編譯 | 未玖
Science, 9 DECEMBER 2022, VOL 378, ISSUE 6624
《科學》2022年12月9日，第378卷，6624期
天文學Astronomy
Aqueous alteration processes in Jezero crater, Mars?implications for organic geochemistry
火星Jezero隕石坑的水蝕變過程-對有機地球化學的影響
▲ 作者：EVA L. SCHELLER, JOSEPH RAZZELL HOLLIS, EMILY L. CARDARELLI, ANDREW STEELE, LUTHER W. BEEGLE, ROHIT BHARTIA, ET AL.
▲ 鏈接：
https://www.science.org/doi/10.1126/science.abo5204
▲ 摘要：
2021年2月，“毅力”號火星車在火星Jezero隕石坑著陸。
研究組通過用拉曼和發光掃描宜居環境有機物和化學品（SHERLOC）的儀器對隕石坑內的三種巖石進行深紫外拉曼和熒光光譜分析。他們確定了不同時期兩種不同古代水環境的證據。
與液態水的反應在富橄欖石的火成巖中形成碳酸鹽。巖石中存在硫酸鹽-高氯酸鹽混合物，可能由巖石被鹽水后期改性形成。在這些巖石中發現了與芳香有機化合物一致的熒光特征，保存在與兩種水環境相關的礦物中。
▲ Abstract：
The Perseverance rover landed in Jezero crater, Mars in February 2021. We used the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument to perform deep ultraviolet Raman and fluorescence spectroscopy of three rocks within the crater. We identify evidence for two distinct ancient aqueous environments at different times. Reactions with liquid water formed carbonates in an olivine-rich igneous rock. A sulfate-perchlorate mixture is present in the rocks, probably formed by later modifications of the rocks by brine. Fluorescence signatures consistent with aromatic organic compounds occur throughout these rocks, preserved in minerals related to both aqueous environments.
物理學Physics
Giant electric field–induced strain in lead-free piezoceramics
無鉛壓電陶瓷中的巨大場致應變
▲ 作者：GENG HUANGFU, KUN ZENG, BINQUAN WANG, JIE WANG, ZHENGQIAN FU, FANGFANG XU, ET AL.
▲ 鏈接：
https://www.science.org/doi/10.1126/science.ade2964
▲ 摘要：
壓電致動器以其快速響應和精確位移在許多行業中都不可或缺。大多數商用壓電致動器含有鉛，對環境構成了威脅。
研究組通過常規固相反應法合成了無需任何后處理的鍶（Sr）摻雜(K,Na)NbO3無鉛壓電陶瓷，獲得了巨大應變（1.05%）和大信號的壓電應變系數（2100 pm/V）。產生超高電應變的基本機制是缺陷偶極子和疇切換之間的相互作用。
該無鉛壓電陶瓷在20 kV/cm下的抗疲勞性能、熱穩定性和應變值（0.25%）可與商用Pb(Zr,Ti)O3基陶瓷相媲美甚至更優，顯示出巨大的實際應用潛力。該材料有望為壓電制動器提供一種簡單組成的無鉛替代品，并為高性能壓電設計提供一個范例。
▲ Abstract：
Piezoelectric actuators are indispensable over a wide range of industries for their fast response and precise displacement. Most commercial piezoelectric actuators contain lead, posing environmental challenges. We show that a giant strain (1.05%) and a large-signal piezoelectric strain coefficient (2100 picometer/volt) are achieved in strontium (Sr)–doped (K,Na)NbO3 lead-free piezoceramics, being synthesized by the conventional solid-state reaction method without any post treatment. The underlying mechanism responsible for the ultrahigh electrostrain is the interaction between defect dipoles and domain switching. The fatigue resistance, thermal stability, and strain value (0.25%) at 20 kilovolt/centimeter are comparable with or better than those of commercial Pb(Zr,Ti)O3-based ceramics, showing great potential for practical applications. This material may provide a lead-free alternative with a simple composition for piezoelectric actuators and a paradigm for the design of high-performance piezoelectrics.
