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Nature, 2 April 2020, Volume 580 Issue 7801
《自然》2020年4月2日，第580卷，7801期
南极研究
Antarctic Studies
Temperate rainforests near the South Pole during peak Cretaceous warmth
在白垩纪最温暖期，南极附近有雨林
▲ 作者：Johann P. Klages、Ulrich Salzmann、the Science Team of Expedition PS104，et al.
▲ 链接：
https://www.nature.com/articles/s41586-020-2148-5
▲ 摘要
白垩纪中期是过去1.4亿年里最热的一段时间之一，这是由于大气中二氧化碳含量约为百万分之一千（1000ppm）的缘故。由于几乎没有来自南极圈南部的近端地质记录，极地冰是否能在这样的环境条件下存在是有争议的。
在这里，研究人员分析了从南极西部大陆架获得的沉积层序——迄今为止报告的最南端白垩纪记录——并表明，在土伦阶—桑托阶（9200万至8300万年前），一个稳健的低地雨林环境存在于大约82°S的古纬度。
该记录包含了一个完整的3米长的原位化石根网络，它嵌在包含各种花粉和孢子的泥岩基质中。气候模型模拟表明，在高纬度出现这种温带气候，需要大气二氧化碳浓度为每百万体积1120~1680 ppm，以及植被和地表没有被南极冰川覆盖。
▲ Abstract
The mid-Cretaceous period was one of the warmest intervals of the past 140 million years, driven by atmospheric carbon dioxide levels of around 1,000 parts per million by volume. In the near absence of proximal geological records from south of the Antarctic Circle, it is disputed whether polar ice could exist under such environmental conditions. Here we use a sedimentary sequence recovered from the West Antarctic shelf—the southernmost Cretaceous record reported so far—and show that a temperate lowland rainforest environment existed at a palaeolatitude of about 82° S during the Turonian–Santonian age (92 to 83 million years ago). This record contains an intact 3-metre-long network of in situ fossil roots embedded in a mudstone matrix containing diverse pollen and spores. A climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric carbon dioxide concentrations of 1,120–1,680 parts per million by volume and a vegetated land surface without major Antarctic glaciation, highlighting the important cooling effect exerted by ice albedo under high levels of atmospheric carbon dioxide.
Tracking of marine predators to protect Southern Ocean ecosystems
追踪海洋捕食者以保护南部海洋生态系统
▲ 作者：Mark A. Hindell、Ryan R. Reisinger、Ben Raymond，et al.
▲ 链接：
https://www.nature.com/articles/s41586-020-2126-y
▲ 摘要
地球南部海洋生态系统正受到资源开发和气候变化的压力。减缓这些影响需要确定和保护具有生态意义的地区（AES），这些地区到目前为止还没有在洋盆范围内确定。
在这里，通过对海洋捕食者的整体水平跟踪，研究人员确定了这一全球重要地区的AES，并评估了当前的威胁和保护水平。
通过对17种鸟类和哺乳动物的4000多个足迹的整合，科学家发现了大西洋和印度洋亚南极岛屿周围，以及南极大陆架上的AES。研究人员指出，捕鱼压力不成比例地集中在AES内部，并预计下个世纪的气候变化将给这些地区带来压力，特别是南极大陆周围。
目前，40°S以南海域仅有7.1%已受到正式保护，其中AES总量占29%。研究人员认为，需要建立和定期修订海洋生态系统保护网络，以便长期减轻对南部海洋生态系统日益增加的压力。
▲ Abstract
Southern Ocean ecosystems are under pressure from resource exploitation and climate change. Mitigation requires the identification and protection of Areas of Ecological Significance (AESs), which have so far not been determined at the ocean-basin scale. Here, using assemblage-level tracking of marine predators, we identify AESs for this globally important region and assess current threats and protection levels. Integration of more than 4,000 tracks from 17 bird and mammal species reveals AESs around sub-Antarctic islands in the Atlantic and Indian Oceans and over the Antarctic continental shelf. Fishing pressure is disproportionately concentrated inside AESs, and climate change over the next century is predicted to impose pressure on these areas, particularly around the Antarctic continent. At present, 7.1% of the ocean south of 40°S is under formal protection, including 29% of the total AESs. The establishment and regular revision of networks of protection that encompass AESs are needed to provide long-term mitigation of growing pressures on Southern Ocean ecosystems.
物理学 Physics
Experimental demonstration of memory-enhanced quantum communication
存储增强量子通信的实验演示
▲ 作者：M. K. Bhaskar、R. Riedinger、M. D. Lukin，et al.
