编译 | 李言
Nature, 9 June 2022, Volume 606 Issue 7913
《自然》2022年6月9日，第606卷，7913期
天文学Astronomy
Binarity of a protostar affects the evolution of the disk and planets
原恒星的双星系统影响尘埃盘和行星系统的演化
▲ 作者：Jes K. Jørgensen, Rajika L. Kuruwita, Daniel Harsono et al.
▲ 链接：
https://www.nature.com/articles/s41586-022-04659-4
▲ 摘要：
在所有与太阳类似的恒星中，近一半是双星或多星系统，这可能会影响恒星及其最初阶段的演化及其原行星盘。NGC 1333-IRAS2A是一个年轻的双原恒星系统，位于英仙座分子云中。
众所周知，NGC 1333-IRAS2A驱动天空中几乎相互垂直的两极外流，并通过长波长连续体观测分解为双星VLA1和VLA2。在此，我们报告了一系列分子种类的空间和光谱分辨观察。
我们将这些结果与详细的磁流体动力学仿真模型进行了比较：结果显示，在恒星周围盘上的非均匀吸积发生在周期性的爆发中，驱动了一个摆动的喷射流。我们的结论是，二元性和多重性极大地影响了新兴恒星的性质，以及原行星盘的物理和化学结构，因此可能会影响任何新兴的行星系。
▲ Abstract：
Nearly half of all stars similar to our Sun are in binary or multiple systems, which may affect the evolution of the stars and their protoplanetary disks during their earliest stages. NGC 1333-IRAS2A is a young, Class 0, low-mass protostellar system located in the Perseus molecular cloud. It is known to drive two bipolar outflows that are almost perpendicular to each other on the sky and is resolved into binary components, VLA1 and VLA2, through long wavelength continuum observations . Here we report spatially and spectrally resolved observations of a range of molecular species. We compare these to detailed magnetohydrodynamic simulations: the comparisons show that inhomogeneous accretion onto the circumstellar disks occurs in episodic bursts, driving a wobbling jet. We conclude that binarity and multiplicity in general strongly affect the properties of the emerging stars, as well as the physical and chemical structures of the protoplanetary disks and therefore potentially any emerging planetary systems.
化学Chemistry
Discovery of non-squalene triterpenes
非角鲨烯来源三萜的发现
▲ 作者：Hui Tao, Lukas Lauterbach, Guangkai Bian, Rong Chen et al.
▲ 链接：
https://www.nature.com/articles/s41586-022-04773-3
▲ 摘要：
在此，我们研究了两种丝状真菌来源的I型嵌合萜类合酶，即Talaromyces verruculosus talaropentaene synthase (TvTS)和Macrophomina phaseolina macrophomene synthase (MpMS)。
这两种酶都使用二甲基烯丙基二磷酸和异戊烯基二磷酸或六戊烯基二磷酸作为底物，据我们所知，这是非角鲨烯依赖的三萜生物合成的首例。我们通过同位素标记实验研究了TvTS和MpMS的环化机理及其产物的绝对构型。
通过对TvTS和全长MpMS萜类环化酶结构域的分析，可以进一步了解它们的催化机制。我们开发了一个基于AlphaFold2的筛选平台来挖掘第三个丝状真菌来源的I型嵌合萜类合酶，即 Colletotrichum gloeosporioides colleterpenol synthase (CgCS)。我们的发现确定了三萜生物合成的一种新的酶机制，并增强了对自然界中萜类生物合成的理解。
▲ Abstract：
In this study, two fungal chimeric class I TrTSs, Talaromyces verruculosus talaropentaene synthase (TvTS) and Macrophomina phaseolina macrophomene synthase (MpMS), were characterized. Both enzymes use dimethylallyl diphosphate and isopentenyl diphosphate or hexaprenyl diphosphate as substrates, representing the first examples, to our knowledge, of non-squalene-dependent triterpene biosynthesis. The cyclization mechanisms of TvTS and MpMS and the absolute configurations of their products were investigated in isotopic labelling experiments. Structural analyses of the terpene cyclase domain of TvTS and full-length MpMS provide detailed insights into their catalytic mechanisms. An AlphaFold2-based screening platform was developed to mine a third TrTS, Colletotrichum gloeosporioides colleterpenol synthase (CgCS). Our findings identify a new enzymatic mechanism for the biosynthesis of triterpenes and enhance understanding of terpene biosynthesis in nature.
