编译 | 李言
Science, 26 MARCH 2021, VOL 371, ISSUE 6536
《科学》2021年3月26日，第371卷，6536期
动物学Zoology
Hunting the eagle killer: A cyanobacterial neurotoxin causes vacuolar myelinopathy
追捕雄鹰杀手：一种蓝藻神经毒素导致的空泡性髓鞘病变
▲ 作者：Steffen Breinlinger, Tabitha J. Phillips, Brigette N. Haram, Jan Mareš, José A. Martínez Yerena, et al.
▲ 链接：
https://science.sciencemag.org/content/371/6536/eaax9050
▲ 摘要
空泡性髓鞘病变是一种致命的神经系统疾病，最初是在美国阿肯色州的秃鹰大规模神秘死亡事件中发现的。几十年来，这种野生动物疾病病因一直未能得到科学家们的关注，但疾病却继续在美国东南部的淡水水库中蔓延。
最近的研究表明，空泡性髓鞘病变是由生长在水生植被（主要是入侵的黑藻）上的附生蓝藻引起的。Aetokthonotoxin是一种由蓝藻细菌产生的五溴化双吲哚生物碱，在此，我们报告它的鉴定、生物合成基因簇和生物活性。
我们认为这种蓝藻神经毒素是空泡性髓鞘病变的病因，并讨论环境因素——特别是溴的可用性——促进毒素的产生。
▲ Abstract
Vacuolar myelinopathy is a fatal neurological disease that was initially discovered during a mysterious mass mortality of bald eagles in Arkansas in the United States. The cause of this wildlife disease has eluded scientists for decades while its occurrence has continued to spread throughout freshwater reservoirs in the southeastern United States. Recent studies have demonstrated that vacuolar myelinopathy is induced by consumption of the epiphytic cyanobacterial species Aetokthonos hydrillicola growing on aquatic vegetation, primarily the invasive Hydrilla verticillata. Here, we describe the identification, biosynthetic gene cluster, and biological activity of aetokthonotoxin, a pentabrominated biindole alkaloid that is produced by the cyanobacterium A. hydrillicola. We identify this cyanobacterial neurotoxin as the causal agent of vacuolar myelinopathy and discuss environmental factors—especially bromide availability—that promote toxin production.
环境科学Environmental Science
A 35-million-year record of seawater stable Sr isotopes reveals a fluctuating global carbon cycle
3500万年的海水锶同位素记录揭示波动的全球碳循环
▲ 作者：Adina Paytan, Elizabeth M. Griffith, Anton Eisenhauer, et al.
▲ 链接：
https://science.sciencemag.org/content/371/6536/1346
▲ 摘要
海水中主要成分浓度和同位素组成的变化反映了其源汇的变化。因为控制这些来源的许多过程都与碳循环有关，这些记录可以让我们了解是什么驱动了二氧化碳和气候在过去的变化。在此，我们提供了一个来自远洋重晶石的稳定锶(Sr)同位素记录。我们的锶非传统稳定同位素记录表现出复杂的变化规律，首先在3500 ~ 1500万年之间下降，然后在1500 ~500万年之间上升，然后在距今500万年间再次下降。数值模拟结果表明，与现今海水相比，锶浓度的相关波动约为±25%。我们认为锶非传统稳定同位素反映了生物成因碳酸盐的矿物学和埋藏位置的变化。
▲ Abstract
Changes in the concentration and isotopic composition of the major constituents in seawater reflect changes in their sources and sinks. Because many of the processes controlling these sources and sinks are tied to the cycling of carbon, such records can provide insights into what drives past changes in atmospheric carbon dioxide and climate. Here, we present a stable strontium (Sr) isotope record derived from pelagic marine barite. Our δ88/86Sr record exhibits a complex pattern, first declining between 35 and 15 million years ago (Ma), then increasing from 15 to 5 Ma, before declining again from ~5 Ma to the present. Numerical modeling reveals that the associated fluctuations in seawater Sr concentrations are about ±25% relative to present-day seawater. We interpret the δ88/86Sr data as reflecting changes in the mineralogy and burial location of biogenic carbonates.
物理学Physics
Controlling quantum many-body dynamics in driven Rydberg atom arrays
驱动里德堡原子阵列中的量子多体动力学控制
▲ 作者：D. Bluvstein, A. Omran, H. Levine, A. Keesling, et al.
▲ 链接：
https://science.sciencemag.org/content/371/6536/1355
▲ 摘要
控制多体系统中的非平衡量子动力学具有挑战性，因为相互作用通常会导致热化和混沌在希尔伯特空间中蔓延。
我们研究了由3 ~ 200个强相互作用量子位元组成的一维和二维多体系统在快速结束后的非平衡动力学。利用一个基于里德堡原子阵列的可编程量子模拟器，我们证明了与所谓的量子多体疤痕相关的相干恢复可以通过周期驱动来稳定，从而产生类似于离散时间晶体阶的鲁棒次谐波响应。
我们映射希尔伯特空间动力学、几何依赖、相图和系统尺寸依赖这一现象，演示了在多体系统中引导复杂动力学的新方法，并使量子信息科学的潜在应用成为可能。
▲ Abstract
The control of nonequilibrium quantum dynamics in many-body systems is challenging because interactions typically lead to thermalization and a chaotic spreading throughout Hilbert space. We investigate nonequilibrium dynamics after rapid quenches in a many-body system composed of 3 to 200 strongly interacting qubits in one and two spatial dimensions. Using a programmable quantum simulator based on Rydberg atom arrays, we show that coherent revivals associated with so-called quantum many-body scars can be stabilized by periodic driving, which generates a robust subharmonic response akin to discrete time-crystalline order. We map Hilbert space dynamics, geometry dependence, phase diagrams, and system-size dependence of this emergent phenomenon, demonstrating new ways to steer complex dynamics in many-body systems and enabling potential applications in quantum information science.
