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发布日期：2024-07-01 作者：开博
编译 | 未玖
Nature, 2 May 2024 , VOL 629, ISSUE 8010《天然》2024年5月2日，第629卷，8010期
天文学Astronomy
A magnetar giant flare in the nearby starburst galaxy M82
星暴星系M82四周的一颗磁星庞大耀斑
▲ 作者：Sandro Mereghetti, Michela Rigoselli, Ruben Salvaterra, Dominik Patryk Pacholski, James Craig Rodi, Diego Gotz, et al.
▲ 链接：
https://www.nature.com/articles/s41586-024-07285-4
▲ 摘要：
磁星庞大耀斑是一种罕有的爆发事务，在不到1秒钟的时候里，从年青的中子星释放出高达1047尔格的伽马射线，磁场高达1015?16 G。年夜约50年来，在银河系和年夜麦哲伦星云的磁星上只不雅测到三次如许的耀斑。
这个小样本可经由过程系外事务的发现而扩年夜，由于几分之一秒庞大耀斑的亮度可到达1046尔格/s以上，这使其在几十兆秒差距内可见。但是，在这些距离上，很难将它们与短伽马射线暴（GRBs）辨别开来；远很多、能量年夜很多（1050?53尔格）的事务凡是源在紧凑的双星归并。
人们已提出一些具有分歧置信区间的短GRBs，这是四周星系中的候选磁星庞大耀斑。研究组报导了GRB 231115A的不雅测成果，其与星暴星系M82的位置一致。GRB 231115A的光谱特征，加上爆发长度，在几小时内取得的X射线和光学对应物的限制，和缺少引力波旌旗灯号，毫无疑问地证实了此次爆发是来自M82磁星的庞大耀斑。
▲ Abstract：
Magnetar giant flares are rare explosive events releasing up to 1047?erg in gamma rays in less than 1?second from young neutron stars with magnetic fields up to 1015?16?G. Only three such flares have been seen from magnetars in our Galaxy and in the Large Magellanic Cloud in roughly 50?years. This small sample can be enlarged by the discovery of extragalactic events, as for a fraction of a second giant flares reach luminosities above 1046ergs?1, which makes them visible up to a few tens of megaparsecs. However, at these distances they are difficult to distinguish from short gamma-ray bursts (GRBs); much more distant and energetic (1050?53erg) events, originating in compact binary mergers. A few short GRBs have been proposed, with different amounts of confidence, as candidate giant magnetar flares in nearby galaxies. Here we report observations of GRB 231115A, positionally coincident with the starburst galaxy M82. Its spectral properties, along with the length of the burst, the limits on its X-ray and optical counterparts obtained within a few hours, and the lack of a gravitational wave signal, unambiguously qualify this burst as a giant flare from a magnetar in M82.
材料科学Materials Science
Bevel-edge epitaxy of ferroelectric rhombohedral boron nitride single crystal
铁电斜方六面体氮化硼单晶的斜边外延
▲ 作者：Li Wang, Jiajie Qi, Wenya Wei, Mengqi Wu, Zhibin Zhang, Xiaomin Li, et al.
