作者:冯维维 来源:科学网微信公众号 发布时间:2023/7/15 21:04:18
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《自然》(20230713出版)一周论文导读

 

编译 | 冯维维

Nature, 13 July 2023, Volume 619 Issue 7969

《自然》2023年7月13日,第619卷,7969期

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物理学Physics

XGalaxies in voids assemble their stars slowly

空洞星系缓慢地聚合其恒星

▲ 作者:Jesús Domínguez-Gómez, Isabel Pérez, Tomás Ruiz-Lara, Reynier F. Peletier, Patricia Sánchez-Blázquez, Ute Lisenfeld, Jesús Falcón-Barroso, Manuel Alcázar-Laynez, María Argudo-Fernández, Guillermo Blázquez-Calero, Hélène Courtois, Salvador Duarte Puertas, Daniel Espada, Estrella Florido, Rubén García-Benito, Andoni Jiménez, Kathryn Kreckel, Mónica Relao, Laura Sánchez-Menguiano, Thijs van der Hulst, Rien van de Weygaert, Simon Verley & Almudena Zurita

▲ 链接:

https://www.nature.com/articles/s41586-023-06109-1

▲ 摘要:

宇宙中的星系以网状结构分布,诞生于不同的大尺度环境:密集的星系团、细长的细丝、片状的壁和称为空洞的低密度区域。科学家推测空洞中的低密度会影响其星系的性质。

事实上,此前的研究表明,空洞中的星系平均颜色更蓝、质量更小,且比密度更大的大尺度环境中的星系具有更晚的形态和更高的当前恒星形成率。然而,在观测上尚未证明过空洞中的恒星形成历史(SFH)与细丝、壁和星团中的恒星形成历史有何本质上的不同。

研究者展示了空洞星系比密度更大的大尺度环境中的星系平均有更慢的SFH。他们还发现两种主要的SFH类型存在于所有环境中:“短时间尺度”星系在早期不受其大尺度环境的影响,而只在其生命后期;“长时间尺度”星系不断受到其环境和恒星质量的影响。这两种类型在空隙中都比在丝、壁和星系团中进化得慢。

▲ Abstract:

 Galaxies in the Universe are distributed in a web-like structure characterized by different large-scale environments: dense clusters, elongated filaments, sheetlike walls and under-dense regions, called voids. The low density in voids is expected to affect the properties of their galaxies. Indeed, previous studies have shown that galaxies in voids are, on average, bluer and less massive, and have later morphologies and higher current star formation rates than galaxies in denser large-scale environments. However, it has never been observationally proved that the star formation histories (SFHs) in voids are substantially different from those in filaments, walls and clusters. Here we show that void galaxies have had, on average, slower SFHs than galaxies in denser large-scale environments. We also find two main SFH types present in all the environments: ‘short-timescale’ galaxies are not affected by their large-scale environment at early times but only later in their lives; ‘long-timescale’ galaxies have been continuously affected by their environment and stellar mass. Both types have evolved more slowly in voids than in filaments, walls and clusters.

Resolved imaging confirms a radiation belt around an ultracool dwarf

高分辨率成像证实一颗超冷矮星周围存在辐射带

▲ 作者:Melodie M. Kao, Amy J. Mioduszewski, Jackie Villadsen & Evgenya L. Shkolnik

▲ 链接:

https://www.nature.com/articles/s41586-023-06138-w

▲ 摘要:

高辐射带存在于所有大尺度的太阳系行星磁层:地球、木星、土星、天王星和海王星。这些持续存在的赤道地带的相对论粒子能量高达数十兆电子伏特,可延伸至行星半径的十倍以上,发射出逐渐变化的无线电辐射,并影响近地卫星的表面化学。

最近的观测表明,统称为超冷矮星的极低质量的恒星和褐矮星,可以产生类似行星的无线电发射,如大规模磁层电流周期性爆发的极光。它们也表现出缓慢变化的静态无线电发射,据了解可追踪低水平的日冕耀斑,尽管偏离了以经验为依据的多波长耀斑关系。

研究者展示了超低温矮星LSR J1835 + 3259在8.4 GHz的高分辨率成像,表明它的静态无线电发射是空间分辨的,并追踪到双叶和轴对称结构,在形态上与木星辐射带相似。这两个叶瓣之间的距离高达18个超冷矮星半径,研究者在一年多的时间里进行了三次观测,发现其稳定存在。

