编译 | 冯维维
Nature, Dec. 2022, Volume 612 Issue 7939
《自然》2022年12月，第612卷7939期
生态学Ecology
A 2-million-year-old ecosystem in Greenland uncovered by environmental DNA
古DNA揭开200万年前格陵兰生态系统面纱
▲ 作者：Kurt H. Kjær, Mikkel Winther Pedersen, Bianca De Sanctis, Binia De Cahsan, Thorfinn S. Korneliussen, Christian S. Michelsen, Karina K. Sand, Stanislav Jelavić, Anthony H. Ruter, Astrid M. A. Schmidt, Kristian K. Kjeldsen, Eske Willerslev, etc.
▲ 链接：
https://www.nature.com/articles/s41586-022-05453-y
▲ 摘要：
Kap Kobenhavn组是一片极地沙漠，位于北格陵兰的皮里地。此前研究显示，该地区在约300万~200万年前的气候要温暖很多，气温比现在高11~19℃。
然而，由于脊椎动物化石的稀缺，人们对当时居住在北极区的生物群落不甚了解。通过分析迄今恢复的最早的古代环境DNA，研究人员绘制了格陵兰北部约200万年前生态系统的样貌，包括曾存在的动物和植物物种。使人们能以前所未有的程度探究并理解一个古代生态系统，同时揭示了一个没有现代等同物的生态系统。
作者对从Kap Kobenhavn组5个不同遗址采集的41例有机质富集沉积物样本进行了DNA提取和测序。他们利用这些DNA重现了古代生态系统的样貌：一片生长着杨树、桦树和崖柏以及各种北极和北方灌木、草本植物的开阔北方林。
DNA记录证实了野兔的存在，来自遗址的线粒体DNA还揭示了其他动物存在的痕迹，包括乳齿象、驯鹿、啮齿动物和雁类。他们还恢复了海洋生物的古DNA，这些古DNA提示曾存在一个大西洋鲎种群。
作者认为，这或许意味着Kap Kobenhavn在更新世早期有着更温暖的地表水环境，与之前的预测一致。该结果证明了利用古代环境DNA追溯200万年前生物群落演化的潜力。
▲ Abstract：
Late Pliocene and Early Pleistocene epochs 3.6 to 0.8 million years ago1 had climates resembling those forecasted under future warming2. Palaeoclimatic records show strong polar amplification with mean annual temperatures of 11–19 °C above contemporary values3,4. The biological communities inhabiting the Arctic during this time remain poorly known because fossils are rare5. Here we report an ancient environmental DNA6 (eDNA) record describing the rich plant and animal assemblages of the Kap København Formation in North Greenland, dated to around two million years ago. The record shows an open boreal forest ecosystem with mixed vegetation of poplar, birch and thuja trees, as well as a variety of Arctic and boreal shrubs and herbs, many of which had not previously been detected at the site from macrofossil and pollen records. The DNA record confirms the presence of hare and mitochondrial DNA from animals including mastodons, reindeer, rodents and geese, all ancestral to their present-day and late Pleistocene relatives. The presence of marine species including horseshoe crab and green algae support a warmer climate than today. The reconstructed ecosystem has no modern analogue. The survival of such ancient eDNA probably relates to its binding to mineral surfaces. Our findings open new areas of genetic research, demonstrating that it is possible to track the ecology and evolution of biological communities from two million years ago using ancient eDNA.
