编译 | 未玖

Science, 28 OCTOBER 2022, VOL 378, ISSUE 6618

《科学》2022年10月28日，第378卷，6618期

天文学Astronomy

Largest recent impact craters on Mars: Orbital imaging and surface seismic co-investigation

火星上最近最大的撞击坑：轨道成像和表面地震联合调查

▲ 作者：L. V. POSIOLOVA, P. LOGNONNÉ, W. B. BANERDT, J. CLINTON, G. S. COLLINS, T. KAWAMURA, ET AL.

▲ 链接：

▲ 摘要：

2021年下半年，火星上形成了两个直径>130米的撞击坑。这是火星侦察轨道飞行器自16年前开始运行以来发现的两个最大的新撞击坑。该撞击造成了洞察号在其3年任务期间记录的两次最大地震事件（震级大于4级）。

轨道图像和地震地面运动的结合，使人们能够研究大气稀薄行星撞击过程的地下和大气能量分配，并首次直接测试已知事件距离的火星深部-内部地震模型。35°N的撞击处挖出了大块的水冰，这是在火星上直接观察到冰的最低纬度。

▲ Abstract：

Two >130-meter-diameter impact craters formed on Mars during the later half of 2021. These are the two largest fresh impact craters discovered by the Mars Reconnaissance Orbiter since operations started 16 years ago. The impacts created two of the largest seismic events (magnitudes greater than 4) recorded by InSight during its 3-year mission. The combination of orbital imagery and seismic ground motion enables the investigation of subsurface and atmospheric energy partitioning of the impact process on a planet with a thin atmosphere and the first direct test of martian deep-interior seismic models with known event distances. The impact at 35°N excavated blocks of water ice, which is the lowest latitude at which ice has been directly observed on Mars.

Surface waves and crustal structure on Mars

火星表面波和地壳结构

▲ 作者：D. KIM, W. B. BANERDT, S. CEYLAN, D. GIARDINI, V. LEKIĆ, P. LOGNONNÉ, ET AL.

▲ 链接：

▲ 摘要：

研究组探测到火星上两颗陨石撞击产生的表面波。通过测量撞击着陆器路径上的群速度弥散，他们获得了远离洞察号着陆器的地壳结构的直接约束条件。

赤道二分线以北的地壳在5~30千米深度范围内的横波速度约为每秒3.2千米，深度变化不大。这意味着着陆器下方的地壳密度比推测的要高，表明表面波穿过的火山区域要么成分不同，要么孔隙度减少。

在着陆点下方10千米深处观察到较低的速度和地壳分层并非一个全球性特征。表面波揭示的结构变化对火星地壳形成和厚度的模型具有重要意义。

▲ Abstract：

We detected surface waves from two meteorite impacts on Mars. By measuring group velocity dispersion along the impact-lander path, we obtained a direct constraint on crustal structure away from the InSight lander. The crust north of the equatorial dichotomy had a shear wave velocity of approximately 3.2 kilometers per second in the 5- to 30-kilometer depth range, with little depth variation. This implies a higher crustal density than inferred beneath the lander, suggesting either compositional differences or reduced porosity in the volcanic areas traversed by the surface waves. The lower velocities and the crustal layering observed beneath the landing site down to a 10-kilometer depth are not a global feature. Structural variations revealed by surface waves hold implications for models of the formation and thickness of the martian crust.

材料科学Materials Science

Plastic deformation in silicon nitride ceramics via bond switching at coherent interfaces

氮化硅陶瓷在共格界面上通过键切换产生塑性变形

▲ 作者：JIE ZHANG, GUANGHUA LIU, WEI CUI, YIYAO GE, SONGMO DU, YIXUAN GAO, ET AL.

▲ 链接：

▲ 摘要：

共价键合陶瓷具有优异的性能（包括硬度、强度、化学惰性、耐热性和耐腐蚀性），但由于其室温脆性，如何实现更广泛的应用颇具挑战。与金属中的原子可以沿着滑移面滑动以变形不同，共价键合陶瓷由于原子间共价键的强定向性，其变形需要断键。这最终会导致加载时发生断裂。

研究组提出了一种可变形共价键合氮化硅（Si3N4）陶瓷的设计方法，其特点是具有共格界面的双相结构。在共格界面上实现了连续键切换，这有利于应力诱导相变，并最终产生塑性变形能力。

▲ Abstract：

Covalently bonded ceramics exhibit preeminent properties—including hardness, strength, chemical inertness, and resistance against heat and corrosion—yet their wider application is challenging because of their room-temperature brittleness. In contrast to the atoms in metals that can slide along slip planes to accommodate strains, the atoms in covalently bonded ceramics require bond breaking because of the strong and directional characteristics of covalent bonds. This eventually leads to catastrophic failure on loading. We present an approach for designing deformable covalently bonded silicon nitride (Si3N4) ceramics that feature a dual-phase structure with coherent interfaces. Successive bond switching is realized at the coherent interfaces, which facilitates a stress-induced phase transformation and, eventually, generates plastic deformability.

化学Chemistry

Stereochemical editing logic powered by the epimerization of unactivated tertiary stereocenters

未激活三级立体中心的差向异构助力立体化学编辑逻辑

▲ 作者：YU-AN ZHANG, VIGNESH PALANI, ALEXANDER E. SEIM, YONG WANG, KATHLEEN J. WANG AND ALISON E. WENDLANDT.

