编译｜冯维维

Science,14 Jan 2022,Volume 375 Issue 6577

《科学》2022年1月14日，第375卷，6577期


化学

Chemistry


Organic synthesis associated with serpentinization and carbonation on early Mars

火星有机物的非生物合成

▲ 作者：A. STEELE, L. G. BENNING, R. WIRTHA. SCHREIBERT. ARAKI, 2F. M. MCCUBBIN, M. D. FRIESL. R. NITTLER, J. WANG, K. ROGERS

▲ 链接：

▲ 摘要

火星探测器在该行星表面暴露的古老岩石中发现了复杂的有机分子，并在其现代大气中发现了甲烷。目前还不清楚是什么过程产生了这些有机物，一些科学家认为其中包括生物和非生物来源。

作者在纳米层面分析了火星陨石ALH 84001的矿物学，发现了在热液流体对玄武岩的水相蚀变过程中发生的蛇纹石化和碳酸化反应驱动了有机合成的证据。结果表明，40亿年前，火星上曾发生有机分子的非生物生产。

▲ Abstract

Mars rovers have found complex organic molecules in the ancient rocks exposed on the planet’s surface and methane in the modern atmosphere. It is unclear what processes produced these organics, with proposals including both biotic and abiotic sources. Steele et al. analyzed the nanoscale mineralogy of the Mars meteorite ALH 84001 and found evidence of organic synthesis driven by serpentinization and carbonation reactions that occurred during the aqueous alteration of basalt rock by hydrothermal fluids. The results demonstrate that abiotic production of organic molecules operated on Mars 4 billion years ago.


Ultrahard magnetism from mixed-valence dilanthanide complexes with metal-metal bonding

含金属-金属键合的二镧混合价配合物的持久磁性

▲ 作者：COLIN A. GOULD, K. RANDALL MCCLAIN, DANIEL RETA, JON G. C. KRAGSKOW, DAVID A. MARCHIORI, ELLA LACHMAN, XEUN-SANG CHOI, JAMES G. ANALYTIS, R. DAVID BRITT, JEFFREY R. LONG

▲ 链接：

▲ 摘要

镧系配位化合物在液氮温度附近的持久磁性引起了人们的关注，远高于替代分子磁体。

作者报道称，引入金属-金属键能提高矫顽力。碘离子桥接的铽或镝二聚体的还原导致金属之间形成一个单电子键，这迫使其他价电子排成一条直线。在50开氏度和60开氏度下，铽和镝的矫顽力分别超过14特斯拉。在50开尔文和60开尔文以下的铽和镝化合物分别超过14特斯拉。

▲ Abstract

Lanthanide coordination compounds have attracted attention for their persistent magnetic properties near liquid nitrogen temperature, well above alternative molecular magnets. Gould et al. report that introducing metal-metal bonding can enhance coercivity. Reduction of iodide-bridged terbium or dysprosium dimers resulted in a single electron bond between the metals, which enforced alignment of the other valence electrons. The resultant coercive fields exceeded 14 tesla below 50 and 60 kelvin for the terbium and dysprosium compounds, respectively.


物理学

Physics


Distinguishing between non-abelian topological orders in a quantum Hall system

量子霍尔系统中非交换拓扑阶的区分

▲ 作者：BIVAS DUTTA, WENMIN YANGRON MELCER, HEMANTA KUMAR KUNDU, MOTY HEIBLUM, VLADIMIR UMANSKY, YUVAL OREG, ADY STERN, DAVID MROSS

▲ 链接：

▲ 摘要

量子霍尔态可在低温和强磁场的存在下在二维电子气体中形成，它很早就被认为具有非平凡的拓扑性质。其中最有趣的是在朗道水平填充因子为5/2时出现的状态。

理论计算表明了5/2基态和相关拓扑顺序的几种可能性，但在实验中区分它们是棘手的。作者开发了一种方法，将5/2状态的区域与整数填充的区域连接起来，测量结果支持了粒子孔的Pfaffian阶。该技术可用于量子霍尔环境中其他奇异态的研究。

▲ Abstract

Quantum Hall states, which form in two-dimensional electron gases at low temperatures and in the presence of strong magnetic fields, have long been known to have nontrivial topological properties. Among the most intriguing is the state that arises at the Landau level filling factor of 5/2. Theoretical calculations suggest several possibilities for the 5/2 ground state and associated topological order but distinguishing among them experimentally is tricky. Dutta et al. developed a method for doing so by interfacing a region in the 5/2 state with a region at an integer filling, and the measurements provided support for the particle-hole Pfaffian order. The technique can be used for the investigation of other exotic states in the quantum Hall setting.



