编译 | 未玖

Nature,13 February 2025, Volume 638, Issue 8050《自然》2025年2月13日，第638卷，8050期

天文学Astronomy

Directly imaging the cooling flow in the Phoenix cluster

直接成像凤凰星团中的冷却流

▲ 作者：Michael Reefe, Michael McDonald, Marios Chatzikos, Jerome Seebeck, Richard Mushotzky, Sylvain Veilleux, et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08369-x

▲ 摘要：在许多星系团的中心，炽热（大约107开尔文）星系团内介质可变得足够致密，以至于其本应在短时间内冷却。然而，在大质量中心星系中测量到的恒星形成率很低，且冷却气体中没有软X射线，这表明大多数气体从未冷却过。这就是所谓的冷却流问题。

最新观测表明，黑洞喷流使绝大多数气体保持在高温状态。任何星系团中的所有气相中，冷却流尚未实现全绘制。

研究组展示了使用詹姆斯韦伯太空望远镜对凤凰星团的观测，绘制了[Ne vi] λ 7.652-μm发射线，使人们能够在大尺度上探测105.5? K的气体。这些数据显示了扩展的[Ne vi]发射，与星系团内介质的冷却峰、最冷的气相和活跃恒星形成的位置同空间存在。
综上所述，这意味着最近发生了一次快速冷却，导致了冷却速度短暂飙升，研究组估计为每年5000~23000个太阳质量。这些数据提供了星系团核心温度在105 K到106 K之间的大规模气体分布图景，并强调了黑洞反馈在调节冷却和促进冷却方面的关键作用。

▲ Abstract：In the centres of many galaxy clusters, the hot (approximately 107 kelvin) intracluster medium can become dense enough that it should cool on short timescales. However, the low measured star formation rates in massive central galaxies and the absence of soft X-ray lines from the cooling gas suggest that most of this gas never cools. This is known as the cooling flow problem. The latest observations suggest that black hole jets are maintaining the vast majority of gas at high temperatures. A cooling flow has yet to be fully mapped through all the gas phases in any galaxy cluster. Here we present observations of the Phoenix cluster using the James Webb Space Telescope to map the [Ne vi] λ 7.652-μm emission line, enabling us to probe the gas at 105.5?kelvin on large scales. These data show extended [Ne vi] emission that is cospatial with the cooling peak in the intracluster medium, the coolest gas phases and the sites of active star formation. Taken together, these imply a recent episode of rapid cooling, causing a short-lived spike in the cooling rate, which we estimate to be 5,000–23,000 solar masses per year. These data provide a large-scale map of gas at temperatures between 105?kelvin and 106?kelvin in a cluster core, and highlight the critical role that black hole feedback has in not only regulating cooling but also promoting it.

The bulk motion of gas in the core of the Centaurus galaxy cluster

半人马座星系团核心气体的整体流动

▲ 作者：XRISM collaboration

▲ 链接：https://www.nature.com/articles/s41586-024-08561-z

▲ 摘要：星系团包含大量被称为星系团内介质（ICM）的热电离气体。在疏散星系团核心中，ICM的辐射冷却时间短于星系团年龄。

然而，与冷却相关的线发射缺失表明加热机制抵消了冷却，来自活动星系核（AGNs）的反馈是最有可能的来源。湍流和整体流动，如星系团势阱中核心气体的振荡（冲击）运动，也被认为是核心外部热量分布的机制。

研究组用X射线成像和光谱任务卫星对半人马座星系团进行X射线光谱观测。结果发现，热气体沿着相对于中心星系的视线流动，在距离中心约30 kpc的范围内，速度从130 km s?1到310 km s?1。这表明整体流动与核心气体晃动一致。

虽然整体流动可防止中心冷却气体的过度积聚，但亦可分散AGN注入的热量，并从周围的ICM中引入热能。核心气体的速度色散仅为≤120 km s?1，甚至在AGN的10 kpc范围内亦是如此。这表明AGN对周围ICM流动的影响在星系团中是有限的。

