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Experimental protocol for single-shot irradiation studies on optical materials at the SXFEL facility
Ultra-intense and ultra-short x-ray free-electron lasers (XFELs) impose rigorous requirements on the damage resistance of optical materials. The investigations of interactions between XFELs and optical materials are vital for both evaluating the durability of optical components applied in XFEL beamlines and elucidating the fundamental physics of light–matter interaction under extreme conditions. In this paper, we report an experimental protocol for single-shot irradiation studies on optical materials at the Shanghai Soft X-ray Free-Electron Laser (SXFEL) facility, including detailed descriptions of the XFEL beamline layout, experimental setup, incident angle calibration, pulse-energy measurement, focused FEL spot size characterization, and irradiation procedures. Following this experimental protocol, single-shot irradiation was performed on a Si wafer at the SXFEL under normal incidence. A damage threshold of 0.22 ± 0.06 J/cm2 was determined at a photon energy of 517 eV. It is in good agreement with the fluence calculated based on the melting dose of Si, confirming thermal ablation as the dominant damage mechanism.
Posttranslational generation of carboxylate ligands from aliphatic side chains in the photosynthetic oxygen-evolving complex
Photosynthetic oxygen evolution is catalyzed by the Mn 4 CaO 5 cluster within the oxygen-evolving complex (OEC) of photosystem II (PSII). Although oxygenic photosynthesis likely arose before the Great Oxidation Event (~2.4 billion years ago), how the OEC emerged in ancestral PSII remains unresolved. We previously showed that cyanobacterial mutants in which Asp or Glu ligands of the Mn 4 CaO 5 cluster were replaced with His or Asn/Gln underwent posttranslational conversion back to the original carboxylate residues. Here, we examined whether aliphatic amino acids lacking reactive side chains can also undergo similar conversion, thereby testing the generality of this phenomenon. Mutations of D1-Asp170 to Val/Leu/Ile and of D1-Glu189 to Leu/Ile resulted in posttranslational generation of Asp/Glu or their derivatives, partially restoring O 2 -evolving activity. Notably, nonstandard Asp/Glu derivatives also appear capable of functioning as carboxylate ligands for the Mn 4 CaO 5 cluster. This transformation of aliphatic residues represents a distinct type of posttranslational modification. Together, these findings demonstrate that posttranslational generation of carboxylate ligands from diverse amino acid residues, including aliphatic side chains, is a general feature of the OEC. Such intrinsic chemical plasticity of the OEC supports the hypothesis that posttranslational amino acid conversion played a critical role in the origin and evolution of the OEC, enabling photosynthetic oxygen production that transformed Earth’s environment and promoted the evolution of life.
Duplex dendrite growth kinetics and grain structure orientation features of containerlessly manufactured Fe–Cr–Ni alloys
The formation mechanism of the metastable δ phase in two undercooled liquid Fe–Cr–Ni alloys with different Cr/Ni ratios was investigated in situ by the electromagnetic levitation method. As for the Fe–13%Cr–5%Ni alloy, the δ phase dendrite grew primarily from alloy melt at all levels of undercooling, and the solid/liquid interface migration rate increased monotonously as the undercooling rose, leading to significant refinement of lath martensite with enhanced texture in the microstructure. In particular, large amounts of metastable δ phase were preserved among the martensitic laths to ambient temperature at high undercooling. Competitive nucleation between the γ phase and metastable δ phase was observed in real time in the Fe–14.6%Ni–4.4%Cr alloy. The growth velocity of the primary phase dropped suddenly from 10.4 to 3.9 m s−1 once the undercooling exceeded the critical value of 110 K, indicating that the metastable δ phase grew preferentially from alloy melt. Subsequently, the γ phase nucleated in the δ phase with multi-point feature, while the duration time of the metastable δ phase decreased from 0.55 to 0.15 ms as the undercooling rose. The rapidly solidified Fe–14.6%Ni–4.4%Cr alloy was composed of lath martensite completely. As undercooling increased, the fraction of high-angle grain boundaries declined from 39.9% to 13.9%, and the microstructure transformed from coarse columnar grain to equiaxed grain with more consistent orientation.
