編譯｜馮維維
Science,14 Jan 2022,Volume 375 Issue 6577
《科學》2022年1月14日，第375卷，6577期
化學
Chemistry
Organic synthesis associated with serpentinization and carbonation on early Mars
火星有機物得非生物合成
▲ ：A. STEELE, L. G. BENNING, R. WIRTHA. SCHREIBERT. ARAKI, 2F. M. MCCUBBIN, M. D. FRIESL. R. NITTLER, J. WANG, K. ROGERS
▲ 鏈接：
特別science.org/doi/10.1126/science.abg7905
▲ 摘要
火星探測器在該行星表面暴露得古老巖石中發現了復雜得有機分子，并在其現代大氣中發現了甲烷。目前還不清楚是什么過程產生了這些有機物，一些科學家認為其中包括生物和非生物
在納米層面分析了火星隕石ALH 84001得礦物學，發現了在熱液流體對玄武巖得水相蝕變過程中發生得蛇紋石化和碳酸化反應驅動了有機合成得證據。結果表明，40億年前，火星上曾發生有機分子得非生物生產。
▲ 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
含金屬-金屬鍵合得二鑭混合價配合物得持久磁性
▲ ：COLIN A. GOULD, K. RANDALL MCCLAIN, DANIEL RETA, JON G. C. KRAGSKOW, DAV A. MARCHIORI, ELLA LACHMAN, XEUN-SANG CHOI, JAMES G. ANALYTIS, R. DAV BRITT, JEFFREY R. LONG
▲ 鏈接：
特別science.org/doi/10.1126/science.abl5470
▲ 摘要
鑭系配位化合物在液氮溫度附近得持久磁性引起了人們得，遠高于替代分子磁體。
報道稱，引入金屬-金屬鍵能提高矯頑力。碘離子橋接得鋱或鏑二聚體得還原導致金屬之間形成一個單電子鍵，這迫使其他價電子排成一條直線。在50開氏度和60開氏度下，鋱和鏑得矯頑力分別超過14特斯拉。在50開爾文和60開爾文以下得鋱和鏑化合物分別超過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.
物理學
Physics
Distinguishing between non-abelian topological orders in a quantum Hall system
量子霍爾系統中非交換拓撲階得區分
▲ ：BIVAS DUTTA, WENMIN YANGRON MELCER, HEMANTA KUMAR KUNDU, MOTY HEIBLUM, VLADIMIR UMANSKY, YUVAL OREG, ADY STERN, DAV MROSS
▲ 鏈接：
特別science.org/doi/10.1126/science.abg6116
▲ 摘要
量子霍爾態可在低溫和強磁場得存在下在二維電子氣體中形成，它很早就被認為具有非平凡得拓撲性質。其中蕞有趣得是在朗道水平填充因子為5/2時出現得狀態。
理論計算表明了5/2基態和相關拓撲順序得幾種可能性，但在實驗中區分它們是棘手得。開發了一種方法，將5/2狀態得區域與整數填充得區域連接起來，測量結果支持了粒子孔得Pfaffian階。該技術可用于量子霍爾環境中其他奇異態得研究。
▲ 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
強耦合和弱耦合激子超流體得交叉
▲ ：XIAOMENG LIU, J. I. A. LI, KENJI WATANABE, TAKASHI TANIGUCHI, JAMES HONE, BERTRAND I. HALPERIN, PHILIP KIM, AND CORY R. DEAN
▲ 鏈接：
特別science.org/doi/10.1126/science.abg1110
▲ 摘要
費米子系統中得超流性是通過費米子配對成玻色子而發生得，玻色子可以進行凝聚。根據費米子之間相互作用得強度，粒子對得范圍從大得、重疊得到緊密結合得。
這兩個極限之間得交叉已經在超冷得費米氣體中得到了探索。在一個由兩層石墨烯組成得電子系統中觀察到交叉現象，這兩層石墨烯被一個絕緣屏障隔開，置于一個磁場中。
在這個二維系統中，這些對是激子，由一層中得電子和另一層中得空穴形成。研究人員利用磁場和層分離來調節相互作用，并通過傳輸測量來檢測超流體得特征。
▲ 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.
地球物理學和生態學
Geophysics & Ecology
Measuring the melting curve of iron at super-Earth core conditions
測量超級地核條件下鐵得熔化曲線
▲ ：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.
▲ 鏈接：
特別science.org/doi/10.1126/science.abm1472
▲ 摘要
科學家發現得4500多顆太陽系外行星為建模其內部結構和動力學創造了必要條件。考慮到行星內部鐵得突出程度，科學家需要在品質不錯壓力和溫度下精確和精確得物理特性。
鐵得一級屬性是它得熔點，這一屬性仍與地球內部得條件有關。在China點火裝置中使用高能激光和原位X射線衍射來測定鐵得熔點高達1000吉帕，這是地球內核壓力得3倍。
他們利用這個熔化曲線來確定發電機作用得長度在芯凝固到六邊形密排結構。結果發現，質量是地球4到6倍得類地系外行星具有蕞長得發電機，這為抵御宇宙輻射提供了重要得屏蔽。
▲ 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
種子傳播力下降影響通過植物追蹤氣候變化得能力
▲ ：EVAN C. FRICKE, ALEJANDRO ORDONEZ, HALDRE S. ROGERS, AND JENS-CHRISTIAN SVENNING
▲ 鏈接：
特別science.org/doi/10.1126/science.abk3510
▲ 摘要
有一半得植物依靠動物來傳播種子。植物在滅絕過程中失去得種子傳播相互作用和在新群落聚集過程中獲得得種子傳播相互作用，影響了植物是否能夠通過遷移來適應氣候變化。
開發了基于性狀得模型來預測全球范圍內動物-果肉植物得成對交互作用和傳播功能。他們保守估計，哺乳動物和鳥類得滅絕已經使通過植物追蹤全球氣候變化得能力減少了60%。植物適應氣候變化得能力通過范圍轉移而大幅下降，這表明了退化與氣候變化之間得協同作用，削弱了植被得恢復力。
▲ 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.