crossover between strongly coupled and weakly coupled exciton superfluids

强耦合和弱耦合激子超流体的交叉

▲ 作者：XIAOMENG LIU, J. I. A. LI, KENJI WATANABE, TAKASHI TANIGUCHI, JAMES HONE, BERTRAND I. HALPERIN, PHILIP KIM, AND CORY R. DEAN

▲ 链接：

▲ 摘要

费米子系统中的超流性是通过费米子配对成玻色子而发生的，玻色子可以进行凝聚。根据费米子之间相互作用的强度，粒子对的范围从大的、重叠的到紧密结合的。

这两个极限之间的交叉已经在超冷的费米气体中得到了探索。作者在一个由两层石墨烯组成的电子系统中观察到交叉现象，这两层石墨烯被一个绝缘屏障隔开，置于一个磁场中。

在这个二维系统中，这些对是激子，由一层中的电子和另一层中的空穴形成。研究人员利用磁场和层分离来调节相互作用，并通过传输测量来检测超流体的特征。

▲ Abstract

Superfluidity in fermionic systems occurs through the pairing of fermions into bosons, which can undergo condensation. Depending on the strength of the interactions between fermions, the pairs range from large and overlapping to tightly bound. The crossover between these two limits has been explored in ultracold Fermi gases. Liu et al. observed the crossover in an electronic system consisting of two layers of graphene separated by an insulating barrier and placed in a magnetic field. In this two-dimensional system, the pairs were excitons formed from an electron in one layer and a hole in the other. The researchers used magnetic field and layer separation to tune the interactions and detected the signatures of superfluidity through transport measurements.


地球物理学和生态学

Geophysics & Ecology


Measuring the melting curve of iron at super-Earth core conditions

测量超级地核条件下铁的熔化曲线

▲ 作者：RICHARD G. KRAUS, RUSSELL J. HEMLEY, SUZANNE J. ALI, JONATHAN L. BELOF, LORIN X. BENEDICTJOEL BERNIER, DAVE BRAUNR. E. COHEN, GILBERT W. COLLINS, JON H. EGGERT, etc.

▲ 链接：

▲ 摘要

科学家发现的4500多颗太阳系外行星为建模其内部结构和动力学创造了必要条件。考虑到行星内部铁的突出程度，科学家需要在极端压力和温度下精确和精确的物理特性。

铁的一级属性是它的熔点，这一属性仍与地球内部的条件有关。作者在国家点火装置中使用高能激光和原位X射线衍射来测定铁的熔点高达1000吉帕，这是地球内核压力的3倍。

他们利用这个熔化曲线来确定发电机作用的长度在芯凝固到六边形密排结构。结果发现，质量是地球4到6倍的类地系外行星具有最长的发电机，这为抵御宇宙辐射提供了重要的屏蔽。

▲ Abstract

The discovery of more than 4500 extrasolar planets has created a need for modeling their interior structure and dynamics. Given the prominence of iron in planetary interiors, we require accurate and precise physical properties at extreme pressure and temperature. A first-order property of iron is its melting point, which is still debated for the conditions of Earth’s interior. We used high-energy lasers at the National Ignition Facility and in situ x-ray diffraction to determine the melting point of iron up to 1000 gigapascals, three times the pressure of Earth’s inner core. We used this melting curve to determine the length of dynamo action during core solidification to the hexagonal close-packed (hcp) structure. We find that terrestrial exoplanets with four to six times Earth’s mass have the longest dynamos, which provide important shielding against cosmic radiation.


The effects of defaunation on plants’ capacity to track climate change

种子传播力下降影响通过植物追踪气候变化的能力

▲ 作者：EVAN C. FRICKE, ALEJANDRO ORDONEZ, HALDRE S. ROGERS, AND JENS-CHRISTIAN SVENNING

▲ 链接：

▲ 摘要

有一半的植物依靠动物来传播种子。植物在灭绝过程中失去的种子传播相互作用和在新群落聚集过程中获得的种子传播相互作用，影响了植物是否能够通过迁移来适应气候变化。

作者开发了基于性状的模型来预测全球范围内动物-果肉植物的成对交互作用和传播功能。他们保守估计，哺乳动物和鸟类的灭绝已经使通过植物追踪全球气候变化的能力减少了60%。植物适应气候变化的能力通过范围转移而大幅下降，这表明了退化与气候变化之间的协同作用，削弱了植被的恢复力。

▲ Abstract

Half of all plant species rely on animals to disperse their seeds. Seed dispersal interactions lost through defaunation and gained during novel community assembly influence whether plants can adapt to climate change through migration. We develop trait-based models to predict pairwise interactions and dispersal function for fleshy-fruited plants globally. We conservatively estimate that mammal and bird defaunation has already reduced the capacity of plants to track climate change by 60% globally. This strong reduction in the ability of plants to adapt to climate change through range shifts shows a synergy between defaunation and climate change that undermines vegetation resilience.