编译 | 未玖
Science, 3 JUN 2022, VOL 376, ISSUE 6597
《科学》2022年6月3日，第376卷，6597期
物理学Physics
Fractal photonic topological insulators
分形光子拓扑绝缘体
▲ 作者：TOBIAS BIESENTHAL, LUKAS J. MACZEWSKY, ZHAOJU YANG, MARK KREMER, MORDECHAI SEGEV, ALEXANDER SZAMEIT, ET AL.
▲ 链接：
https://www.science.org/doi/10.1126/science.abm2842
▲ 摘要：
拓扑绝缘体构成了一种新型物质状态，包含围绕绝缘体的无散射边缘态。传统观点认为绝缘体必不可少，因为其中定义了描述系统拓扑特性的不变量。
课题组研究了基于完全由边缘位点组成的精确分形的分形拓扑绝缘体。他们提供了实验证明，尽管缺乏体带，但螺旋波导的光子晶格支持拓扑保护的手征边缘态；并表明，与相应的蜂窝晶格相比，该拓扑分形系统中的光传输速度更快。
通过超越体边界对应的限制，该研究工作为扩大对拓扑绝缘子的认识奠定了基础，并开启了拓扑分形的新篇章。
▲ Abstract：
Topological insulators constitute a newly characterized state of matter that contains scatter-free edge states surrounding an insulating bulk. Conventional wisdom regards the insulating bulk as essential, because the invariants that describe the topological properties of the system are defined therein. Here, we study fractal topological insulators based on exact fractals composed exclusively of edge sites. We present experimental proof that, despite the lack of bulk bands, photonic lattices of helical waveguides support topologically protected chiral edge states. We show that light transport in our topological fractal system features increased velocities compared with the corresponding honeycomb lattice. By going beyond the confines of the bulk-boundary correspondence, our findings pave the way toward an expanded perception of topological insulators and open a new chapter of topological fractals.
材料科学Materials Science
Rational design of mixed-matrix metal-organic framework membranes for molecular separations
用于分子分离的混合基质金属-有机框架膜的合理设计
▲ 作者：SHUVO JIT DATTA, ALVARO MAYORAL, NARASIMHA MURTHY SRIVATSA BETTAHALLI, PRASHANT M. BATT, MADHAVAN KARUNAKARAN, IONELA DANIELA CARJA, ET AL.
▲ 链接：
https://www.science.org/doi/10.1126/science.abe0192
▲ 摘要：
用于分离有价值商品的传统分离技术是能源密集型的，消耗了全世界15%的能源。混合基质膜结合了可加工聚合物和选择性吸附剂，有潜力将吸附剂不同的分离特性整合到可加工基质中。
研究组报道了基于三个互锁标准的高效混合基质金属-有机框架膜的合理设计和构建：（i） 氟化金属-有机框架AlFFIVE-1-Ni，作为一种分子筛吸附剂，可选择性增强硫化氢和二氧化碳扩散，同时排除甲烷；（ii）将晶体形态裁剪成具有最大暴露（001）面的纳米片；以及（iii）聚合物基质中（001）纳米片的面内排列和实现[001]-取向膜。
在实际工作条件下，该膜从天然气中分离出的硫化氢和二氧化碳含量极高。这种方法提供了将其他关键吸附剂转化为可加工基质的巨大潜力。
▲ Abstract：
Conventional separation technologies to separate valuable commodities are energy intensive, consuming 15% of the worldwide energy. Mixed-matrix membranes, combining processable polymers and selective adsorbents, offer the potential to deploy adsorbent distinct separation properties into processable matrix. We report the rational design and construction of a highly efficient, mixed-matrix metal-organic framework membrane based on three interlocked criteria: (i) a fluorinated metal-organic framework, AlFFIVE-1-Ni, as a molecular sieve adsorbent that selectively enhances hydrogen sulfide and carbon dioxide diffusion while excluding methane; (ii) tailoring crystal morphology into nanosheets with maximally exposed (001) facets; and (iii) in-plane alignment of (001) nanosheets in polymer matrix and attainment of [001]-oriented membrane. The membrane demonstrated exceptionally high hydrogen sulfide and carbon dioxide separation from natural gas under practical working conditions. This approach offers great potential to translate other key adsorbents into processable matrix.
Polytriazole membranes with ultrathin tunable selective layer for crude oil fractionation
用于原油分馏的超薄可调选择层聚三唑膜
▲ 作者：STEFAN CHISCA, VALENTINA-ELENA MUSTEATA, WEN ZHANG, SERHII VASYLEVSKYI, GHEORGHE FALCA, EDY ABOU-HAMAD, ET AL.
▲ 链接：
https://www.science.org/doi/10.1126/science.abm7686
▲ 摘要：
材料设计及将其制造成能够处理工业条件和分离复杂非水混合物的膜是一个重大挑战。
研究组报道了一种制造聚三唑膜的通用策略，该膜具有10 nm薄选择性层，包含用于分离碳氢化合物的亚纳米通道。该过程采用经典的非溶剂诱导相分离方法和热交联。膜的选择性可调至典型纳滤范围的下限（200至1000 g mole−1）。
聚三唑膜对C10以下碳氢化合物（140 g mole−1）的富集效率高达80%~95%。这些膜优先分离石蜡而非芳烃组分，因此适合集成在原油分馏的混合蒸馏系统中。
▲ Abstract：
The design of materials and their manufacture into membranes that can handle industrial conditions and separate complex nonaqueous mixtures are challenging. We report a versatile strategy to fabricate polytriazole membranes with 10-nanometer-thin selective layers containing subnanometer channels for the separation of hydrocarbons. The process involves the use of the classical nonsolvent-induced phase separation method and thermal cross-linking. The membrane selectivity can be tuned to the lower end of the typical nanofiltration range (200 to 1000 gram mole−1). The polytriazole membrane can enrich up to 80 to 95% of the hydrocarbon content with less than 10 carbon atoms (140 gram mole−1). These membranes preferentially separate paraffin over aromatic components, making them suitable for integration in hybrid distillation systems for crude oil fractionation.
