Nature,做作周论 6 July 2023, VOL 619, ISSUE 7968

《做作》2023年7月6日，第619卷
，出书7968期

?文导

地舆学Astronomy

X-ray polarization evidence for a 200-year-old flare of Sgr A

Sgr A* 200年耀斑的X射线偏振证据

▲ 作者：Frédéric Marin, Eugene Churazov, Ildar Khabibullin, Riccardo Ferrazzoli, Laura Di Gesu, Thibault Barnouin, et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06064-x

▲ 摘要：

河汉系中间有一个品质约为太阳400万倍的黑洞（人马座A* ，Sgr A），做作周论当初颇为清静，出书其亮度比沉闷星系核低多少个数目级。文导星系中间地域致密气体对于SgrA* X射线的做作周论反射为钻研其以前数百年以及数千年的耀斑行动提供了一种措施 。

从Sgr A*临近重大份子云审核到的出书X射线不断体的形态以及强荧光铁线与反射天气不同 。假如这种批注精确，文导反射的做作周论不断辐射理当是极化的。

钻研组报道了运用成像X射线偏振探测器在河汉系中间份子云倾向上的出书偏振X射线发射的审核服从。经丈量偏振度为31%±11%，文导偏振角为- 48°±11°。做作周论

所测偏振角与Sgr A*为主要发射源的出书偏振角相不同，偏振度表明约莫200年前 ，文导Sgr A*的X射线光度与塞弗特星系的光度曾经持久至关。

▲ Abstract：

The centre of the Milky Way Galaxy hosts a black hole with a solar mass of about 4 million (Sagittarius A* (Sgr A)) that is very quiescent at present with a luminosity many orders of magnitude below those of active galactic nuclei. Reflection of X-rays from Sgr A* by dense gas in the Galactic Centre region offers a means to study its past flaring activity on timescales of hundreds and thousands of years. The shape of the X-ray continuum and the strong fluorescent iron line observed from giant molecular clouds in the vicinity of Sgr A* are consistent with the reflection scenario. If this interpretation is correct, the reflected continuum emission should be polarized. Here we report observations of polarized X-ray emission in the direction of the molecular clouds in the Galactic Centre using the Imaging X-ray Polarimetry Explorer. We measure a polarization degree of 31%±11%, and a polarization angle of 48°±11°. The polarization angle is consistent with Sgr?A* being the primary source of the emission, and the polarization degree implies that some 200 years ago, the X-ray luminosity of Sgr?A* was briefly comparable to that of a Seyfert galaxy.

质料迷信Materials Science

Liquid metal for high-entropy alloy nanoparticles synthesis

液态金属用于高熵合金纳米颗粒的分解

▲ 作者
：Guanghui Cao, Jingjing Liang, Zenglong Guo, Kena Yang, Gang Wang, Huiliu Wang, et al.

▲ 链接 ：

https://www.nature.com/articles/s41586-023-06082-9

▲ 摘要
：

高熵合金纳米颗粒（HEA-NPs）作为功能质料具备广漠的运用远景。可是，到当初为止 ，已经实现的高熵合金仅限于相似元素的调色板 ，这极大地拦阻了差距运用的质料妄想、功能优化以及机理探究。

钻研组发现
，给予其余元素负混合焓的液态金属可提供晃动的热力学条件，并作为事实的动态混合储层，从而在以及善反映条件下分解多种金属元素的HEA-NPs。所波及的元素具备普遍的原子半径（1.24-1.97 ?）以及熔点（303-3683 K）。

钻研组经由混合焓调谐实现为了纳米颗粒的精确制作妄想 ，此外复原位捉拿了实时转换历程（即从液态金属到结晶HEA-NPs），证明了合金化历程中的动态裂变-聚变行动 。

▲ Abstract：

High-entropy alloy nanoparticles (HEA-NPs) show great potential as functional materials. However, thus far, the realized high-entropy alloys have been restricted to palettes of similar elements, which greatly hinders the material design, property optimization and mechanistic exploration for different applications. Herein, we discovered that liquid metal endowing negative mixing enthalpy with other elements could provide a stable thermodynamic condition and act as a desirable dynamic mixing reservoir, thus realizing the synthesis of HEA-NPs with a diverse range of metal elements in mild reaction conditions. The involved elements have a wide range of atomic radii (1.24–1.97 ) and melting points (303–3,683 K). We also realized the precisely fabricated structures of nanoparticles via mixing enthalpy tuning. Moreover, the real-time conversion process (that is, from liquid metal to crystalline HEA-NPs) is captured in situ, which confirmed a dynamic fission–fusion behaviour during the alloying process.