Gender pay gaps in the social sciences
We provide a longitudinal, multifield analysis of the gender pay gap in academia that directly links individual-level salaries to measures of scholarly productivity. Using administrative data from the ten campuses that comprise the University of California system, we combine detailed pay records with bibliometric data on publications and citations for faculty in five major social science fields. We find a raw gender pay gap of 23%, which decreases to 4.3% after controlling for field, campus, and cohort. Including controls for job title and scholarly productivity has little effect on the estimated gap, although they substantially increase explanatory power. A decomposition shows that 17% of the gap is unexplained, persisting across junior and senior faculty. We also find a large, persistent gender gap in publications, but no citation gap once output and career length are considered. Field-level analysis reveals that pay gaps are not universal: They persist in Business, Sociology, and Anthropology, but are absent in Economics, Political Science, and smaller social science fields. Our results suggest that pay transparency is insufficient to eliminate salary disparities and that more equal representation within the field is not a prerequisite for pay equity. Our study isolates the residual gap that remains unexplained by productivity or seniority, challenging the view that these factors fully account for gender pay differences. Taken together, our findings highlight the role of field-specific norms and institutional structures, offering directions to promote equitable compensation in academia.
Topological electromagnetics in anisotropic media: Theory and application to magnetized plasmas
This Tutorial reviews the mathematical foundations of topological electromagnetics in anisotropic continuum media, using magnetized plasmas as a representative case study. Particular emphasis is placed on the mathematical tools and physical concepts commonly employed in the analysis of topological phenomena in complex electromagnetic materials, and on providing a unified introduction to concepts that are often presented from different perspectives in the literature. We begin by reviewing core concepts in differential geometry and introduce topological invariants in real-space geometry. We then discuss their relevance to topological quantities in electromagnetics, such as Berry curvature and Chern numbers, while emphasizing that these quantities differ in their underlying definitions. The framework is applied to the computation of bulk band topology and surface-wave dispersion relations by constructing decaying field solutions and enforcing boundary conditions. Examples are presented for surface-wave propagation at interfaces between a magnetized plasma and air, dielectric, or metallic media, in both two-dimensional and three-dimensional configurations. This Tutorial offers a foundation for future investigations, including experiments, and supports the development of analytical and numerical methods for other anisotropic, dispersive, and topologically nontrivial media.
Record-low 2025 and 2026 ice extents restore Arctic winter sea-ice decline
Recent analyses have suggested that the decadal rate of Arctic winter sea-ice extent decline weakened in the early 2020s, with 20-y trends becoming statistically insignificant. Here we show from more up-to-date observations that the exceptionally low 2025 and 2026 ice extent winters reversed this picture, with sea-ice extent during the growth and peak phases returning to record lows and 20-y decline trends becoming significant again. Further analysis of CMIP6 model analogues shows that the observed 2025 decline was unusual but physically plausible under comparable Arctic warming, and is more consistent with ongoing winter sea ice reduction than with a return to values seen in the early 2020s.
Design and optimization of a compact double-layer Helmholtz resonator acoustic metamaterial for low-frequency broadband sound absorption
Acoustic metamaterials offer a promising approach for low-frequency sound absorption and have broad applications in noise control and architectural acoustics. In this study, a double-layer Helmholtz resonator acoustic metamaterial, consisting of a slit-neck Helmholtz resonator and an embedded-neck Helmholtz resonator, is proposed. By exploiting the coupling effect of the double-layer structure, the design produces two absorption peaks while maintaining high space utilization and relatively low structural complexity. Theoretical and numerical models were established to investigate the absorption mechanism of the unit cell and the effects of key structural parameters. The results show that thermal–viscous dissipation is mainly concentrated in the neck regions, and the two absorption peaks can be independently tuned by adjusting the structural parameters. As a result, the unit cell achieves absorption coefficients above 0.9 over 285–349 Hz with a thickness of only 1/22 of the corresponding wavelength. A genetic algorithm is then employed to optimize the parallel configuration. With a thickness of 50 mm, two parallel units achieve absorption coefficients above 0.9 over 259–359 Hz, while four parallel units achieve absorption coefficients above 0.8 over 283–501 Hz, with both configurations approaching the minimum thickness dictated by the acoustic causality constraint. Finally, impedance tube experiments validate the proposed design. This work provides a new strategy for the design of acoustic metamaterials capable of efficient broadband sound absorption below 500 Hz.