信息科学Information Science
Memristive technologies for data storage, computation, encryption, and radio-frequency communication
用于数据存储、计算、加密和射频通信的忆阻器技术
▲ 作者：MARIO LANZA, ABU SEBASTIAN, WEI D. LU, MANUEL LE GALLO, MENG-FAN CHANG, DEJI AKINWANDE, ET AL.
▲ 链接：
https://www.science.org/doi/10.1126/science.abj9979
▲ 摘要：
将电阻器与存储器功能结合在一起，使电压脉冲能够以非易失性方式改变其电阻进而改变其存储器状态的忆阻器，已在存储器应用的集成电路中初步实现。
然而，忆阻器还可应用于许多其他技术，如交叉阵列中的非冯·诺依曼内存计算、用于数据安全的随机数生成以及用于移动通信的射频开关。
在商业固态电子电路和其他潜在应用中忆阻器集成的进展将取决于亟待解决的性能和可靠性挑战。
▲ Abstract：
Memristive devices, which combine a resistor with memory functions such that voltage pulses can change their resistance (and hence their memory state) in a nonvolatile manner, are beginning to be implemented in integrated circuits for memory applications. However, memristive devices could have applications in many other technologies, such as non–von Neumann in-memory computing in crossbar arrays, random number generation for data security, and radio-frequency switches for mobile communications. Progress toward the integration of memristive devices in commercial solid-state electronic circuits and other potential applications will depend on performance and reliability challenges that still need to be addressed, as described here.
地球科学Earth Science
Functional connectivity of the world’s protected areas
世界保护区的功能连通性
▲ 作者：A. BRENNAN, R. NAIDOO, L. GREENSTREET, Z. MEHRABI, N. RAMANKUTTY AND C. KREMEN
▲ 链接：
https://www.science.org/doi/10.1126/science.abl8974
▲ 摘要：
全球政策呼吁连接保护区（PA），以保护动物和基因在不断变化的景观中流动，但目前全球PA网络是否支持动物迁徙以及在哪里连接保护区最为关键，在很大程度上仍不得而知。
在这项研究中，研究组绘制了世界陆地PA的功能连通性地图，并通过哺乳动物迁徙的视角量化了国家PA的连通性。研究组发现，减少人类足迹可能比增加新的PA更能改善连通性，尽管这两种策略结合在一起会使收益最大化。
全球最重要的哺乳动物集中迁徙区域仍未受到保护，其中71%与全球生物多样性优先区域重叠，6%发生在人类中高度改造的陆地上。关键连接区域的保护和恢复可以维护PA连通性，同时支持其他全球保护优先事项。
▲ Abstract：
Global policies call for connecting protected areas (PAs) to conserve the flow of animals and genes across changing landscapes, yet whether global PA networks currently support animal movement—and where connectivity conservation is most critical—remain largely unknown. In this study, we map the functional connectivity of the world’s terrestrial PAs and quantify national PA connectivity through the lens of moving mammals. We find that mitigating the human footprint may improve connectivity more than adding new PAs, although both strategies together maximize benefits. The most globally important areas of concentrated mammal movement remain unprotected, with 71% of these overlapping with global biodiversity priority areas and 6% occurring on land with moderate to high human modification. Conservation and restoration of critical connectivity areas could safeguard PA connectivity while supporting other global conservation priorities.
From white to green: Snow cover loss and increased vegetation productivity in the European Alps
从白到绿：欧洲阿尔卑斯山积雪覆盖面减少，植被生产力增加
▲ 作者：SABINE B. RUMPF, MATHIEU GRAVEY, OLIVIER BR?NNIMANN, MISKA LUOTO, CARMEN CIANFRANI, GREGOIRE MARIETHOZ, ET AL.
▲ 链接：
https://www.science.org/doi/10.1126/science.abn6697
▲ 摘要：
山脉是生物多样性和生态系统服务的热点区域，但其变暖速度大约是全球平均水平的两倍。气候变化可能会减少阿尔卑斯山的积雪覆盖，提高植被生产力，就像在北极一样。
研究组证明，在过去40年间，树线以上77%的欧洲阿尔卑斯山经历了绿化（生产力增加）和<1%的褐变（生产力下降）。在此期间，积雪明显减少，但减少区域小于10%。
这些趋势只是弱相关：在夏季气候变化的推动下，温暖地区的绿化占主导地位，而在降水变化的推动下，积雪衰退在较冷温度下达到顶峰。
绿化可以增加碳汇，但这不太可能超过负面影响，包括反照率和水可用性降低、永久冻土融化和栖息地丧失。
▲ Abstract：
Mountains are hotspots of biodiversity and ecosystem services, but they are warming about twice as fast as the global average. Climate change may reduce alpine snow cover and increase vegetation productivity, as in the Arctic. Here, we demonstrate that 77% of the European Alps above the tree line experienced greening (productivity gain) and <1% browning (productivity loss) over the past four decades. Snow cover declined significantly during this time, but in <10% of the area. These trends were only weakly correlated: Greening predominated in warmer areas, driven by climatic changes during summer, while snow cover recession peaked at colder temperatures, driven by precipitation changes. Greening could increase carbon sequestration, but this is unlikely to outweigh negative implications, including reduced albedo and water availability, thawing permafrost, and habitat loss.
