科研
科研
编译|李言
Nature, 31 October 2024, Volume 634 Issue 8036
《自然》, 2024年10月31日，第634卷，8036期
天文学Astronomy
Selection bias obfuscates the discovery of fast radio burst sources
选择性偏差模糊了快速射电暴源的发现
▲ 作者：Mohit Bhardwaj, Jimin Lee & Kevin Ji▲ 链接：https://www.nature.com/articles/s41586-024-08065-w
▲摘要：在此，我们提供实证证据，利用非定向巡天发现的快速射电暴的宿主星系样本，证明在具有大倾角的星系中探测快速射电暴存在显著的选择偏差。这种与倾向性相关的偏差可能导致论文研究中报告的快速射电暴发生率被严重低估（约低估一半），且不支持此前球状星团作为快速射电暴主要来源的推测。这些结论对快速射电暴祖模型和有针对性的快速射电暴随访策略具有重要意义。
我们进一步研究了这种偏差对不同宿主环境下快速射电暴相对发生率的影响。我们的分析表明，快速射电暴宿主星系中的散射可能是观测偏差的原因。然而，需要更大的局部快速射电暴样本，以准确量化散射对倾斜相关选择偏差的贡献。
▲ Abstract：Here we present empirical evidence for a substantial selection bias against detecting FRBs in galaxies with large inclination angles (edge-on) using a sample of hosts identified for FRBs discovered by untargeted surveys. This inclination-related bias probably leads to a significant underestimation (by about a factor of two) of the FRB rates reported in the literature and disfavours globular clusters as the dominant origin of FRB sources, as previously speculated. These conclusions have important implications for FRB progenitor models and targeted FRB follow-up strategies. We further investigate the impact of this bias on the relative rate of FRBs in different host environments. Our analysis suggests that scattering in FRB hosts is probably responsible for the observed bias. However, a larger sample of localized FRBs is required to robustly quantify the contribution of scattering to the inclination-related selection bias.
化学Chemistry
Smooth trends in fermium charge radii and the impact of shell effects镄电荷半径的平滑趋势和壳层效应的影响▲ 作者：Jessica Warbinek, Elisabeth Rickert et al.▲ 链接：https://www.nature.com/articles/s41586-024-08062-z
▲摘要：在此，我们展示了镄（Z=100）同位素链的激光光谱测量和一个关键区域扩展的中子同位素链（Z=102）数据。采用多种生产方案和不同的先进技术来确定原子跃迁中的同位素位移，从中提取核均方电荷半径的变化。
一系列基于能量密度泛函的核模型很好地再现了观察到的核尺寸的平滑演变。模型预测的显著一致性和不同同位素预测的相似性都表明，与较轻的原子核相比，壳层效应对原子核大小的影响较小。
▲ Abstract：Here we present laser spectroscopy measurements along the fermium (Z = 100) isotopic chain and an extension of data in the nobelium isotopic chain (Z = 102) across a key region. Multiple production schemes and different advanced techniques were applied to determine the isotope shifts in atomic transitions, from which changes in the nuclear mean-square charge radii were extracted. A range of nuclear models based on energy density functionals reproduce well the observed smooth evolution of the nuclear size. Both the remarkable consistency of model prediction and the similarity of predictions for different isotopes suggest a transition to a regime in which shell effects have a diminished effect on the size compared with lighter nuclei.
材料科学Material Sciences
A graphite thermal Tesla valve driven by hydrodynamic phonon transport一种流体动力声子输运驱动的石墨热特斯拉阀▲ 作者：Xin Huang, Roman Anufriev et al.▲ 链接：https://www.nature.com/articles/s41586-024-08052-1
▲摘要：在此，我们使用声子流体力学方法，在同位素富集的石墨晶体中实现热传导整流。我们在90纳米厚的石墨中设计了一个微米级的特斯拉阀，在45K时，观测到相反方向的热导率差异可识别为15.2%。
这项研究标志着在微尺度和纳米尺度电子器件中使用集体声子行为进行热管理的重要一步，为固体中的热整流开辟道路。
▲ Abstract：Here we demonstrate a phonon hydrodynamics approach to realize the rectification of heat conduction in isotopically enriched graphite crystals. We design a micrometre-scale Tesla valve within 90-nm-thick graphite and experimentally observe a discernible 15.2% difference in thermal conductivity between opposite directions at 45 K. This work marks an important step towards using collective phonon behaviour for thermal management in microscale and nanoscale electronic devices, paving the way for thermal rectification in solids.
地球科学Earth Science
Common occurrences of subsurface heatwaves and cold spells in ocean eddies
海洋涡旋中常见的次表层热浪和冷浪
▲ 作者：Qingyou He, Weikang Zhan et al.
▲ 链接：https://www.nature.com/articles/s41586-024-08051-2
▲摘要：在此，我们提供了全球观测证据，证明中尺度涡旋在次表层热浪和冷浪的发生和增强中发挥了重要作用。我们发现，在深度100米以下测量到的80%的热浪和冷浪与表层情况不一致。与表层冷浪和海洋涡旋之间的弱联系相反，全球海洋中近三分之一的次表层热浪/冷浪、以及亚热带环流和中纬度主流系统中一半以上的此类事件发生在反气旋（气旋）涡旋中。
在过去的几十年里，这些与涡旋相关的极端温度以高于背景水平的速度加剧，这表明随着全球持续变暖，海洋涡旋对次表层热浪和冷浪的影响越来越大。
▲ Abstract：Here we present global observational evidence for the important role of mesoscale eddies in the occurrence and intensification of subsurface MHWs and MCSs. We found that 80% of measured MHWs and MCSs below a depth of 100 m do not concur with surface events. In contrast to the weak link between surface MHWs (MCSs) and ocean eddies, nearly one-third of subsurface MHWs (MCSs) in the global ocean, and more than half of such events in subtropical gyres and mid-latitude main current systems, occur within anticyclonic (cyclonic) eddies. These eddy-associated temperature extremes have intensified at rates greater than background level in past decades, suggesting a growing impact of ocean eddies on subsurface MHWs and MCSs with ongoing global warming.