物理学Physics
Observation of ultracold atomic bubbles in orbital microgravity
轨道微重力下观测的超冷原子气泡
▲ 作者：R. A. Carollo, D. C. Aveline, B. Rhyno et al.
▲ 链接：
https://www.nature.com/articles/s41586-022-04639-8
▲ 摘要：
在此，我们报告美国国家航空航天局（NASA）在国际空间站上的冷原子实验室通过射频修整协议观测到的超冷原子气泡。我们观察了不同尺寸和初始温度下的气泡结构，同时探索了气泡热力学，证明与膨胀相关的冷却情况。
我们用几微米厚度的超冷薄膜实现了超过1毫米大小的气泡陷阱的部分覆盖，我们观察了壳结构的动力学投影到自由演化的谐波约束。这些观测是在太空中对超冷原子进行的首批测量之一，我们利用恒定重力来探索在地球上极难创造的量子系统。
这一工作为今后在轨道微重力下研究玻色-爱因斯坦凝聚态泡、其激发特性及演化过程中拓扑结构的作用打下了基础。
▲ Abstract：
Here we report observations from the NASA Cold Atom Lab facility onboard the International Space Station of bubbles of ultracold atoms created using a radiofrequency-dressing protocol. We observe bubble configurations of varying size and initial temperature, and explore bubble thermodynamics, demonstrating substantial cooling associated with inflation. We achieve partial coverings of bubble traps greater than one millimetre in size with ultracold films of inferred few-micrometre thickness, and we observe the dynamics of shell structures projected into free-evolving harmonic confinement. The observations are among the first measurements made with ultracold atoms in space, using perpetual freefall to explore quantum systems that are prohibitively difficult to create on Earth. This work heralds future studies (in orbital microgravity) of the Bose–Einstein condensed bubble, the character of its excitations and the role of topology in its evolution.
Observation of Cooper pairs in a mesoscopic two-dimensional Fermi gas
介观二维费米气体中库珀对的观测
▲ 作者：Marvin Holten, Luca Bayha, Keerthan Subramanian et al.
▲ 链接：
https://www.nature.com/articles/s41586-022-04678-1
▲ 摘要：
在此，我们对介观二维费米气体中的库珀对进行了直接观测。我们应用了一种成像方案，能提取具有单粒子和自旋分辨率的强相互作用费米气体的完全就地动量分布情况。
超冷气体使我们能够在完全不相互作用、不配对的系统和弱引力之间进行自由调节，我们在费米表面发现了库珀对相关性。我们的介观系统与原子核、超导粒子或量子点的物理密切相关。
在实验中，通过对相互作用、粒子数量和潜在景观的精确控制，我们在这项工作中建立的可观测对象不仅为响应有关介观系统、同时也为回答它们与宏观世界联系的长期问题提供了方法。
▲ Abstract：
Here we directly observe Cooper pairs in a mesoscopic two-dimensional Fermi gas. We apply an imaging scheme that enables us to extract the full in situ momentum distribution of a strongly interacting Fermi gas with single-particle and spin resolution. Our ultracold gas enables us to freely tune between a completely non-interacting, unpaired system and weak attractions, where we find Cooper pair correlations at the Fermi surface. When increasing the attractive interactions even further, the pairs gradually turn into deeply bound molecules that break up the Fermi surface. Our mesoscopic system is closely related to the physics of nuclei, superconducting grains or quantum dots. With the precise control over the interactions, particle number and potential landscape in our experiment, the observables we establish in this work provide an approach for answering longstanding questions concerning not only such mesoscopic systems but also their connection to the macroscopic world.
