Science, 21February 2020, Vol 367, Issue 6480

《科学》2020年2月21日，第367卷，6480期

环境科学

Environmental Sciences

Old carbon reservoirs were not important in the deglacial methane budget

旧的碳储层在冰消期甲烷预算中并不重要

▲ 作者：M. N. Dyonisius, V. V. Petrenko, A. M. Smith, Q. Hua, B. Yang, J. Schmitt, et al.

▲ 链接：

https://science.sciencemag.org/content/367/6480/907

▲ 摘要：

永久冻土层和甲烷水合物是对气候敏感的大型碳储层，随着地球持续变暖，它们有可能释放大量的温室气体——甲烷。

我们从已消失的冰川的冰核同位素中测量甲烷（Δ14C， δ13C， δD），进行一个现代气候变暖的部分模拟。

研究结果表明，由于冰川融化造成的旧碳储层甲烷排放量很小（小于每年19兆的甲烷排放量，95%置信区间），并据此讨论未来气候变暖所导致的类似甲烷排放量。

我们的结果还表明，在前工业全新世，生物量燃烧产生的甲烷每年排放22至56兆（95%置信区间），与现在相当。

▲ Abstract

Permafrost and methane hydrates are large, climate-sensitive old carbon reservoirs that have the potential to emit large quantities of methane, a potent greenhouse gas, as the Earth continues to warm. We present ice core isotopic measurements of methane (Δ14C, δ13C, and δD) from the last deglaciation, which is a partial analog for modern warming. Our results show that methane emissions from old carbon reservoirs in response to deglacial warming were small (<19 teragrams of methane per year, 95% confidence interval) and argue against similar methane emissions in response to future warming. Our results also indicate that methane emissions from biomass burning in the pre-Industrial Holocene were 22 to 56 teragrams of methane per year (95% confidence interval), which is comparable to today.

动物学Zoology

Bumble bees display cross-modal object recognition between visual and tactile senses

大黄蜂在视觉和触觉之间进行跨模态目标识别

▲ 作者：Cwyn Solvi, Selene Gutierrez Al-Khudhairy, Lars Chittka

▲ 链接：

https://science.sciencemag.org/content/367/6480/910

▲ 摘要：

许多动物会把物体的形状和诱因联系起来。然而，这样的行为不在记忆中存储可以被一种以上的感觉模态访问的图像也是可能发生的。

探索物体形状是否存在模态独立的内部表征的一种方法是研究跨模态识别——以一种感觉模态体验一个物体，然后在另一种感觉模态中识别它。

我们证明，经过训练的大黄蜂仅通过触觉（在黑暗中）或视觉（在光照中，但禁止接触物体）就能分辨出两个不同形状的物体（立方体和球体），然后仅通过其他感官信息就能分辨出同样的物体。

我们的实验证明，大黄蜂有能力通过模态独立的内部表征整合感官信息。

▲ Abstract

Many animals can associate object shapes with incentives. However, such behavior is possible without storing images of shapes in memory that are accessible to more than one sensory modality. One way to explore whether there are modality-independent internal representations of object shapes is to investigate cross-modal recognition—experiencing an object in one sensory modality and later recognizing it in another. We show that bumble bees trained to discriminate two differently shaped objects (cubes and spheres) using only touch (in darkness) or vision (in light, but barred from touching the objects) could subsequently discriminate those same objects using only the other sensory information. Our experiments demonstrate that bumble bees possess the ability to integrate sensory information in a way that requires modality-independent internal representations.

物理学Physics

Cooling of a levitated nanoparticle to the motional quantum ground state

将悬浮的纳米粒子冷却至量子基态

▲ 作者：Uroš Delić, Manuel Reisenbauer, Kahan Dare, David Grass, Vladan Vuletić, et al.

▲ 链接：

https://science.sciencemag.org/content/367/6480/892

▲ 摘要：

在大尺寸和质量状态下对复杂粒子的量子控制为基础物理的传感应用和测试提供了机会。然而，实现物质的这种极端量子态仍然是一个重大挑战。

我们演示了一种结合了固体光学捕获和腔隙介导的光-物质相互作用的量子界面。通过对光腔中捕获激光的频率和位置的精确控制，我们在室温下用激光将捕获的纳米粒子冷却到它的量子基态。

该粒子由108个原子组成，与当前的玻色-爱因斯坦凝聚类似，密度与固体一致。我们的冷却技术与光学捕获相结合，可能使涉及不可实现的大质量粒子叠加态成为可能。

▲ Abstract

Quantum control of complex objects in the regime of large size and mass provides opportunities for sensing applications and tests of fundamental physics. The realization of such extreme quantum states of matter remains a major challenge. We demonstrate a quantum interface that combines optical trapping of solids with cavity-mediated light-matter interaction. Precise control over the frequency and position of the trap laser with respect to the optical cavity allowed us to laser-cool an optically trapped nanoparticle into its quantum ground state of motion from room temperature. The particle comprises 108 atoms, similar to current Bose-Einstein condensates, with the density of a solid object. Our cooling technique, in combination with optical trap manipulation, may enable otherwise unachievable superposition states involving large masses.

