Nature, Volume 621 Issue 7978, 14 September 2023
《自然》，2023年9月14日，第621卷，7978期
物理学Physics
Subsecond periodic radio oscillations in a microquasar
微类星体的亚秒周期无线电振荡
▲ 作者：Pengfu Tian, Ping Zhang, Wei Wang, Pei Wang, Xiaohui Sun, Jifeng Liu, Bing Zhang, Zigao Dai, Feng Yuan, Shuangnan Zhang, Qingzhong Liu, Peng Jiang, Xuefeng Wu, Zheng Zheng, Jiashi Chen, Di Li, Zonghong Zhu, Zhichen Pan, Hengqian Gan, Xiao Chen & Na Sai
▲ 链接：
https://www.nature.com/articles/s41586-023-06336-6
▲ 摘要：
强大的相对论性喷流是所有尺度吸积黑洞普遍存在的特征之一。GRS1915 + 105是一个著名的快速旋转黑洞X射线双星，超光速射电发射运动表明其具有相对论性喷流，被称为“微类星体”。过去30年里，它表现出持续的X射线活动，X射线带的准周期振荡约为1至10Hz以及34和67Hz。
这些振荡可能起源于内部吸积盘，但也有人认为有其他的起源。射电观测发现其具有准周期耀斑或振荡的可变光曲线，周期约为20至50分钟。研究者报告了发生在2021年1月和2022年6月的1.05至1.45G Hz无线电频段中检测到的源的大约5 Hz瞬态周期性振荡特征的两个实例。在振荡阶段也观察到圆偏振。
▲ Abstract：
Powerful relativistic jets are one of the ubiquitous features of accreting black holes in all scales. GRS 1915 + 105 is a well-known fast-spinning black-hole X-ray binary with a relativistic jet, termed a ‘microquasar’, as indicated by its superluminal motion of radio emission. It has exhibited persistent X-ray activity over the last 30 years, with quasiperiodic oscillations of approximately 1–10 Hz and 34 and 67 Hz in the X-ray band. These oscillations probably originate in the inner accretion disk, but other origins have been considered11. Radio observations found variable light curves with quasiperiodic flares or oscillations with periods of approximately 20–50 min. Here we report two instances of approximately 5-Hz transient periodic oscillation features from the source detected in the 1.05- to 1.45-GHz radio band that occurred in January 2021 and June 2022. Circular polarization was also observed during the oscillation phase.
Quantum oscillations of the quasiparticle lifetime in a metal
金属中准粒子寿命的量子振荡
▲ 作者：：Nico Huber, Valentin Leeb, Andreas Bauer, Georg Benka, Johannes Knolle, Christian Pfleiderer & Marc A. Wilde
▲ 链接：
https://www.nature.com/articles/s41586-023-06330-y
▲ 摘要：
经过近一个世纪的研究，金属的低洼激发如何能用非相互作用带的有效单粒子理论很好地解释，仍然是一个谜。真实材料中丰富的相互作用提出了超越有效的单粒子、单波段行为现象的直接光谱特征问题。研究者报道了三维拓扑半金属CoSi中量子振荡的识别，它在两个基本方面违背了标准描述。
首先，振荡频率对应于两个带的半经典准粒子轨道的差，因为轨道的一半会与洛伦兹力相反，所以是禁止的。其次，振荡存在于50K以上，与所有其他振荡成分形成强烈对比，它们在几个开尔文以下就消失了。
研究者发现这与半经典准粒子生命周期(QPL)的量子振荡的通用模型计算非常一致。它们存在的唯一前提是至少两个电子轨道的非线性耦合，例如，由于缺陷或集体激励上的半经典准粒子散射，QPL的量子振荡对于具有多个轨道的朗道量子化的任何金属都是通用的。它们与拓扑半金属、非常规超导体、稀土化合物和Rashba系统中的某些频率一致，并允许识别和测量相关现象，例如，二维材料和多波段金属中。
▲ Abstract：
Following nearly a century of research, it remains a puzzle that the low-lying excitations of metals are remarkably well explained by effective single-particle theories of non-interacting bands. The abundance of interactions in real materials raises the question of direct spectroscopic signatures of phenomena beyond effective single-particle, single-band behaviour. Here we report the identification of quantum oscillations (QOs) in the three-dimensional topological semimetal CoSi, which defy the standard description in two fundamental aspects. First, the oscillation frequency corresponds to the difference of semiclassical quasiparticle (QP) orbits of two bands, which are forbidden as half of the trajectory would oppose the Lorentz force. Second, the oscillations exist up to above 50 K, in strong contrast to all other oscillatory components, which vanish below a few kelvin. Our findings are in excellent agreement with generic model calculations of QOs of the QP lifetime (QPL). Because the only precondition for their existence is a nonlinear coupling of at least two electronic orbits, for example, owing to QP scattering on defects or collective excitations, such QOs of the QPL are generic for any metal featuring Landau quantization with several orbits. They are consistent with certain frequencies in topological semimetals unconventional superconductors10,11, rare-earth compounds and Rashba systems, and permit to identify and gauge correlation phenomena, for example, in two-dimensional materials and multiband metals.
