Science, 12 April 2024, Volume 384 Issue 6692
《科学》2024年4月12日，第384卷，6692期
天体物理学Astrophysics
A magnetic massive star has experienced a stellar merger
经历了恒星合并的一颗大质量磁性恒星
▲ 作者：A. J. FROST, H. SANA et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adg7700
▲ 摘要：
我们使用多历元干涉和光谱观测来描述HD 148937，这是一个由两颗大质量恒星组成的双星系统。我们发现其中只有一颗恒星具有磁性，且它看起来比伴星更年轻。该系统的特性和周围的双极星云可以用两颗恒星合并（在先前的三重系统中）产生磁性大质量恒星的模型来重现。
我们的结果提供了观测证据以证明至少在一些大质量恒星中，磁场是通过恒星合并形成的。
▲ Abstract：
We used multi-epoch interferometric and spectroscopic observations to characterize HD 148937, a binary system of two massive stars. We found that only one star is magnetic and that it appears younger than its companion. The system properties and a surrounding bipolar nebula can be reproduced with a model in which two stars merged (in a previous triple system) to produce the magnetic massive star. Our results provide observational evidence that magnetic fields form in at least some massive stars through stellar mergers.
化学Chemistry
Thin adhesive oil films lead to anomalously stable mixtures of water in oil
薄粘接油膜使得水的混合物在油里异常稳定
▲ 作者：CLAIRE NANNETTE, JEAN BAUDRY et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adj6728
▲ 摘要：
油和水的混合，只能通过将一种液体的液滴分散到另一种液体中才能实现。当两个液滴相互靠近时，将它们分开的薄膜总是变得不稳定，导致液滴聚在一起。避免这种不稳定性的唯一已知方法是通过添加第三种成分，通常是表面活性剂，使得薄膜稳定在其平衡厚度上。
我们观察到，通过一层薄的油流体膜将两个水滴分开，会导致水滴之间的粘附相互作用。此外，在不使用任何表面活性剂或溶剂的情况下，这种相互作用可以防止它们聚结的时间长达数周。
▲ Abstract：
Oil and water can only be mixed by dispersing droplets of one fluid in the other. When two droplets approach one another, the thin film that separates them invariably becomes unstable, causing the droplets to coalesce. The only known way to avoid this instability is through addition of a third component, typically a surfactant, which stabilizes the thin film at its equilibrium thickness. We report the observation that a thin fluid film of oil separating two water droplets can lead to an adhesive interaction between the droplets. Moreover, this interaction prevents their coalescence over timescales of several weeks, without the use of any surfactant or solvent.
物理学Physics
Realization of an atomic quantum Hall system in four dimensions
四维空间中原子量子霍尔系统的实现
▲ 作者：JEAN-BAPTISTE BOUHIRON, AURéLIEN FABRE et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adf8459
▲ 摘要：
我们报告一个四维演化的原子量子霍尔系统的实现，其中两个空间维度和两个合成维度编码在镝原子的大自旋中。通过对非线性电磁响应的全面表征，我们测量了接地带的非平凡拓扑指数，并观察了相关的各向异性超边缘模式。
与D≤3的平面轨道不同，我们还激发了非平面回旋加速器运动。我们的研究或使四维空间中强相关的拓扑液体研究成为可能，归纳分数量子霍尔态。
▲ Abstract：
We report the realization of an atomic quantum Hall system evolving in four dimensions (4D), with two spatial dimensions and two synthetic ones encoded in the large spin of dysprosium atoms. We measure the nontrivial topological index of the ground band through a full characterization of the nonlinear electromagnetic response and observe the associated anisotropic hyperedge modes. We also excite nonplanar cyclotron motion, in contrast to the planar orbits in D ≤ 3. Our work may enable the investigation of strongly correlated topological liquids in 4D, generalizing fractional quantum Hall states.