一个研究人员从一个沉积核中取样进行DNA测序。图片来自NOVA, HHMI Tangled Bank Studios和Handful of Films
Plastic futures and their CO2 emissions
塑料“期货”及其二氧化碳排放
▲ 作者：Paul Stegmann, Vassilis Daioglou, Marc Londo, Detlef P. van Vuuren & Martin Junginger
▲ 链接：
https://www.nature.com/articles/s41586-022-05422-5
▲ 摘要：
在所有大宗材料中，塑料的产量增长最为强劲，已占全球温室气体排放的4.5%。如果没有新的政策实施，预计到2050年全球塑料需求将翻一番，到2100年将增加两倍以上，二氧化碳排放量几乎也会增加。
作者分析了全球塑料行业在2100年前的三种备选二氧化碳减排途径，涵盖了从生产到废物管理的整个生命周期。
研究结果表明，通过把生物基碳固存在塑料制品中，将生物质使用和垃圾填埋相结合，可以实现长期的负排放；然而，这涉及到对初级原料的持续依赖。在没有额外生物经济推动的情况下，循环经济方法可减少30%的资源消耗，并在2050年之前实现10%的减排，同时降低长期负排放的潜力。
循环生物经济方法将循环利用与更高的生物质使用结合起来，最终可以将该领域变成一个净碳汇，同时逐步淘汰垃圾填埋和减少资源消耗。研究改善了物质流动和循环经济在全球能源和排放模型中的表现，并提供了对塑料行业长期动态的洞察。
▲ Abstract：
Plastics show the strongest production growth of all bulk materials and are already responsible for 4.5% of global greenhouse gas emissions. If no new policies are implemented, we project a doubling of global plastic demand by 2050 and more than a tripling by 2100, with an almost equivalent increase in CO2 emissions. Here we analyse three alternative CO2 emission-mitigation pathways for the global plastics sector until 2100, covering the entire life cycle from production to waste management. Our results show that, through bio-based carbon sequestration in plastic products, a combination of biomass use and landfilling can achieve negative emissions in the long term; however, this involves continued reliance on primary feedstock. A circular economy approach without an additional bioeconomy push reduces resource consumption by 30% and achieves 10% greater emission reductions before 2050 while reducing the potential of negative emissions in the long term. A circular bioeconomy approach combining recycling with higher biomass use could ultimately turn the sector into a net carbon sink, while at the same time phasing out landfilling and reducing resource consumption. Our work improves the representation of material flows and the circular economy in global energy and emission models, and provides insight into long-term dynamics in the plastics sector.
物理学Physics
Integrated femtosecond pulse generator on thin-film lithium niobate
旋转超晶格在铌酸锂薄膜上集成飞秒脉冲发生器
▲ 作者：Mengjie Yu, David Barton III, Rebecca Cheng, Christian Reimer, Prashanta Kharel, Lingyan He, Linbo Shao, Di Zhu, Yaowen Hu, Hannah R. Grant, Leif Johansson, Yoshitomo Okawachi, Alexander L. Gaeta, Mian Zhang & Marko Lončar
▲ 链接：
https://www.nature.com/articles/s41586-022-05345-1
▲ 摘要：
集成飞秒脉冲和频率梳源是广泛应用的关键组件，包括光学原子钟、微波光子学、光谱学、光波合成、变频、通信、激光雷达、光学计算和天文学。脉冲产生的主要方法依赖于具有三阶非线性或半导体增益的微谐振腔内的锁模。
然而，这些方法在噪声性能、波长和重复率可调性方面受到限制。通过使用电光调制器调制连续波单频激光器，亚皮秒脉冲可以在没有锁模的情况下合成。
作者使用级联低损耗电光振幅和相位调制器和啁啾布拉格光栅，形成一个时间透镜系统，在集成铌酸锂光子平台上展示了一个芯片级飞秒脉冲源。
该装置由连续波分布反馈激光芯片驱动，由单个连续波微波源控制，不需要任何稳定或锁定。他们测量了具有30千兆赫重复频率的飞秒脉冲序列（520飞秒持续时间），具有12.6纳米10分贝光学带宽的平顶光学光谱，单个梳线功率超过0.1毫瓦，脉冲能量为0.54皮焦耳。
研究结果代表了一种可调的、鲁棒的和低成本的集成脉冲光源，其连续波到脉冲的转换效率比以前的集成光源高一个数量级。该脉冲发生器或能在超快光学测量或分布式量子计算机网络等领域得到应用。
▲ Abstract：
Integrated femtosecond pulse and frequency comb sources are critical components for a wide range of applications, including optical atomic clocks, microwave photonics, spectroscopy, optical wave synthesis, frequency conversion, communications, lidar, optical computing and astronomy. The leading approaches for on-chip pulse generation rely on mode-locking inside microresonators with either third-order nonlinearity or with semiconductor gain. These approaches, however, are limited in noise performance, wavelength and repetition rate tunability . Alternatively, subpicosecond pulses can be synthesized without mode-locking, by modulating a continuous-wave single-frequency laser using electro-optic modulators. Here we demonstrate a chip-scale femtosecond pulse source implemented on an integrated lithium niobate photonic platform, using cascaded low-loss electro-optic amplitude and phase modulators and chirped Bragg grating, forming a time-lens system. The device is driven by a continuous-wave distributed feedback laser chip and controlled by a single continuous-wave microwave source without the need for any stabilization or locking. We measure femtosecond pulse trains (520-femtosecond duration) with a 30-gigahertz repetition rate, flat-top optical spectra with a 10-decibel optical bandwidth of 12.6 nanometres, individual comb-line powers above 0.1 milliwatts, and pulse energies of 0.54 picojoules. Our results represent a tunable, robust and low-cost integrated pulsed light source with continuous-wave-to-pulse conversion efficiencies an order of magnitude higher than those achieved with previous integrated sources. Our pulse generator may find applications in fields such as ultrafast optical measurement or networks of distributed quantum computers.