地球科学geoscience
Instantaneous tracking of earthquake growth with elastogravity signals
用弹性重力信号即时跟踪地震发展
▲ 作者：Andrea Licciardi, Quentin Bletery, Bertrand Rouet-Leduc et al.
▲ 链接：
https://www.nature.com/articles/s41586-022-04672-7
▲ 摘要：
在此，我们的研究表明在达到一定震级后，即时弹性重力信号（PEGS）可以被用于实时跟踪地震的发展。我们开发了一种深度学习模型，利用日本区域宽频地震检波器在地震波到达之前记录的PEGS所携带的信息。
在利用经验噪声增强训练合成波形数据库后，我们展示了该算法可以即时跟踪震源时间函数的真实数据。我们的模型通过使用一部分通常被视为噪音的地震图数据，打开了对大地震破裂演化的“真实即时”追踪，并且可以改变海啸预警情况。
▲ Abstract：
Here we show that PEGS can be used in real time to track earthquake growth instantaneously after the event reaches a certain magnitude. We develop a deep learning model that leverages the information carried by PEGS recorded by regional broadband seismometers in Japan before the arrival of seismic waves. After training on a database of synthetic waveforms augmented with empirical noise, we show that the algorithm can instantaneously track an earthquake source time function on real data. Our model unlocks ‘true real-time’ access to the rupture evolution of large earthquakes using a portion of seismograms that is routinely treated as noise, and can be immediately transformative for tsunami early warning.
考古学Archeology
Lidar reveals pre-Hispanic low-density urbanism in the Bolivian Amazon
激光雷达揭示了前西班牙的玻利维亚亚马逊地区低密度城市化
▲ 作者：Heiko Prümers, Carla Jaimes Betancourt, José Iriarte, Mark Robinson & Martin Schaich
▲ 链接：
https://www.nature.com/articles/s41586-022-04780-4
▲ 摘要：
在此，我们展示了亚马逊地区西南大草原的卡萨阿拉比文化遗址（大约公元500年至公元1400年）的激光雷达数据，揭示了在一个密集的四层聚落系统中存在的两个巨大遗址（147公顷和315公顷）。
迄今为止，卡萨阿拉比文化遗址占地约4500平方公里，其中一个大型定居点占约500平方公里。这些大型居民点的市政建筑包括阶梯式平台，其顶部有u形结构、矩形平台丘和锥形金字塔（高达22米）。大型居民点被排列整齐的多边形河岸包围，它是中心节点，通过绵延数公里的笔直的凸起堤道与排列较低的居民点相连。
由运河和水库组成的大量输水系统，在人为改造的景观中完善了聚落系统。我们的研究结果表明，卡萨拉贝文化遗址的定居模式代表了一种热带低密度城市模式，这在亚马逊地区以前从未被研究过。
▲ Abstract：
Here we present lidar data of sites belonging to the Casarabe culture (around AD 500 to AD 1400) in the Llanos de Mojos savannah–forest mosaic, southwest Amazonia, revealing the presence of two remarkably large sites (147 ha and 315 ha) in a dense four-tiered settlement system. The Casarabe culture area, as far as known today, spans approximately 4,500 km2, with one of the large settlement sites controlling an area of approximately 500 km2. The civic-ceremonial architecture of these large settlement sites includes stepped platforms, on top of which lie U-shaped structures, rectangular platform mounds and conical pyramids (which are up to 22 m tall). The large settlement sites are surrounded by ranked concentric polygonal banks and represent central nodes that are connected to lower-ranked sites by straight, raised causeways that stretch over several kilometres. Massive water-management infrastructure, composed of canals and reservoirs, complete the settlement system in an anthropogenically modified landscape. Our results indicate that the Casarabe-culture settlement pattern represents a type of tropical low-density urbanism that has not previously been described in Amazonia.
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