化学Chemistry
Sustainably sourced components to generate high-strength adhesives
利用可持续采购组件生产高强度粘合剂
▲ 作者：Clayton R. Westerman, Bradley C. McGill & Jonathan J. Wilker
▲ 链接：
https://www.nature.com/articles/s41586-023-06335-7
▲ 摘要：
几乎所有粘合剂都是从石油中提取的，可以形成永久的粘合剂，阻碍材料的回收分离以及垃圾填埋场废弃物的降解。
当试图从石油原料转向可持续材料生态系统时，现有的选择受到性能低、成本高或缺乏所需规模可用性的影响。研究者提出了一种可持续来源的粘合剂系统，由环氧大豆油、苹果酸和单宁酸制成，其性能可与目前的工业产品相媲美。
这种粘合剂可在各种条件下固化，从使用吹风机5分钟到在180℃的烤箱中固化24小时。金属基材之间的附着力高达18MPa左右，在最好的情况下，性能超过了传统的环氧树脂，这是最强大的现代粘合剂。所有组件都是生物质衍生的，成本低，且可用量大。新粘合剂或有助于材料的可持续粘合。
▲ Abstract：
Nearly all adhesives are derived from petroleum, create permanent bonds, frustrate materials separation for recycling and prevent degradation in landfills. When trying to shift from petroleum feedstocks to a sustainable materials ecosystem, available options suffer from low performance, high cost or lack of availability at the required scales. Here we present a sustainably sourced adhesive system, made from epoxidized soy oil, malic acid and tannic acid, with performance comparable to that of current industrial products. Joints can be cured under conditions ranging from use of a hair dryer for 5 min to an oven at 180 °C for 24 h. Adhesion between metal substrates up to around 18 MPa is achieved, and, in the best cases, performance exceeds that of a classic epoxy, the strongest modern adhesive. All components are biomass derived, low cost and already available in large quantities. Manufacturing at scale can be a simple matter of mixing and heating, suggesting that this new adhesive may contribute towards the sustainable bonding of materials.
Single molecule infrared spectroscopy in the gas phase
气相单分子红外光谱
▲ 作者：Aaron Calvin, Scott Eierman, Zeyun Peng, Merrell Brzeczek, Lincoln Satterthwaite & David Patterson
▲ 链接：
https://www.nature.com/articles/s41586-023-06351-7
▲ 摘要：
光谱学是一种关键的分析工具，提供了对分子结构有价值的见解，并被广泛用于识别化学样品。标记光谱学是作用光谱学的一种形式，其中通过失去弱附着的惰性“标记”粒子(例如He、Ne、N2)来检测分子离子对单个光子的吸收。
吸收光谱由标签损失率作为入射辐射频率的函数导出。到目前为止，所有气相多原子分子的光谱都局限于大分子系，因此由于存在多种化学和同分异构体，光谱解释变得复杂。
研究者提出了一种新的标记光谱方案来分析最纯净的样品：单个气相分子。他们通过测量单个气相(C7H7+)分子离子的红外光谱来证明该技术。该方法的高灵敏度揭示了传统标记方法未观察到的光谱特征。
原则上，该方法可通过一次识别一个组成分子来分析多组分混合物。单分子灵敏度将作用光谱学扩展到稀有样品，例如来自外星的样品，或者在传统作用方法中密度过低的数量密度下形成的反应中间体。
▲ Abstract：
Spectroscopy is a key analytical tool that provides valuable insight into molecular structure and is widely used to identify chemical samples. Tagging spectroscopy is a form of action spectroscopy in which the absorption of a single photon by a molecular ion is detected via the loss of a weakly attached, inert ‘tag’ particle (for example, He, Ne, N2). The absorption spectrum is derived from the tag loss rate as a function of incident radiation frequency. So far, all spectroscopy of gas phase polyatomic molecules has been restricted to large molecular ensembles, thus complicating spectral interpretation by the presence of multiple chemical and isomeric species. Here we present a novel tagging spectroscopic scheme to analyse the purest possible sample: a single gas phase molecule. We demonstrate this technique with the measurement of the infrared spectrum of a single gas phase tropylium (C7H7+) molecular ion. The high sensitivity of our method revealed spectral features not previously observed using traditional tagging methods. Our approach, in principle, enables analysis of multicomponent mixtures by identifying constituent molecules one at a time. Single molecule sensitivity extends action spectroscopy to rare samples, such as those of extraterrestrial origin or to reactive reaction intermediates formed at number densities that are too low for traditional action methods.