Chiral assemblies of pinwheel superlattices on substrates
基板上风车超晶格的手性组装
▲ 作者：Shan Zhou, Jiahui Li, Jun Lu, Haihua Liu, Ji-Young Kim, Ahyoung Kim, Lehan Yao, Chang Liu, Chang Qian, Zachary D. Hood, Xiaoying Lin, Wenxiang Chen, Thomas E. Gage, Ilke Arslan, Alex Travesset, Kai Sun, Nicholas A. Kotov & Qian Chen
▲ 链接：
https://www.nature.com/articles/s41586-022-05384-8
▲ 摘要：
手性超晶格独特的拓扑结构和物理性质使得它们在纳米颗粒自组装中备受追捧，但其在（元）材料方面具有挑战性。作者展示了四面体金纳米颗粒可从具有角到角连接的类钙钛矿低密度相，转变为具有角到边连接和更密集包装的风车组件。
而角共享组件是非手性的，风车超晶格在固体基底上变得强烈的镜像不对称，如手性测量所示。液相透射电子显微镜和计算模型表明，纳米粒子之间的范德华斯和静电相互作用控制着热力学平衡。
四面体之间可变的角到边连接使手性得以微调。通过光子诱导近场电子显微镜和时域有限差分模拟，双分子层超晶格的结构域显示出很强的手征活性。基板支撑的手性超晶格的简单性和多功能性促进了具有不同寻常的光学、机械和电子特性的超结构涂层的制造。
▲ Abstract：
The unique topology and physics of chiral superlattices make their self-assembly from nanoparticles highly sought after yet challenging in regard to (meta)materials. Here we show that tetrahedral gold nanoparticles can transform from a perovskite-like, low-density phase with corner-to-corner connections into pinwheel assemblies with corner-to-edge connections and denser packing. Whereas corner-sharing assemblies are achiral, pinwheel superlattices become strongly mirror asymmetric on solid substrates as demonstrated by chirality measures. Liquid-phase transmission electron microscopy and computational models show that van der Waals and electrostatic interactions between nanoparticles control thermodynamic equilibrium. Variable corner-to-edge connections among tetrahedra enable fine-tuning of chirality. The domains of the bilayer superlattices show strong chiroptical activity as identified by photon-induced near-field electron microscopy and finite-difference time-domain simulations. The simplicity and versatility of substrate-supported chiral superlattices facilitate the manufacture of metastructured coatings with unusual optical, mechanical and electronic characteristics.
Spin–orbit microlaser emitting in a four-dimensional Hilbert space
自旋轨道微激光在四维希尔伯特空间的发射
▲ 作者：Zhifeng Zhang, Haoqi Zhao, Shuang Wu, Tianwei Wu, Xingdu Qiao, Zihe Gao, Ritesh Agarwal, Stefano Longhi, Natalia M. Litchinitser, Li Ge & Liang Feng
▲ 链接：
https://www.nature.com/articles/s41586-022-05339-z
▲ 摘要：
迈向下一代高容量、抗噪声通信和计算技术的一步，是信息空间维度的大幅增加，以及具有奇异群对称性的N维（N > 2）希尔伯特空间上叠加态的合成。
尽管光子器件和系统发展迅速，但由于缺乏足够的可重构性来满足2（N−1）自由度的严格要求，片上信息技术大多局限于两级系统，这在本质上与合成维数的增加有关。
即使对最近出现的矢量激光器和微腔进行了广泛的努力，以扩展维度，但根据需要积极调整光的多样化、高维叠加态仍然是一个挑战。作者展示了一种用于芯片级柔性生成和任意四能级态操纵的高维自旋轨道微激光器。
通过非厄米合成规范场耦合的两个微腔被设计成发射自旋轨道耦合状态的光与六自由度。在自由空间中发射的激光束的矢量状态可以映射到定义SU（4）对称性的布洛赫超球上，演示高维叠加态的动态生成和高保真重构。
▲ Abstract：
A step towards the next generation of high-capacity, noise-resilient communication and computing technologies is a substantial increase in the dimensionality of information space and the synthesis of superposition states on an N-dimensional (N > 2) Hilbert space featuring exotic group symmetries. Despite the rapid development of photonic devices and systems, on-chip information technologies are mostly limited to two-level systems owing to the lack of sufficient reconfigurability to satisfy the stringent requirement for 2(N − 1) degrees of freedom, intrinsically associated with the increase of synthetic dimensionalities. Even with extensive efforts dedicated to recently emerged vector lasers and microcavities for the expansion of dimensionalities, it still remains a challenge to actively tune the diversified, high-dimensional superposition states of light on demand. Here we demonstrate a hyperdimensional, spin–orbit microlaser for chip-scale flexible generation and manipulation of arbitrary four-level states. Two microcavities coupled through a non-Hermitian synthetic gauge field are designed to emit spin–orbit-coupled states of light with six degrees of freedom. The vectorial state of the emitted laser beam in free space can be mapped on a Bloch hypersphere defining an SU(4) symmetry, demonstrating dynamical generation and reconfiguration of high-dimensional superposition states with high fidelity.
