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物理学Physics Two waves of massive stars running away from the young cluster R136 两波年夜质量恒星正从年青的星团R136中逃逸 ▲ 作者：Mitchel Stoop, Alex de Koter, Lex Kaper, Sarah Brands, Simon Portegies Zwart, Hugues Sana, Fiorenzo Stoppa, Mark Gieles, Laurent Mahy, Tomer Shenar, Difeng Guo, Gijs Nelemans Steven Rieder ▲链接： https://www.nature.com/articles/s41586-024-08013-8 ▲摘要： 年夜质量恒星首要在星团或星协中构成的。它们的辐射场、恒星风和超新星强烈地影响着本地的情况。在星团生命的最初几百万年里，年夜质量恒星被动态地喷射出来，并以高速逃离星团。但是，动态弹射脱轨的产率束缚较差。 研究者陈述了从年夜麦哲伦星云的年青星团R136中喷射出的55颗年夜质量逃逸恒星的样本。对盖亚数据的天体丈量学阐发揭露了两个动态弹出的逃逸通道。第一个通道向各个标的目的喷射年夜质量恒星，与R136降生时代和以后的动力学彼此感化一致。第二个通道以首选标的目的发射恒星，可能与星团彼此感化有关。 他们发现，最初降生在R136的最亮恒星中，有23%~33%是逃逸恒星。模子猜测较着低估了年夜质量恒星的动态逃逸率。是以，它们在塑造和加热星际和星系介质中的感化，和它们在驱动星系外流中的感化，比之前想象的要主要很多。 ▲ Abstract： Massive stars are predominantly born in stellar associations or clusters. Their radiation fields, stellar winds and supernovae strongly impact their local environment. In the first few million years of a cluster s life, massive stars are dynamically ejected and run away from the cluster at high speed. However, the production rate of dynamically ejected runaways is poorly constrained. Here we report on a sample of 55 massive runaway stars ejected from the young cluster R136 in the Large Magellanic Cloud. An astrometric analysis of Gaia data reveals two channels of dynamically ejected runaways. The first channel ejects massive stars in all directions and is consistent with dynamical interactions during and after the birth of R136. The second channel launches stars in a preferred direction and may be related to a cluster interaction. We found that 23 33% of the most luminous stars initially born in R136 are runaways. Model predictionshave significantly underestimated the dynamical escape fraction of massive stars. Consequently, their role in shaping and heating the interstellar and galactic media and their role in driving galactic outflows are far more important than previously thought. Harnessing plasticity in sequential metamaterials for ideal shock absorption 操纵序贯超材料的塑性实现抱负的减震 ▲ 作者：Wenfeng Liu, Shahram Janbaz, David Dykstra, Bernard Ennis Corentin Coulais ▲链接： https://www.nature.com/articles/s41586-024-08037-0 ▲摘要： 机械超材料表示出低密度下的高刚度、加强的能量接收、外形变形、挨次变形、互动性和鲁棒波导等有趣的特征。到今朝为止，超材料设计首要依靠在几何，材料的非线性，如粘弹性、断裂和塑性，在很年夜水平上被解除在设计道理以外。事实上，塑性变形传统上被视为一种掉效模式，是以被谨慎地避免。 在这里，研究者拥抱塑性，而不是发现塑性和愚昧不不变性之间的奥妙均衡，并将其称之为 取得愚昧 。他们操纵 取得愚昧 来设计在肆意年夜的步调序列中顺次愚昧的超材料，同时连结承载能力，并操纵持续屈就愚昧来制造连系了刚度和耗散的超材料。这两种特征凡是是不相容的，并且可以屡次利用。 这类崇高高贵材料表示出优良的减震机能。研究者暗示，该发现为超材料东西箱增添了可塑性，使机械超材料成为一项具有年夜范围出产潜力的新兴手艺。 ▲ Abstract： Mechanical metamaterials exhibit interesting properties such as high stiffness at low density, enhanced energy absorption, shape morphing, sequential deformations, auxeticity and robust waveguiding. Until now, metamaterial design has primarily relied on geometry, and materials nonlinearities such as viscoelasticity, fracture and plasticity have been largely left out of the design rationale. In fact, plastic deformations have been traditionally seen as a failure mode and thereby carefully avoided. Here we embrace plasticity instead and discover a delicate balance between plasticity and buckling instability, which we term yield buckling . We exploit yield buckling to design metamaterials that buckle sequentially in an arbitrary