编译 | 未玖

Nature, 2 March 2023, VOL 615, ISSUE 795

《自然》2023年3月2日，第615卷，7950期

天文学Astronomy

A shared accretion instability for black holes and neutron stars

黑洞和中子星的共吸积不稳定性

▲ 作者：F. M. Vincentelli, J. Neilsen, A. J. Tetarenko, Y. Cavecchi, N. Castro Segura, S. del Palacio, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05648-3

▲ 摘要：

致密天体周围的吸积盘在高光度下预计会进入不稳定阶段。当吸积产生的辐射压力改变了盘的粘度，导致内盘在短时间内循环损耗和重新填充时，可能会出现一种不稳定性。

然而，这种情况只在单个恒星质量黑洞中得到了定量验证。尽管在个别情况下有这些循环迹象，但在大多数明亮的吸积中子星和黑洞的可变发射中，这种不稳定性的明显缺失一直是个谜。

研究组报道了在一颗吸积中子星周围存在相同的多波长不稳定性。此外还表明，如果吸积盘不稳定，在耗尽或重新填充内盘的跃迁过程中产生相对论性抛射，那么高吸积率下黑洞和中子星的电磁波谱（从无线电到X射线）可变性就能得到一致的解释。

这种新的关联使研究组能够确定导致高吸积致密天体快速多波长变化的主要物理组成。

▲ Abstract：

Accretion disks around compact objects are expected to enter an unstable phase at high luminosity. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the cyclic depletion and refilling of the inner disk on short timescales. Such a scenario, however, has only been quantitatively verified for a single stellar-mass black hole. Although there are hints of these cycles in a few isolated cases, their arent absence in the variable emission of most bright accreting neutron stars and black holes has been a continuing puzzle. Here we report the presence of the same multiwavelength instability around an accreting neutron star. Moreover, we show that the variability across the electromagnetic spectrum—from radio to X-ray—of both black holes and neutron stars at high accretion rates can be explained consistently if the accretion disks are unstable, producing relativistic ejections during transitions that deplete or refill the inner disk. Such a new association allows us to identify the main physical components responsible for the fast multiwavelength variability of highly accreting compact objects.

物理学Physics

Critical role of hydrogen for superconductivity in nickelates

氢在镍酸盐超导中的关键作用

▲ 作者：Xiang Ding, Charles C. Tam, Xuelei Sui, Yan Zhao, Minghui Xu, Jaewon Choi, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05657-2

▲ 摘要：

迄今为止，新发现的镍酸盐超导体仅存在于与金属氢化物拓扑反应合成的外延薄膜中。该方法通过顶端氧脱嵌将镍酸盐从钙钛矿结构转变为无限层结构。这种化学反应可能会引入氢（H），影响最终材料的物理性能。遗憾的是，H对大多数表征技术不敏感，并且由于其重量轻而难以检测。

研究组发现，在最佳Sr掺杂的Nd0.8Sr0.2NiO2H外延薄膜中，二次离子质谱显示大量的H以Nd0.8Sr0.2NiO2Hx（x≅0.2-0.5）的形式存在。在0.22≤x≤0.28极窄的H掺杂窗口内发现零电阻率，明确证实了H在超导中的关键作用。

共振非弹性X射线散射证明了源于顶端氧脱嵌的巡游间隙s（IIS）轨道的存在。密度泛函理论计算表明，电负性H-占据顶端氧位点，湮灭了IIS轨道，减少了IIS-Ni三维轨道杂化。这使得掺杂H的Nd0.8Sr0.2NiO2Hx的电子结构更加二维化，并可能与观测到的超导性有关。研究组强调了H是外延无限层镍酸盐超导性的重要组成部分。

▲ Abstract：

The newly discovered nickelate superconductors so far only exist in epitaxial thin films synthesized by a topotactic reaction with metal hydrides. This method changes the nickelates from the perovskite to an infinite-layer structure by deintercalation of apical oxygens. Such a chemical reaction may introduce hydrogen (H), influencing the physical properties of the end materials. Unfortunately, H is insensitive to most characterization techniques and is difficult to detect because of its light weight. Here, in optimally Sr dopedNd0.8Sr0.2NiO2Hepitaxial films, secondary-ion mass spectroscopy shows abundant H existing in the form ofNd0.8Sr0.2NiO2H (x≅0.2-0.5). Zero resistivity is found within a very narrow H-doping window of 0.22≤x≤0.28, showing unequivocally the critical role of H in superconductivity. Resonant inelastic X-ray scattering demonstrates the existence of itinerant interstitial s (IIS) orbitals originating from apical oxygen deintercalation. Density functional theory calculations show that electronegative H– occupies the apical oxygen sites annihilating IIS orbitals, reducing the IIS–Ni 3d orbital hybridization. This leads the electronic structure of H-dopedNd0.8Sr0.2NiO2Hxto be more two-dimensional-like, which might be relevant for the observed superconductivity. We highlight that H is an important ingredient for superconductivity in epitaxial infinite-layer nickelates.

