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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
南極研究
Antarctic Studies
Temperate rainforests near the South Pole during peak Cretaceous warmth
在白堊紀最溫暖期，南極附近有雨林
▲ 作者：Johann P. Klages、Ulrich Salzmann、the Science Team of Expedition PS104，et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-020-2148-5
▲ 摘要
白堊紀中期是過去1.4億年裡最熱的一段時間之一，這是由於大氣中二氧化碳含量約為百萬分之一千（1000ppm）的緣故。由於幾乎沒有來自南極圈南部的近端地質記錄，極地冰是否能在這樣的環境條件下存在是有爭議的。
在這裡，研究人員分析了從南極西部大陸架獲得的沉積層序——迄今為止報告的最南端白堊紀記錄——並表明，在土倫階—桑託階（9200萬至8300萬年前），一個穩健的低地雨林環境存在於大約82°S的古緯度。
該記錄包含了一個完整的3米長的原位化石根網絡，它嵌在包含各種花粉和孢子的泥岩基質中。氣候模型模擬表明，在高緯度出現這種溫帶氣候，需要大氣二氧化碳濃度為每百萬體積1120~1680 ppm，以及植被和地表沒有被南極冰川覆蓋。
▲ 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
追蹤海洋捕食者以保護南部海洋生態系統
▲ 作者：Mark A. Hindell、Ryan R. Reisinger、Ben Raymond，et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-020-2126-y
▲ 摘要
地球南部海洋生態系統正受到資源開發和氣候變化的壓力。減緩這些影響需要確定和保護具有生態意義的地區（AES），這些地區到目前為止還沒有在洋盆範圍內確定。
在這裡，通過對海洋捕食者的整體水平跟蹤，研究人員確定了這一全球重要地區的AES，並評估了當前的威脅和保護水平。
通過對17種鳥類和哺乳動物的4000多個足跡的整合，科學家發現了大西洋和印度洋亞南極島嶼周圍，以及南極大陸架上的AES。研究人員指出，捕魚壓力不成比例地集中在AES內部，並預計下個世紀的氣候變化將給這些地區帶來壓力，特別是南極大陸周圍。
目前，40°S以南海域僅有7.1%已受到正式保護，其中AES總量佔29%。研究人員認為，需要建立和定期修訂海洋生態系統保護網絡，以便長期減輕對南部海洋生態系統日益增加的壓力。
▲ 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.
物理學 Physics
Experimental demonstration of memory-enhanced quantum communication
存儲增強量子通信的實驗演示
▲ 作者：M. K. Bhaskar、R. Riedinger、M. D. Lukin，et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-020-2103-5
▲ 摘要
在量子科學和工程中，遠距離傳輸量子信息的能力是至關重要的。雖然一些量子通訊的應用，例如安全的量子密鑰分發，已經成功部署，但它們的範圍目前受到光子損耗的限制，不能使用簡單測量和重複策略來擴展，而不損害無條件的安全性。
在這裡，研究人員使用一個單一的固態自旋存儲器集成在一個納米光子鑽石諧振器上，以實現異步光子Bell態測量，這是量子中繼器的關鍵組成部分。
在一個原理證明的實驗中，研究人員演示了高保真操作，有效地使量子通信的速率超過了理想的損失等效直接傳輸方法。這些結果代表了邁向實用量子中繼器和大規模量子網絡的關鍵一步。
▲ 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
被捕獲鑽石運動的自旋冷卻
▲ 作者：T. Delord、P. Huillery、L. Nicolas、G. Hétet
▲ 鏈接：
https://www.nature.com/articles/s41586-020-2133-z
▲ 摘要
觀察和控制宏觀量子系統一直是量子物理研究的驅動力。特別是，單個量子系統和機械振盪器之間的強耦合正在被積極地研究。雖然用自旋系統的相干控制機械運動的讀出和用原始振盪器單自旋讀出都已得到證明，但使用長壽命電子自旋對宏觀物體運動的溫度控制尚未見報道。
在這裡，研究人員觀察了被捕獲的微金剛石的運動的自旋相關扭矩和自旋冷卻。利用微波和激光的聯合激發氮—空位中心自旋，以作用於金剛石定向，並通過一個動態的反作用來冷卻金剛石振動。此外，通過在非線性系統中驅動系統，研究人員證明了自旋—機械耦合激發的雙穩定性和自持續相干振盪，這為自旋驅動非經典運動狀態的產生提供了前景。
研究人員表示，這種由電場梯度在真空下保持在一定位置的懸浮金剛石，可以作為一個羅盤，具有可控的損耗，在高精度扭矩傳感、模擬自旋玻色子問題和探測量子相變方面有潛在的用途。
在單自旋極限下，利用超純納米級金剛石，研究人員可以在環境條件下實現氮—空位中心自旋的量子非自毀讀出，實現遙遠的單個自旋之間的確定性糾纏和物質波干涉測量。
▲ 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.
遺傳學 Genetics
A genomic and epigenomic atlas of prostate cancer in Asian populations
亞洲人群前列腺癌的基因組和表觀基因組圖譜
▲ 作者：Jing Li、Chuanliang Xu、Yinghao Sun，et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-020-2135-x
▲ 摘要
前列腺癌是全球第二常見的男性癌症。在過去10年中，大規模的綜合基因組學研究通過描述成千上萬病人的遺傳和表觀遺傳特徵，增強了人們對該病的認識。然而，這些研究中描述的大多數腫瘤是從西方人群中獲得的。
這裡，研究人員通過對2554例前列腺腫瘤的系統比較，繪製了亞洲人群前列腺癌基因圖譜，研究表明中國患者的基因組突變特徵與西方患者明顯不同。
研究人員分析了來自中國原發性前列腺癌患者的208份腫瘤組織樣品和匹配的健康對照組織的全基因組、轉錄組和DNA甲基化數據。結果發現，中國患者的基因組改變特徵與西方人群明顯不同：41%的腫瘤包含FOXA1突變，18%的ZNF292和CHD1缺失。研究人員表示，基因組和表觀基因組的變化是相關的，並且可以預測疾病的表型和進展。
該研究揭示了東西方人前列腺癌基因組圖譜的巨大差異，發現了與前列腺癌預後及生存相關的新基因，將為前列腺癌的治療、診斷和預後檢測提供新的基礎。
▲ 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
人類細胞體節時鐘的體外特徵
▲ 作者：Margarete Diaz-Cuadros、Daniel E. Wagner、Olivier Pourquié，et al.
▲ 鏈接：
https://www.nature.com/articles/s41586-019-1885-9
▲ 摘要
在胚胎發生的早期，一種細胞時鐘的每一次“滴答”都會促進體節的形成，所產生的體節最終變成了脊椎骨。但一直以來人們尚未證實這種分節時鐘是否存在於人類中。但對嚴重脊柱分節缺陷患者的遺傳分析表明，與小鼠分節時鐘相關的循環基因在人類中有多個同源基因。
這裡，研究人員建立了一個系統，逐個細胞查看時鐘基因的動態。結果顯示，體外產生的人類前體節中胚層（PSM）細胞重現了分節時鐘的振盪。人PSM細胞的振盪週期是小鼠細胞的兩倍（5小時與2.5小時），但同樣受到FGF、WNT、Notch和YAP信號的調節。研究人員還證明了FGF信號控制振盪的相位和週期。
該研究發現的人類分節時鐘代表了理解人類發育生物學的重要里程碑。
▲ 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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