large sequence of steps whilst keeping a load-bearing capacity. We make use of sequential yield buckling to create metamaterials that combine stiffness and dissipation two properties that are usually incompatible and that can be used several times. Hence, our metamaterials exhibit superior shock-absorption performance. Our findings add plasticity to the metamaterial toolbox and make mechanical metamaterials a burgeoning technology with serious potential for mass production. Quasi-periodic X-ray eruptions years after a nearby tidal disruption event 准周期性的x射线喷发，产生在四周的潮汐粉碎事务数年后 ▲ 作者：M. Nicholl, D. R. Pasham, A. Mummery, M. Guolo, K. Gendreau, G. C. Dewangan, E. C. Ferrara, R. Remillard, C. Bonnerot, J. Chakraborty, A. Hajela, V. S. Dhillon, A. F. Gillan, J. Greenwood, M. E. Huber, A. Janiuk, G. Salvesen, S. van Velzen, A. Aamer, K. D. Alexander, C. R. Angus, Z. Arzoumanian, K. Auchettl, E. Berger, D. R. Young ▲链接： https://www.nature.com/articles/s41586-024-08023-6 ▲摘要： 准周期爆发（QPEs）是来自星系焦点的软X射线的发光爆发，在数小时到数周的时候标准上反复。这些罕有系统背后的机制尚不肯定，但年夜大都理论都触及超年夜质量黑洞（SMBHs）四周的吸积盘履历不不变或与近轨道上的恒星物体彼此感化。 有人提出，当SMBH粉碎一颗途经的恒星时，可能会构成这个圆盘，这意味着很多QPE应当在可不雅测到的潮汐粉碎事务（TDEs）之前产生。两个已知的QPE源显示出与TDE一致的静态光度的持久衰减，两个不雅测到的TDE也显示出与个体喷发一致的X射线耀斑。TDE和QPE也优先呈现在近似的星系中。但是，没有确认的反复QPE与光谱确认的TDE或在峰值亮度下不雅察到的光学TDE有关。 在这里，研究者陈述了从AT2019qiz探测到的9个平均复发时候约为48小时的X射线QPE， AT2019qiz是一个四周和普遍研究的光学选择TDE。他们检测并摹拟了吸积盘的X射线，紫外线（UV）和光学发射，并注解轨道天体与吸积盘碰撞为QPE供给了公道的注释。 ▲ Abstract： Quasi-periodic eruptions (QPEs) are luminous bursts of soft X-rays from the nuclei of galaxies, repeating on timescales of hours to weeks. The mechanism behind these rare systems is uncertain, but most theories involve accretion disks around supermassive black holes (SMBHs) undergoing instabilities or interacting with a stellar object in a close orbit. It has been suggested that this disk could be created when the SMBH disrupts a passing star, implying that many QPEs should be preceded by observable tidal disruption events (TDEs). Two known QPE sources show long-term decays in quiescent luminosity consistent with TDEs and two observed TDEs have exhibited X-ray flares consistent with individual eruptions. TDEs and QPEs also occur preferentially in similar galaxies15. However, no confirmed repeating QPEs have been associated with a spectroscopically confirmed TDE or an optical TDE observed at peak brightness. Here we report the detection of nine X-ray QPEs with a mean recurrence time of approximately 48 h from AT2019qiz, a nearby and extensively studied optically selected TDE. We detect and model the X-ray, ultraviolet (UV) and optical emission from the accretion disk and show that an orbiting body colliding with this disk provides a plausible explanation for the QPEs. Electronic rotons and Wigner crystallites in a two-dimensional dipole liquid 二维偶极子液体中的电子质子和维格纳晶体 ▲ 作者：Soobin Park, Minjae Huh, Chris Jozwiak, Eli Rotenberg, Aaron Bostwick Keun Su Kim ▲链接： https://www.nature.com/articles/s41586-024-08045-0 ▲摘要： 朗道提出的注释超流体液氦的一个要害概念是质子的量籽粒子的根基激起。液体华夏子的不法则摆列致使了质子的非周期色散，这对理解分数目子霍尔液体（磁质子）和玻色-爱因斯坦凝集体的超固体性起着要害感化。即便对二维电子或偶极子液体，在没有磁场的环境下，排挤性彼此感化也被猜测会构成一个扭转最小值，这可以用来追踪向维格纳晶体和超导的改变，虽然这还没有被不雅察到。 在这里，研究者陈述了在碱金属离子的二维偶极子液体中不雅察到的这类电子质子向黑磷的表层供给电子。他们的数据揭露了惊人的非周期色散，其特点是有限动量下的局部能量最小。跟着偶极子密度的下降，彼此感化跨越了动能，质子间隙减小到0，就像在晶体中一样，这是维格纳结晶的旌旗灯号。该模子显示了由偶极子之间的斥力引发的短程有序的主要性，这可以看做是漂浮在费米液体海洋中的维格纳晶体（气泡或条纹）的构成。