材料科学Materials Science

Ladderphane copolymers for high-temperature capacitive

energy storage

Ladderphane共聚物助力高温电容储能

▲ 作者：Jie Chen, Yao Zhou, Xingyi Huang, Chunyang Yu, Donglin Han, Ao Wang, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05671-4

▲ 摘要：

为了在高温下进行电容储能，需要介电聚合物将低导电性与高导热性结合起来。这些看似矛盾性质的共存对现有聚合物而言仍是一个长期挑战。

研究组报道了一类Ladderphane共聚物，在高电场和高温下，其电导率比现有聚合物至少低一个数量级。结果表明，该Ladderphane共聚物在200℃时的放电能量密度为5.34 J cm−3，充放电效率为90%，优于现有的介电聚合物和复合材料。

Ladderphane共聚物通过π-π堆叠相互作用自组装成高度有序的阵列，从而获得了垂直平面方向1.96±0.06 W m−1K−1的本征热导率。共聚物薄膜的高导热性允许有效的焦耳散热，因此，在高温和高电场下具有优异的循环稳定性。

共聚物击穿自愈能力的展示进一步表明，Ladderphane结构有望助力极端条件下工作的高能量密度聚合物电容器。

▲ Abstract：

For capacitive energy storage at elevated temperatures, dielectric polymers are required to integrate low electrical conduction with high thermal conductivity. The coexistence of these seemingly contradictory properties remains a persistent challenge for existing polymers. We describe here a class of ladderphane copolymers exhibiting more than one order of magnitude lower electrical conductivity than the existing polymers at high electric fields and elevated temperatures. Consequently, the ladderphane copolymer possesses a discharged energy density of 5.34?J?cm?3 with a charge–discharge efficiency of 90% at 200?°C, outperforming the existing dielectric polymers and composites. The ladderphane copolymers self-assemble into highly ordered arrays by π–π stacking interactions, thus giving rise to an intrinsic through-plane thermal conductivity of 1.96?±?0.06?W?m−1K−1. The high thermal conductivity of the copolymer film permits efficient Joule heat dissipation and, accordingly, excellent cyclic stability at elevated temperatures and high electric fields. The demonstration of the breakdown self-healing ability of the copolymer further suggests the promise of the ladderphane structures for high-energy-density polymer capacitors operating under extreme conditions.

化学Chemistry

Electrochemical reactor dictates site selectivity in N-heteroarene carboxylations

电化学反应器决定了N-杂芳烃羧化反应的位点选择性

▲ 作者：Guo-Quan Sun, Peng Yu, Wen Zhang, Wei Zhang, Yi Wang, Li-Li Liao, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05667-0

▲ 摘要：

吡啶和相关的N-杂芳烃广泛存在于药品、农用化学品和其他生物活性化合物中。位点选择性C-H功能化为制备这些药物活性产物提供了直接途径。例如，烟酸衍生物可通过C-H羧化反应制备，但这种转变仍很难实现。

研究组描述了一种使用二氧化碳直接羧化吡啶的电化学策略进展。电解设置的选择产生了不同的位点选择性：分隔的电化学电解池导致C5羧化，而未分隔的电解池促进C4羧化。人们认为未分隔的电解池反应通过成对电解机制运行，其中阴极和阳极事件在改变位点选择性方面起着关键作用。

具体而言，阳极生成的碘通过氢原子转移，优先与C4-羧化途径中的关键自由基阴离子中间体发生反应，从而通过Curtin-Hammett原理改变了反应的选择性。转化的范围可扩大到广泛N-杂芳烃，包括联吡啶和三联吡啶、嘧啶、吡嗪和喹啉。

▲ Abstract：

Pyridines and related N-heteroarenes are commonly found in pharmaceuticals, agrochemicals and other biologically active compounds. Site-selective C–H functionalization would provide a direct way of making these medicinally active products. For example, nicotinic acid derivatives could be made by C–H carboxylation, but this remains an elusive transformation. Here we describe the development of an electrochemical strategy for the direct carboxylation of pyridines using CO2. The choice of the electrolysis setup gives rise to divergent site selectivity: a divided electrochemical cell leads to C5 carboxylation, whereas an undivided cell promotes C4 carboxylation. The undivided-cell reaction is proposed to operate through a paired-electrolysis mechanism, in which both cathodic and anodic events play critical roles in altering the site selectivity. Specifically, anodically generated iodine preferentially reacts with a key radical anion intermediate in the C4-carboxylation pathway through hydrogen-atom transfer, thus diverting the reaction selectivity by means of the Curtin–Hammett principle. The scope of the transformation was expanded to a wide range of N-heteroarenes, including bipyridines and terpyridines, pyrimidines, pyrazines and quinolines.