信息科學Information Science
Competition-level code generation with AlphaCode
AlphaCode競賽級別代碼生成
▲ 作者：YUJIA LI, DAVID CHOI, JUNYOUNG CHUNG, NATE KUSHMAN, JULIAN SCHRITTWIESER, RéMI LEBLOND, ET AL.
▲ 鏈接：
https://www.science.org/doi/10.1126/science.abq1158
▲ 摘要：
編程是一種強大而普遍的解決問題的工具。能夠幫助程序員甚至自己生成程序的系統可以使編程更高效、更易訪問。最近基于轉換器的神經網絡模型顯示出令人驚艷的代碼生成能力，但在需要解決問題技能的更復雜任務（如競爭性編程問題）上仍表現不佳。
研究組介紹了AlphaCode，這是一個用于代碼生成的系統，在Codeforces平臺上最近的編程競賽模擬評估中平均排名前54.3%。
AlphaCode通過使用經過專門訓練、基于轉換器的網絡生成數百萬個不同程序，然后對這些程序進行過濾和聚類，最多只提交10個，從而高效解決問題。該結果標志著人工智能系統首次在編程競賽中表現出色。
▲ Abstract：
Programming is a powerful and ubiquitous problem-solving tool. Systems that can assist programmers or even generate programs themselves could make programming more productive and accessible. Recent transformer-based neural network models show impressive code generation abilities yet still perform poorly on more complex tasks requiring problem-solving skills, such as competitive programming problems. Here, we introduce AlphaCode, a system for code generation that achieved an average ranking in the top 54.3% in simulated evaluations on recent programming competitions on the Codeforces platform. AlphaCode solves problems by generating millions of diverse programs using specially trained transformer-based networks and then filtering and clustering those programs to a maximum of just 10 submissions. This result marks the first time an artificial intelligence system has performed competitively in programming competitions.
材料科學Materials Science
Liquid metal synthesis solvents for metallic crystals
在液態金屬溶劑中合成金屬晶體
▲ 作者：SHUHADA A. IDRUS-SAIDI, JIANBO TANG, STEPHANIE LAMBIE, JIALUO HAN, MOHANNAD MAYYAS, MOHAMMAD B. GHASEMIAN, ET AL.
▲ 鏈接：
https://www.science.org/doi/10.1126/science.abm2731
▲ 摘要：
在自然界中，雪花冰晶排列成各種對稱的六邊結構。當鋅（Zn）在液態鎵（Ga）中溶解并結晶時，研究組展示了這一類比。利用低熔點Ga作為“金屬溶劑”，合成了一系列片狀鋅晶體。
研究組利用電毛細管調制和真空過濾相結合的方法降低液態金屬溶劑的表面張力，從液態金屬溶劑中提取出這些金屬晶體。液態金屬生長的晶體具有高度形態多樣性和持久對稱性。
將這一概念擴展到其他單一和二元金屬溶質和Ga基溶劑，通過界面穩定性的從頭算模擬闡明了生長機制。該策略為從液態金屬溶劑中創建高結晶、形狀可控的金屬或多金屬精細結構提供了通用路徑。
▲ Abstract：
In nature, snowflake ice crystals arrange themselves into diverse symmetrical six-sided structures. We show an analogy of this when zinc (Zn) dissolves and crystallizes in liquid gallium (Ga). The low-melting-temperature Ga is used as a “metallic solvent” to synthesize a range of flake-like Zn crystals. We extract these metallic crystals from the liquid metal solvent by reducing its surface tension using a combination of electrocapillary modulation and vacuum filtration. The liquid metal–grown crystals feature high morphological diversity and persistent symmetry. The concept is expanded to other single and binary metal solutes and Ga-based solvents, with the growth mechanisms elucidated through ab initio simulation of interfacial stability. This strategy offers general routes for creating highly crystalline, shape-controlled metallic or multimetallic fine structures from liquid metal solvents.