Quantum anomalous Hall effect in intrinsic magnetic topological insulator MnBi2Te4

本征磁性拓扑绝缘体MnBi2Te4中的量子反常霍尔效应

▲ 作者：Yujun Deng, Yijun Yu, Meng Zhu Shi, Zhongxun Guo, Zihan Xu, Jing Wang, et al.

▲ 链接：

https://science.sciencemag.org/content/367/6480/895

▲ 摘要：

在磁性拓扑绝缘体中，非平庸的拓扑能带结构与长程磁有序的结合将诱导出一系列新奇量子现象和拓扑物态，如量子反常霍尔效应和轴子绝缘体。

在这项研究中，我们探讨了本征磁性拓扑绝缘体MnBi2Te4薄层的量子传输。

在这个层状的范德瓦尔斯晶体中，铁磁层与层之间则形成反铁磁耦合；然而，当样品有奇数7层时，MnBi2Te4薄层变成铁磁性。

在5层厚度的薄层样品中在1.4K温度和零磁场的条件下观察到量子反常霍尔效应，并且通过外磁场进一步改善薄层样品中的铁磁排列，可以将实现量子化的温度提高到6.5K。

结果表明MnBi2Te4是进一步探索具有自发时间反演对称性破缺的各种拓扑现象的理想场所。

▲ Abstract

In a magnetic topological insulator, nontrivial band topology combines with magnetic order to produce exotic states of matter, such as quantum anomalous Hall (QAH)insulators and axion insulators. In this work, we probe quantum transport in MnBi2Te4 thin flakes—a topological insulator with intrinsic magnetic order. In this layered van der Waals crystal, the ferromagnetic layers couple antiparallel to each other; atomically thin MnBi2Te4, however, becomes ferromagnetic when the sample has an odd number of septuple layers. We observea zero-field QAH effect in a five–septuple-layer specimen at 1.4 kelvin, and an external magnetic field further raises the quantization temperature to 6.5kelvin by aligning all layers ferromagnetically. The results establish MnBi2Te4 as an ideal arena for further exploring various topological phenomena with a spontaneously broken time-reversal symmetry.

Intrinsic quantized anomalous Hall effect in a moiré heterostructure

莫尔异质结构的本征量子反常霍尔效应

▲ 作者：M. Serlin, C. L. Tschirhart, H. Polshyn, Y. Zhang, J. Zhu, K. Watanabe, T. Taniguchi, et al.

▲ 链接：

https://science.sciencemag.org/content/367/6480/900

▲ 摘要：

量子反常霍尔（QAH）效应结合了拓扑结构和磁性，在零磁场下产生精确量子化的霍尔电阻。我们报告了QAH效应扭曲的双层石墨烯对齐六角氮化硼。

这种效应是由固有的强相互作用所驱动的，使电子极化成单一的自旋和谷分辨的莫尔微带。

与磁掺杂体系相比，测量到的输运能量图要大于用于磁排序的居里温度，并且将其量子化到0.1%的克里青常数范围内，可以在零磁场条件下保持几个开尔文的温度。

小至1毫微安的电流可控制地在相反极化状态之间切换磁序，形成电可重写的磁存储器。

▲ Abstract

The quantum anomalous Hall (QAH) effect combines topology and magnetism to produce precisely quantized Hall resistance at zero magnetic field. We report the observation of a QAH effect in twisted bilayer graphene aligned to hexagonal boron nitride. The effect is driven by intrinsic strong interactions, which polarize the electrons into a single spin- and valley-resolved moiré miniband with Chern number C = 1. In contrast to magnetically doped systems, the measured transport energy gap is larger than the Curie temperature for magnetic ordering, and quantization to within 0.1% of the von Klitzing constant persists to temperatures of several kelvin at zero magnetic field. Electrical currents as small as 1 nanoampe recontrollably switch the magnetic order between states of opposite polarization, forming an electrically rewritable magnetic memory.