地球科学Earth Science

Primary N2–He gas field formation in intracratonic sedimentary basins

克拉通内沉积盆地原生N2–He气田形成

▲ 作者：Anran Cheng, Barbara Sherwood Lollar, Jon G. Gluyas & Chris J. Ballentine

▲ 链接：

https://www.nature.com/articles/s41586-022-05659-0

▲ 摘要：

氦、氮和氢在大陆地壳深处不断产生。静止大陆地壳的概念脱气模型主要基于一种假设，即这些气体溶解在水中，浅层沉积系统的垂直输运通过在充满水的孔隙空间内扩散。气相出溶是浓缩氦和形成社会资源的关键。

研究组证明仅来自结晶基底的地壳氮（与地壳氦-4生成成比例的稳态脱气）就可以在一些沉积盆地底部达到足够浓度，形成自由气相。利用与沉积盆地演化耦合的气体扩散模型，研究组使用一个经典的克拉通内沉积盆地（北美威利斯顿盆地）证明，在该盆地中，早在大约1.4亿年前，地壳氮达到饱和并形成气相。氦分裂成气相。

这种气体形成机制解释了在该盆地和其他盆地的基底沉积岩性学中观测到的原生氮气-氦气，预测了地壳气相氢的共同存在，并由于相溶解度缓冲作用，使氦气流入上覆地层的通量减少了约30%。该气相形成机制的确定为定量评估世界范围内类似陆内沉积盆地的氦-氢资源潜力提供了依据。

▲ Abstract：

Helium, nitrogen and hydrogen are continually generated within the deep continental crust. Conceptual degassing models for quiescent continental crust are dominated by an assumption that these gases are dissolved in water, and that vertical transport in shallower sedimentary systems is by diffusion within water-filled pore space. Gas-phase exsolution is crucial for concentrating helium and forming a societal resource. Here we show that crustal nitrogen from the crystalline basement alone—degassing at a steady state in proportion to crustal helium-4 generation—can reach sufficient concentrations at the base of some sedimentary basins to form a free gas phase. Using a gas diffusion model coupled with sedimentary basin evolution, we demonstrate, using a classic intracratonic sedimentary basin (Williston Basin, North America), that crustal nitrogen reaches saturation and forms a gas phase; in this basin, as early as about 140?million years ago. Helium partitions into this gas phase. This gas formation mechanism accounts for the observed primary nitrogen–helium gas discovered in the basal sedimentary lithology of this and other basins, predicts co-occurrence of crustal gas-phase hydrogen, and reduces the flux of helium into overlying strata by about 30?per cent because of phase solubility buffering. Identification of this gas phase formation mechanism provides a quantitative insight to assess the helium and hydrogen resource potential in similar intracontinental sedimentary basins found worldwide.

Oceanic climate changes threaten the sustainability of Asia’s water tower

海洋气候变化威胁亚洲水塔的可持续性

▲ 作者：Qiang Zhang, Zexi Shen, Yadu Pokhrel, Daniel Farinotti, Vijay P. Singh, Chong-Yu Xu, et al.

▲ 链接：

https://www.nature.com/articles/s41586-022-05643-8

▲ 摘要：

被称为亚洲水塔的青藏高原（TP）周围亚洲高山区（HMA）的水资源可持续性引发了广泛关注，因为HMA保护了数百万人免受水资源短缺的影响。然而，TP陆地蓄水（TWS）中观察到的异质性趋势背后机制尚不清楚。

研究组使用拉格朗日粒子弥散模型和卫星观测，将2003-年间南部TP每月约1 Gt的TWS下降归因于来自北大西洋东南部的西风带降水-蒸发（PME）亏缺。HMA阻断了PME亏缺向中央TP的扩散，导致TWS每月增加约0.5 Gt。

此外，暖化导致的积雪和冰川融化以及干燥导致的TWS耗竭削弱了HMA山脉的阻挡，导致TP的TWS亏缺自2009年以来持续向北扩大。

对-年间卫星观测验证的两种排放情景下的未来预测表明，到21世纪末，TP中高达84%（情景SSP245）和97%（情景SSP585）的区域可能受到TWS亏缺的影响。该研究结果表明，HMA的水系统走向不可持续，这可能会加剧下游的水资源危机。

▲ Abstract：

Water resources sustainability in High Mountain Asia (HMA) surrounding the Tibetan Plateau (TP)—known as Asia’s water tower—has triggered widespread concerns because HMA protects millions of people against water stress. However, the mechanisms behind the heterogeneous trends observed in terrestrial water storage (TWS) over the TP remain poorly understood. Here we use a Lagrangian particle dispersion model and satellite observations to attribute about 1?Gt of monthly TWS decline in the southern TP during 2003– to westerlies-carried deficit in precipitation minus evaporation (PME) from the southeast North Atlantic. We further show that HMA blocks the propagation of PME deficit into the central TP, causing a monthly TWS increase by about 0.5?Gt. Furthermore, warming-induced snow and glacial melt as well as drying-induced TWS depletion in HMA weaken the blocking of HMA’s mountains, causing persistent northward expansion of the TP’s TWS deficit since 2009. Future projections under two emissions scenarios verified by satellite observations during 2020– indicate that, by the end of the twenty-first century, up to 84% (for scenario SSP245) and 97% (for scenario SSP585) of the TP could be afflicted by TWS deficits. Our findings indicate a trajectory towards unsustainable water systems in HMA that could exacerbate downstream water stress.