生态和气候Ecology & Climate
Marine heatwaves are not a dominant driver of change in demersal fishes
海洋热浪不是导致底栖鱼类变化的主要因素
▲ 作者：Alexa L. Fredston, William W. L. Cheung, Thomas L. Frölicher, Zoë J. Kitchel, Aurore A. Maureaud, James T. Thorson, Arnaud Auber, Bastien Mérigot, Juliano Palacios-Abrantes, Maria Lourdes D. Palomares, Laurène Pecuchet, Nancy L. Shackell & Malin L. Pinsky
▲ 链接：
https://www.nature.com/articles/s41586-023-06439-0
▲ 摘要：
近几十年来，海洋热浪与负面生态效应有关。如果海洋热浪经常导致群落重组和鱼类生物量崩溃，那么对生态系统、渔业和人类社区来说，后果可能是灾难性的。然而，海洋热浪对鱼类生物量或群落组成的负面影响程度，甚至它们的影响是否可以与自然和采样变异性区分开来，仍不清楚。研究者通过分析从北美和欧洲跨越亚热带到北极的大陆架生态系统的82322份长期科学调查样本，研究了1993年至2019年248次海底热浪对海洋鱼类的影响。
研究者表明海洋热浪对鱼类生物量的影响通常很小，不能与自然和采样变异性区分开来。此外，在这些生态系统中，海洋热浪并不总是与热带化（暖缘物种的增加）或去森林化（冷缘物种的减少）相关。虽然海洋热浪过后偶尔会出现生物量急剧下降的情况，但这只是例外，并非普遍现象。在海洋生态系统高度多变的背景下，海洋热浪并没有推动支持世界上许多最大和最具生产力渔业的鱼类群落的生物量变化或群落更替。
▲ Abstract：
Marine heatwaves have been linked to negative ecological effects in recent decades. If marine heatwaves regularly induce community reorganization and biomass collapses in fishes, the consequences could be catastrophic for ecosystems, fisheries and human communities. However, the extent to which marine heatwaves have negative impacts on fish biomass or community composition, or even whether their effects can be distinguished from natural and sampling variability, remains unclear. We investigated the effects of 248 sea-bottom heatwaves from 1993 to 2019 on marine fishes by analysing 82,322 hauls (samples) from long-term scientific surveys of continental shelf ecosystems in North America and Europe spanning the subtropics to the Arctic. Here we show that the effects of marine heatwaves on fish biomass were often minimal and could not be distinguished from natural and sampling variability. Furthermore, marine heatwaves were not consistently associated with tropicalization (gain of warm-affiliated species) or deborealization (loss of cold-affiliated species) in these ecosystems. Although steep declines in biomass occasionally occurred after marine heatwaves, these were the exception, not the rule. Against the highly variable backdrop of ocean ecosystems, marine heatwaves have not driven biomass change or community turnover in fish communities that support many of the world’s largest and most productive fisheries.
Persistent equatorial Pacific iron limitation under ENSO forcing
ENSO强迫下赤道太平洋铁的持续限制
▲ 作者：Thomas J. Browning, Mak A. Saito, Shungudzemwoyo P. Garaba, Xuechao Wang, Eric P. Achterberg, C. Mark Moore, Anja Engel, Matthew R. Mcllvin, Dawn Moran, Daniela Voss, Oliver Zielinski & Alessandro Tagliabue
▲ 链接：
https://www.nature.com/articles/s41586-023-06439-0
▲ 摘要：
目前预估的海洋净初级生产力对气候变化的响应高度不确定。相关模式研究表明，低纬度太平洋浮游植物营养限制的气候敏感性起着至关重要的作用，但这一点很少受到观测的约束。研究者发现物理强迫的变化通过多个厄尔尼诺/南方涛动(ENSO)周期驱动赤道太平洋铁限制强度的连贯波动，但最先进的气候模型高估了两倍。
该评估首先结合了野外营养添加实验、蛋白质组学和水上高光谱辐射测量，表明浮游植物对铁限制的生理反应导致叶绿素标准化浮游植物荧光的大约三倍变化。
然后，研究者利用连续18年的卫星荧光记录来量化气候引起的营养限制变异。这种天气条件限制为确定净初级生产力对气候变化模型预测的现实性提供了一种强有力的方法。
▲ Abstract：
Projected responses of ocean net primary productivity to climate change are highly uncertain1. Models suggest that the climate sensitivity of phytoplankton nutrient limitation in the low-latitude Pacific Ocean plays a crucial role, but this is poorly constrained by observations. Here we show that changes in physical forcing drove coherent fluctuations in the strength of equatorial Pacific iron limitation through multiple El Niño/Southern Oscillation (ENSO) cycles, but that this was overestimated twofold by a state-of-the-art climate model. Our assessment was enabled by first using a combination of field nutrient-addition experiments, proteomics and above-water hyperspectral radiometry to show that phytoplankton physiological responses to iron limitation led to approximately threefold changes in chlorophyll-normalized phytoplankton fluorescence. We then exploited the >18-year satellite fluorescence record to quantify climate-induced nutrient limitation variability. Such synoptic constraints provide a powerful approach for benchmarking the realism of model projections of net primary productivity to climate changes.
转自：“科学网”微信公众号
如有侵权，请联系本站删除！
