropy energies of these monolayers are significantly dependent on the transition metal element M and effective Hubbard U value. An increase in the U value results in an orientation switch between an in-plane and an out-of-plane easy axis in some MX2 monolayers. This work enriches the family of 2D auxetic and nanomagnetic materials and provides a theoretical basis for their applications in next-generation flexible and spin-based nanodevices.

Liver fibrosis burden and risk of incident arrhythmia in metabolic dysfunction-associated steatotic liver disease

How accurate are foundational machine learning interatomic potentials for heterogeneous catalysis?

Foundational machine-learning interatomic potentials (MLIPs) are being developed at a rapid pace, promising closer and closer approximation to ab initio accuracy. This unlocks the possibility to simulate much larger length and time scales. However, benchmarks for these MLIPs are usually limited to ordered, crystalline, and bulk materials. Hence, reported performance does not necessarily reflect MLIP performance accurately in real applications such as heterogeneous catalysis. Here, we systematically analyze zero-shot performance of 80 different MLIPs, evaluating tasks typical for heterogeneous catalysis across a range of different datasets, including adsorption and reaction on surfaces of alloyed metals, oxides, and metal–oxide interfacial systems. We demonstrate that current-generation foundational MLIPs can already perform with high accuracy for applications such as predicting vacancy formation energies of perovskite oxides or zero-point energies of supported nanoclusters. However, limitations also exist. We find that many MLIPs catastrophically fail when applied to magnetic materials, and structure relaxation in the MLIP generally increases the energy prediction error compared to single-point evaluation of a previously optimized structure. Comparing low-cost, task-specific models to foundational MLIPs, we highlight some core differences between these model approaches and show that—if considering only accuracy—these models can compete with the current generation of best-performing MLIPs. Furthermore, we show that no single MLIP universally performs best, requiring users to investigate MLIP suitability for their desired application.

Programmable multiple ion beams based on a magneto-optical trap ion source

We report a programmable multiple ion beam system developed by combing a magneto-optical trap ion source with a spatial light modulator (SLM). Neutral rubidium atoms are trapped into a magneto-optical trap and cooled to 700 μK. An excitation laser beam, the intensity distribution of which is shaped into a square array by the SLM, selectively excites the cold atoms, which are subsequently ionized by an ionization laser beam. The ions are then extracted by an electric field to produce multiple ion beams. A 3×3 ion beam array has been generated. The size of each beams is 180 μm, and the transversal reduced emittance of multiple ion beams at the source is evaluated to be 1.65 × 10−9 m radeV. We also demonstrate the generation of ion bunches with a user-defined spatial pattern. In the future, by integrating this programmable multiple ion beam system with high reduction ion optics, it is possible to generate nanoscale multiple focused ion beams for the potential applications in maskless patterning and direct writing lithography.

Default mode network resting-state functional connectivity and event centrality in adult acute trauma survivors