Nature, 31 August 2023, Volume 620 Issue 7976
《自然》2023年8月31日，第620卷，7976期
天文学Astronomy
A binary pulsar in a 53-minute orbit
轨道周期为53分钟的脉冲星双星系统
▲ 作者：Z. Pan, J. G. Lu, P. Jiang et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06308-w
▲ 摘要：
蜘蛛类脉冲星是一种近轨道上有一颗伴星的中子星。伴星向中子星释放物质，使其旋转至毫秒周期，而轨道缩短至小时内。
在此，我们报告对双毫秒脉冲星PSR J1953+1844 （M71E）的射电观测，它的轨道周期为53.3分钟，伴星质量约为0.07 M⊙。它是一个微弱的x射线源，距离球状星团M71的中心2.5弧分。
▲ Abstract：
Spider pulsars are neutron stars that have a companion star in a close orbit. The companion star sheds material to the neutron star, spinning it up to millisecond rotation periods, while the orbit shortens to hours. Here we report radio observations of the binary millisecond pulsar PSR J1953+1844 (M71E) that show it to have an orbital period of 53.3 minutes and a companion with a mass of around 0.07 M⊙. It is a faint X-ray source and located 2.5 arcminutes from the centre of the globular cluster M71.
化学Chemistry
First observation of 28O
首次检测到氧-28
▲ 作者：Y. Kondo, N. L. Achouri et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06352-6
▲ 摘要：
在此，我们报告了通过它们衰变成氧-24和4个中子，第一次观察到了氧-28和氧-27。氧-28的核是非常有趣，因为它有8个质子和20个中子这样“神奇”的数字，在核结构的标准壳层模型图像中，它预计是相对少数所谓的“双重神奇”核之一。
氧-28和氧-27都被发现存在狭窄的低共振，它们的衰变能量在这里与复杂的理论模型的结果进行了比较，包括大规模的壳模型计算和新开发的统计方法。
在这两种情况下，潜在的核相互作用都是从量子色动力学的有效场论推导出来的。最后，结果表明，氟-29梁产生氧-28的截面与不呈现封闭20个中子壳结构的截面一致。
▲ Abstract：
Here we report on the first observation of 28O and 27O through their decay into 24O and four and three neutrons, respectively. The 28O nucleus is of particular interest as, with the Z = 8 and N = 20 magic numbers, it is expected in the standard shell-model picture of nuclear structure to be one of a relatively small number of so-called ‘doubly magic’ nuclei. Both 27O and 28O were found to exist as narrow, low-lying resonances and their decay energies are compared here to the results of sophisticated theoretical modelling, including a large-scale shell-model calculation and a newly developed statistical approach. In both cases, the underlying nuclear interactions were derived from effective field theories of quantum chromodynamics. Finally, it is shown that the cross-section for the production of 28O from a 29F beam is consistent with it not exhibiting a closed N = 20 shell structure.
物理学Physics
Frustration- and doping-induced magnetism in a Fermi–Hubbard simulator
费米-哈伯德模拟器中阻挫和掺杂诱导的磁力现象
▲ 作者：Muqing Xu, Lev Haldar Kendrick et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06280-5
▲ 摘要：
在此，我们在各向异性光学晶格中使用从正方形到三角形连续可调谐的超冷费米子，研究了具有可控挫折和掺杂的哈伯德模型的局部自旋有序现象。
在半填充和强相互作用U/t≈9时，我们在单点水平上观察到挫折如何减小磁相关的范围，并驱动从共线奈尔反铁磁体到短程相关120°螺旋相的转变。
在半填充之外，三角形极限显示了在空穴掺杂侧反铁磁相关增强，而在粒子掺杂超过20%时，铁磁关联反转提示了动力学磁性在阻挫系统中的作用。这项工作为探索三角形晶格中可能的手性有序相或超导相铺平了道路，并实现了可能是描述铜材料超导性所必需的t-t '方形晶格哈伯德模型
▲ Abstract：
Here we investigate the local spin order of a Hubbard model with controllable frustration and doping, using ultracold fermions in anisotropic optical lattices continuously tunable from a square to a triangular geometry. At half-filling and strong interactions U/t ≈ 9, we observe at the single-site level how frustration reduces the range of magnetic correlations and drives a transition from a collinear Néel antiferromagnet to a short-range correlated 120° spiral phase. Away from half-filling, the triangular limit shows enhanced antiferromagnetic correlations on the hole-doped side and a reversal to ferromagnetic correlations at particle dopings above 20%, hinting at the role of kinetic magnetism in frustrated systems. This work paves the way towards exploring possible chiral ordered or superconducting phases in triangular lattices and realizing t–t′ square lattice Hubbard models that may be essential to describe superconductivity in cuprate materials.