Severe floods increase long-term opioid overdose mortality
The relationship between climate disasters and substance use-related harms has been understudied. This study employed a mixed methods research design to assess the impact of severe floods on opioid overdose mortality and identify mechanisms driving this relationship. Drawing on opioid overdose death data from NCHS, presidential disaster declarations from FEMA, and severe storm event data from NOAA, we found severe floods in rural Appalachia led to a significant increase in county-level overdose mortality that persisted for a decade postflood. We then collected retrospective qualitative data from 17 stakeholders regarding the floods that occurred in Eastern Kentucky in July 2022. Interviews suggested this increase in overdose mortality was perpetuated by decreased access to treatment, recovery, and harm reduction services; increased trauma; increased instability; and persistent stigma around help-seeking. Due to the predicted continuation of these disasters, understanding their impact on substance use-related harms is essential to mitigating future damage.
Acoustic orbital angular momentum capture and detection via gradient spoof-fluid-spoof waveguides
Acoustic orbital angular momentum (OAM), with its unique helical wavefront structure and orthogonality, offers innovative technical approaches for fields, such as acoustic communication, particle manipulation, and acoustic imaging. However, the efficient capturing, separation, and accurate detection of acoustic vortex remain a core bottleneck that hinders their practical utilization. Here, we propose a compact OAM-capturing device based on a cylindrical spoof-fluid-spoof waveguide with gradient groove depths, which enables precise modulation of the dispersion behavior of acoustic vortices of different OAM modes through an axially linear gradient in groove depth. Within the operating frequency band, acoustic vortices with different topological charges l = 1, 2, 3 are successively captured at distinct spatial positions along the waveguide axis. This device features a compact structure, operates without external control, and offers considerable design flexibility, providing a passive solution for the efficient detection and separation of acoustic vortices. It shows promising potential for applications in acoustic communication, signal recognition, and ventilated sound insulation.
The 2026 western US snow drought was about four times more likely due to climate change
In the spring of 2026, anomalously low snow conditions in the western United States threatened winter recreation and water supplies. Here, we investigate: to what extent was this snow drought attributable to the climate change that has occurred since the pre-industrial period? We find that a snow drought this severe across the western United States was approximately 4.4 [95% CI: 2.6, 9.4] times more likely in the current climate than in the preindustrial period. In the Upper Colorado River Basin, the snow drought was approximately 14 times more likely [0.09, 4,300]. Given a projected increase in the frequency of snow droughts at least this severe in a moderately high emissions warming scenario, the lived experience of this event may help scientists, resource managers, and the public consider what western US snow might look like if greenhouse gas emissions are not aggressively reduced.
Polarization-sensitive photodetectors based on two-dimensional layered In4(P2Se6)3
Two-dimensional (2D) materials are gaining significant interest for polarization-sensitive photodetection because of their anisotropic photoelectric properties. This study presents the preparation of high-quality single crystals of In4(P2Se6)3 and examines their optical properties and lattice vibrations. The intensity of the Raman modes changes periodically as the sample is rotated during the polarized Raman spectroscopy, revealing a clear anisotropic Raman response. Furthermore, the photodetector based on In4(P2Se6)3 thin flakes shows polarization-sensitive photoresponse, achieving a responsivity of 131.13 mA/W with a dichroic ratio of 1.50. The results indicate that In4(P2Se6)3 is a promising material for polarization-sensitive photodetectors, potentially stimulating further research into metal phosphorus trichalcogenides.
Particles of echovirus 18 open to release their genomes in vivo
Enteroviruses cause a broad spectrum of human diseases, ranging from mild respiratory or gastrointestinal infections to severe neurological disorders such as aseptic meningitis and encephalitis. Enterovirus cell entry involves receptor-mediated endocytosis followed by destabilizing rearrangements of the virus capsid that enable genome release. However, the mechanism of enterovirus genome release has not been visualized in infected cells. Here, we used cryoelectron tomography and microscopy to image echovirus 18 (E18) entry into host cells and its interaction with the neonatal Fc receptor (FcRn). 30 min postinfection, endosomes and cytoplasm contained empty capsids missing one or several pentamers of capsid proteins, providing evidence that in vivo E18 releases its genome through capsid opening. In vitro, FcRn binding induced the expulsion of pocket factors from hydrophobic pockets in VP1, priming the virus for uncoating. The cryoelectron microscopy reconstruction of genome-containing particles of E18 inside infected cells did not reveal pocket factors, indicating that receptor binding triggers the same priming process during infection. We did not detect activated particles in infected cells, suggesting that these intermediates are short-lived and rapidly release their genomes in vivo. Our results identify capsid opening as the in vivo mechanism of echovirus 18 genome release, providing structural evidence for a process previously only inferred from in vitro experiments.