机械工程Mechanical Engineering

Harnessing a paper-folding mechanism for reconfigurable DNA origami

运用折纸机构妨碍可重构DNA折纸

▲ 作者 ：Myoungseok Kim, Chanseok Lee, Kyounghwa Jeon, Jae Young Lee, Young-Joo Kim, Jae Gyung Lee, et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06181-7

▲ 摘要 ：

折纸机构因其在将可变形态以及刚度编程到妄想中的配合能耐以及优势 ，已经被普遍用于可重构宏不雅零星的构建。可是 ，尽管基于DNA自组装的种种动态妄想已经被开拓进去，但由于缺少适宜的妄想原则，很少被用于构建份子水平零星 
。

钻研组提出了一种运用折纸机构来建树可重构DNA折纸妄想的措施
。其主要脑子是建树一个参考平面线框妄想 ，边缘凭证折纸中的折痕图案 ，以便折叠成种种目的形态。

钻研组运用DNA链位移以高产率实现为了多少种类似纸张的折叠以及睁开方式 ，并揭示了正交折叠、可一再折叠以及睁开、基于折叠的microRNA检测以及荧光信号操作 。由pH值或者光源变更触发的宽慰照应性折叠以及睁开也可能实现。

此外，经由接管分层组装 ，钻研组以高度可编程的方式扩展了折纸机构的妄想空间以及重大性。因其高可编程性以及可扩展性，钻研组期望所提出的基于折纸的重构措施将增长重大份子零星的睁开 。

▲ Abstract：

The paper-folding mechanism has been widely adopted in building of reconfigurable macroscale systems because of its unique capabilities and advantages in progra妹妹ing variable shapes and stiffness into a structure. However, it has barely been exploited in the construction of molecular-level systems owing to the lack of a suitable design principle, even though various dynamic structures based on DNA self-assembly have been developed. Here we propose a method to harness the paper-folding mechanism to create reconfigurable DNA origami structures. The main idea is to build a reference, planar wireframe structure whose edges follow a crease pattern in paper folding so that it can be folded into various target shapes. We realized several paper-like folding and unfolding patterns using DNA strand displacement with high yield. Orthogonal folding, repeatable folding and unfolding, folding-based microRNA detection and fluorescence signal control were demonstrated. Stimuli-responsive folding and unfolding triggered by pH or light-source change were also possible. Moreover, by employing hierarchical assembly we could expand the design space and complexity of the paper-folding mechanism in a highly progra妹妹able manner. Because of its high progra妹妹ability and scalability, we expect that the proposed paper-folding-based reconfiguration method will advance the development of complex molecular systems.

化学Chemistry

General cross-coupling reactions with adaptive dynamic homogeneous catalysis

具备自顺应动态均相催化的通用交织偶联反映

▲ 作者 ：Indrajit Ghosh, Nikita Shlapakov, Tobias A. Karl, Jonas Düker, Maksim Nikitin, Julia V. Burykina, et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06087-4

▲ 摘要：

交织偶联反映是今世有机分解中最紧张的转化之一
。尽管思考到种种妄想
，当初已经报道的（杂）芳基卤化物以及亲核试剂偶联配体的规模颇为大，但相夹杂合物类此外反映条件差距很大 ，需要重新逐个优化反映条件
。

钻研组介绍了在可见光驱动的氧化复原反映条件下，镍自顺应动态均相催化（AD-HoC）对于通用C（sp2）-（杂）原子偶联反映的催化熏染 。催化系统的自调节性子实现为了交织偶联反映中数十种差距规范亲核试剂的重大分类
。

在可预料的反映条件下，九种差距成键反映（即C（sp2）–S、Se 、N、P、B、O、C（sp三 、sp二 、sp）、Si、Cl）数以百计的分解实例综合证明了这一点。催化反映中间以及条件因退出的亲核试剂或者（假如需要）商业重价胺碱而有所差距。

▲ Abstract ：

Cross-coupling reactions are among the most important transformations in modern organic synthesis. Although the range of reported (het)aryl halides and nucleophile coupling partners is very large considering various protocols, the reaction conditions vary considerably between compound classes, necessitating renewed case-by-case optimization of the reaction conditions. Here we introduce adaptive dynamic homogeneous catalysis (AD-HoC) with nickel under visible-light-driven redox reaction conditions for general C(sp2)–(hetero)atom coupling reactions. The self-adjustive nature of the catalytic system allowed the simple classification of dozens of various classes of nucleophiles in cross-coupling reactions. This is synthetically demonstrated in nine different bond-forming reactions (in this case, C(sp2)–S, Se, N, P, B, O, C(sp3, sp2, sp), Si, Cl) with hundreds of synthetic examples under predictable reaction conditions. The catalytic reaction centre(s) and conditions differ from one another by the added nucleophile, or if required, a co妹妹ercially available inexpensive amine base.

