编译 | 未玖
Science, 18 FEBRUARY 2022, VOL 375, ISSUE 6582
《科学》2022年2月18日，第375卷，6582期
物理学Physics
Isospin magnetism and spin-polarized superconductivity in Bernal bilayer graphene
Bernal双层石墨烯的同位旋磁性和自旋极化超导性
▲ 作者：HAOXIN ZHOU, LUDWIG HOLLEIS, YU SAITO, LIAM COHEN, WILLIAM HUYNH, CAITLIN L. PATTERSON, ET AL.
▲ 链接：
▲ 摘要
在传统超导体中，库珀配对发生在自旋相反的电子之间。
研究组观察了当掺杂到由大垂直电场产生的鞍点范霍夫奇点时，Bernal双层石墨烯的自旋极化超导性。他们观察到电子相位之间的静电栅极调谐跃迁级联，以同位旋空间中的极化为特征，同位旋空间由自旋和动量空间谷自由度组合定义。
虽然所有这些相在零磁场下都是金属的，但研究组观察到在有限磁场B‖≈150 mT平行施加于二维薄片上时，会发生向超导状态的转变。
超导性发生在对称破缺转变附近，仅存在于顺磁超导体预期的B‖极限之上，观测到的转变临界温度TC≈30 mK，与自旋三重态序参数一致。
▲ Abstract
In conventional superconductors, Cooper pairing occurs between electrons of opposite spin. We observe spin-polarized superconductivity in Bernal bilayer graphene when doped to a saddle-point van Hove singularity generated by a large applied perpendicular electric field. We observe a cascade of electrostatic gate-tuned transitions between electronic phases distinguished by their polarization within the isospin space defined by the combination of the spin and momentum-space valley degrees of freedom. Although all of these phases are metallic at zero magnetic field, we observe a transition to a superconducting state at finite magnetic field B‖≈ 150 milliteslas applied parallel to the two-dimensional sheet. Superconductivity occurs near a symmetry-breaking transition and exists exclusively above the B‖ limit expected of a paramagnetic superconductor with the observed transition critical temperature TC ≈ 30 millikelvins, consistent with a spin-triplet order parameter.
材料科学Materials Science
Self-assembled monolayers direct a LiF-rich interphase toward long-life lithium metal batteries
自组装单分子层形成富LiF界面相，实现长寿命锂金属电池
▲ 作者：YUJING LIU, XINYONG TAO, YAO WANG, CHI JIANG, CONG MA, OUWEI SHENG, ET AL.
▲ 链接：
▲ 摘要
高能量密度锂（Li）金属电池（LMB）有望应用于储能，但由于其电解质不可控降解，会形成不稳定的固电解质界面（SEI）。
在这项研究中，研究组设计了具有高密度和长程有序极性羧基的自组装单分子膜（SAM），与氧化铝涂层隔膜相连以提供强大偶极矩，从而提供多余的电子以加速锂双（三氟甲磺酰）亚胺中碳-氟键断裂的降解动力学。
由此可生成富氟化锂（LiF）纳米晶的SEI，促进Li+的快速转移，并抑制Li枝晶的生长。尤其是在高阴极负载、有限锂过剩和低电解质条件下，SAM赋予了全电池显著增强的循环能力。
因此，该工作将长期建立的SAM技术扩展到一个平台，以控制电解质降解和SEI的形成，从而实现超长寿命的LMB。
▲ Abstract
High–energy density lithium (Li) metal batteries (LMBs) are promising for energy storage applications but suffer from uncontrollable electrolyte degradation and the consequently formed unstable solid-electrolyte interphase (SEI). In this study, we designed self-assembled monolayers (SAMs) with high-density and long-range–ordered polar carboxyl groups linked to an aluminum oxide–coated separator to provide strong dipole moments, thus offering excess electrons to accelerate the degradation dynamics of carbon-fluorine bond cleavage in Li bis(trifluoromethanesulfonyl)imide. Hence, an SEI with enriched lithium fluoride (LiF) nanocrystals is generated, facilitating rapid Li+ transfer and suppressing dendritic Li growth. In particular, the SAMs endow the full cells with substantially enhanced cyclability under high cathode loading, limited Li excess, and lean electrolyte conditions. As such, our work extends the long-established SAMs technology into a platform to control electrolyte degradation and SEI formation toward LMBs with ultralong life spans.