Designing better electrolytes
設計更好的電解質
▲ 作者：Y. SHIRLEY MENG, VENKAT SRINIVASAN, AND KANG XU
▲ 鏈接：
https://www.science.org/doi/10.1126/science.abq3750
▲ 摘要：
電解質和相關界面相構成了支持新興電池化學組成的關鍵組件，有望提供誘人的能量，但涉及嚴苛的相和結構復雜性。設計更好的電解質和界面相是這些電池成功的關鍵。
作為與設備中其他所有組件連接的唯一組件，電解質必須同時滿足多個標準。這些需求包括在電極之間絕緣電子的同時傳輸離子，并保持對極端化學性質電極（強氧化陰極和強還原陽極）的穩定性。
在大多數先進的電池中，兩個電極在遠遠超過電解質熱力學穩定性極限的電位下工作，因此必須通過電解質和電極之間犧牲反應形成的界面在動力學上實現其穩定性。
▲ Abstract：
Electrolytes and the associated interphases constitute the critical components to support the emerging battery chemistries that promise tantalizing energy but involve drastic phase and structure complications. Designing better electrolytes and interphases holds the key to the success of these batteries. As the only component that interfaces with every other component in the device, an electrolyte must satisfy multiple criteria simultaneously. These include transporting ions while insulating electrons between the electrodes and maintaining stability against electrodes of extreme chemical natures: the strongly oxidative cathode and the strongly reductive anode. In most advanced batteries, the two electrodes operate at potentials far beyond the thermodynamic stability limits of electrolytes, so the stability therein has to be realized kinetically through an interphase formed from the sacrificial reactions between electrolyte and electrodes.
化學Chemistry
Catalytic asymmetric C–H insertion reactions of vinyl carbocations
乙烯基碳正離子的催化不對稱C-H插入反應
▲ 作者：SEPAND K. NISTANAKI, CHLOE G. WILLIAMS, BENJAMIN WIGMAN, JonATHAN J. WONG, BRITTANY C. HAAS, STASIK POPOV, ET AL.
▲ 鏈接：
https://www.science.org/doi/10.1126/science.ade5320
▲ 摘要：
從藥物的制備到天然產物的酶促構建，碳正離子是分子合成的核心。盡管這些活性中間體在自然界中具有立體選擇性，但利用合成催化劑對碳正離子進行對映體控制仍頗具挑戰性。
許多共振穩定的三配位碳正離子，如亞胺和氧代碳鎓離子，已被應用于催化對映選擇性反應。然而，它們的雙配位對應物（芳基和乙烯基碳正離子）卻沒有，盡管它們在化學合成中有新興用途。
研究組報道了一種高對映選擇性的乙烯基碳正離子碳-氫（C-H）插入反應，由亞氨基二磷酸亞胺酯有機催化劑來實現。
這類催化劑的活性位點限制不僅能夠有效地控制對映體，還擴大了乙烯基正離子C-H插入化學的范圍，從而拓寬了這種無過渡金屬C(sp3)–H功能化平臺的用途。
▲ Abstract：
From the preparation of pharmaceuticals to enzymatic construction of natural products, carbocations are central to molecular synthesis. Although these reactive intermediates are engaged in stereoselective processes in nature, exerting enantiocontrol over carbocations with synthetic catalysts remains challenging. Many resonance-stabilized tricoordinated carbocations, such as iminium and oxocarbenium ions, have been applied in catalytic enantioselective reactions. However, their dicoordinated counterparts (aryl and vinyl carbocations) have not, despite their emerging utility in chemical synthesis. We report the discovery of a highly enantioselective vinyl carbocation carbon–hydrogen (C–H) insertion reaction enabled by imidodiphosphorimidate organocatalysts. Active site confinement featured in this catalyst class not only enables effective enantiocontrol but also expands the scope of vinyl cation C–H insertion chemistry, which broadens the utility of this transition metal–free C(sp3)–H functionalization platform.