材料科学Materials Science

Disassembling 2D van der Waals crystals into macroscopic monolayers and reassembling into artificial lattices

将二维范德瓦尔斯晶体分解成宏观单层，再重新组装成人工晶格

▲ 作者：Fang Liu, Wenjing Wu, Yusong Bai, Sang Hoon Chae, Qiuyang Li, Jue Wang, James Hone, et al.

▲ 链接：

https://science.sciencemag.org/content/367/6480/903

▲ 摘要：

来自层状范德瓦尔斯（vdW）晶体的二维材料对电子、光电和量子器件有很大的应用前景，但技术实现由于缺乏高通量的技术来剥离具有足够尺寸和高质量的单晶层而受到阻碍。

在此，我们提供一种简单的方法，将vdW单晶一层一层地分解成单分子层，获得接近单位的产率，尺寸仅受大块晶体尺寸的限制。宏观单层膜的质量可与传统粘性胶带剥离法所得的微观单层膜的质量相媲美。

单分子层可以组装成宏观的人工结构，包括具有断裂的反转对称性和显著增强的非线性光学响应的过渡金属硫族化合物多层结构。

这种方法使我们离大规模生产具有可控性能的宏观单层和块状人工材料又近了一步。

▲ Abstract

Two-dimensional materials from layered van der Waals (vdW) crystals hold great promise for electronic, optoelectronic, and quantum devices, but technological implementation will be hampered by the lack of high-through put techniques forexfoliating single-crystal monolayers with sufficient size and high quality. Here, we report a facile method to disassemble vdW single crystals layer by layer into monolayers with near-unity yield and with dimensions limited only by bulk crystal sizes. The macroscopic monolayers are comparable in quality to microscopic monolayers from conventional Scotch tape exfoliation. The monolayers can be assembled into macroscopic artificial structures, including transition metal dichalcogenide multilayers with broken inversion symmetry and substantially enhanced nonlinear optical response. This approach takes us one step closer to mass production of macroscopic monolayers and bulk-like artificial materials with controllable properties.

医学Medical Science

Pulmonary surfactant–biomimetic nanoparticles potentiate heterosubtypic influenza immunity

肺表面活性物质—仿生纳米颗粒增强异型流感的免疫力

▲ 作者：Ji Wang, Peiyu Li, Yang Yu, Yuhong Fu, Hongye Jiang, Min Lu, Zhiping Sun, et al.

▲ 链接：

https://science.sciencemag.org/content/367/6480/eaau0810

▲ 摘要：

目前的流感疫苗只能对同源病毒提供保护。我们合成了包裹环鸟苷酸—一磷酸腺苷（cGAMP）的肺表面活性物质（PS）-仿生脂质体，它是干扰素基因诱导物STING（干扰素基因的刺激物）的激动剂。

该佐剂（PS-GAMP）通过模拟病毒感染的早期阶段而不伴有过度炎症，可有效增强流感疫苗诱导的小鼠体液和CD8+ T细胞的免疫反应。

经鼻内注射PS-GAMP促进的H1N1疫苗2天后，在维持肺内常驻记忆CD8+T细胞的同时，被H1N1和H3N2、H5N1和H7N9病毒引发了至少6个月的强交叉保护。

其可调性随后在对雪貂的实验中得到验证。当肺泡上皮细胞（AECs）缺乏Sting或缝隙连接被阻断时，PS-GAMP介导的调节作用在体内被显著消除。因此，AECs在配置异型免疫中起着关键作用。

▲ Abstract

Current influenz avaccines only confer protection against homologous viruses. We synthesized pulmonary surfactant (PS)–biomimetic liposomes encapsulating 2′,3′-cyclic guanosine monophosphate–adenosine monophosphate (cGAMP), an agonist of the interferon geneinducer STING (stimulator of interferon genes). The adjuvant (PS-GAMP) vigorously augmented influenza vaccine–induced humoral and CD8+T cell immune responses in mice by simulating the early phase of viral infection without concomitant excess inflammation. Two days after intranasal immunizationwith PS-GAMP–adjuvanted H1N1 vaccine, strong cross-protection was elicited against distant H1N1 and heterosubtypic H3N2, H5N1, and H7N9 viruses for at least 6 months while maintaining lung-resident memory CD8+T cells. Adjuvanticity was then validated in ferrets. When alveolar epithelial cells(AECs) lacked Sting or gap junctions were blocked, PS-GAMP–mediated adjuvanticity was substantially abrogated in vivo. Thus, AECs play a pivotalrole in configuring heterosubtypic immunity.

相关热词 : 《科学》