地球科学Earth Science
Size, distribution, and vulnerability of the global soil inorganic carbon
全球土壤无机碳储量的规模、分布和脆弱性
▲ 作者：YUANYUAN HUANG , XIAODONG SONG et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adi7918
▲ 摘要：
通过编译223593个实地测量数据并开发机器学习模型，我们认为，全球土壤在地表2米深度上以土壤无机碳形式储存了2305±636（±1 SD）亿吨碳。在未来的情景中，与陆地生态系统氮添加相关的土壤酸化将在未来30年减少全球土壤无机碳高达230亿吨的碳，其中印度和中国受影响最大。
我们对当前陆地—水的碳储量和内陆水碳酸盐化学的综合研究表明，每年至少有1.13±3.3亿吨无机碳通过土壤流失到内陆水域，对大气和水圈碳动态产生的影响巨大却被忽视了。
▲ Abstract：
By compiling 223,593 field-based measurements and developing machine-learning models, we report that global soils store 2305 ± 636 (±1 SD) billion tonnes of carbon as SIC over the top 2-meter depth. Under future scenarios, soil acidification associated with nitrogen additions to terrestrial ecosystems will reduce global SIC (0.3 meters) up to 23 billion tonnes of carbon over the next 30 years, with India and China being the most affected. Our synthesis of present-day land-water carbon inventories and inland-water carbonate chemistry reveals that at least 1.13 ± 0.33 billion tonnes of inorganic carbon is lost to inland-waters through soils annually, resulting in large but overlooked impacts on atmospheric and hydrospheric carbon dynamics.
生物学Biology
Two inhibitory neuronal classes govern acquisition and recall of spinal sensorimotor adaptation
两类抑制神经元控制脊髓感觉运动适应的习得和回忆
▲ 作者：SIMON LAVAUD, CHARLOTTE BICHARA et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adf6801
▲ 摘要：
通过一个简单的条件反射范例，我们发现背侧抑制神经元通过调节一组特定体感信息的传递来增强与肢体位置相关的条件反射线索的显著性，从而适应保护性肢体退缩行为。
相比之下，维持先前获得的运动适应需要腹侧抑制闰绍细胞。操纵闰绍细胞并不影响适应性本身，但可以灵活地改变适应性行为的表达。这些发现确定了一个涉及两种不同脊髓抑制性神经元群的回路基础，能使持久的感觉运动适应独立于大脑。
▲ Abstract：
Using a simple conditioning paradigm, we found that dorsal inhibitory neurons are indispensable for adapting protective limb-withdrawal behavior by regulating the transmission of a specific set of somatosensory information to enhance the saliency of conditioning cues associated with limb position. By contrast, maintaining previously acquired motor adaptation required the ventral inhibitory Renshaw cells. Manipulating Renshaw cells does not affect the adaptation itself but flexibly alters the expression of adaptive behavior. These findings identify a circuit basis involving two distinct populations of spinal inhibitory neurons, which enables lasting sensorimotor adaptation independently from the brain.
Nitrogen-fixing organelle in a marine alga
海藻中的固氮细胞器
▲ 作者：TYLER H. COALE, VALENTINA LOCONTE et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adk1075
▲ 摘要：
共生相互作用是调节真核生物碳和能量代谢的叶绿体和线粒体细胞器进化的关键。在这里，我们表明地中海候选蓝藻（UCYN-A）已经紧密地整合到藻类细胞结构和细胞器分裂中，并且它进口由藻类基因组编码的蛋白质。
这些都是细胞器的特征，表明UCYN-A已经进化到超越了内共生，并作为早期进化阶段的氮固定细胞器或“硝化质体”发挥作用。
▲ Abstract：
Symbiotic interactions were key to the evolution of chloroplast and mitochondria organelles, which mediate carbon and energy metabolism in eukaryotes. Here we show that UCYN-A has been tightly integrated into algal cell architecture and organellar division and that it imports proteins encoded by the algal genome. These are characteristics of organelles and show that UCYN-A has evolved beyond endosymbiosis and functions as an early evolutionary stage N2-fixing organelle, or “nitroplast.”
