Science, 25 AUG 2023, VOL 381, ISSUE 6660
《科学》2023年8月25日，第381卷，6660期
天文学Astronomy
Picoflare jets power the solar wind emerging from a coronal hole on the Sun
皮级耀斑喷流为太阳日冕洞产生的太阳风提供动力
▲ 作者：L. P. Chitta, A. N. Zhukov, D. Berghmans, H. Peter, S. Parenti, S. Mandal, et al.
▲ 链接：
https://www.science.org/doi/full/10.1126/science.ade5801
▲ 摘要：
日冕洞是太阳上磁场线开放的区域，也是太阳风的来源区，但太阳风如何从日冕洞中产生尚不清楚。
研究组用太阳轨道航天器上的极紫外成像仪观测到了一个日冕洞，并发现了几百千米尺度的喷流，持续20到100秒，速度达到每秒约100千米。这些喷流由磁重联驱动，动能在“皮级耀斑”范围内。喷流是间歇性的，但在观测到的日冕洞内分布广泛。
研究组认为，这种皮级耀斑喷流可以产生足够的高温等离子体来维持太阳风，并且太阳风从日冕洞中以小尺度高度间歇性的流出方式出现。
▲ Abstract：
Coronal holes are areas on the Sun with open magnetic field lines. They are a source region of the solar wind, but how the wind emerges from coronal holes is not known. We observed a coronal hole using the Extreme Ultraviolet Imager on the Solar Orbiter spacecraft. We identified jets on scales of a few hundred kilometers, which last 20 to 100 seconds and reach speeds of ~100 kilometers per second. The jets are powered by magnetic reconnection and have kinetic energy in the picoflare range. They are intermittent but widespread within the observed coronal hole. We suggest that such picoflare jets could produce enough high-temperature plasma to sustain the solar wind and that the wind emerges from coronal holes as a highly intermittent outflow at small scales.
材料科学Materials Science
Pneumatic cells toward absolute Gaussian morphing
气动单元助力绝对高斯变形
▲ 作者：Tian Gao, José Bico & Benoît Roman
▲ 链接：
https://www.science.org/doi/full/10.1126/science.adi2997
▲ 摘要：
在地球平面地图上，大陆不可避免地会发生扭曲。反过来，正如高斯在其开创性定理中所述，在两个方向上同时弯曲一块板需要修改面内距离。
虽然具有程序化面内变形的新兴建筑材料能够实现这种形状改变，但需要对局部弯曲进行额外控制，以精确调控所生成三维表面的最终形状。
受单子叶植物叶片中泡状细胞的启发，研究组展示了如何设计平板的内部结构，以在加压时同时编程弯曲和面内扭曲，从而形成目标外壳形状。这些具有可控刚度和快速驱动的表面使用消费级材料制造，为大规模变形机器人应用开辟了道路。
▲ Abstract：
On a flat map of the Earth, continents are inevitably distorted. Reciprocally, curving a plate simultaneously in two directions requires a modification of in-plane distances, as Gauss stated in his seminal theorem. Although emerging architectured materials with programmed in-plane distortions are capable of such shape morphing, an additional control of local bending is required to precisely set the final shape of the resulting three-dimensional surface. Inspired by bulliform cells in leaves of monocotyledon plants, we show how the internal structure of flat panels can be designed to program bending and in-plane distortions simultaneously when pressurized, leading to a targeted shell shape. These surfaces with controlled stiffness and fast actuation are manufactured using consumer-grade materials and open a route to large-scale shape-morphing robotics applications.
化学Chemistry
Ternary NiMo-Bi liquid alloy catalyst for efficient hydrogen production from methane pyrolysis
三元NiMo-Bi液态合金催化剂助力甲烷热解高效制氢
▲ 作者：Luning Chen, Zhigang Song, Shuchen Zhang, Chung-Kai Chang, Yu-Chun Chuang, Xinxing Peng, et al.
