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2024年12月11日，《科学》（20221209出版）一周论文导读2022-12-12 10:26·科学网编译 | 未玖Science, 9 DECEMBER 2022, VOL 378, ISSUE 6624《科学》2022年12月9日，第378卷，6624期天文学AstronomyAqueous alteration processes in Jezero crater, Mars?implications for organic geochemistry火星Jezero陨石坑的水蚀变过程-对有机地球化学的影响▲ 作者：EVA L. SCHELLER, JOSEPH RAZZELL HOLLIS, EMILY L. CARDARELLI, ANDREW STEELE, LUTHER W. BEEGLE, ROHIT BHARTIA, ET AL.▲ 链接：https://www.science.org/doi/10.1126/science.abo5204▲ 摘要：2021年2月，“毅力”号火星车在火星Jezero陨石坑着陆。研究组通过用拉曼和发光扫描宜居环境有机物和化学品（SHERLOC）的仪器对陨石坑内的三种岩石进行深紫外拉曼和荧光光谱分析。他们确定了不同时期两种不同古代水环境的证据。与液态水的反应在富橄榄石的火成岩中形成碳酸盐。岩石中存在硫酸盐-高氯酸盐混合物，可能由岩石被盐水后期改性形成。在这些岩石中发现了与芳香有机化合物一致的荧光特征，保存在与两种水环境相关的矿物中。▲ 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.物理学PhysicsGiant electric field–induced strain in lead-free piezoceramics无铅压电陶瓷中的巨大场致应变▲ 作者：GENG HUANGFU, KUN ZENG, BINQUAN WANG, JIE WANG, ZHENGQIAN FU, FANGFANG XU, ET AL.▲ 链接：https://www.science.org/doi/10.1126/science.ade2964▲ 摘要：压电致动器以其快速响应和精确位移在许多行业中都不可或缺。大多数商用压电致动器含有铅，对环境构成了威胁。研究组通过常规固相反应法合成了无需任何后处理的锶（Sr）掺杂(K,Na)NbO3无铅压电陶瓷，获得了巨大应变（1.05%）和大信号的压电应变系数（2100 pm/V）。产生超高电应变的基本机制是缺陷偶极子和畴切换之间的相互作用。该无铅压电陶瓷在20 kV/cm下的抗疲劳性能、热稳定性和应变值（0.25%）可与商用Pb(Zr,Ti)O3基陶瓷相媲美甚至更优，显示出巨大的实际应用潜力。该材料有望为压电制动器提供一种简单组成的无铅替代品，并为高性能压电设计提供一个范例。▲ 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.信息科学Information ScienceCompetition-level code generation with AlphaCodeAlphaCode竞赛级别代码生成▲ 作者：YUJIA LI, DAVID CHOI, JUNYOUNG CHUNG, NATE KUSHMAN, JULIAN SCHRITTWIESER, R?MI LEBLOND, ET AL.▲ 链接：https://www.science.org/doi/10.1126/science.abq1158▲ 摘要：编程是一种强大而普遍的解决问题的工具。能够帮助程序员甚至自己生成程序的系统可以使编程更高效、更易访问。最近基于转换器的神经网络模型显示出令人惊艳的代码生成能力，但在需要解决问题技能的更复杂任务（如竞争性编程问题）上仍表现不佳。研究组介绍了AlphaCode，这是一个用于代码生成的系统，在Codeforces平台上最近的编程竞赛模拟评估中平均排名前54.3%。AlphaCode通过使用经过专门训练、基于转换器的网络生成数百万个不同程序，然后对这些程序进行过滤和聚类，最多只提交10个，从而高效解决问题。该结果标志着人工智能系统首次在编程竞赛中表现出色。▲ 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.材料科学Materials ScienceLiquid metal synthesis solvents for metallic crystals在液态金属溶剂中合成金属晶体▲ 作者：SHUHADA A. IDRUS-SAIDI, JIANBO TANG, STEPHANIE LAMBIE, JIALUO HAN, MOHANNAD MAYYAS, MOHAMMAD B. GHASEMIAN, ET AL.▲ 链接：https://www.science.org/doi/10.1126/science.abm2731▲ 摘要：在自然界中，雪花冰晶排列成各种对称的六边结构。当锌（Zn）在液态镓（Ga）中溶解并结晶时，研究组展示了这一类比。利用低熔点Ga作为“金属溶剂”，合成了一系列片状锌晶体。研究组利用电毛细管调制和真空过滤相结合的方法降低液态金属溶剂的表面张力，从液态金属溶剂中提取出这些金属晶体。液态金属生长的晶体具有高度形态多样性和持久对称性。将这一概念扩展到其他单一和二元金属溶质和Ga基溶剂，通过界面稳定性的从头算模拟阐明了生长机制。该策略为从液态金属溶剂中创建高结晶、形状可控的金属或多金属精细结构提供了通用路径。▲ 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设计更好的电解质▲ 作者：Y. SHIRLEY MENG, VENKAT SRINIVASAN, AND KANG XU▲ 链接：https://www.science.org/doi/10.1126/science.abq3750▲ 摘要：电解质和相关界面相构成了支持新兴电池化学组成的关键组件，有望提供诱人的能量，但涉及严苛的相和结构复杂性。设计更好的电解质和界面相是这些电池成功的关键。作为与设备中其他所有组件连接的唯一组件，电解质必须同时满足多个标准。这些需求包括在电极之间绝缘电子的同时传输离子，并保持对极端化学性质电极（强氧化阴极和强还原阳极）的稳定性。在大多数先进的电池中，两个电极在远远超过电解质热力学稳定性极限的电位下工作，因此必须通过电解质和电极之间牺牲反应形成的界面在动力学上实现其稳定性。▲ 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.化学ChemistryCatalytic asymmetric C–H insertion reactions of vinyl carbocations乙烯基碳正离子的催化不对称C-H插入反应▲ 作者：SEPAND K. NISTANAKI, CHLOE G. WILLIAMS, BENJAMIN WIGMAN, JONATHAN J. WONG, BRITTANY C. HAAS, STASIK POPOV, ET AL.▲ 链接：https://www.science.org/doi/10.1126/science.ade5320▲ 摘要：从药物的制备到天然产物的酶促构建，碳正离子是分子合成的核心。尽管这些活性中间体在自然界中具有立体选择性，但利用合成催化剂对碳正离子进行对映体控制仍颇具挑战性。许多共振稳定的三配位碳正离子，如亚胺和氧代碳鎓离子，已被应用于催化对映选择性反应。然而，它们的双配位对应物（芳基和乙烯基碳正离子）却没有，尽管它们在化学合成中有新兴用途。研究组报道了一种高对映选择性的乙烯基碳正离子碳-氢（C-H）插入反应，由亚氨基二磷酸亚胺酯有机催化剂来实现。这类催化剂的活性位点限制不仅能够有效地控制对映体，还扩大了乙烯基正离子C-H插入化学的范围，从而拓宽了这种无过渡金属C(sp3)–H功能化平台的用途。▲ 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.
《66尘66成长模式视频-威九国际精彩片段6》2022年础笔笔...66尘66成长模式视频-威九国际精彩片段6冲火热视频在线...
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