研究成果注解，电子质子（和赝隙）的首要发源是强相干的。 ▲ Abstract： A key concept proposed by Landau to explain superfluid liquid helium is the elementary excitation of quantum particles called rotons. The irregular arrangement of atoms in a liquid leads to the aperiodic dispersion of rotons, which played a pivotal role in understanding fractional quantum Hall liquids (magneto-rotons) and the supersolidity of Bose Einstein condensates. Even for a two-dimensional electron or dipole liquid, in the absence of a magnetic field, the repulsive interactions have been predicted to form a roton minimum, which can be used to trace the transition to Wigner crystals and superconductivity although this has not yet been observed. Here, we report the observation of such electronic rotons in a two-dimensional dipole liquid of alkali-metal ions donating electrons to surface layers of black phosphorus. Our data reveal the striking aperiodic dispersion of rotons, which is characterized by a local minimum of energy at finite momentum. As the density of dipoles decreases so that interactions dominate over the kinetic energy, the roton gap reduces to 0, as in a crystal, signalling Wigner crystallization. Our model shows the importance of short-range order arising from repulsion between dipoles, which can be viewed as the formation of Wigner crystallites (bubbles or stripes) floating in the sea of a Fermi liquid. Our results reveal that the primary origin of electronic rotons (and the pseudogap) is strong correlations. 生态学Ecology Islands are key for protecting the world s plant endemism 岛屿对庇护世界特有植物很要害 ▲ 作者：Julian Schrader, Patrick Weigelt, Lirong Cai, Mark Westoby, Jos Mar a Fern ndez-Palacios, Francisco J. Cabezas, Gregory M. Plunkett, Tom A. Ranker, Kostas A. Triantis, Panayiotis Trigas, Yasuhiro Kubota Holger Kreft ▲链接： https://www.nature.com/articles/s41586-024-08036-1 ▲摘要： 岛屿是闻名的自然进化尝试室，撑持着很多在其他处所找不到的物种。岛屿的庇护也值得高度存眷，很多岛屿特有物种今朝遭到要挟或已灭尽。在这里，研究者提出了一份尺度化的清单，列出了所有已知的维管植物，并记实了它们的地舆和系统发育散布和庇护风险。 研究者对304103莳植物的阐发注解，94052种（31%）原生在岛屿，占全球陆地面积的5.3%。此中，63280种是岛屿特有物种，占全球植物多样性的21%。此中四分之三仅限在年夜型或孤立的岛屿。与世界植物区系比拟，岛屿特有植物在生命树中长短随机散布的，共有1.005亿年怪异的系统发育汗青，此中17个科、1702个属完满是岛屿独有的。 在国际天然庇护同盟指定的所有维管植物庇护种别中，22%是岛屿特有植物。在这些特有物种中，51%遭到要挟，55%有记实的全球灭尽产生在岛屿上。研究者发现，在所有单岛特有物种中，只有6%呈现在合适结合国30 30庇护方针的岛屿上。需要采纳告急办法，包罗恢复活境、断根入侵物种和移处所案，以庇护世界岛屿植物群。研究者暗示，该清单量化了岛屿生物的怪异性，为将来的岛屿植物区系研究供给了根本，并强调了采纳庇护步履的火急需要。 ▲ Abstract： Islands are renowned as evolutionary laboratories and support many species that are not found elsewhere. Islands are also of great conservation concern, with many of their endemic species currently threatened or extinct. Here we present a standardized checklist of all known vascular plants that occur on islands and document their geographical and phylogenetic distribution and conservation risk. Our analyses of 304,103 plant species reveal that 94,052 species (31%) are native to islands, which constitute 5.3% of the global landmass4. Of these, 63,280 are island endemic species, which represent 21% of global plant diversity. Three-quarters of these are restricted to large or isolated islands. Compared with the world flora, island endemics are non-randomly distributed within the tree of life, with a total of 1,005 billion years of unique phylogenetic history with 17 families and 1,702 genera being entirely endemic to