▲ 链接：
https://www.science.org/doi/full/10.1126/science.adh8872
▲ 摘要：
甲烷热解（MP）是一种颇具潜力的无二氧化碳制氢技术，只产生固体碳副产物。然而，开发一种高效催化剂来实现在中等温度下的稳定甲烷热解一直极具挑战性。
研究组提出了一种新型高效催化剂，通过添加Mo对Ni-Bi液态合金进行改性来制备三元NiMo-Bi液态合金催化剂（LAC）。
该催化剂表现出相当低的活化能（81.2千焦/摩尔），可在450~800℃温度间实现MP，制氢效率为每克镍每分钟4.05毫升。在800℃下，该催化剂表现出100%的H2选择性和120小时的稳定性。
▲ Abstract：
Methane pyrolysis (MP) is a potential technology forCO2-free hydrogen production that generates only solid carbon by-products. However, developing a highly efficient catalyst for stable methane pyrolysis at a moderate temperature has been challenging. We present a new and highly efficient catalyst created by modifying a Ni-Bi liquid alloy with the addition of Mo to produce a ternary NiMo-Bi liquid alloy catalyst (LAC). This catalyst exhibited a considerably low activation energy of 81.2 kilojoules per mole, which enabled MP at temperatures between 450 and 800 Celsius and a hydrogen generation efficiency of 4.05 ml per gram of nickel per minute. At 800 Celsius, the catalyst exhibited 100% H2 selectivity and 120 hours of stability.
Aminodealkenylation: Ozonolysis and copper catalysis convert C(sp3)–C(sp2) bonds to C(sp3)–N bonds
氨基脱烯化：臭氧分解和铜催化将C(sp3) -C (sp2)键转化为C(sp3) -N键
▲ 作者：Zhiqi He, Jose Antonio Moreno, Manisha Swain, Jason Wu & Ohyun Kwon
▲ 链接：
https://www.science.org/doi/full/10.1126/science.adi4758
▲ 摘要：
烯烃π键胺化已经取得了很大进展。相比之下，相邻C(sp3) -C (sp2) σ键的类似功能化要少见得多。
研究组报道了在温和反应条件下臭氧分解和铜催化如何使烯烃C(sp3) -C (sp2) σ键断裂交叉偶联反应形成新的C(sp3) -N键，并将这种非常规转化应用于激素、药物试剂、肽和核苷的后期修饰。
研究组还将大量易得的萜烯和萜类化合物与氮亲核试剂偶联，以获得人工萜类生物碱和复杂的手性胺。另外还使用商业化学品α-甲基苯乙烯作为甲基化试剂，在一个合成步骤中直接从经典核苷制备甲基化核苷。
该机理研究揭示了一种不寻常的铜离子对协同过程。
▲ Abstract：
Great efforts have been directed toward alkene π bond amination. In contrast, analogous functionalization of the adjacent C(sp3)–C(sp2) σ bonds is much rarer. Here we report how ozonolysis and copper catalysis under mild reaction conditions enable alkene C(sp3)–C(sp2) σ bond–rupturing cross-coupling reactions for the construction of new C(sp3)–N bonds. We have used this unconventional transformation for late-stage modification of hormones, pharmaceutical reagents, peptides, and nucleosides. Furthermore, we have coupled abundantly available terpenes and terpenoids with nitrogen nucleophiles to access artificial terpenoid alkaloids and complex chiral amines. In addition, we applied a commodity chemical, α-methylstyrene, as a methylation reagent to prepare methylated nucleosides directly from canonical nucleosides in one synthetic step. Our mechanistic investigation implicates an unusual copper ion pair cooperative process.
Tandem propane dehydrogenation and surface oxidation catalysts for selective propylene synthesis
串联丙烷脱氢和表面氧化催化剂助力选择性丙烯合成
▲ 作者：Wei Wang, Sai Chen, Chunlei Pei, Ran Luo, Jiachen Sun, Hongbo Song, et al.