▲ 链接：

▲ 摘要：

复杂目标物的立体选择性合成需要精确的化学转换协调，同时建立所需键的连通性和空间定向。

在这项工作中，研究组描述了一种手性分子及其异构体合成的互补范式，即在后期调整分子的三维结构。这一策略成功的关键是开发了一种温和且高度通用的光催化方法，它由十钨酸盐聚阴离子和二硫化物助催化剂组成，使先前构型固定的未激活三级生成中心实现相互转化。

研究组通过快速构建使用现有工具很难制备的手性支架，以及复杂目标物的后期立体编辑，展示了这种方法的多功能性（以及立体编辑逻辑的实现）。

▲ Abstract：

The stereoselective synthesis of complex targets requires the precise orchestration of chemical transformations that simultaneously establish the connectivity and spatial orientation of desired bonds. In this work, we describe a complementary paradigm for the synthesis of chiral molecules and their isomers, which tunes the three-dimensional structure of a molecule at a late stage. Key to the success of this strategy is the development of a mild and highly general photocatalytic method composed of decatungstate polyanion and disulfide cocatalysts, which enable the interconversion of unactivated tertiary stereogenic centers that were previously configurationally fixed. We showcase the versatility of this method—and the implementation of stereoediting logic—by the rapid construction of chiral scaffolds that would be challenging to access using existing tools and by the late-stage stereoediting of complex targets.

Closed-loop optimization of general reaction conditions for heteroaryl Suzuki-Miyaura coupling

杂芳基Suzuki-Miyaura偶联反应通用条件的闭环优化

▲ 作者：NICHOLAS H. ANGELLO, VANDANA RATHORE, WIKTOR BEKER, AGNIESZKA WOŁOS, EDWARD R. JIRA, RAFAŁ ROSZAK, ET AL.

▲ 链接：

▲ 摘要：

有机反应的通用条件很重要，但却罕见，确定它们的努力通常只考虑化学空间的狭窄区域。要发现更通用的反应条件，就需要考虑从大矩阵基质和高维反应条件基质交叉而成的化学空间的广阔区域，这使得详尽的实验不切实际。

研究组报道了一个简单的闭环工作流，利用数据引导矩阵向下选择、不确定性最小化机器学习和机器人实验来发现通用反应条件。

应用于杂芳基Suzuki-Miyaura交叉偶联这种极具挑战性和重要性的问题时，研究组确定了一个通用条件，与之前使用传统方法开发的广泛使用的基准相比，平均产率翻了一番。该研究为解决具有大搜索空间的多维化学优化问题提供了一个实用的路线图。

▲ Abstract：

General conditions for organic reactions are important but rare, and efforts to identify them usually consider only narrow regions of chemical space. Discovering more general reaction conditions requires considering vast regions of chemical space derived from a large matrix of substrates crossed with a high-dimensional matrix of reaction conditions, rendering exhaustive experimentation impractical. Here, we report a simple closed-loop workflow that leverages data-guided matrix down-selection, uncertainty-minimizing machine learning, and robotic experimentation to discover general reaction conditions. Application to the challenging and consequential problem of heteroaryl Suzuki-Miyaura cross-coupling identified conditions that double the average yield relative to a widely used benchmark that was previously developed using traditional approaches. This study provides a practical road map for solving multidimensional chemical optimization problems with large search spaces.

公共卫生Public Health

Evolution and antiviral activity of a human protein of retroviral origin

逆转录病毒来源人类蛋白质的进化和抗病毒活性

▲ 作者：JOHN A. FRANK, MANVENDRA SINGH, HARRISON B. CULLEN, RAPHAEL A. KIROU, MERIEM BENKADDOUR-BOUMZAOUAD, JOSE L. CORTES, ET AL.

▲ 链接：

▲ 摘要：

内源性逆转录病毒是源自古老种系感染的哺乳动物基因组的丰富组成部分。在一些哺乳动物中，由这些元件编码的包膜蛋白可以抵御外源性病毒，但这种活性在人类内源性表达的包膜中尚未被证实。

研究组报道，人类基因组拥有大量包膜衍生序列，具有抑制逆转录病毒感染的潜力。为了验证这一点，他们对包膜衍生蛋白Suppressyn进行了表征。结果发现Suppressyn在人类着床前胚胎和发育中的胎盘中，使用其祖先逆转录病毒启动子表达。

细胞培养分析表明，Suppressyn及其类人直系同源物可抑制现存哺乳动物D型逆转录病毒的感染。该数据支持宿主免疫和基因组防御的逆转录病毒包膜共选择的通用模型。

▲ Abstract：

Endogenous retroviruses are abundant components of mammalian genomes descended from ancient germline infections. In several mammals, the envelope proteins encoded by these elements protect against exogenous viruses, but this activity has not been documented with endogenously expressed envelopes in humans. We report that the human genome harbors a large pool of envelope-derived sequences with the potential to restrict retroviral infection. To test this, we characterized an envelope-derived protein, Suppressyn. We found that Suppressyn is expressed in human preimplantation embryos and developing placenta using its ancestral retroviral promoter. Cell culture assays showed that Suppressyn, and its hominoid orthologs, could restrict infection by extant mammalian type D retroviruses. Our data support a generalizable model of retroviral envelope co-option for host immunity and genome defense.