▲ 链接：
https://www.nature.com/articles/s41586-020-2103-5
▲ 摘要
在量子科学和工程中，远距离传输量子信息的能力是至关重要的。虽然一些量子通讯的应用，例如安全的量子密钥分发，已经成功部署，但它们的范围目前受到光子损耗的限制，不能使用简单测量和重复策略来扩展，而不损害无条件的安全性。
在这里，研究人员使用一个单一的固态自旋存储器集成在一个纳米光子钻石谐振器上，以实现异步光子Bell态测量，这是量子中继器的关键组成部分。
在一个原理证明的实验中，研究人员演示了高保真操作，有效地使量子通信的速率超过了理想的损失等效直接传输方法。这些结果代表了迈向实用量子中继器和大规模量子网络的关键一步。
▲ Abstract
The ability to communicate quantum information over long distances is of central importance in quantum science and engineering. Although some applications of quantum communication such as secure quantum key distribution are already being successfully deployed, their range is currently limited by photon losses and cannot be extended using straightforward measure-and-repeat strategies without compromising unconditional security. Alternatively, quantum repeaters, which utilize intermediate quantum memory nodes and error correction techniques, can extend the range of quantum channels. However, their implementation remains an outstanding challenge, requiring a combination of efficient and high-fidelity quantum memories, gate operations, and measurements. Here we use a single solid-state spin memory integrated in a nanophotonic diamond resonator to implement asynchronous photonic Bell-state measurements, which are a key component of quantum repeaters. In a proof-of-principle experiment, we demonstrate high-fidelity operation that effectively enables quantum communication at a rate that surpasses the ideal loss-equivalent direct-transmission method while operating at megahertz clock speeds. These results represent a crucial step towards practical quantum repeaters and large-scale quantum networks.
Spin-cooling of the motion of a trapped diamond
被捕获钻石运动的自旋冷却
▲ 作者：T. Delord、P. Huillery、L. Nicolas、G. Hétet
▲ 链接：
https://www.nature.com/articles/s41586-020-2133-z
▲ 摘要
观察和控制宏观量子系统一直是量子物理研究的驱动力。特别是，单个量子系统和机械振荡器之间的强耦合正在被积极地研究。虽然用自旋系统的相干控制机械运动的读出和用原始振荡器单自旋读出都已得到证明，但使用长寿命电子自旋对宏观物体运动的温度控制尚未见报道。
在这里，研究人员观察了被捕获的微金刚石的运动的自旋相关扭矩和自旋冷却。利用微波和激光的联合激发氮—空位中心自旋，以作用于金刚石定向，并通过一个动态的反作用来冷却金刚石振动。此外，通过在非线性系统中驱动系统，研究人员证明了自旋—机械耦合激发的双稳定性和自持续相干振荡，这为自旋驱动非经典运动状态的产生提供了前景。
研究人员表示，这种由电场梯度在真空下保持在一定位置的悬浮金刚石，可以作为一个罗盘，具有可控的损耗，在高精度扭矩传感、模拟自旋玻色子问题和探测量子相变方面有潜在的用途。
在单自旋极限下，利用超纯纳米级金刚石，研究人员可以在环境条件下实现氮—空位中心自旋的量子非自毁读出，实现遥远的单个自旋之间的确定性纠缠和物质波干涉测量。
▲ Abstract
Observing and controlling macroscopic quantum systems has long been a driving force in quantum physics research. In particular, strong coupling between individual quantum systems and mechanical oscillators is being actively studied. Whereas both read-out of mechanical motion using coherent control of spin systems and single-spin read-out using pristine oscillators have been demonstrated, temperature control of the motion of a macroscopic object using long-lived electronic spins has not been reported. Here we observe a spin-dependent torque and spin-cooling of the motion of a trapped microdiamond. Using a combination of microwave and laser excitation enables the spins of nitrogen–vacancy centres to act on the diamond orientation and to cool the diamond libration via a dynamical back-action. Furthermore, by driving the system in the nonlinear regime, we demonstrate bistability and self-sustained coherent oscillations stimulated by spin–mechanical coupling, which offers the prospect of spin-driven generation of non-classical states of motion. Such a levitating diamond—held in position by electric field gradients under vacuum—can operate as a ‘compass’ with controlled dissipation and has potential use in high-precision torque sensing, emulation of the spin-boson problem and probing of quantum phase transitions. In the single-spin limit and using ultrapure nanoscale diamonds, it could allow quantum non-demolition read-out of the spin of nitrogen–vacancy centres at ambient conditions, deterministic entanglement between distant individual spins and matter-wave interferometry.
遗传学 Genetics
A genomic and epigenomic atlas of prostate cancer in Asian populations
亚洲人群前列腺癌的基因组和表观基因组图谱
▲ 作者：Jing Li、Chuanliang Xu、Yinghao Sun，et al.
