原文地址：http://news.sciencenet.cn/htmlnews/2023/8/507295.shtm
編譯 | 未玖
Science, 25 AUG 2023, VOL 381, ISSUE 6660
《科學》2023年8月25日，第381卷，6660期
天文學Astronomy
Picoflare jets power the solar wind emerging from a coronal hole on the Sun
皮級耀斑噴流為太陽日冕洞產生的太陽風提供動力
▲ 作者：L. P. Chitta, A. N. Zhukov, D. Berghmans, H. Peter, S. Parenti, S. Mandal, et al.
▲ 鏈接：
https://www.science.org/doi/full/10.1126/science.ade5801
▲ 摘要：
日冕洞是太陽上磁場線開放的區域，也是太陽風的來源區，但太陽風如何從日冕洞中產生尚不清楚。
研究組用太陽軌道航天器上的極紫外成像儀觀測到了一個日冕洞，并發現了幾百千米尺度的噴流，持續20到100秒，速度達到每秒約100千米。這些噴流由磁重聯驅動，動能在“皮級耀斑”范圍內。噴流是間歇性的，但在觀測到的日冕洞內分布廣泛。
研究組認為，這種皮級耀斑噴流可以產生足夠的高溫等離子體來維持太陽風，并且太陽風從日冕洞中以小尺度高度間歇性的流出方式出現。
▲ 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.
材料科學Materials Science
Pneumatic cells toward absolute Gaussian morphing
氣動單元助力絕對高斯變形
▲ 作者：Tian Gao, José Bico & Beno?t Roman
▲ 鏈接：
https://www.science.org/doi/full/10.1126/science.adi2997
▲ 摘要：
在地球平面地圖上，大陸不可避免地會發生扭曲。反過來，正如高斯在其開創性定理中所述，在兩個方向上同時彎曲一塊板需要修改面內距離。
雖然具有程序化面內變形的新興建筑材料能夠實現這種形狀改變，但需要對局部彎曲進行額外控制，以精確調控所生成三維表面的最終形狀。
受單子葉植物葉片中泡狀細胞的啟發，研究組展示了如何設計平板的內部結構，以在加壓時同時編程彎曲和面內扭曲，從而形成目標外殼形狀。這些具有可控剛度和快速驅動的表面使用消費級材料制造，為大規模變形機器人應用開辟了道路。
▲ 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.
化學Chemistry
Ternary NiMo-Bi liquid alloy catalyst for efficient hydrogen production from methane pyrolysis
三元NiMo-Bi液態合金催化劑助力甲烷熱解高效制氫
▲ 作者：Luning Chen, Zhigang Song, Shuchen Zhang, Chung-Kai Chang, Yu-Chun Chuang, Xinxing Peng, et al.
▲ 鏈接：
https://www.science.org/doi/full/10.1126/science.adh8872
▲ 摘要：
甲烷熱解（MP）是一種頗具潛力的無二氧化碳制氫技術，只產生固體碳副產物。然而，開發一種高效催化劑來實現在中等溫度下的穩定甲烷熱解一直極具挑戰性。
研究組提出了一種新型高效催化劑，通過添加Mo對Ni-Bi液態合金進行改性來制備三元NiMo-Bi液態合金催化劑（LAC）。
該催化劑表現出相當低的活化能（81.2千焦/摩爾），可在450~800℃溫度間實現MP，制氫效率為每克鎳每分鐘4.05毫升。在800℃下，該催化劑表現出100%的H2選擇性和120小時的穩定性。
▲ 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
氨基脫烯化：臭氧分解和銅催化將C(sp3) -C (sp2)鍵轉化為C(sp3) -N鍵
▲ 作者：Zhiqi He, Jose Antonio Moreno, Manisha Swain, Jason Wu & Ohyun Kwon
▲ 鏈接：
https://www.science.org/doi/full/10.1126/science.adi4758
▲ 摘要：
烯烴π鍵胺化已經取得了很大進展。相比之下，相鄰C(sp3) -C (sp2) σ鍵的類似功能化要少見得多。
研究組報道了在溫和反應條件下臭氧分解和銅催化如何使烯烴C(sp3) -C (sp2) σ鍵斷裂交叉偶聯反應形成新的C(sp3) -N鍵，并將這種非常規轉化應用于激素、藥物試劑、肽和核苷的后期修飾。
研究組還將大量易得的萜烯和萜類化合物與氮親核試劑偶聯，以獲得人工萜類生物堿和復雜的手性胺。另外還使用商業化學品α-甲基苯乙烯作為甲基化試劑，在一個合成步驟中直接從經典核苷制備甲基化核苷。
該機理研究揭示了一種不尋常的銅離子對協同過程。
▲ 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
串聯丙烷脫氫和表面氧化催化劑助力選擇性丙烯合成
▲ 作者：Wei Wang, Sai Chen, Chunlei Pei, Ran Luo, Jiachen Sun, Hongbo Song, et al.
▲ 鏈接：
https://www.science.org/doi/full/10.1126/science.adi3416
▲ 摘要：
丙烷直接脫氫（PDH）制丙烯是一種理想的商業反應，但高度吸熱，且受到熱力學平衡的嚴重限制。以水氧化去除氫的途徑具有安全性和成本挑戰。
研究組將化學循環-選擇性氫（H2）燃燒和PDH與多功能釩酸鐵-氧化釩（FeVO4-VOx）氧化還原催化劑偶聯。良好分散在氧化鋁（Al2O3）上的VOx提供了脫氫位點，毗鄰的納米級FeVO3充當后續H2燃燒的氧載體。在550℃下實現了丙烷轉化率為42.7%，丙烯選擇性為81.3%，FeVO4再氧化在200次化學循環后仍保持穩定。
基于催化實驗、光譜表征和理論計算，研究組提出了一種氫溢出介導的耦合機制。在VOx位點產生的氫物種遷移到鄰近的FeVO4進行燃燒，從而使PDH向丙烯轉移。脫氫和燃燒位點間的“毗鄰度”有利于這種機制。
▲ 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.
地球科學Earth Science
Action needed to make carbon offsets from forest conservation work for climate change mitigation
亟需采取行動使森林保護工作產生的碳抵消用于減緩氣候變化
▲ 作者：Thales A. P. West, Sven Wunder, Erin O. Sills, Jan B?rner, Sami W. Rifai, Alexandra N. Neidermeier, et al.
▲ 鏈接：
https://www.science.org/doi/full/10.1126/science.ade3535
▲ 摘要：
自愿避免毀林項目的碳抵消是根據與事前毀林基線相關的績效產生的。
研究組使用因果推斷的綜合控制方法對三大洲六個國家的26個此類項目點的影響進行了分析。結果發現大多數項目并沒有顯著減少森林砍伐。而對于那些減少了森林砍伐的項目，減少幅度也遠遠低于聲稱的數額。
根據控制區觀察到的毀林情況，這反映了項目事前基線和事后反事實之間的差異。為碳抵消干預措施構建毀林基線的方法急需修訂，以便正確地將減少的毀林歸因于項目，從而既保持對森林保護的激勵，又保持全球碳核算的完整性。
▲ Abstract：