《自然》（20221222出版）一周论文导读

编译 | 未玖

Nature, 22 December 2022, VOL 612, ISSUE 7941

《自然》2022年12月22日，第612卷，7941期

天文学Astronomy

Vela pulsar wind nebula X-rays are polarized to near the synchrotron limit

船帆座脉冲星风星云X射线偏振至接近同步加速器极限

▲ 作者：Fei Xie, Alessandro Di Marco, Fabio La Monaca, Kuan Liu, Fabio Muleri, Niccolò Bucciantini, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05476-5

▲ 摘要：

脉冲星风星云由相对论电子和正电子外流在激波前沿撞击周围超新星残骸或星际介质而形成。船帆座脉冲星风星云由一颗年轻的脉冲星（B0833-45，年龄11000年）提供动力，位于一个被称为船帆座X的扩展结构内，该结构本身就位于超新星残骸内部。

之前的X射线观测显示了两个突出的弧，被喷流和反喷流一分为二。射电图显示，星云外部区域的线性偏振度高达60%。

研究组报道了对星云内部部分的X射线观测，那里的偏振度在前沿可超过60%，接近同步加速器辐射所能产生的理论极限。他们推断，与超新星残骸的情况相反，脉冲星风星云中的电子在高度均匀的磁场中被加速，且很少或没有湍流。

▲ Abstract：

Pulsar wind nebulae are formed when outflows of relativistic electrons and positrons hit the surrounding supernova remnant or interstellar medium at a shock front. The Vela pulsar wind nebula is powered by a young pulsar (B0833-45, aged 11,000 years) and located inside an extended structure called Vela X, which is itself inside the supernova remnant. Previous X-ray observations revealed two prominent arcs that are bisected by a jet and counter jet. Radio maps have shown high linear polarization of 60% in the outer regions of the nebula. Here we report an X-ray observation of the inner part of the nebula, where polarization can exceed 60% at the leading edge—approaching the theoretical limit of what can be produced by synchrotron emission. We infer that, in contrast with the case of the supernova remnant, the electrons in the pulsar wind nebula are accelerated with little or no turbulence in a highly uniform magnetic field.

材料科学Materials Science

A membrane-based seawater electrolyser for hydrogen generation

用于制氢的膜基海水电解槽

▲ 作者：Heping Xie, Zhiyu Zhao, Tao Liu, Yifan Wu, Cheng Lan, Wenchuan Jiang, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05379-5

▲ 摘要：

使用可再生能源为输入的电化学盐水电解是大规模生产绿氢的一种非常理想和可持续的方法；然而，由于海水复杂成分引发的电极副反应和腐蚀问题，其实际可行性受到耐久性不足的严重挑战。尽管利用聚阴离子涂层来抑制氯离子腐蚀或制造高选择性电催化剂的催化剂工程已被广泛开发，并取得了一定成功，但在实际应用中仍远不能令人满意。

通过使用预脱盐工艺间接分离海水可避免副反应和腐蚀问题，但需要额外的能源投入，在经济上不具有吸引力。此外，独立庞大的海水淡化系统使海水电解系统在尺寸上缺乏灵活性。

研究组提出了一种直接海水电解制氢的方法，从根本上解决了副反应和腐蚀问题。演示系统在实际应用条件下，在250 mA/cm2的电流密度下稳定运行了3200多个小时，没有出现故障。

该策略以类似淡水裂解的方式实现了高效、尺寸灵活、可扩展的海水直接电解，且运行成本没有明显增加，具有很高的实际应用潜力。重要的是，这种结构和机制有望进一步应用于同时进行水基废水处理、资源回收以及一步制氢。

▲ Abstract：

Electrochemical saline water electrolysis using renewable energy as input is a highly desirable and sustainable method for the mass production of green hydrogen; however, its practical viability is seriously challenged by insufficient durability because of the electrode side reactions and corrosion issues arising from the complex components of seawater. Although catalyst engineering using polyanion coatings to suppress corrosion by chloride ions or creating highly selective electrocatalysts has been extensively exploited with modest success, it is still far from satisfactory for practical applications. Indirect seawater splitting by using a pre-desalination process can avoid side-reaction and corrosion problems, but it requires additional energy input, making it economically less attractive. In addition, the independent bulky desalination system makes seawater electrolysis systems less flexible in terms of size. Here we propose a direct seawater electrolysis method for hydrogen production that radically addresses the side-reaction and corrosion problems. A demonstration system was stably operated at a current density of 250 milliamperes per square centimetre for over 3,200 hours under practical application conditions without failure. This strategy realizes efficient, size-flexible and scalable direct seawater electrolysis in a way similar to freshwater splitting without a notable increase in operation cost, and has high potential for practical application. Importantly, this configuration and mechanism promises further applications in simultaneous water-based effluent treatment and resource recovery and hydrogen generation in one step.