对于受LSR J1835 + 3259磁偶极子约束的等离子体,研究者估计其电子能量为15 MeV,与木星的辐射带一致。该结果证实了最近对恒星质量序列两端辐射带的预测,并支持更广泛地重新研究旋转磁偶极子在棕矮星、完全对流的M矮星和大质量恒星产生非热静态射电辐射的过程。

▲ Abstract:

Radiation belts are present in all large-scale Solar System planetary magnetospheres: Earth, Jupiter, Saturn, Uranus and Neptune. These persistent equatorial zones of relativistic particles up to tens of megaelectron volts in energy can extend further than ten times the planet’s radius, emit gradually varying radio emissions and affect the surface chemistry of close-in moons. Recent observations demonstrate that very low-mass stars and brown dwarfs, collectively known as ultracool dwarfs, can produce planet-like radio emissions such as periodically bursting aurorae from large-scale magnetospheric currents. They also exhibit slowly varying quiescent radio emissions hypothesized to trace low-level coronal flaring despite departing from empirical multiwavelength flare relationships. Here we present high-resolution imaging of the ultracool dwarf LSR J1835+3259 at 8.4GHz, demonstrating that its quiescent radio emission is spatially resolved and traces a double-lobed and axisymmetrical structure that is similar in morphology to the Jovian radiation belts. Up to 18 ultracool dwarf radii separate the two lobes, which are stably present in three observations spanning more than one year. For plasma confined by the magnetic dipole of LSR J1835+3259, we estimate 15MeV electron energies, consistent with Jupiter’s radiation belts. Our results confirm recent predictions of radiation belts at both ends of the stellar mass sequence and support broader re-examination of rotating magnetic dipoles in producing non-thermal quiescent radio emissions from brown dwarfs7, fully convective M dwarfs20 and massive stars.

化学Chemistry

Organic–inorganic covalent–ionic molecules for elastic ceramic plastic

弹性陶瓷塑料用有机-无机共价离子分子

▲ 作者:Weifeng Fang, Zhao Mu, Yan He, Kangren Kong, Kai Jiang, Ruikang Tang & Zhaoming Liu

▲ 链接:

https://www.nature.com/articles/s41586-023-06117-1

▲ 摘要:

尽管有机-无机杂化材料在机械、光学、电子和生物医学等领域发挥着不可替代的作用,但由于有机共价键和无机离子键在分子结构上的不同行为,分离的有机-无机杂化分子(目前仅限于共价化合物)很少被用于制备杂化材料。研究者将典型的共价键和离子键整合在一个分子内,形成有机-无机杂化分子,可用于自底向上合成杂化材料。

有机共价硫辛酸(TA)与无机离子型碳酸钙低聚物(CCO)通过酸碱反应结合,得到具有代表性的分子式TA2Ca(CaCO3)2的TA - CCO杂化分子。其双重反应性涉及有机TA段和无机CCO段的共聚,产生各自的共价和离子网络。

这两个网络通过TA-CCO络合物相互连接,在得到的杂化材料中形成共价离子双连续结构,从而统一了矛盾的机械性能。有机-无机杂化分子的自下而上构建为杂化材料的分子工程提供了一条可行的途径,补充了经典的有机-无机杂化材料制造方法。

▲ Abstract:

Although organic–inorganic hybrid materials have played indispensable roles as mechanical, optical, electronic and biomedical materials, isolated organic–inorganic hybrid molecules (at present limited to covalent compounds) are seldom used to prepare hybrid materials, owing to the distinct behaviours of organic covalent bonds and inorganic ionic bonds in molecular construction. Here we integrate typical covalent and ionic bonds within one molecule to create an organic–inorganic hybrid molecule, which can be used for bottom-up syntheses of hybrid materials. A combination of the organic covalent thioctic acid (TA) and the inorganic ionic calcium carbonate oligomer (CCO) through an acid–base reaction provides a TA–CCO hybrid molecule with the representative molecular formula TA2Ca(CaCO3)2. Its dual reactivity involving copolymerization of the organic TA segment and inorganic CCO segment generates the respective covalent and ionic networks. The two networks are interconnected through TA–CCO complexes to form a covalent–ionic bicontinuous structure within the resulting hybrid material, poly(TA–CCO), which unifies paradoxical mechanical properties. The bottom-up creation of organic–inorganic hybrid molecules provides a feasible pathway for the molecular engineering of hybrid materials, thereby supplementing the classical methodology used for the manufacture of organic–inorganic hybrid materials.