▲ 链接：
https://www.nature.com/articles/s41586-020-2135-x
▲ 摘要
前列腺癌是全球第二常见的男性癌症。在过去10年中，大规模的综合基因组学研究通过描述成千上万病人的遗传和表观遗传特征，增强了人们对该病的认识。然而，这些研究中描述的大多数肿瘤是从西方人群中获得的。
这里，研究人员通过对2554例前列腺肿瘤的系统比较，绘制了亚洲人群前列腺癌基因图谱，研究表明中国患者的基因组突变特征与西方患者明显不同。
研究人员分析了来自中国原发性前列腺癌患者的208份肿瘤组织样品和匹配的健康对照组织的全基因组、转录组和DNA甲基化数据。结果发现，中国患者的基因组改变特征与西方人群明显不同：41%的肿瘤包含FOXA1突变，18%的ZNF292和CHD1缺失。研究人员表示，基因组和表观基因组的变化是相关的，并且可以预测疾病的表型和进展。
该研究揭示了东西方人前列腺癌基因组图谱的巨大差异，发现了与前列腺癌预后及生存相关的新基因，将为前列腺癌的治疗、诊断和预后检测提供新的基础。
▲ Abstract
Prostate cancer is the second most common cancer in men worldwide. Over the past decade, large-scale integrative genomics efforts have enhanced our understanding of this disease by characterizing its genetic and epigenetic landscape in thousands of patients. However, most tumours profiled in these studies were obtained from patients from Western populations. Here we produced and analysed whole-genome, whole-transcriptome and DNA methylation data for 208 pairs of tumour tissue samples and matched healthy control tissue from Chinese patients with primary prostate cancer. Systematic comparison with published data from 2,554 prostate tumours revealed that the genomic alteration signatures in Chinese patients were markedly distinct from those of Western cohorts: specifically, 41% of tumours contained mutations in FOXA1 and 18% each had deletions in ZNF292 and CHD1. Alterations of the genome and epigenome were correlated and were predictive of disease phenotype and progression. Coding and noncoding mutations, as well as epimutations, converged on pathways that are important for prostate cancer, providing insights into this devastating disease. These discoveries underscore the importance of including population context in constructing comprehensive genomic maps for disease.
In vitro characterization of the human segmentation clock
人类细胞体节时钟的体外特征
▲ 作者：Margarete Diaz-Cuadros、Daniel E. Wagner、Olivier Pourquié，et al.
▲ 链接：
https://www.nature.com/articles/s41586-019-1885-9
▲ 摘要
在胚胎发生的早期，一种细胞时钟的每一次“滴答”都会促进体节的形成，所产生的体节最终变成了脊椎骨。但一直以来人们尚未证实这种分节时钟是否存在于人类中。但对严重脊柱分节缺陷患者的遗传分析表明，与小鼠分节时钟相关的循环基因在人类中有多个同源基因。
这里，研究人员建立了一个系统，逐个细胞查看时钟基因的动态。结果显示，体外产生的人类前体节中胚层（PSM）细胞重现了分节时钟的振荡。人PSM细胞的振荡周期是小鼠细胞的两倍（5小时与2.5小时），但同样受到FGF、WNT、Notch和YAP信号的调节。研究人员还证明了FGF信号控制振荡的相位和周期。
该研究发现的人类分节时钟代表了理解人类发育生物学的重要里程碑。
▲ Abstract
The segmental organization of the vertebral column is established early in embryogenesis, when pairs of somites are rhythmically produced by the presomitic mesoderm (PSM). The tempo of somite formation is controlled by a molecular oscillator known as the segmentation clock. Although this oscillator has been well-characterized in model organisms, whether a similar oscillator exists in humans remains unknown. Genetic analyses of patients with severe spine segmentation defects have implicated several human orthologues of cyclic genes that are associated with the mouse segmentation clock, suggesting that this oscillator might be conserved in humans. Here we show that human PSM cells derived in vitro—as well as those of the mouse—recapitulate the oscillations of the segmentation clock. Human PSM cells oscillate with a period two times longer than that of mouse cells (5 h versus 2.5 h), but are similarly regulated by FGF, WNT, Notch and YAP signalling. Single-cell RNA sequencing reveals that mouse and human PSM cells in vitro follow a developmental trajectory similar to that of mouse PSM in vivo. Furthermore, we demonstrate that FGF signalling controls the phase and period of oscillations, expanding the role of this pathway beyond its classical interpretation in ‘clock and wavefront’ models. Our work identifying the human segmentation clock represents an important milestone in understanding human developmental biology.
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