材料科学Materials Science
Stabilizing black-phase formamidinium perovskite formation at room temperature and high humidity
室温高湿条件下稳定黑相甲酰胺钙钛矿的形成
▲ 作者：Wei Hui, Lingfeng Chao, Hui Lu, Fei Xia, et al.
▲ 链接：
https://science.sciencemag.org/content/371/6536/1359
▲ 摘要
黑相甲酰胺铅碘（α-FAPbI3）钙钛矿在各种环境条件下的稳定被认为是太阳能电池的必要条件。然而，在α-FAPbI3的温度敏感性和其加工过程中严格控制湿度的要求方面仍然存在挑战。
在次，我们报道不考虑湿度和温度的稳定α-FAPbI3的合成，基于从离子液体甲酸甲胺中生长的垂直排列的碘化铅薄膜。
这种垂直生长的结构具有许多纳米级离子通道，这些通道有助于碘化甲酰胺渗透到碘化铅薄膜中，从而快速、稳定地转化为α-FAPbI3。我们获得了功率转换效率为24.1%的太阳能电池。未封装的电池在85°C和连续光胁迫条件下分别保持了80%和90%的初始效率。
▲ Abstract
The stabilization of black-phase formamidinium lead iodide (α-FAPbI3) perovskite under various environmental conditions is considered necessary for solar cells. However, challenges remain regarding the temperature sensitivity of α-FAPbI3 and the requirements for strict humidity control in its processing. Here we report the synthesis of stable α-FAPbI3, regardless of humidity and temperature, based on a vertically aligned lead iodide thin film grown from an ionic liquid, methylamine formate. The vertically grown structure has numerous nanometer-scale ion channels that facilitate the permeation of formamidinium iodide into the lead iodide thin films for fast and robust transformation to α-FAPbI3. A solar cell with a power-conversion efficiency of 24.1% was achieved. The unencapsulated cells retain 80 and 90% of their initial efficiencies for 500 hours at 85°C and continuous light stress, respectively.
Three-dimensional vectorial imaging of surface phonon polaritons
表面声子-极化子的三维矢量成像
▲ 作者：Xiaoyan Li, Georg Haberfehlner, Ulrich Hohenester, Odile Stéphan, et al.
▲ 链接：
https://science.sciencemag.org/content/371/6536/1364
▲ 摘要
表面声子-极化子（SPhPs）是出现在纳米结构材料表面的光子-声子耦合激发。尽管它们强烈地影响纳米材料的光学和热行为，但没有一种技术能够揭示它们的电磁状态密度的完整三维(3D)矢量图。
在扫描透射电子显微镜中使用高度单色的电子束，我们可以将纳米级MgO立方体中不同的SPhP信号看作是光束位置、能量损失和倾斜角度的函数。将SPhPs的响应描述为本征模态，并用于声子表面电磁场的层析重建。
这样的三维信息为纳米尺度物理现象的研究提供了广阔的前景，并且对于纳米结构的设计和优化具有非常重要的价值。
▲ Abstract
Surface phonon polaritons (SPhPs) are coupled photon-phonon excitations that emerge at the surfaces of nanostructured materials. Although they strongly influence the optical and thermal behavior of nanomaterials, no technique has been able to reveal the complete three-dimensional (3D) vectorial picture of their electromagnetic density of states. Using a highly monochromated electron beam in a scanning transmission electron microscope, we could visualize varying SPhP signatures from nanoscale MgO cubes as a function of the beam position, energy loss, and tilt angle. The SPhPs’ response was described in terms of eigenmodes and used to tomographically reconstruct the phononic surface electromagnetic fields of the object. Such 3D information promises insights in nanoscale physical phenomena and is invaluable to the design and optimization of nanostructures for fascinating new uses.
Enhanced optical asymmetry in supramolecular chiroplasmonic assemblies with long-range order
超分子等离子组合物的增强光学不对称性
▲ 作者：Jun Lu, Yao Xue, Kalil Bernardino, Ning-Ning Zhang, Weverson R. Gomes, et al.
▲ 链接：
https://science.sciencemag.org/content/371/6536/1368
▲ 摘要
等离子体纳米粒子的手性组装具有较强的圆二色性，而不具有较强的光学不对称性，这是由于强散射所造成的电场和磁场组合的不利限制。
在此，我们证明了这些限制可以通过类似于液晶的纳米颗粒的长程组织方式来克服。这种组织方式类似于液晶，并在金纳米棒与人类胰岛淀粉样多肽的螺旋组合中发现。
在组装螺旋中激活的具有反平行方向的偶极子的强大的、偏振相关的光谱偏移和能量态的减少散射使光学不对称性g因子增加了超过4600倍。
这种类似液晶的颜色变化和纳米棒加速的纤维性颤动使药物在复杂的生物介质中筛选成为可能。长程序的改进也可以为高光学不对称材料的设计提供结构指导。
▲ Abstract
Chiral assemblies of plasmonic nanoparticles are known for strong circular dichroism but not for high optical asymmetry, which is limited by the unfavorable combination of electrical and magnetic field components compounded by strong scattering. Here, we show that these limitations can be overcome by the long-range organization of nanoparticles in a manner similar to the liquid crystals and found in helical assemblies of gold nanorods with human islet amyloid polypeptides. A strong, polarization-dependent spectral shift and the reduced scattering of energy states with antiparallel orientation of dipoles activated in assembled helices increased optical asymmetry g-factors by a factor of more than 4600. The liquid crystal–like color variations and the nanorod-accelerated fibrillation enable drug screening in complex biological media. Improvement of long-range order can also provide structural guidance for the design of materials with high optical asymmetry.
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