Science Bulletin最新文献

Fast radio bursts (FRBs) remain one of the most puzzling astrophysical phenomena. While most FRBs are detected only once or sporadically, we present the identification of FRB 20190520B as the first persistently active source over a continuous span of ∼4 years. This rare long-term activity enabled a detailed investigation of its dispersion measure (DM) evolution. We also report that FRB 20190520B exhibits a substantial decrease in DM at a global rate of (-12.4±0.3) pc cm^-3yr^-1, exceeding previous FRB's DM variation measurements by a factor of three and surpassing those observed in pulsars by orders of magnitude. The magnitude and consistency of the DM evolution, along with a high host DM contribution, strongly indicate that the source resides in a dense, expanding ionized medium, likely a young supernova remnant (SNR).

Glacial lake outburst floods (GLOFs) are among the most severe cryospheric hazards in the Himalaya. While previous studies have primarily focused on the characteristics and causes of GLOFs, strategies for mitigating their disaster impacts remain underexplored. This study introduces China's Glacial Lake Management System (GLMS) and evaluates its potential for regional replication in reducing damage caused by GLOFs. We find that while GLOF frequency shows a statistically insignificant decrease from 1990 to 2023, downstream damage has intensified, yet appears relatively mitigated within China across the Himalaya following the implementation of the GLMS. Further hydrodynamic modelling suggests that glacial lakes will continue to expand in the future, with total growth expected to triple relative to the 2000-2020 period. These expansions could increase GLOF exposure by over 27% for high-risk lakes and by more than 40% in regions outside China without targeted interventions. However, implementing GLMS engineering measures could reduce the intensity of future floods by 24%, with even greater reductions outside China-29% compared to 21% within China. Building on China's lake management experience and recognizing the transboundary nature of GLOFs, the comprehensive framework we propose for region-wide glacial lake risk reduction across the Himalaya integrates engineering measures, early warning systems, and community responses. This framework addresses the urgent need for proactive and coordinated mitigation strategies in densely populated high-mountain regions.

Mutations in cytoplasmic DNA-degrading enzymes can lead to the accumulation of cytoplasmic DNA (cytoDNA), which excessively activates DNA-sensing pathways and exacerbates inflammatory aging. Reducing cytoDNA levels to suppress DNA-sensing mechanisms is therefore critical for treating elderly-onset rheumatoid arthritis (EORA). In this study, we constructed Trex1 mRNA loaded lipid nanoparticles (LNPs) via microfluidics and prepared DNase I loaded polydopamine (PDA) nanoparticles through oxidative polymerization. These two components were co-encapsulated into methacrylated hyaluronic acid (HAMA) microspheres using microfluidic photopolymerization. The LNPs incorporate cationic lipids to facilitate mRNA loading and promote endosomal escape, enabling efficient translation of TREX1 and subsequent recognition and degradation of cytoDNA. Meanwhile, cationic mesoporous polydopamine electrostatically adsorbs and degrades extracellular DNA. The microspheres function as a reservoir for sustained nanoparticles release, enabling synergistic inhibition of DNA sensing pathways. This microsphere based vaccine upregulates TREX1 expression in antigen presenting cells (APCs) and reduces cytoDNA levels, thereby suppressing overactivation of the cGAS-STING signaling axis and promoting immune tolerance. It also attenuates the differentiation of CD4⁺ T cells into Th1, Th2, Th17, and Treg subsets. In an aged rat model of rheumatoid arthritis, vaccination significantly attenuated soft tissue edema, synovial inflammation, and articular cartilage and bone destruction. By clearing excess cytoDNA and restraining DNA-sensing hyperactivation, this vaccine induces cellular immune tolerance and represents a promising therapeutic strategy for rheumatoid arthritis in the elderly.

Hydrogen peroxide (H₂O₂) photosynthesis from H₂O and O₂ remains a significant challenge due to the sluggish hydrogen donation process, which stems from the high O-H bond dissociation energy of water. In this study, we propose an effective strategy to accelerate the water oxidation reaction (WOR) by anchoring single palladium atoms (Pd-CNO₂) onto a keto-anthraquinone covalent organic framework (KfAQ-Pd), achieving remarkable H₂O₂ production rates of 3828 μmol h^-1 g^-1 under visible light irradiation (λ > 420 nm) in neutral water. Both experimental observations and theoretical simulations reveal that the Pd-CNO₂ configuration induces an upward shift in the d-band center and enhances the hydrophilicity of KfAQ. This modification effectively disrupts the hydrogen-bond network within adsorbed water clusters, thereby promoting the cleavage of the dangling O-H bonds in H₂O molecules and facilitating efficient hydrogen donation. The generated H₃O⁺ species are subsequently reduced in-situ by photogenerated electrons, leading to the hydrogenation of anthraquinone moieties and ultimately driving efficient H₂O₂ photosynthesis. Overall, these findings highlight the pivotal role of single Pd atoms in enhancing water dissociation and hydrogen transfer, offering a promising new paradigm for solar-driven, environmentally friendly H₂O₂ synthesis in neutral aqueous systems.