Non-optimal yet useful bandgap combinations for multijunction solar cells
The optimal bandgap combinations for multijunction solar cells are well known. The bandgaps used in practical devices may deviate from these optimal values depending on the availability of suitable materials. This work explores the non-ideal but still useful bandgap combinations that exist for multijunction cells with up to six subcells. It is found that principal component analysis can be utilized to establish rules of thumb for how the bandgaps in multijunction devices should be collectively adjusted to maintain high efficiency. This realization allows bandgap configurations with high theoretical efficiency to be identified with a few easy calculations, as demonstrated by a practical example.
Guanidine fuels rapid resurrection of desert cyanobacteria
In desert ecosystems, microbial activity is driven by brief hydration pulses but is severely limited by persistent nutrient scarcity. Cyanobacteria serve as essential pioneer photoautotrophs, maintaining biogeochemical cycles and ecosystem stability in these arid landscapes. However, their ability to quickly reactivate after rehydration is critically restricted by nitrogen availability. Although the nitrogen demand can be met later by biological nitrogen fixation, it is ineffective and irrelevant during early rehydration due to the high energy costs and delayed activation of nitrogenase, creating a critical metabolic bottleneck. Here we demonstrate that the desert cyanobacterium Nostoc flagelliforme overcomes this limitation by activating a previously overlooked guanidine carboxylase pathway, which sustains the rapid remobilization of internal nitrogen reserves upon rehydration. Transcriptional analysis using a luciferase reporter system reveals that pathway activity is tightly coupled to both hydration and nitrogen status. Disruption of the guanidine-specific riboswitch abolishes induction of the guanidine carboxylase pathway, underscoring its essential role in recovery from desiccation. Furthermore, comparative genomics reveals that the genes encoding this pathway, along with its cognate riboswitch, are widespread among terrestrial cyanobacteria. Phylogenetic analysis indicates they were acquired via horizontal gene transfer from nonphotosynthetic bacteria. Our findings establish an ecological role for guanidine in desert ecosystems and uncover a conserved mechanism that aids cyanobacterial resilience in xeric environments.
Epitaxial registry and transport properties in V4O7 thin films
We report the growth of V4O7 thin films deposited simultaneously on amorphous SiO2 and crystalline c-cut Al2O3 substrates. X-ray diffraction shows that films grown on SiO2 are polycrystalline with no preferred orientation, while films grown on Al2O3 exhibit a well-defined out-of-plane orientation and an in-plane registry consistent with epitaxial growth. Transmission electron microscopy confirms the crystallographic relationship between the V4O7 film and the Al2O3 substrate. Atomic force microscopy indicates substantially lower surface roughness for films grown on Al2O3 (∼6 nm) compared to those grown on SiO2 (∼22 nm), and Raman spectroscopy confirms stabilization of the same V4O7 phase on both substrates. Electrical transport measurements reveal a metal–insulator transition near 244 K for both substrates, with thermal hysteresis not exceeding ∼1 K. Although the transition temperature remains essentially unchanged, films grown on Al2O3 exhibit higher conductivity over the entire temperature range, exceeding that of films grown on SiO2 by approximately two orders of magnitude at 100 K and by a factor of five at 300 K. These results indicate that the conductivity differences are consistent with variations in microstructural connectivity associated with crystallographic order.
α-fluoro-β-alanine functions as a β-arrestin1-biased ligand of S1PR2 to upregulate DPD expression in cancer cells
α-fluoro-β-alanine (FBAL), a catabolite of the chemotherapeutic agent 5-fluorouracil (5-FU), has attracted significant attention due to its cardiotoxicity and neurotoxicity. However, its association with 5-FU resistance, a major obstacle in cancer treatment, has rarely been reported. In this study, FBAL was identified as a β-arrestin1-biased ligand of sphingosine 1-phosphate receptor 2 (S1PR2), which upregulates dihydropyrimidine dehydrogenase (DPD) expression and drives 5-FU resistance in colorectal cancer. Mechanistically, following exposure to FBAL, S1PR2, a G protein–coupled receptor (GPCR), is phosphorylated by recruiting G protein–coupled receptor kinase 6 (GRK6). Phosphorylated S1PR2 coupled with β-arrestin1, but not G proteins, to activate the MEK/ERK/AP-1 pathway and promote DPYD transcription. Ser343 was identified as the key phosphorylation site of S1PR2 using IP-MS analysis. This residue within the C-terminal domain mediates receptor interaction with β-arrestin-1 to activate the β-arrestin-1-dependent ERK pathway, as was confirmed in HCT116 S1PR2KO-ΔC cells and HCT116 S1PR2KO-S343A cells. In vivo , mice bearing orthotopic xenografts of HCT116 S1PR2KO-S343A cells exhibited significantly enhanced higher sensitivity to 5-FU treatment compared to those HCT116 S1PR2KO-WT cells following FBAL. Taken together, this study showed that exposure to FBAL induces S1PR2 phosphorylation at Ser343 within the C-terminal mediated by GRK6, activating the β-arrestin1-dependent ERK pathway to upregulate DPD expression. This study not only delineates a phosphorylation-dependent signaling pathway in chemoresistance but also establishes S1PR2 as a promising therapeutic target for overcoming 5-FU resistance in cancer.