地球科学Earth Science
Reducing adverse impacts of Amazon hydropower expansion
减少亚马逊流域水电站扩建的不利影响
▲ 作者：ALEXANDER S. FLECKER, QINRU SHI, RAFAEL M. ALMEIDA, HÉCTOR ANGARITA, JONATHAN M. GOMES-SELMAN, ROOSEVELT GARCÍA-VILLACORTA, et al.
▲ 链接：
▲ 摘要
在整个亚马逊地区350多个地点修建水电站大坝，需要战略评估对地球上最大、生物多样性最丰富流域提供的众多生态系统服务之间的权衡。这些服务在空间上是可变的，因此新建大坝的集体影响在很大程度上取决于它们的配置。
研究组使用多目标优化来确定选址组合，在实现能源生产目标的同时，将对河流流量、河流连通性、沉积物运输、鱼类多样性和温室气体排放的影响降至最低。他们发现，不协调的、一个接一个大坝的水电扩建导致了生态系统服务效益的丧失。
将水电开发造成的进一步损害降至最低，需要考虑整个流域的各种环境影响，以及亚马逊流域国家之间的合作。该研究结果为评估跨界流域的水电扩张提供了一个可推广的模型。
▲ Abstract
Proposed hydropower dams at more than 350 sites throughout the Amazon require strategic evaluation of trade-offs between the numerous ecosystem services provided by Earth’s largest and most biodiverse river basin. These services are spatially variable, hence collective impacts of newly built dams depend strongly on their configuration. We use multiobjective optimization to identify portfolios of sites that simultaneously minimize impacts on river flow, river connectivity, sediment transport, fish diversity, and greenhouse gas emissions while achieving energy production goals. We find that uncoordinated, dam-by-dam hydropower expansion has resulted in forgone ecosystem service benefits. Minimizing further damage from hydropower development requires considering diverse environmental impacts across the entire basin, as well as cooperation among Amazonian nations. Our findings offer a transferable model for the evaluation of hydropower expansion in transboundary basins.
考古学Archaeology
Forgotten books: The application of unseen species models to the survival of culture
被遗忘的书籍：看不见的物种模型在文化生存中的应用
▲ 作者：MIKE KESTEMONT, FOLGERT KARSDORP, ELISABETH DE BRUIJN, MATTHEW DRISCOLL, KATARZYNA A. KAPITAN, PÁDRAIG Ó MACHÁIN, et al.
▲ 链接：
▲ 摘要
对古代文化的研究往往因人工制品残存而受阻，因此人们通常低估了历史社会中文化生产的多样性。
为了纠正这种幸存者偏差，研究组应用生态学中看不见的物种模型来衡量中世纪欧洲叙事故事的缺失，比如亚瑟王的传奇故事。所得到的估计与缺乏的历史证据相一致。
除了图书馆火灾等事件外，研究组还发现，在面对非物质损失时，文化群体的初始均匀性是这些组合稳定性的一个被忽视因素。
研究组将岛屿文献中提高的均匀性与岛屿群落生态和文化多样性的类似描述联系起来。这些分析呼吁在遗产科学中推广该方法。
▲ Abstract
The study of ancient cultures is hindered by the incomplete survival of material artifacts, so we commonly underestimate the diversity of cultural production in historic societies. To correct this survivorship bias, we applied unseen species models from ecology to gauge the loss of narratives from medieval Europe, such as the romances about King Arthur. The estimates obtained are compatible with the scant historic evidence. In addition to events such as library fires, we identified the original evenness of cultural populations as an overlooked factor in these assemblages’ stability in the face of immaterial loss. We link the elevated evenness in island literatures to analogous accounts of ecological and cultural diversity in insular communities. These analyses call for a wider application of these methods across the heritage sciences.
仿生学Bionics
Biomimetic fracture model of lizard tail autotomy
蜥蜴自断尾的仿生骨折模型
▲ 作者：NAVAJIT S BABAN, AJYMURAT OROZALIEV, SEBASTIAN KIRCHHOF, CHRISTOPHER J STUBBS, AND YONG-AK SONG.