地球迷信Earth Science

Medieval demise of a Himalayan giant su妹妹it induced by mega-landslide

巨型滑坡导致了中世纪时喜马拉雅巨型山峰的崛起

▲ 作者 ：Jér?me Lavé, Cyrielle Guérin, Pierre G. Valla, Valery Guillou, Thomas Rigaudier, Lucilla Benedetti, et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06040-5

▲ 摘要：

尽管人们对于喜马拉雅山脉的侵蚀妨碍了大批钻研
，但尚不清晰喜马拉雅山脉的高峰是若何被侵蚀的。

尽管谷底被冰川实用侵蚀，但侵蚀从冰斗缩短到冰峰线前壁的冰缘历程强度彷佛随着海拔飞腾而急剧着落。这种比力表明，喜马拉雅最高峰侵蚀水平较低，且远低于地域岩石抬升率 ，这激发了人们对于其临时演化的质疑 。

钻研组报道了公元1190年摆布安纳普尔纳地块（尼泊尔中部）爆发的一次重大岩石滑坡的地质证据 ，波及岩石总体积约为23 km3。这一使命使一座古山顶坍塌 
，其高峰可能在海拔8000米以上 。

钻研数据表明
，高海拔侵蚀的一种方式可能是巨型岩石滑坡，导致山脊高程猛然飞腾数百米 ，并最终克制喜马拉雅山峰不可比例的削减 。这种与陡坡以及高笔直无关的侵蚀方式源自峰值基底更大的机械强度
，或者因高海拔永世冻土层的存在。

巨型岩石滑坡也对于景不雅演化以及做作磨难有影响：大批的零碎聚积物可能填满卑劣150多公里的山谷，在一个世纪或者更长的光阴里逾越了喜马拉雅河流的聚积物负荷 。

▲ Abstract：

Despite numerous studies on Himalayan erosion, it is not known how the very high Himalayan peaks erode. Although valley floors are efficiently eroded by glaciers, the intensity of periglacial processes, which erode the headwalls extending from glacial cirques to crest lines, seems to decrease sharply with altitude. This contrast suggests that erosion is muted and much lower than regional rock uplift rates for the highest Himalayan peaks, raising questions about their long-term evolution. Here we report geological evidence for a giant rockslide that occurred around 1190 AD in the Annapurna massif (central Nepal), involving a total rock volume of about 23 km3. This event collapsed a palaeo-su妹妹it, probably culminating above 8,000?m in altitude. Our data suggest that a mode of high-altitude erosion could be mega-rockslides, leading to the sudden reduction of ridge-crest elevation by several hundred metres and ultimately preventing the disproportionate growth of the Himalayan peaks. This erosion mode, associated with steep slopes and high relief, arises from a greater mechanical strength of the peak substratum, probably because of the presence of permafrost at high altitude. Giant rockslides also have implications for landscape evolution and natural hazards: the massive supply of finely crushed sediments can fill valleys more than 150 km farther downstream and overwhelm the sediment load in Himalayan rivers for a century or more.

Safe and just Earth system boundaries

清静公平的地球零星领土

▲ 作者：Johan Rockstr?m, Joyeeta Gupta, Dahe Qin, Steven J. Lade, Jesse F. Abrams, Lauren S. Andersen, et al.

▲ 链接：

https://www.nature.com/articles/s41586-023-06083-8

▲ 摘要 ：

地球零星的晃动性以及复原力与人类福祉不可分割地分割在一起
，但人们普遍意见不到两者间的相互依存性；因此 ，其每一每一被自力看待。

钻研组运用建模以及文献评估来量化全天下以及亚全天下尺度入地气 、生物圈、水以及营养循环以及气溶胶的清静以及公平的地球零星领土（ESBs）
。他们提出ESBs以坚持地球零星的复原力以及晃动性（清静ESBs） ，并最大限度地削减地球零星变更对于人类组成的严轻伤害（对于正义而言需要但非短缺的条件）。更严厉的清静或者公平领土配置了综合清静以及公平ESB。

该钻研服从表明，对于天气以及大气气溶胶负荷，公平思考比清静思考更能约束综合ESBs
。8个全天下量化的清静以及公平ESB中有7个已经越界 ，在全天下逾越一半的陆地面积内至少有两个地域清静以及公平ESB也已经越界
。

钻研组以为 ，该评估为尔后针对于所有人呵护全天下公域提供了一个定量根基 。

▲ Abstract：

The stability and resilience of the Earth system and human well-being are inseparably linked, yet their interdependencies are generally under-recognized; consequently, they are often treated independently. Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, water and nutrient cycles, and aerosols at global and subglobal scales. We propose ESBs for maintaining the resilience and stability of the Earth system (safe ESBs) and minimizing exposure to significant harm to humans from Earth system change (a necessary but not sufficient condition for justice). The stricter of the safe or just boundaries sets the integrated safe and just ESB. Our findings show that justice considerations constrain the integrated ESBs more than safety considerations for climate and atmospheric aerosol loading. Seven of eight globally quantified safe and just ESBs and at least two regional safe and just ESBs in over half of global land area are already exceeded. We propose that our assessment provides a quantitative foundation for safeguarding the global co妹妹ons for all people now and into the future.