▲ Abstract：Galaxy clusters contain vast amounts of hot ionized gas known as the intracluster medium (ICM). In relaxed cluster cores, the radiative cooling time of the ICM is shorter than the age of the cluster. However, the absence of line emission associated with cooling suggests heating mechanisms that offset the cooling, with feedback from active galactic nuclei (AGNs) being the most likely source. Turbulence and bulk motions, such as the oscillating (‘sloshing’) motion of the core gas in the cluster potential well, have also been proposed as mechanisms for heat distribution from the outside of the core. Here we present X-ray spectroscopic observations of the Centaurus galaxy cluster with the X-Ray Imaging and Spectroscopy Mission satellite. We find that the hot gas flows along the line of sight relative to the central galaxy, with velocities from 130?km?s?1 to 310?km?s?1 within about 30?kpc of the centre. This indicates bulk flow consistent with core gas sloshing. Although the bulk flow may prevent excessive accumulation of cooled gas at the centre, it could distribute the heat injected by the AGN and bring in thermal energy from the surrounding ICM. The velocity dispersion of the gas is found to be only ?120?km?s?1 in the core, even within about 10?kpc of the AGN. This suggests that the influence of the AGN on the surrounding ICM motion is limited in the cluster.

材料科学Materials Science

Metal-halide porous framework superlattices

金属卤化物多孔骨架超晶格

▲ 作者：Wenqiang Zhang, Hong Jiang, Yikuan Liu, Yue Hu, Athulya Surendran Palakkal, Yujie Zhou, et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08447-0

▲ 摘要：通过构建具有化学成分空间调制的超晶格结构，可创建具有可定制周期性电势景观和可调谐电子和光学特性的人造材料。具有一维可设计电位调制的传统半导体超晶格实现了高电子迁移率晶体管和量子级联激光器。

最近，通过多尺度构建单元的自组装或引导组装，人们构建了一组多样化的超晶格，包括零维纳米簇和纳米颗粒、一维纳米棒和纳米线、二维纳米层和纳米片，以及混合二维分子组装体。这些自组装超晶格具有二维或三维的周期性结构调制，但由于组成单元之间界面处不可避免的结构无序，通常缺乏原子精度。

研究组报告了由零维、一维和二维构建单元的周期性排列组成的多维单晶超晶格的一锅合成法。利用锆（IV）金属有机骨架作为主模板，通过配位辅助组装策略实现金属卤化物亚晶格的定向成核和精确生长，他们合成了一系列单晶多孔超晶格。

单晶X射线晶体学和高分辨率透射电子显微镜清晰地分辨出具有确定性原子坐标的高阶超晶格结构。用选定的胺分子进一步处理可产生具有高度可调光致发光和手性光学性质的钙钛矿样超晶格。

该研究创建了一个高阶单晶多孔超晶格平台，为定制传统晶体固体无法实现的电子、光学和量子特性提供了机遇。

▲ Abstract：The construction of superlattices with a spatial modulation of chemical compositions allows for the creation of artificial materials with tailorable periodic potential landscapes and tunable electronic and optical properties. Conventional semiconductor superlattices with designable potential modulation in one dimension has enabled high-electron-mobility transistors and quantum-cascade lasers. More recently, a diverse set of superlattices has been constructed through self-assembly or guided assembly of multiscale building units, including zero-dimensional nanoclusters and nanoparticles, one-dimensional nanorods and nanowires, two-dimensional nanolayers and nanosheets, and hybrid two-dimensional molecular assemblies. These self-assembled superlattices feature periodic structural modulation in two or three dimensions, but often lack atomic precision owing to the inevitable structural disorder at the interfaces between the constituent units. Here we report a one-pot synthesis of multi-dimensional single-crystalline superlattices consisting of periodic arrangement of zero-, one- and two-dimensional building units. By exploiting zirconium (IV) metal–organic frameworks as host templates for directed nucleation and precise growth of metal-halide sublattices through a coordination-assisted assembly strategy, we synthesize a family of single-crystalline porous superlattices. Single-crystal X-ray crystallography and high-resolution transmission electron microscopy clearly resolve the high-order superlattice structure with deterministic atomic coordinates. Further treatment with selected amine molecules produces perovskite-like superlattices with highly tunable photoluminescence and chiroptical properties. Our study creates a platform of high-order single-crystalline porous superlattices, opening opportunities to tailor the electronic, optical and quantum properties beyond the reach of conventional crystalline solids.