▲ 链接：
https://www.nature.com/articles/s41586-024-07286-3
▲ 摘要：
在二维电介质家族中，斜方六面体氮化硼（rBN）不但具有六方氮化硼的优胜机能（包罗低介电常数和耗散、强电绝缘性、杰出的化学不变性、高导热性和无悬空键的原子平展性），并且还具有源在面内和面外中间对称破缺的有效光学非线性和界面铁电性。但是，因为需要史无前例的发展节制来调和每层的晶格取向和每一个界面的滑动矢量，制备年夜尺寸单晶rBN层仍颇具挑战。
研究组报导了一种利用斜边外延来制备厘米尺寸单晶rBN层的简单方式，在相邻镍概况上具有切确的层间ABC堆叠。成果在斜面（110）处成功地切确制造了阶地面（100）聚束台阶边沿的单晶镍基底，同时指导每一个BN层中一致的硼-氮键取向，并经由过程每一个斜面四周的成核来指导BN层的斜方六面体堆叠。
研究组验证了原生BN层的纯斜方六面体相，并在高居里温度下表示出稳健、平均和可切换的铁电性。该工作为单晶二维层的切确堆叠节制发展供给了有用路子，并为基在堆叠二维材料的合用多功能器件奠基了根本。
▲ Abstract：
Within the family of two-dimensional dielectrics, rhombohedral boron nitride (rBN) is considerably promising owing to having not only the superior properties of hexagonal boron nitride—including low permittivity and dissipation, strong electrical insulation, good chemical stability, high thermal conductivity and atomic flatness without dangling bonds—but also useful optical nonlinearity and interfacial ferroelectricity originating from the broken in-plane and out-of-plane centrosymmetry. However, the preparation of large-sized single-crystal rBN layers remains a challenge, owing to the requisite unprecedented growth controls to coordinate the lattice orientation of each layer and the sliding vector of every interface. Here we report a facile methodology using bevel-edge epitaxy to prepare centimetre-sized single-crystal rBN layers with exact interlayer ABC stacking on a vicinal nickel surface. We realized successful accurate fabrication over a single-crystal nickel substrate with bunched step edges of the terrace facet (100) at the bevel facet (110), which simultaneously guided the consistent boron–nitrogen bond orientation in each BN layer and the rhombohedral stacking of BN layers via nucleation near each bevel facet. The pure rhombohedral phase of the as-grown BN layers was verified, and consequently showed robust, homogeneous and switchable ferroelectricity with a high Curie temperature. Our work provides an effective route for accurate stacking-controlled growth of single-crystal two-dimensional layers and presents a foundation for applicable multifunctional devices based on stacked two-dimensional materials.
High-performance fibre battery with polymer gel electrolyte
聚合物凝胶电解质的高机能纤维电池
▲ 作者：Chenhao Lu, Haibo Jiang, Xiangran Cheng, Jiqing He, Yao Long, Yingfan Chang, et al.
▲ 链接：
https://www.nature.com/articles/s41586-024-07343-x
▲ 摘要：
聚合物凝胶电解质替换液体电解质是公认的解决可穿着电池平安性问题和实现高柔性的通用有用路子。但是，因为润湿不足，聚合物凝胶电解质与电极之间的界面较差，发生了更差的电化学机能，特殊是在电池变形时。
研究组报导了一种设计电极通道布局的策略，以整合聚合物凝胶电解质，并构成慎密不变的界面，以实现高机能可穿着电池。作为演示，多个电极纤维一路扭转构成摆列通道，同时每一个电极纤维的概况设计有收集通道。
单体溶液起首沿着摆列通道有用渗入，然落后入收集通道。然后，这些单体被聚合成凝胶电解质，并与电极构成慎密不变的界面。所得纤维锂离子电池（FLB）表示出较高的电化学机能（例如，能量密度约为128 Wh kg?1）。
该策略还实现了FLB的出产，速度高达每绕组单位3600 mh?1。持续的FLB被编织成50 cm×30 cm的纺织品，供给2975 mAh的输出容量。FLB纺织品在极端前提下平安工作，例如- 40℃和80℃的温度和- 0.08 MPa的真空。FLB有望利用在消防和太空摸索。
▲ Abstract：
Replacement of liquid electrolytes with polymer gel electrolytes is recognized as a general and effective way of solving safety problems and achieving high flexibility in wearable batteries. However, the poor interface between polymer gel electrolyte and electrode, caused by insufficient wetting, produces much poorer electrochemical properties, especially during the deformation of the battery. Here we report a strategy for designing channel structures in electrodes to incorporate polymer gel electrolytes and to form intimate and stable interfaces for high-performance wearable batteries. As a demonstration, multiple electrode fibres were rotated together to form aligned channels, while the surface of each electrode fibre was designed with networked channels. The monomer solution was effectively infiltrated first along the aligned channels and then into the networked channels. The monomers were then polymerized to produce a gel electrolyte and form intimate and stable interfaces with the electrodes. The resulting fibre lithium-ion battery (FLB) showed high electrochemical performances (for example, an energy density of about 128?Wh?kg?1. This strategy also enabled the production of FLBs with a high rate of 3,600?mh?1per winding unit. The continuous FLBs were woven into a 50?cm?×?30?cm textile to provide an output capacity of 2,975?mAh. The FLB textiles worked safely under extreme conditions, such as temperatures of ?40?°C and 80?°C and a vacuum of ?0.08?MPa. The FLBs show promise for applications in firefighting and space exploration.