Linear-in-temperature resistivity for optimally superconducting (Nd,Sr)NiO2

具镍酸盐让超导体无序程度降低

▲ 作者:IKyuho Lee, Bai Yang Wang, Motoki Osada, Berit H. Goodge, Tiffany C. Wang, Yonghun Lee, Shannon Harvey, Woo Jin Kim, Yijun Yu, Chaitanya Murthy, Srinivas Raghu, Lena F. Kourkoutis & Harold Y. Hwang

▲ 链接:

https://www.nature.com/articles/s41586-023-06129-x

▲ 摘要:

在物质的各种强相关相附近发生的超导性引起了对其正常状态性质的广泛关注,以了解超导性产生的状态。最近在层状镍酸盐中发现的超导性引起了类似的兴趣。但由于这些亚稳化合物的材料限制,掺杂无限层镍酸盐薄膜的输运测量受到阻碍:特别是高密度的扩展缺陷。

研究者通过移动到生长和还原条件更稳定的底物(LaAlO3)0.3(Sr2TaAlO6)0.7,可以合成基本没有扩展缺陷的Nd1-xSrxNiO2掺杂系列。

在不掺杂的情况下,正常状态电阻率在欠掺杂状态下表现为低温上升,在最佳掺杂状态下表现为线性行为,在过掺杂状态下表现为二次温度依赖关系。这在现象上与铜氧化物相似,尽管有关键的区别——即没有绝缘母化合物、多带电子结构和莫特-哈伯德轨道排列,而不是铜氧化物的电荷转移绝缘体。

无论是在转变温度和掺杂范围方面,研究者进一步观察到超导性的增强。这些结果表明,随着镍酸盐无序程度的降低,两个超导族的电子性质趋于一致。

▲ Abstract:

The occurrence of superconductivity in proximity to various strongly correlated phases of matter has drawn extensive focus on their normal state properties, to develop an understanding of the state from which superconductivity emerges. The recent finding of superconductivity in layered nickelates raises similar interests. However, transport measurements of doped infinite-layer nickelate thin films have been hampered by materials limitations of these metastable compounds: in particular, a high density of extended defects. Here, by moving to a substrate(LaAlO3)0.3(Sr2TaAlO6)0.7 that better stabilizes the growth and reduction conditions, we can synthesize the doping series of Nd1-xSrxNiO2 essentially free from extended defects. In their absence, the normal state resistivity shows a low-temperature upturn in the underdoped regime, linear behaviour near optimal doping and quadratic temperature dependence for overdoping. This is phenomenologically similar to the copper oxides despite key distinctions—namely, the absence of an insulating parent compound, multiband electronic structure and a Mott–Hubbard orbital alignment rather than the charge-transfer insulator of the copper oxides. We further observe an enhancement of superconductivity, both in terms of transition temperature and range of doping. These results indicate a convergence in the electronic properties of both superconducting families as the scale of disorder in the nickelates is reduced.  

生态和气候Ecology & Climate

Plastic debris in lakes and reservoirs

湖泊和水库中的塑料碎片

▲ 作者:Veronica Nava, Sudeep Chandra, Julian Aherne, María B. Alfonso, Ana M. Anto-Geraldes, Katrin Attermeyer, Roberto Bao, Mireia Bartrons, Stella A. Berger, Marcin Biernaczyk, Raphael Bissen, Justin D. Brookes, David Brown, Miguel Caedo-Argüelles, Moisés Canle, Camilla Capelli, Rafael Carballeira, José Luis Cereijo, Sakonvan Chawchai, Sren T. Christensen, Kirsten S. Christoffersen, Elvira de Eyto, Jorge Delgado, Tyler N. Dornan, …Barbara Leoni Show authors

▲ 链接:

https://www.nature.com/articles/s41586-023-06168-4

▲ 摘要:

塑料垃圾被认为在全球淡水生态系统中普遍存在。然而,由于缺乏全面和可比较的数据,对其分布进行严格评估具有挑战性。研究者提出了一项标准化的跨国调查,评估淡水生态系统中塑料碎片的丰度和类型。

他们对38个湖泊和水库的地表水进行了采样,分布在地理位置和湖泊属性的梯度上,目的是确定与塑料观察增加相关的因素,结果在所有被研究的湖泊和水库中都发现了塑料碎片,这表明这些生态系统在塑料污染循环中起着关键作用。