化学Chemistry

Two-dimensional polyaniline crystal with metallic out-of-plane conductivity

具有面外金属性电导率的二维聚苯胺晶体

▲ 作者：Tao Zhang, Shu Chen, Petko St. Petkov, Peng Zhang, Haoyuan Qi, Nguyen Ngan Nguyen, et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08387-9

▲ 摘要：线性导电聚合物表现出由沿聚合物链移动的移动载流子施加的弹道传输，但由于缺乏分子间有序和电子耦合，在扩展维度（即聚合物链或层之间）上的电导率仍然很弱。

研究组报道了一种多层堆叠的二维聚苯胺（2DPANI）晶体，其具有高导电性的面外金属性电荷输运。该材料包括层间距为3.59 ?的柱状π阵列和由聚苯胺链交织形成的周期性菱面体晶格。电子自旋共振谱揭示了2DPANI晶格中显著的电子离域。第一性原理计算表明，Cl -桥接层堆叠促进了2DPANI的面内二维共轭和层间强电子耦合。

为了评估局部光学电导率，研究组使用太赫兹和红外纳米光谱技术来揭示德鲁德型电导率，其红外等离子体频率及外推的局部直流电导率约为200 S cm?1 。导电扫描探针显微镜显示，其面外电导率异常高，约为15 S cm?1 。通过垂直和横向微器件进行的电荷传输测量显示，面外电导率（约7 S cm?1 ）和面内电导率（约16 S cm?1 ）相当高。

垂直微器件的电导率随温度的降低而增强，表现出独特的面外金属性输运行为。通过使用这种多层堆叠的二维导电聚合物设计，研究组预测在面内相互作用之外实现强电子耦合，有望实现三维金属性电导率。

▲ Abstract：Linear conducting polymers show ballistic transport, imposed by mobile carriers moving along the polymer chains, whereas conductance in the extended dimension, that is, between polymer strands or layers, remains weak due to the lack of intermolecular ordering and electronic coupling. Here we report a multilayer-stacked two-dimensional polyaniline (2DPANI) crystal, which shows metallic out-of-plane charge transport with high electrical conductivity. The material comprises columnar π arrays with an interlayer distance of 3.59?? and periodic rhombohedral lattices formed by interwoven polyaniline chains. Electron spin resonance spectroscopy reveals significant electron delocalization in the 2DPANI lattices. First-principles calculations indicate the in-plane 2D conjugation and strong interlayer electronic coupling in 2DPANI facilitated by the Cl-bridged layer stacking. To assess the local optical conductivity, we used terahertz and infrared nanospectroscopy to unravel a Drude-type conductivity with an infrared plasma frequency and an extrapolated local d.c. conductivity of around 200?S?cm?1. Conductive scanning probe microscopy showed an unusually high out-of-plane conductivity of roughly 15?S?cm?1. Transport measurements through vertical and lateral micro-devices revealed comparable high out-of-plane (roughly 7?S?cm?1) and in-plane conductivity (roughly 16?S?cm?1). The vertical micro-devices further showed increasing conductivity with decreasing temperature, demonstrating unique out-of-plane metallic transport behaviour. By using this multilayer-stacked 2D conducting polymer design, we predict the achievement of strong electronic coupling beyond in-plane interactions, potentially reaching three-dimensional metallic conductivity.

H-bonded organic frameworks as ultrasound-programmable delivery platform

氢键有机框架助力超声可编程传输平台

▲ 作者：Wenliang Wang, Yanshu Shi, Wenrui Chai, Kai Wing Kevin Tang, Ilya Pyatnitskiy, Yi Xie, et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08401-0

▲ 摘要：使用非侵入性超声精确控制深层组织内的机械化学激活，对于促进人们对基础生物医学科学的理解和彻底改变疾病治疗策略具有深远意义。然而，一种具有明确定义超声激活的理论指导机械响应材料系统尚待探索。

研究组提出了利用多孔氢键有机框架（HOFs）作为聚焦超声（FUS）可编程触发药物激活工具包的概念，通过按需裂解超分子相互作用来控制脑深部的特定细胞事件。他们建立了机械化学断裂和超声力学的可视化理论模型，为合理设计机械响应材料以实现可编程控制提供了有价值的指导。