化学Chemistry
Long-term continuous ammonia electrosynthesis
持久持续氨电合成
▲ 作者：Shaofeng Li, Yuanyuan Zhou, Xianbiao Fu, Jakob B. Pedersen, Mattia Saccoccio, Suzanne Z. Andersen, et al.
▲ 链接：
https://www.nature.com/articles/s41586-024-07276-5
▲ 摘要：
氨在化肥和化学工业中相当主要，被认为是一种无碳燃料。在情况前提下，氮电合成氨为哈伯-博世工艺供给了一个有吸引力的替换方案，锂介导的氮还原代表了一种有前程的持续流氨电合成方式，将氮还原与氢氧化相连系。但是，因为聚合和挥发性问题，凡是用作溶剂的四氢呋喃阻碍了持久氨出产。
研究组展现了链醚基电解质可实现持久持续氨合成。他们发现链醚基溶剂表示出非聚合特征和高沸点（162℃），并在气体分散电极上构成致密的固体-电解质界面层，增进氨在气相中的释放，确保电解质的不变性。
研究组演示了在1 bar压力和室温下，该溶剂在25 cm2电极的活动电解槽中持续运行300小时，实现了电流到氨的效力为64±1%，气相氨含量高达约98%。该研究成果凸起了溶剂在持久持续氨合成中的要害感化。
▲ Abstract：
Ammonia is crucial as a fertilizer and in the chemical industry and is considered to be a carbon-free fuel. Ammonia electrosynthesis from nitrogen under ambient conditions offers an attractive alternative to the Haber–Bosch process, and lithium-mediated nitrogen reduction represents a promising approach to continuous-flow ammonia electrosynthesis, coupling nitrogen reduction with hydrogen oxidation. However, tetrahydrofuran, which is commonly used as a solvent, impedes long-term ammonia production owing to polymerization and volatility problems. Here we show that a chain-ether-based electrolyte enables long-term continuous ammonia synthesis. We find that a chain-ether-based solvent exhibits non-polymerization properties and a high boiling point (162?°C) and forms a compact solid-electrolyte interphase layer on the gas diffusion electrode, facilitating ammonia release in the gas phase and ensuring electrolyte stability. We demonstrate 300?h of continuous operation in a flow electrolyser with a 25?cm2 electrode at 1?bar pressure and room temperature, and achieve a current-to-ammonia efficiency of 64?±?1% with a gas-phase ammonia content of approximately 98%. Our results highlight the crucial role of the solvent in long-term continuous ammonia synthesis.
Stereoselective amino acid synthesis by photobiocatalytic oxidative coupling
光生物催化氧化偶结合成立体选择性氨基酸
▲ 作者：Tian-Ci Wang, Binh Khanh Mai, Zheng Zhang, Zhiyu Bo, Jiedong Li, Peng Liu, et al.
▲ 链接：
https://www.nature.com/articles/s41586-024-07284-5
▲ 摘要：
操纵光来扩年夜酶反映性的光生物催化比来已成为开辟天然界新化学物资的一种壮大策略。这些系统在小份子催化剂持久没法催化的不合错误称自由基反映中显示出潜力。到今朝为止，非自然光生物催化反映仅限在整体还原和氧化还原中性进程。
研究组报导了光生物催化有机硼试剂和氨基酸之间的不合错误称sp3–sp3氧化交叉偶联反映。该反映需要工程吡哆醛生物催化剂、光氧化还原催化剂和氧化剂的协同利用。经由过程自由基机制从头改进吡哆醛-5′-磷酸依靠酶家族（即苏氨酸醛缩酶），对甘氨酸和α-支链氨基酸底物进行α-C–H功能化，发生一系列具有最多两个持续立体中间的α-三代替和四代替的非经典氨基酸。
吡哆醛自由基酶的定向进化实现了一级和二级自由基前体（包罗苄基、烯丙基和烷基硼试剂）以对映体节制和非对映体节制的体例偶联。协同光氧化还原-吡哆醛生物催化为sp3–sp3氧化偶联供给了一个平台，实现了化学或生物学未知的立体选择性份子间自由基转化。
▲ Abstract：
Photobiocatalysis—where light is used to expand the reactivity of an enzyme—has recently emerged as a powerful strategy to develop chemistries that are new to nature. These systems have shown potential in asymmetric radical reactions that have long eluded small-molecule catalysts. So far, unnatural photobiocatalytic reactions are limited to overall reductive and redox-neutral processes. Here we report photobiocatalytic asymmetric sp3–sp3oxidative cross-coupling between organoboron reagents and amino acids. This reaction requires the cooperative use of engineered pyridoxal biocatalysts, photoredox catalysts and an oxidizing agent开博体育. We repurpose a family of pyridoxal-5′-phosphate-dependent enzymes, threonine aldolases, for the α-C–H functionalization of glycine and α-branched amino acid substrates by a radical mechanism, giving rise to a range of α-tri- and tetrasubstituted non-canonical amino acids possessing up to two contiguous stereocentres. Directed evolution of pyridoxal radical enzymes allowed primary and secondary radical precursors, including benzyl, allyl and alkylboron reagents, to be coupled in an enantio- and diastereocontrolled fashion. Cooperative photoredox–pyridoxal biocatalysis provides a platform for sp3–sp3 oxidative coupling, permitting the stereoselective, intermolecular free-radical transformations that are unknown to chemistry or biology.