研究结果表明,两种类型的湖泊特别容易受到塑料污染:一种是人口稠密和城市化地区的湖泊和水库;另一种是沉积面积高、蓄水时间长、人为影响程度高的大型湖泊和水库。不同湖泊的塑料浓度差异很大;在污染最严重的地区,浓度达到甚至超过了报告的亚热带海洋环流,海洋区域收集了大量的碎片。该研究结果强调了在污染管理和持续提供湖泊生态系统服务的背景下,在解决塑料污染时包括湖泊和水库的重要性。

▲ Abstract:

Plastic debris is thought to be widespread in freshwater ecosystems globally. However, a lack of comprehensive and comparable data makes rigorous assessment of its distribution challenging. Here we present a standardized cross-national survey that assesses the abundance and type of plastic debris (>250 μm) in freshwater ecosystems. We sample surface waters of 38 lakes and reservoirs, distributed across gradients of geographical position and limnological attributes, with the aim to identify factors associated with an increased observation of plastics. We find plastic debris in all studied lakes and reservoirs, suggesting that these ecosystems play a key role in the plastic-pollution cycle. Our results indicate that two types of lakes are particularly vulnerable to plastic contamination: lakes and reservoirs in densely populated and urbanized areas and large lakes and reservoirs with elevated deposition areas, long water-retention times and high levels of anthropogenic influence. Plastic concentrations vary widely among lakes; in the most polluted, concentrations reach or even exceed those reported in the subtropical oceanic gyres, marine areas collecting large amounts of debris. Our findings highlight the importance of including lakes and reservoirs when addressing plastic pollution, in the context of pollution management and for the continued provision of lake ecosystem services.

A warming-induced reduction in snow fraction amplifies rainfall extremes

由变暖引起的雪量减少放大了极端降雨

▲ 作者:Mohammed Ombadi, Mark D. Risser, Alan M. Rhoades & Charuleka Varadharajan 

▲ 链接:

https://www.nature.com/articles/s41586-023-06092-7

▲ 摘要:

在气候变暖的情况下,极端降水事件的强度预计会增加,这对自然和人工环境中的水可持续性构成了巨大挑战。特别重要的是极端降雨,它们会瞬间引发径流并与洪水、滑坡和土壤侵蚀有关。然而,迄今为止,关于降水极值强化的大量文献尚未单独考察降水相的极值,即液体降水和固体降水。

研究表明北半球高海拔地区极端降雨的增加被放大了,平均每升温1摄氏度就会增加15%——是大气中水蒸气增加的预期速率的两倍。研究者利用气候再分析数据集和未来模式预估表明,这种增加是由于变暖引起的从雪到雨的转变导致的。

此外,研究还证明了极端降水预估的模式间不确定性可以通过雪雨分配的变化(决定系数0.47)得到很好的解释。研究结果表明,高海拔地区是未来容易受到极端降雨相关灾害风险影响的“热点”,因此需要强有力的气候适应计划来减轻潜在风险。此外,研究结果为减少极端降雨预测中的模式不确定性提供了一条途径。

▲ Abstract:

The intensity of extreme precipitation events is projected to increase in a warmer climate, posing a great challenge to water sustainability in natural and built environments. Of particular importance are rainfall (liquid precipitation) extremes owing to their instantaneous triggering of runoff and association with floods, landslides and soil erosion. However, so far, the body of literature on intensification of precipitation extremes has not examined the extremes of precipitation phase separately, namely liquid versus solid precipitation. Here we show that the increase in rainfall extremes in high-elevation regions of the Northern Hemisphere is amplified, averaging 15 per cent per degree Celsius of warming—double the rate expected from increases in atmospheric water vapour. We utilize both a climate reanalysis dataset and future model projections to show that the amplified increase is due to a warming-induced shift from snow to rain. Furthermore, we demonstrate that intermodel uncertainty in projections of rainfall extremes can be appreciably explained by changes in snow–rain partitioning (coefficient of determination 0.47). Our findings pinpoint high-altitude regions as ‘hotspots’ that are vulnerable to future risk of extreme-rainfall-related hazards, thereby requiring robust climate adaptation plans to alleviate potential risk. Moreover, our results offer a pathway towards reducing model uncertainty in projections of rainfall extremes.   

 
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