为了证明这种方法的实用性，研究组将设计药物氯氮平N-氧化物（CNO）封装到用于FUS门控释放的最佳HOF纳米晶体中，以激活小鼠和大鼠腹侧被盖区（VTA）的工程G蛋白偶联受体，即使在9毫米深度的组织内也能实现靶神经回路调节，潜伏期仅为数秒。

这项工作证明了超声精确控制分子相互作用的能力，并开发了超声波可编程的HOF，以非侵入性和时空性地控制细胞事件，有望实现精确分子治疗。

▲ Abstract：The precise control of mechanochemical activation within deep tissues using non-invasive ultrasound holds profound implications for advancing our understanding of fundamental biomedical sciences and revolutionizing disease treatments. However, a theory-guided mechanoresponsive materials system with well-defined ultrasound activation has yet to be explored. Here we present the concept of using porous hydrogen-bonded organic frameworks (HOFs) as toolkits for focused ultrasound (FUS) programmably triggered drug activation to control specific cellular events in the deep brain, through on-demand scission of the supramolecular interactions. A theoretical model is developed to potentially visualize the mechanochemical scission and ultrasound mechanics, providing valuable guidelines for the rational design of mechanoresponsive materials to achieve programmable control. To demonstrate the practicality of this approach, we encapsulate the designer drug clozapine N-oxide (CNO) into the optimal HOF nanocrystals for FUS-gated release to activate engineered G-protein-coupled receptors in the ventral tegmental area (VTA) of mice and rats and hence achieve targeted neural circuit modulation even at depth 9?mm with a latency of seconds. This work demonstrates the capability of ultrasound to precisely control molecular interactions and develops ultrasound-programmable HOFs to non-invasively and spatiotemporally control cellular events, thereby facilitating the establishment of precise molecular therapeutic possibilities.

社会学Sociology

Regional and institutional trends in assessment for academic promotion

学术晋升评估的区域和机构趋势

▲ 作者：B. H. Lim, C. D’Ippoliti, M. Dominik, A. C. Hernández-Mondragón, K. Vermeir, K. K. Chong, et al.

▲ 链接：https://www.nature.com/articles/s41586-024-08422-9

▲ 摘要：研究绩效评估被广泛认为是维持最高质量标准的重要工具，人们认为选择和竞争会推动进步。学术机构在面临外部研究评估压力的同时，亟需在招聘和晋升方面做出关键决策。

研究组基于190个学术机构的314项政策和58个政府机构的218项政策（涵盖北半球32个国家和南半球89个国家），对学术职业发展的研究评估进行了展望，特别关注晋升为正教授的政策。他们调查了各种晋升标准被提及的频率，并进行了统计分析，以推断各种政策的共性和差异。尽管定量评估方法仍很流行，但与更受地理限制的研究结果一致，其并非适用所有情况。

研究组发现北半球和南半球之间存在差异，机构和国家政策之间亦存在差异，但学科之间的差异较小。中高收入国家对文献计量指标的偏好更为明显。

尽管研究组发现了一些差异，但许多晋升政策都基于对已成为规范的特定职业道路进行假设，而非拥抱多样性。反过来，这限制了研究人员的机会。这些结果挑战了当前实践，并对研究人员、研究管理人员和国家政府具有战略意义。

▲ Abstract：The assessment of research performance is widely seen as a vital tool in upholding the highest standards of quality, with selection and competition believed to drive progress. Academic institutions need to take critical decisions on hiring and promotion, while facing external pressure by also being subject to research assessment. Here we present an outlook on research assessment for career progression with specific focus on promotion to full professorship, based on 314 policies from 190 academic institutions and 218 policies from 58 government agencies, covering 32 countries in the Global North and 89 countries in the Global South. We investigated how frequently various promotion criteria are mentioned and carried out a statistical analysis to infer commonalities and differences across policies. Although quantitative methods of assessment remain popular, in agreement with what is found in more geographically restricted studies, they are not omnipresent. We find differences between the Global North and the Global South as well as between institutional and national policies, but less so between disciplines. A preference for bibliometric indicators is more marked in upper-middle-income countries. Although we see some variation, many promotion policies are based on the assumption of specific career paths that become normative rather than embracing diversity. In turn, this restricts opportunities for researchers. These results challenge current practice and have strategic implications for researchers, research managers and national governments.