考古学Archaeology
Large-scale medieval urbanism traced by UAV–lidar in highland Central Asia在中亚高原通过无人机激光雷达追踪的大规模中世纪城市化遗迹
▲ 作者：Michael D. Frachetti, Jack Berner, Xiaoyi Liu, Edward R. Henry, Farhod Maksudov & Tao Ju
▲ 链接：https://www.nature.com/articles/s41586-024-08086-5
▲摘要：在此，我们展示了在中亚进行的无人驾驶飞行器激光雷达调查的结果，这些调查是在乌兹别克斯坦东南部最近发现的两个考古遗址——塔什布拉克和图贡布拉克——进行的。这些遗址位于海拔约2000—2200米的地方，是最新被记录下来的、位于亚洲中世纪丝绸之路（公元6—11世纪）的山区十字路口的大型高海拔城市中心。
尽管隐藏在几个世纪的地表下，我们将高分辨率的表面建模与半自动特征检测相结合，在图贡布拉克描绘了120公顷的纪念碑防御工事和建筑的详细平面图，从而展示了前现代中亚最大的高原城市群之一。
中亚山区是丝绸之路的重要纽带，对中亚山区中世纪社区广泛的城市基础设施和技术生产的记录为研究中世纪欧亚大陆的经济、政治和社会形成中高原人口的参与提供了新视角。
▲ Abstract：Here we present the results of uncrewed aerial vehicle–lidar surveys in Central Asia, conducted at two recently discovered archaeological sites in southeastern Uzbekistan: Tashbulak and Tugunbulak. Situated at around 2,000–2,200 m above sea level, these sites illustrate a newly documented geography of large, high-altitude urban centres positioned along the mountainous crossroads of Asia’s medieval Silk Routes (6th–11th century CE (Common Era). Although hidden by centuries of surface processes, our pairing of very-high-resolution surface modelling with semiautomated feature detection produces a detailed plan of monumental fortifications and architecture spanning 120 ha at Tugunbulak, thereby demonstrating one of the largest highland urban constellations in premodern Central Asia. Documentation of extensive urban infrastructure and technological production among medieval communities in Central Asia’s mountains—a crucial nexus for Silk Road trade networks6—provides a new perspective on the participation of highland populations in the economic, political and social formation of medieval Eurasia.
公共卫生Public Health
Bureaucrat incentives reduce crop burning and child mortality in South Asia
官僚激励减少了南亚的农作物焚烧和儿童死亡率
▲ 作者：Gemma Dipoppa & Saad Gulzar
▲ 链接：https://www.nature.com/articles/s41586-024-08046-z
▲摘要：南亚的空气污染每年造成200万人死亡，是一个非常急迫的卫生事件。在冬季收获月份，农作物秸秆燃烧造成的污染占峰值污染的40—60%。尽管这是非法的，但这种做法仍然很普遍。任何遏制这一问题的解决方案都需要政府采取大规模行动。
在此，我们对负责控制焚烧的官员进行激励是否可以缓解这一现象进行了研究。利用十年来来自卫星的风、火和健康数据以及人口与健康调查项目的调查，我们表明了官僚激励对农作物焚烧产生了影响：当风最有可能将污染引向邻近管辖区时，火灾发生率增加15%；当风污染自己的管辖区时，火灾发生率减少14.5%。这些影响随着官僚激励和能力的增强而扩大。我们还发现，禁止焚烧的官僚行为阻止了潜在的人为焚烧行为，进一步减少了13%的火灾。
最后，利用大气模型，我们估计子宫内暴露于燃烧污染的每增加一个对数，就会使儿童死亡率增加30—36‰，从而强调了官方行动的重要性。与越来越多的人认为焚烧农作物的问题难以解决的观点相反，这些发现强调了现有官员在适当激励下可以改善环境管理和公共卫生结果的具体方法。
▲ Abstract：Air pollution in South Asia is a health emergency, responsible for 2 million deaths every year. Crop residue burning accounts for 40–60% of peak pollution during the winter harvest months. Despite being illegal, this practice remains widespread. Any solution to curb the problem necessitates government action at scale. Here we study whether leveraging the incentives of bureaucrats tasked with controlling burning can mitigate this phenomenon. Using a decade of wind, fire and health data from satellites and surveys from the Demographic and Health Surveys Program, we show that crop burning responds to bureaucrat incentives: fires increase by 15% when wind is most likely to direct pollution to neighbouring jurisdictions, and decrease by 14.5% when it pollutes their own. These effects intensify with stronger bureaucratic incentives and capacity. We also find that bureaucrat action against burning deters future polluters, further reducing fires by 13%. Finally, using an atmospheric model, we estimate that one log increase in in utero exposure to pollution from burning raises child mortality by 30–36 deaths per 1,000 births, underscoring the importance of bureaucrat action. Contrary to the growing beliefs that the problem of crop burning is intractable, these findings highlight specific ways in which existing bureaucrats, when properly incentivized, can improve environmental management and public health outcomes.
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