編譯 | 未玖
Science, 9 DECEMBER 2022, VOL 378, ISSUE 6624
《科學(xué)》2022年12月9日，第378卷，6624期
天文學(xué)Astronomy
Aqueous alteration processes in Jezero crater, Mars?implications for organic geochemistry
火星Jezero隕石坑的水蝕變過(guò)程-對(duì)有機(jī)地球化學(xué)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(hào)火星車在火星Jezero隕石坑著陸。
研究組通過(guò)用拉曼和發(fā)光掃描宜居環(huán)境有機(jī)物和化學(xué)品（SHERLOC）的儀器對(duì)隕石坑內(nèi)的三種巖石進(jìn)行深紫外拉曼和熒光光譜分析。他們確定了不同時(shí)期兩種不同古代水環(huán)境的證據(jù)。
與液態(tài)水的反應(yīng)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(fā)現(xiàn)了與芳香有機(jī)化合物一致的熒光特征，保存在與兩種水環(huán)境相關(guān)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(xué)Physics
Giant electric field–induced strain in lead-free piezoceramics
無(wú)鉛壓電陶瓷中的巨大場(chǎng)致應(yīng)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(dòng)器以其快速響應(yīng)和精確位移在許多行業(yè)中都不可或缺。大多數(shù)商用壓電致動(dòng)器含有鉛，對(duì)環(huán)境構(gòu)成了威脅。
研究組通過(guò)常規(guī)固相反應(yīng)法合成了無(wú)需任何后處理的鍶（Sr）摻雜(K,Na)NbO3無(wú)鉛壓電陶瓷，獲得了巨大應(yīng)變（1.05%）和大信號(hào)的壓電應(yīng)變系數(shù)（2100 pm/V）。產(chǎn)生超高電應(yīng)變的基本機(jī)制是缺陷偶極子和疇切換之間的相互作用。
該無(wú)鉛壓電陶瓷在20 kV/cm下的抗疲勞性能、熱穩(wěn)定性和應(yīng)變值（0.25%）可與商用Pb(Zr,Ti)O3基陶瓷相媲美甚至更優(yōu)，顯示出巨大的實(shí)際應(yīng)用潛力。該材料有望為壓電制動(dòng)器提供一種簡(jiǎn)單組成的無(wú)鉛替代品，并為高性能壓電設(shè)計(jì)提供一個(gè)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(xué)Information Science
Competition-level code generation with AlphaCode
AlphaCode競(jìng)賽級(jí)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(qiáng)大而普遍的解決問(wèn)題的工具。能夠幫助程序員甚至自己生成程序的系統(tǒng)可以使編程更高效、更易訪問(wèn)。最近基于轉(zhuǎn)換器的神經(jīng)網(wǎng)絡(luò)模型顯示出令人驚艷的代碼生成能力，但在需要解決問(wèn)題技能的更復(fù)雜任務(wù)（如競(jìng)爭(zhēng)性編程問(wèn)題）上仍表現(xiàn)不佳。
研究組介紹了AlphaCode，這是一個(gè)用于代碼生成的系統(tǒng)，在Codeforces平臺(tái)上最近的編程競(jìng)賽模擬評(píng)估中平均排名前54.3%。
AlphaCode通過(guò)使用經(jīng)過(guò)專門訓(xùn)練、基于轉(zhuǎn)換器的網(wǎng)絡(luò)生成數(shù)百萬(wàn)個(gè)不同程序，然后對(duì)這些程序進(jìn)行過(guò)濾和聚類，最多只提交10個(gè)，從而高效解決問(wèn)題。該結(jié)果標(biāo)志著人工智能系統(tǒng)首次在編程競(jìng)賽中表現(xiàn)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(xué)Materials Science
Liquid metal synthesis solvents for metallic crystals
在液態(tài)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(duì)稱的六邊結(jié)構(gòu)。當(dāng)鋅（Zn）在液態(tài)鎵（Ga）中溶解并結(jié)晶時(shí)，研究組展示了這一類比。利用低熔點(diǎn)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(xì)管調(diào)制和真空過(guò)濾相結(jié)合的方法降低液態(tài)金屬溶劑的表面張力，從液態(tài)金屬溶劑中提取出這些金屬晶體。液態(tài)金屬生長(zhǎng)的晶體具有高度形態(tài)多樣性和持久對(duì)稱性。
將這一概念擴(kuò)展到其他單一和二元金屬溶質(zhì)和Ga基溶劑，通過(guò)界面穩(wěn)定性的從頭算模擬闡明了生長(zhǎng)機(jī)制。該策略為從液態(tài)金屬溶劑中創(chuàng)建高結(jié)晶、形狀可控的金屬或多金屬精細(xì)結(jié)構(gòu)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(shè)計(jì)更好的電解質(zhì)
▲ 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(zhì)和相關(guān)界面相構(gòu)成了支持新興電池化學(xué)組成的關(guān)鍵組件，有望提供誘人的能量，但涉及嚴(yán)苛的相和結(jié)構(gòu)復(fù)雜性。設(shè)計(jì)更好的電解質(zhì)和界面相是這些電池成功的關(guān)鍵。
作為與設(shè)備中其他所有組件連接的唯一組件，電解質(zhì)必須同時(shí)滿足多個(gè)標(biāo)準(zhǔn)。這些需求包括在電極之間絕緣電子的同時(shí)傳輸離子，并保持對(duì)極端化學(xué)性質(zhì)電極（強(qiáng)氧化陰極和強(qiáng)還原陽(yáng)極）的穩(wěn)定性。
在大多數(shù)先進(jìn)的電池中，兩個(gè)電極在遠(yuǎn)遠(yuǎn)超過(guò)電解質(zhì)熱力學(xué)穩(wěn)定性極限的電位下工作，因此必須通過(guò)電解質(zhì)和電極之間犧牲反應(yīng)形成的界面在動(dòng)力學(xué)上實(shí)現(xiàn)其穩(wěn)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(xué)Chemistry
Catalytic asymmetric C–H insertion reactions of vinyl carbocations
乙烯基碳正離子的催化不對(duì)稱C-H插入反應(yīng)
▲ 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(chǎn)物的酶促構(gòu)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(duì)碳正離子進(jìn)行對(duì)映體控制仍頗具挑戰(zhàn)性。
許多共振穩(wěn)定的三配位碳正離子，如亞胺和氧代碳鎓離子，已被應(yīng)用于催化對(duì)映選擇性反應(yīng)。然而，它們的雙配位對(duì)應(yīng)物（芳基和乙烯基碳正離子）卻沒(méi)有，盡管它們?cè)诨瘜W(xué)合成中有新興用途。
研究組報(bào)道了一種高對(duì)映選擇性的乙烯基碳正離子碳-氫（C-H）插入反應(yīng)，由亞氨基二磷酸亞胺酯有機(jī)催化劑來(lái)實(shí)現(xiàn)。
這類催化劑的活性位點(diǎn)限制不僅能夠有效地控制對(duì)映體，還擴(kuò)大了乙烯基正離子C-H插入化學(xué)的范圍，從而拓寬了這種無(wú)過(guò)渡金屬C(sp3)–H功能化平臺(tái)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.