▲ 链接：
▲ 摘要
蜥蜴自断尾是一种防御捕食者的策略，包括在正常时间坚固附着，但在需要时迅速脱离。
研究组提出了一种利用多尺度层次结构的蜥蜴自断尾仿生骨折模型。这些结构由均匀分布、顶部有大量纳米孔的微柱组成，重现了在蜥蜴尾巴肌肉断裂面上发现的高密度蘑菇状微观结构。
仿生实验表明，在拉伸和剥离模式下，当纳米多孔界面与柔性微柱结合时可增强粘附力。断裂模型表明，基于微观和纳米结构的增韧机制是关键因素。
在湿润条件下，毛细作用辅助的能量耗散与充满液体的微间隙和纳米孔有关，进一步提高了粘附性能。这项研究为蜥蜴自断尾提供了新见解，并为解决粘附问题提供了新的仿生思路。
▲ Abstract
Lizard tail autotomy is an antipredator strategy consisting of sturdy attachment at regular times but quick detachment during need. We propose a biomimetic fracture model of lizard tail autotomy using multiscale hierarchical structures. The structures consist of uniformly distributed micropillars with nanoporous tops, which recapitulate the high-density mushroom-shaped microstructures found on the lizard tail’s muscle fracture plane. The biomimetic experiments showed adhesion enhancement when combining nanoporous interfacial surfaces with flexible micropillars in tensile and peel modes. The fracture modeling identified micro- and nanostructure-based toughening mechanisms as the critical factor. Under wet conditions, capillarity-assisted energy dissipation pertaining to liquid-filled microgaps and nanopores further increased the adhesion performance. This research presents insights on lizard tail autotomy and provides new biomimetic ideas to solve adhesion problems.
公共卫生Public Health
SARS-CoV-2 Omicron variant: Antibody evasion and cryo-EM structure of spike protein–ACE2 complex
新冠奥密克戎变体：抗体逃逸和刺突蛋白-ACE2复合物的冷冻电镜结构
▲ 作者：DHIRAJ MANNAR, JAMES W. SAVILLE, XING ZHU, SHANTI S. SRIVASTAVA, ALISON M. BEREZUK, KATHARINE S. TUTTLE, ET AL.
▲ 链接：
▲ 摘要
最新报道的奥密克戎变体有望取代德尔塔成为全球最流行的新冠病毒变体。
对奥密克戎变体刺突蛋白与人血管紧张素转换酶2（ACE2）复合物进行的冷冻电子显微镜（Cryo EM）结构分析显示，在ACE2受体结合域中，突变残基精氨酸-493、丝氨酸-496和精氨酸-498形成新的盐桥和氢键。
这些强相互作用似乎补偿了奥密克戎的其他突变，例如会降低ACE2结合亲和力的天冬酰胺取代417位赖氨酸（K417N），从而导致德尔塔和奥密克戎变体具有相似的生化ACE2结合亲和力。
中和试验表明，显示奥密克戎刺突蛋白的假病毒表现出更强的抗体逃逸。因此，抗体逃逸增强和ACE2结合强相互作用代表了奥密克戎变体的重要分子特征，或有助于其快速传播。
▲ Abstract
The newly reported Omicron variant is poised to replace Delta as the most prevalent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant across the world. Cryo–electron microscopy (cryo-EM) structural analysis of the Omicron variant spike protein in complex with human angiotensin-converting enzyme 2 (ACE2) reveals new salt bridges and hydrogen bonds formed by mutated residues arginine-493, serine-496, and arginine-498 in the receptor binding domain with ACE2. These interactions appear to compensate for other Omicron mutations such as the substitution of asparagine for lysine at position 417 (K417N) that are known to reduce ACE2 binding affinity, resulting in similar biochemical ACE2 binding affinities for the Delta and Omicron variants. Neutralization assays show that pseudoviruses that display the Omicron spike protein exhibit increased antibody evasion. The increase in antibody evasion and the retention of strong interactions at the ACE2 interface thus represent important molecular features that likely contribute to the rapid spread of the Omicron variant.