地球科学One Earth
Environmental drivers of increased ecosystem respiration in a warming tundra
变暖苔原生态系统呼吸增添的情况驱动身分
▲ 作者：S. L. Maes, J. Dietrich, G. Midolo, S. Schwieger, M. Kummu, V. Vandvik, et al.
▲ 链接：
https://www.nature.com/articles/s41586-024-07274-7
▲ 摘要：
北极和高山苔原生态系统是有机碳的庞大贮存库。天气变暖可能刺激生态系统的呼吸感化，并将碳释放到年夜气中。这类刺激的幅度和延续性和驱动其转变的情况机制仍不明白。这阻碍了全球陆地碳-天气反馈猜测的正确性。
研究组综合了在28个北极和高山苔原站点进行的56个开放顶室原位变暖尝试的136个数据集，这些尝试的运行时候从不到1年至25年不等。成果发现，空气温度平均升高1.4℃[置信区间（CI）0.9-2.0℃]和泥土温度平均升高0.4℃[置信区间（CI）0.2-0.7℃]会致使发展季生态系统呼吸增添30%[CI 22-38%]（n = 136）。
研究成果注解，生态系统呼吸的刺激是因为植物相干呼吸和微生物呼吸的增添（n = 9），而且延续最少25年（n = 136）。天气变暖对呼吸感化的影响水平首要受天气变暖引发的局部泥土前提转变（即总氮浓度和pH值的转变），和这些前提下与情况相干的空间转变（特殊是总氮浓度和碳氮比）所驱动。
氮限制较强的苔原地域和蔼候变暖刺激了植物和微生物营养周转的地域仿佛对变暖的呼吸反映特殊敏感。这些成果强调结局部泥土前提和其变暖引发的转变，对将来天气影响生态系统呼吸的主要性。
▲ Abstract：
Arctic and alpine tundra ecosystems are large reservoirs of organic carbon. Climate warming may stimulate ecosystem respiration and release carbon into the atmosphere. The magnitude and persistency of this stimulation and the environmental mechanisms that drive its variation remain uncertain. This hampers the accuracy of global land carbon–climate feedback projections. Here we synthesize 136 datasets from 56 open-top chamber in situ warming experiments located at 28 arctic and alpine tundra sites which have been running for less than 1?year up to 25?years. We show that a mean rise of 1.4?°C [confidence interval (CI) 0.9–2.0?°C] in air and 0.4?°C [CI 0.2–0.7?°C] in soil temperature results in an increase in growing season ecosystem respiration by 30% [CI 22–38%] (n?=?136). Our findings indicate that the stimulation of ecosystem respiration was due to increases in both plant-related and microbial respiration (n?=?9) and continued for at least 25?years (n?=?136). The magnitude of the warming effects on respiration was driven by variation in warming-induced changes in local soil conditions, that is, changes in total nitrogen concentration and pH and by context-dependent spatial variation in these conditions, in particular total nitrogen concentration and the carbon:nitrogen ratio. Tundra sites with stronger nitrogen limitations and sites in which warming had stimulated plant and microbial nutrient turnover seemed particularly sensitive in their respiration response to warming. The results highlight the importance of local soil conditions and warming-induced changes therein for future climatic impacts on respiration.
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