人工智能Artificial Intelligence
Champion-level drone racing using deep reinforcement learning
使用深度强化学习的冠军级无人机
▲ 作者：Elia Kaufmann, Leonard Bauersfeld et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06419-4
▲ 摘要：
在此，我们介绍Swift，一个可以与人类世界冠军水平的车辆比赛的自主系统。该系统结婚了模拟中的深度强化学习（RL）与物理世界中收集的数据。Swift在现实世界中与三位人类冠军进行了正面交锋，其中包括两个国际联赛的世界冠军。
Swift在与每一位人类冠军的较量中都赢得了几场比赛，并创下了最快的比赛时间。这项研究代表了移动机器人和机器智能的一个里程碑，它可能会激发在其他物理系统中部署基于混合学习的解决方案。
▲ Abstract：
Here we introduce Swift, an autonomous system that can race physical vehicles at the level of the human world champions. The system combines deep reinforcement learning (RL) in simulation with data collected in the physical world. Swift competed against three human champions, including the world champions of two international leagues, in real-world head-to-head races. Swift won several races against each of the human champions and demonstrated the fastest recorded race time. This work represents a milestone for mobile robotics and machine intelligence, which may inspire the deployment of hybrid learning-based solutions in other physical systems.
环境科学Environmental Science
Agricultural pesticide land budget and river discharge to oceans
农药土地预算以及河流向海洋的排放
▲ 作者：Federico Maggi, Fiona H. M. Tang & Francesco N. Tubiello
▲ 链接：
https://www.nature.com/articles/s41586-023-06296-x
▲ 摘要：
在此，我们开发了一个过程模型，计算了92种最常用的农业农药活性物质的水文和生物地球化学，以评估它们通过世界主要流域的途径，并绘制了全球陆地和河流预算的近况，包括向海洋的排放。本研究表明2015年使用的农药年净投入量为0.94Tg，其中82%被生物降解，10%残留在土壤中，7.2%浸出至根区以下。
通过排水，河流以每年每公里−10至100公斤以上的速率吸收0.73克农药。与土壤中的情况相反，进入河流的农药中只有1.1%沿着溪流降解，在超过13000公里长度的河流中超过安全水平（浓度大于1 μg l−1），每年有0.71克农药流入海洋。除草剂是土地（72%）和河流入海（62%）中的主要农药残留。
▲ Abstract：
Here, we develop a process-based model accounting for the hydrology and biogeochemistry of the 92 most used agricultural pesticide active substances to assess their pathways through the principal catchments of the world and draw a near-present picture of the global land and river budgets, including discharge to oceans. Of the 0.94 Tg net annual pesticide input in 2015 used in this study, 82% is biologically degraded, 10% remains as residue in soil and 7.2% leaches below the root zone. Rivers receive 0.73 Gg of pesticides from their drainage at a rate of 10 to more than 100 kg yr−1 km−1. By contrast to their fate in soil, only 1.1% of pesticides entering rivers are degraded along streams, exceeding safety levels (concentrations >1 μg l−1) in more than 13,000 km of river length, with 0.71 Gg of pesticide active ingredients released to oceans every year. Herbicides represent the prevalent pesticide residue on both land (72%) and river outlets (62%).
生物学Biology
Reef-building corals farm and feed on their photosynthetic symbionts
造礁珊瑚养殖并以它们的光合共生生物为食
▲ 作者：Jörg Wiedenmann, Cecilia D’Angelo et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06442-5
▲ 摘要：
在此，我们通过一系列长期的实验表明，仅共生生物对溶解的无机氮和磷的吸收就足以维持珊瑚的快速生长。接下来，考虑到宿主和共生体的氮和磷预算，我们确定这些营养物质是通过共生体“养殖”收集的，并通过消化多余的共生细胞转运到宿主体中。
最后，我们使用了一个大规模的自然实验，通过海鸟给一些珊瑚礁施肥而不给其他珊瑚礁施肥，以表明在我们的实验室实验中建立的共生珊瑚对溶解无机营养物质的有效利用有可能在生态系统层面上促进野生珊瑚的生长。
▲ Abstract：
Here we show, through a series of long-term experiments, that the uptake of dissolved inorganic nitrogen and phosphorus by the symbionts alone is sufficient to sustain rapid coral growth. Next, considering the nitrogen and phosphorus budgets of host and symbionts, we identify that these nutrients are gathered through symbiont ‘farming’ and are translocated to the host by digestion of excess symbiont cells. Finally, we use a large-scale natural experiment in which seabirds fertilize some reefs but not others, to show that the efficient utilization of dissolved inorganic nutrients by symbiotic corals established in our laboratory experiments has the potential to enhance coral growth in the wild at the ecosystem level.
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