Faraday instability in shallow particle-laden liquids under vertical vibration
The Faraday instability of shallow particle-laden liquids under geometric confinement was investigated through combined experimental and theoretical analyses. Water-based suspensions containing micrometer-sized magnetite particles were vertically excited in a cylindrical container, and the effects of particle mass, particle size, and fluid depth on the threshold acceleration and axisymmetric modal responses were examined. Particle loading increased the instability threshold, with the threshold acceleration increasing by up to 29% as the particle mass was increased from 0.05 to 0.15 g. Although the overall particle volume fraction was low, sedimentation formed a basal particle layer near the container bottom. A modified baseline force-detuning-based model with nominal effective-property corrections captures the modal ordering and the overall instability characteristics of shallow particle-laden liquids. Comparison with the experimental results further suggests that sedimented-particle-bed dissipation contributes to the additional threshold increase observed at larger particle masses, larger particle sizes, and higher-order modes.
Electrochemical lateral flow assay with ELISA-level performance for detecting plant diseases in East Africa
Cassava brown streak disease (CBSD) threatens food security for millions in East Africa, yet its control remains limited by the absence of field-deployable molecular diagnostics. Here, we introduce ELLA (Electrochemical Lateral flow assay with Linked Analytics), a battery-free, smartphone-powered electrochemical lateral flow assay that delivers enzyme-linked immunosorbent assay (ELISA)-grade protein detection directly in the field. ELLA integrates near-field communication, a single-chip potentiostat, metal-pin electrodes, and ferrocene-labeled nanoparticles into a fully disposable cassette, enabling quantitative immunoassays without optical instrumentation or centralized laboratory infrastructure. Validated across laboratory studies and extensive field trials in Tanzania, ELLA achieved 95% agreement with ELISA and 89% agreement with RT-qPCR, outperforming ELISA’s limit of detection while maintaining a material cost below US$1. By coupling molecular test results with cloud-linked analytics, we further trained DeepELLA, a smartphone-based image classification model that enables scalable surveillance from field-acquired leaf images. Together, these advances unify electrochemical sensing, digital connectivity, and AI-assisted interpretation, enabling portable, ELISA-level diagnostics for plant, environmental, and health monitoring in resource-limited regions.
Radiation effects in <i>β</i> -Ga2O3-based devices: From atomic-scale damage to radiation hardening strategies
β-Ga2O3, with its ultrawide bandgap and high critical electric field, has emerged as a candidate material of interest for space power electronics and solar-blind ultraviolet photodetectors. Its theoretical breakdown field far exceeds that of SiC and GaN, positioning it as a promising candidate for high-voltage, high-efficiency power devices. However, prolonged exposure to protons, neutrons, heavy ions, and γ-rays in the space radiation environment can induce single-event effects, displacement damage, and total ionizing dose effects, leading to gradual performance degradation or even catastrophic failure. Thus, understanding the physical origins of radiation damage, systematically elucidating the evolution of device failure, and developing effective radiation-hardening strategies have become central challenges in the field. This review focuses on the interplay between defects and charge carriers as a core mechanism, starting from the anisotropy of displacement threshold energies and the dynamics of collision cascades to establish a physical link between key defects and device performance degradation. It provides an in-depth analysis of the synergistic effects of electric-field concentration and thermal accumulation in single-event burnout, the modulation of carrier lifetime by deep-level defects in displacement damage, and the coupled influence of bias conditions and temperature on interface degradation under total ionizing dose. Based on these insights, this review summarizes radiation-hardening technologies, including deep trench structures, phase engineering, and electrical scanning recovery, thereby establishing a comprehensive framework that bridges fundamental physics with practical engineering solutions for the reliable design of Ga2O3-based devices in aerospace and nuclear applications.