he manipulation of light by means of materials with varying refractive index distributions is widespread among natural systems and modern technologies. However, understanding how animals leverage refractive index differences for dynamic color changes and then translating such insight into tunable optical devices remains challenging. We experimentally and computationally demonstrated that iridescent cells (iridophores) containing Bragg reflectors with sinusoidal-wave (rugate) refractive index profiles enable squid dorsal mantle tissues to reversibly transition between nearly transparent and vibrantly colored states. We then drew inspiration from these findings for the design and development of iridophore-inspired multispectral composite materials with tunable visible and infrared functionalities. Our study provides insight into squid dynamic structural coloration mechanisms and furnishes a technology for camouflage, heat management, display, and sensing applications.
Accelerated discovery of stable, extra-large-pore nano zeolites with micro-electron diffraction
利用微电子衍射加速发现稳定的超大孔纳米沸石
▲?作者：CHAO MA, ZHENGHAN ZHANG, MENGDI ZHANG, XUDONG TIAN, CONG LIN, LEI HAN, ET AL.
Stable zeolites with extra-large pores and nano dimensions that are capable of processing large molecules are in high demand but have been difficult to produce. Their complex structures and nanoscale crystal sizes present challenges for analysis using conventional x-ray diffraction techniques, leading to inefficiencies in material development. We report NJU120-1 and NJU120-2, two robust and fully connected aluminosilicate nano zeolites featuring interconnected channel systems with extra-large 22-ring pores. NJU120-1 is a nanosheet with only about 8-nanometer thickness, corresponding to 1.5 unit cells, and NJU120-2 is a nanorod with 50 by 250 nanometer dimensions. Their synthesis optimization was greatly accelerated through rapid structure determination with MicroED, revealing their multidimensional pore structures. Their very large largest-free-sphere diameters of approximately 1.2 nanometers coupled with nano morphologies enabled catalytic cracking of large molecules.
化学Chemistry
Spontaneous formation of urea from carbon dioxide and ammonia in aqueous droplets
二氧化碳和氨在水滴中自发形成尿素
▲?作者：MERCEDE AZIZBAIG MOHAJER, PALLAB BASURI, ANDREI EVDOKIMOV, GROGORY DAVID, DANIEL ZINDEL, EVANGELOS MILIORDOS, ET AL.
Urea is a key molecule in the search for the origin of life and a basic chemical produced in large quantities by industry. Its formation from ammonia and carbon dioxide requires either high pressures and temperatures or, under milder conditions, catalysts or additional reagents. In this study, we observed the spontaneous formation of urea under ambient conditions from ammonia and carbon dioxide in the surface layer of aqueous droplets. Single, optically trapped droplets were probed by using Raman bands as markers. We found the surface layer to act like a microscopic flow reactor, with chemical gradients providing access to unconventional reaction pathways. This observation revealed a general mechanistic scheme for distinctive droplet chemistry. Interfacial chemistry is a possible nonenergetic route for urea formation under prebiotic conditions.
Carbonyl-to-sulfur swap enabled by sequential double carbon-carbon bond activation
In drug development, replacement of a skeletal carbon with a sulfur atom can result in analogs of bioactive compounds with improved properties. Currently, the sulfur analogs are almost exclusively prepared by de novo synthesis; the existing approach to swap carbon with sulfur is inefficient and involves stoichiometric mercury reagents. In this study, we report a two-step carbonyl-to-sulfur (CO-to-S) atom swap approach, enabled by a rationally designed N′-alkyl-hydrazonamide (NAHA) reagent that promotes forming pre-aromatic intermediates twice sequentially by different mechanisms, thereby achieving homolytic cleavage of both α-C-C bonds of the ketone substrates. A Ts-S-Ts (Ts, p-toluenesulfonyl) reagent mediates this process through successive intermolecular and intramolecular alkyl radical trapping by the central sulfur. This method shows a broad substrate scope and excellent chemoselectivity, providing a streamlined route to sulfur-containing scaffolds from readily available ketones.
地球科学Earth Science
Migrating shallow slow slip on the Nankai Trough megathrust captured by borehole observatories
钻孔观测到的南海海沟大逆冲断层上的迁移浅层慢滑
▲?作者：JOSHUA R. EDGINGTON, DEMIAN M. SAFFER AND CHARLES A. WILLIAMS
Patterns of strain accumulation and release offshore in subduction zones are directly linked to the potential for shallow coseismic slip and tsunamigenesis, but these patterns remain elusive. In this work, we analyze formation pore pressure records from three offshore borehole observatories at the Nankai subduction zone, Honshu, Japan, to capture detailed slip-time histories of two slow slip events (SSEs) along the outermost reaches of the plate boundary. Slip initiates ~30 kilometers landward of the trench; migrates seaward at 1 to 2 kilometers per day to within a few kilometers of, and possibly breaching, the trench; and coincides with the onset and migration of tremor and/or very-low-frequency earthquakes. The SSE source region lies in a zone of high pore fluid pressure and low stress, which provides clear observational evidence linking these factors to shallow slow earthquakes.
Interplate slip before, during, and after the 2024 Mw 7 Hyuga-nada earthquake, southwest Japan
2024年日本西南部日向滩7级地震前、中、后期的板块间滑移
▲?作者：SHINZABURO OZAWA, HIROSHI MUNEKANE, HISASHI SUITO AND HIROSHI YARAI
Using Global Navigation Satellite System data, we investigated the interplate slip before, during, and after the 2024 Hyuga-nada earthquake in Japan. Before the earthquake, a moment magnitude (Mw) 6.0 slow-slip event (SSE) was observed from late 2023 in a downdip extension of the mainshock. The coseismic slip was adjacent to the 1996 Hyuga-nada earthquake source. The afterslip resolved near the hypocenter area and in the downdip extension of the mainshock, reaching Mw 6.7 on 16 September 2024. Leading up to the earthquake, the recurrence interval for SSEs in the preslip area shortened from an average of 2 years, estimated from observations over the past 30 years, to 1 year, consistent with simulations in which the weakening of the Nankai megathrust was attributed to the cause.
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