化学Chemistry
Perovskite solar cells based on screen-printed thin films
基于丝网印刷薄膜的钙钛矿太阳能电池
▲ 作者：Changshun Chen, Jianxin Chen, Huchen Han, Lingfeng Chao, Jianfei Hu, Tingting Niu, He Dong, Songwang Yang, Yingdong Xia, Yonghua Chen & Wei Huang
▲ 链接：
https://www.nature.com/articles/s41586-022-05346-0
▲ 摘要：
钙钛矿太阳能电池（PSCs）的一个潜在优势是能够对前驱体进行溶液处理并从溶液中沉积薄膜。作者研究了旋转涂层、叶片涂层、喷涂涂层、喷墨打印和槽模印刷等方法来沉积杂化钙钛矿薄膜。
通过由醋酸甲基铵离子液体溶剂制成的稳定和黏度可调的钙钛矿墨水，他们扩大了沉积方法的范围，包括丝网印刷。作者演示了钙钛矿薄膜厚度（从约120纳米到约1200纳米）、面积（从0.5 × 0.5 cm2到5 × 5 cm2）和不同基材上的图案的控制。印刷速度超过20 cm s−1，油墨使用量接近100%。
在不考虑湿度的环境空气中使用这种沉积方法，获得了最佳的自旋镀膜效率，分别为20.52%（0.05 cm2）和18.12% （1 cm2），而在具有热蒸发金属电极的普通器件中，自旋镀膜效率分别为20.13%和12.52%。
最值得注意的是，成功地探索了在环境空气中使用单机的全丝网印刷设备。相应的光伏电池在0.05 cm2、1.00 cm2和16.37 cm2（小模块）面积上分别表现出14.98%、13.53%和11.80%的高效率，在最大功率点运行300小时以上，初始效率保持在96.75%。
▲ Abstract：
One potential advantage of perovskite solar cells (PSCs) is the ability to solution process the precursors and deposit films from solution. At present, spin coating, blade coating, spray coating, inkjet printing and slot-die printing have been investigated to deposit hybrid perovskite thin films. Here we expand the range of deposition methods to include screen-printing, enabled by a stable and viscosity-adjustable (40–44,000 cP) perovskite ink made from a methylammonium acetate ionic liquid solvent. We demonstrate control over perovskite thin-film thickness (from about 120 nm to about 1,200 nm), area (from 0.5 × 0.5 cm2 to 5 × 5 cm2) and patterning on different substrates. Printing rates in excess of 20 cm s−1 and close to 100% ink use were achieved. Using this deposition method in ambient air and regardless of humidity, we obtained the best efficiencies of 20.52% (0.05 cm2) and 18.12% (1 cm2) compared with 20.13% and 12.52%, respectively, for the spin-coated thin films in normal devices with thermally evaporated metal electrodes. Most notably, fully screen-printing devices with a single machine in ambient air have been successfully explored. The corresponding photovoltaic cells exhibit high efficiencies of 14.98%, 13.53% and 11.80% on 0.05-cm2, 1.00-cm2 and 16.37-cm2 (small-module) areas, respectively, along with 96.75% of the initial efficiency retained over 300 h of operation at maximum power point.