▲ 链接：
https://www.science.org/doi/full/10.1126/science.adi3416
▲ 摘要：
丙烷直接脱氢（PDH）制丙烯是一种理想的商业反应，但高度吸热，且受到热力学平衡的严重限制。以水氧化去除氢的途径具有安全性和成本挑战。
研究组将化学循环-选择性氢（H2）燃烧和PDH与多功能钒酸铁-氧化钒（FeVO4-VOx）氧化还原催化剂偶联。良好分散在氧化铝（Al2O3）上的VOx提供了脱氢位点，毗邻的纳米级FeVO3充当后续H2燃烧的氧载体。在550℃下实现了丙烷转化率为42.7%，丙烯选择性为81.3%，FeVO4再氧化在200次化学循环后仍保持稳定。
基于催化实验、光谱表征和理论计算，研究组提出了一种氢溢出介导的耦合机制。在VOx位点产生的氢物种迁移到邻近的FeVO4进行燃烧，从而使PDH向丙烯转移。脱氢和燃烧位点间的“毗邻度”有利于这种机制。
▲ Abstract：
Direct propane dehydrogenation (PDH) to propylene is a desirable commercial reaction but is highly endothermic and severely limited by thermodynamic equilibrium. Routes that oxidatively remove hydrogen as water have safety and cost challenges. We coupled chemical looping–selective hydrogen (H2) combustion and PDH with multifunctional ferric vanadate–vanadium oxide (FeVO4-VOx) redox catalysts. Well-dispersed VOx supported on aluminum oxide (Al2O3) provides dehydrogenation sites, and adjacent nanoscale FeVO4 acts as an oxygen carrier for subsequent H2 combustion. We achieved an integral performance of 81.3% propylene selectivity at 42.7% propane conversion at 550°C for 200 chemical looping cycles for the reoxidization of FeVO4. Based on catalytic experiments, spectroscopic characterization, and theory calculations, we propose a hydrogen spillover–mediated coupling mechanism. The hydrogen species generated at the VOx sites migrated to adjacent FeVO4 for combustion, which shifted PDH toward propylene. This mechanism is favored by the proximity between the dehydrogenation and combustion sites.
地球科学Earth Science
Action needed to make carbon offsets from forest conservation work for climate change mitigation
亟需采取行动使森林保护工作产生的碳抵消用于减缓气候变化
▲ 作者：Thales A. P. West, Sven Wunder, Erin O. Sills, Jan Börner, Sami W. Rifai, Alexandra N. Neidermeier, et al.
▲ 链接：
https://www.science.org/doi/full/10.1126/science.ade3535
▲ 摘要：
自愿避免毁林项目的碳抵消是根据与事前毁林基线相关的绩效产生的。
研究组使用因果推断的综合控制方法对三大洲六个国家的26个此类项目点的影响进行了分析。结果发现大多数项目并没有显著减少森林砍伐。而对于那些减少了森林砍伐的项目，减少幅度也远远低于声称的数额。
根据控制区观察到的毁林情况，这反映了项目事前基线和事后反事实之间的差异。为碳抵消干预措施构建毁林基线的方法急需修订，以便正确地将减少的毁林归因于项目，从而既保持对森林保护的激励，又保持全球碳核算的完整性。
▲ Abstract：
Carbon offsets from voluntary avoided-deforestation projects are generated on the basis of performance in relation to ex ante deforestation baselines. We examined the effects of 26 such project sites in six countries on three continents using synthetic control methods for causal inference. We found that most projects have not significantly reduced deforestation. For projects that did, reductions were substantially lower than claimed. This reflects differences between the project ex ante baselines and ex post counterfactuals according to observed deforestation in control areas. Methodologies used to construct deforestation baselines for carbon offset interventions need urgent revisions to correctly attribute reduced deforestation to the projects, thus maintaining both incentives for forest conservation and the integrity of global carbon accounting.
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