islands. Of all vascular plants assigned InternationalUnion for Conservation of Nature conservation categories, 22% are island endemics. Among these endemic species, 51% are threatened, and 55% of all documented global extinctions have occurred on islands. We find that of all single-island endemic species, only 6% occur on islands meeting the United Nations 30 30 conservation target. Urgent measures including habitat restoration, invasive species removal and ex situ programmes are needed to protect the world s island flora. Our checklist quantifies the uniqueness of island life, provides a basis for future studies of island floras, and highlights the urgent need to take actions for conserving them. Continental-scale nutrient and contaminant delivery by Pacific salmon 承平洋鲑鱼可在年夜陆层面输送营养和污染物 ▲ 作者：Jessica E. Brandt, Jeff S. Wesner, Gregory T. Ruggerone, Timothy D. Jardine, Collin A. Eagles-Smith, Gabrielle E. Ruso, Craig A. Stricker, Kristofor A. Voss David M. Walters ▲链接： https://www.nature.com/articles/s41586-024-07980-2 ▲摘要： 迁移动物携带的年夜量营养物资对食品网具有生态效益，但可能被配合运输的污染物所抵消。鲑鱼产卵洄游是这一进程的典型，将海洋来历的物资带到内陆生态系统。在那边它们刺激了本地的出产力，但也增添了污染物的表露。此刻承平洋鲑鱼的品貌和生物量都比上个世纪高，这反应了群落布局的重年夜转变，这类转变可能改变了营养物和污染物的输送。 研究者将营养物资和污染物浓度与40年的承平洋鲑鱼年回报连系起来，量化群落布局的转变若何影响北美西部的海洋到淡水输入。鲑鱼每一年向淡水输送数吨的营养物资和数千克的污染物。鲑鱼收益的增添（1976-2015年）使鲑鱼来历的营养物和污染物投入别离增添了30%和20%。这些增添的首要是粉红鲑鱼，它们寿命短，在海洋食品网中的摄取量比其他鲑鱼低，并且营养与污染物的比例最高。 是以，研究者暗示，营养物资的输送比污染物的输送速度更快，跟着时候的推移，鲑鱼的投入对生态更有益。即使如斯，污染物的负荷可能代表了一些鲑鱼捕食者的表露问题。承平洋鲑鱼的例子展现了持久的情况转变若何与年夜空间标准上的营养物资和污染物活动彼此感化，并为摸索其他迁移物种的近似模式供给了一个模子。 ▲ Abstract： The movement of large amounts of nutrients by migrating animals has ecological benefits for recipient food webs that may be offset by co-transported contaminants. Salmon spawning migrations are archetypal of this process, carrying marine-derived materials to inland ecosystems where they stimulate local productivity but also enhance contaminant exposure. Pacific salmon abundance and biomass are higher now than in the last century, reflecting substantial shifts in community structure8 that probably altered nutrient versus contaminant delivery. Here we combined nutrient and contaminant concentrations with 40 years of annual Pacific salmon returns to quantify how changes in community structure influenced marine to freshwater inputs to western North America. Salmon transported tonnes of nutrients and kilograms of contaminants to freshwaters annually. Higher salmon returns (1976 2015) increased salmon-derived nutrient and contaminant inputs by 30% and 20%, respectively. These increases were dominated by pink salmon, which are short-lived, feed lower in marine food webs than other salmon species, and had the highest nutrient-to-contaminant ratios. As a result, the delivery of nutrients increased at a greater rate than the delivery of contaminants, and salmon inputs became more ecologically beneficial over time. Even still, contaminant loadings may represent exposure concerns for some salmon predators. The Pacific salmon example demonstrates how long-term environmental changes interact with nutrient and contaminant movement across large spatial scales and provides a model for exploring similar patterns with other migratory species.特殊声明：本文转载仅仅是出在传布信息的需要，其实不意味着代表本网站不雅点或证实其内容的真实性；如其他媒体、网站或小我从本网站转载利用，须保存本网站注明的“来历”，并自大版权等法令责任；作者假如不但愿被转载或联系转载稿费等事宜，请与我们联系。