Synthesis-on-substrate of quantum dot solids

量子点固体的基底合成

▲ 作者：Yuanzhi Jiang, Changjiu Sun, Jian Xu, Saisai Li, Minghuan Cui, Xinliang Fu, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05486-3

▲ 摘要：

目前人们已在绿色和红色波长中都实现了外部量子效率超过20%的钙钛矿发光二极管（PeLEDs）；然而，蓝光发射的PeLED的性能落后。超小尺寸CsPbBr3量子点是实现高效稳定蓝光PeLEDs颇有前途的候选物，尽管事实证明合成超小尺寸CsPbBr3量子点的单分散溶液挑战性极大，且在浇筑成固体薄膜时难以保持其液相特性。

研究组报道了适当耦合、单分散、超小尺寸钙钛矿量子点薄膜在基底上的直接合成。他们开发了配体结构，能够在基于薄膜的合成过程中控制量子点的尺寸、单分散性和耦合性。

配体上的头基（较高静电势的一侧）提供了空间位阻，抑制了层状钙钛矿的形成。尾端（较低静电势的一侧）使用卤素取代基进行修饰，以增加表面结合能，将生成的晶粒约束到量子限域尺寸。

该方法实现了高单分散性（半峰全宽=23 nm，发射中心为478 nm）和强耦合的结合。实验结果表明，蓝光PeLEDs的外部量子效率在480 nm处为18%，在465 nm处为10%，据研究组所知，这分别为现有钙钛矿蓝光LED最高值的1.5倍和2倍。

▲ Abstract：

Perovskite light-emitting diodes (PeLEDs) with an external quantum efficiency exceeding 20% have been achieved in both green and red wavelengths; however, the performance of blue-emitting PeLEDs lags behind. Ultrasmall CsPbBr3 quantum dots are promising candidates with which to realize efficient and stable blue PeLEDs, although it has proven challenging to synthesize a monodispersed population of ultrasmall CsPbBr3 quantum dots, and difficult to retain their solution-phase properties when casting into solid films. Here we report the direct synthesis-on-substrate of films of suitably coupled, monodispersed, ultrasmall perovskite QDs. We develop ligand structures that enable control over the quantum dots’ size, monodispersity and coupling during film-based synthesis. A head group (the side with higher electrostatic potential) on the ligand provides steric hindrance that suppresses the formation of layered perovskites. The tail (the side with lower electrostatic potential) is modified using halide substitution to increase the surface binding affinity, constraining resulting grains to sizes within the quantum confinement regime. The approach achieves high monodispersity (full-width at half-maximum = 23 nm with emission centred at 478 nm) united with strong coupling. We report as a result blue PeLEDs with an external quantum efficiency of 18% at 480 nm and 10% at 465 nm, to our knowledge the highest reported among perovskite blue LEDs by a factor of 1.5 and 2, respectively.

Additive manufacturing of micro-architected metals via hydrogel infusion

水凝胶灌注实现微结构金属的增材制造

▲ 作者：Max A. Saccone, Rebecca A. Gallivan, Kai Narita, Daryl W. Yee & Julia R. Greer

▲ 链接：

https://www.nature.com/articles/s41586-022-05433-2

▲ 摘要：

金属增材制造（AM）能够生产高价值和高性能部件，应用范围从航空航天到生物医学领域。逐层制造绕过了传统金属加工技术的几何限制，使拓扑优化的零件能够快速有效地制造。现有的AM技术依赖于热引发熔化或烧结来进行零件成型，这是一种昂贵且材料有限的工艺。

研究组报道了一种通过vat光聚合（VP）生产具有微尺度分辨率金属和合金的AM技术。将三维结构的水凝胶注入金属前体，然后煅烧和还原，将水凝胶支架转化为微型化的金属复制品。这种方法代表了VP的范式转变；只有在结构制造完成后才选择材料。

与现有VP策略不同，该策略在打印过程中将目标材料或前驱体结合到感光树脂中，不需要对不同材料的树脂和固化参数进行重新优化，从而实现了快速迭代、成分调整和制造多材料的能力。

研究组演示了临界尺寸约为40μm、使用传统工艺难以制造的金属AM。这种水凝胶衍生金属具有高度孪晶的微结构和异常高的硬度，为制造先进金属微材料提供了一条途径。

▲ Abstract：

Metal additive manufacturing (AM) enables the production of high value and high performance components with applications from aerospace to biomedical fields. Layer-by-layer fabrication circumvents the geometric limitations of traditional metalworking techniques, allowing topologically optimized parts to be made rapidly and efficiently. Existing AM techniques rely on thermally initiated melting or sintering for part shaping, a costly and material-limited proces. We report an AM technique that produces metals and alloys with microscale resolution via vat photopolymerization (VP). Three-dimensional-architected hydrogels are infused with metal precursors, then calcined and reduced to convert the hydrogel scaffolds into miniaturized metal replicas. This approach represents a paradigm shift in VP; the material is selected only after the structure is fabricated. Unlike existing VP strategies, which incorporate target materials or precursors into the photoresin during printing, our method does not require reoptimization of resins and curing parameters for different materials, enabling quick iteration, compositional tuning and the ability to fabricate multimaterials. We demonstrate AM of metals with critical dimensions of approximately 40 µm that are challenging to fabricate by using conventional processes. Such hydrogel-derived metals have highly twinned microstructures and unusually high hardness, providing a pathway to create advanced metallic micromaterials.

地球科学Earth Science

Strong cloud–circulation coupling explains weak trade cumulus feedback

强云-环流耦合解释了弱信风积云反馈

▲ 作者：Raphaela Vogel, Anna Lea Albright, Jessica Vial, Geet George, Bjorn Stevens & Sandrine Bony

▲ 链接：

https://www.nature.com/articles/s41586-022-05364-y

▲ 摘要：

信风区域的浅积云通过反射太阳辐射来冷却地球。信风积云对气候变化的响应是气候预测中的一个关键不确定性因素。气候模型中的信风积云反馈受云底附近云分数变化的控制，高气候敏感度模型表明，由于对流层下层混合增加，云底云量大幅减少。

研究组表明来自EUREC4A（阐明云-环流耦合在气候中的作用）实地活动的新观测结果反驳了这种混合-干燥假说。他们发现混合对云量的动态增加超过了湿度的热力学控制。由于中尺度运动和夹带速率对混合可变性有同等贡献，但对湿度有相反影响，所以混合不会使云干燥。

混合和云量的量级、变率和耦合在气候模式之间以及与EUREC4A观测值之间存在显著差异。具有大量信风积云反馈的模型倾向于夸大云量而非混合对相对湿度的依赖，还夸大了云量的可变性。

研究组的观测分析使得具有大量正反馈的模型不可信，且在过程尺度上支持和解释了弱信风累积反馈。因此，该研究结果反驳了高气候敏感度的重要证据。

▲ Abstract：

Shallow cumulus clouds in the trade-wind regions cool the planet by reflecting solar radiation. The response of trade cumulus clouds to climate change is a key uncertainty in climate projections. Trade cumulus feedbacks in climate models are governed by changes in cloud fraction near cloud base, with high-climate-sensitivity models suggesting a strong decrease in cloud-base cloudiness owing to increased lower-tropospheric mixing. Here we show that new observations from the EUREC4A (Elucidating the role of cloud-circulation coupling in climate) field campaign refute this mixing-desiccation hypothesis. We find the dynamical increase of cloudiness through mixing to overwhelm the thermodynamic control through humidity. Because mesoscale motions and the entrainment rate contribute equally to variability in mixing but have opposing effects on humidity, mixing does not desiccate clouds. The magnitude, variability and coupling of mixing and cloudiness differ markedly among climate models and with the EUREC4A observations. Models with large trade cumulus feedbacks tend to exaggerate the dependence of cloudiness on relative humidity as opposed to mixing and also exaggerate variability in cloudiness. Our observational analyses render models with large positive feedbacks implausible and both support and explain at the process scale a weak trade cumulus feedback. Our findings thus refute an important line of evidence for a high climate sensitivity.

Global hotspots of salt marsh change and carbon emissions

盐沼变化与碳排放的全球热点

▲ 作者：Anthony D. Campbell, Lola Fatoyinbo, Liza Goldberg & David Lagomasino

▲ 链接：

https://www.nature.com/articles/s41586-022-05355-z

▲ 摘要：

盐沼提供碳封存、海岸保护、海平面上升（SLR）适应和休养等生态系统服务。SLR、风暴事件、排水和红树林侵蚀是盐沼损失的已知驱动因素。然而，全球盐沼范围变化的幅度和位置仍不确定。

研究组对2000~2019年的陆地卫星图像进行了全球系统变化分析，以量化盐沼生态系统的损失、收益和恢复，然后估计这些变化对蓝碳储量的影响。2000~2019年，全球盐沼净损失率为0.28%每年，相当于新加坡国土面积的两倍（719 km2）。

全球净损失导致了2000~2019年间16.3（0.4~33.2，90%置信区间）Tg CO2e/年的排放量和0.045（−0.14~0.115）Tg CO2e/年的碳埋藏减少。由于飓风和海岸侵蚀，俄罗斯和美国的盐沼损失在全球占64%。该研究结果强调了盐沼系统对气候变化的脆弱性，如SLR和风暴气旋的加剧。

▲ Abstract：

Salt marshes provide ecosystem services such as carbon sequestration, coastal protection, sea-level-rise (SLR) adaptation and recreation. SLR, storm events, drainage and mangrove encroachment are known drivers of salt marsh loss. However, the global magnitude and location of changes in salt marsh extent remains uncertain. Here we conduct a global and systematic change analysis of Landsat satellite imagery from the years 2000–2019 to quantify the loss, gain and recovery of salt marsh ecosystems and then estimate the impact of these changes on blue carbon stocks. We show a net salt marsh loss globally, equivalent to an area double the size of Singapore (719 km2), with a loss rate of 0.28% year−1 from 2000 to 2019. Net global losses resulted in 16.3 (0.4–33.2, 90% confidence interval) Tg CO2e year−1 emissions from 2000 to 2019 and a 0.045 (−0.14–0.115) Tg CO2e year−1 reduction of carbon burial. Russia and the USA accounted for 64% of salt marsh losses, driven by hurricanes and coastal erosion. Our findings highlight the vulnerability of salt marsh systems to climatic changes such as SLR and intensification of storms and cyclones.