Nature, 8 June 2023, Volume 618 Issue 7964
《自然》2023年6月8日，第618卷，7964期
天文学Astronomy
Temperature inhomogeneities cause the abundance discrepancy in H II regions
温度的不均匀性导致H II 区域丰度差异
▲ 作者：J. Eduardo Méndez-Delgado, César Esteban, Jorge García-Rojas, Kathryn Kreckel & Manuel Peimbert
▲ 链接：
https://www.nature.com/articles/s41586-023-05956-2
▲ 摘要：
在此，我们报告了以t2量化的证明气体中存在温度不均匀性的观测证据。这些不均匀性只影响高度电离的气体，并引起丰度差异问题。
基于碰撞激发线的金属丰度测定需要被修正，因为它们可能被严重低估，特别是在金属丰度较低的区域，例如最近用詹姆斯·韦伯太空望远镜在高z星系中观测到的那些区域。我们提出了估算温度和金属丰度的新经验关系，这对宇宙时内宇宙化学成分的可靠解释十分重要。
▲ Abstract：
Here we report observational evidence that there are temperature inhomogeneities within the gas, quantified byt2. These inhomogeneities affect only highly ionized gas and cause the abundance discrepancy problem. Metallicity determinations based on collisionally excited lines must be revised because these may be severely underestimated, especially in regions of lower metallicity such as those recently observed with the James Webb Space Telescope in high-z galaxies. We present new empirical relations for estimation of temperature and metallicity, critical for a robust interpretation of the chemical composition of the Universe over cosmic time.
物理学Physics
Dynamic optical response of solids following 1-fs-scale photoinjection
1飞秒尺度光注入后固体的动态光学响应
▲ 作者：Dmitry A. Zimin, Nicholas Karpowicz, Muhammad Qasim, Matthew Weidman, Ferenc Krausz & Vladislav S. Yakovlev
▲ 链接：
https://www.nature.com/articles/s41586-023-05986-w
▲ 摘要：
在此，我们将场分辨光学计量应用于这些动力学，并报告了对近1飞秒载流子注入后的最初几飞秒内硅和二氧化硅的光学性质演变的直接观察结果。
我们观察到，德鲁德-洛仑兹响应在几个飞秒内形成，比反向等离子体频率短得多。这与之前在太赫兹领域的测量结果形成对比，同时也是加速基于电子的信号处理的核心。
▲ Abstract：
Here we apply field-resolved optical metrology to these dynamics and report the direct observation of the evolving optical properties of silicon and silica during the first few femtoseconds following a near-1-fs carrier injection. We observe that the Drude–Lorentz response forms within several femtoseconds—a time interval much shorter than the inverse plasma frequency. This is in contrast to previous measurements in the terahertz domain and central to the quest to speed up electron-based signal processing.
化学Chemistry
Copper-catalysed enantioconvergent alkylation of oxygen nucleophiles
铜催化氧亲核试剂的对映选择性会聚烷基化反应
▲ 作者：Caiyou Chen & Gregory C. Fu
▲ 链接：
https://www.nature.com/articles/s41586-023-06001-y
▲ 摘要：
在此，我们创造了一个容易获得的铜催化剂，它可以实现一系列氧亲核试剂与α-卤代酰胺的对映体会聚的取代反应；反应可以在温和条件下产生，并且兼容各种官能团。
该催化剂在实现氧亲核试剂和氮亲核试剂的对映选择性会聚烷基化反应具有独特的效果，为过渡金属催化剂的潜力提供了支持，同时为实现杂原子亲核试剂的对映选择性会聚烷基化提供了解决方案。
▲ Abstract：
Here we establish that a readily available copper catalyst can achieve an array of enantioconvergent substitution reactions of α-haloamides, a useful family of electrophiles, by oxygen nucleophiles; the reaction proceeds under mild conditions in the presence of a wide variety of functional groups. The catalyst is uniquely effective in being able to achieve enantioconvergent alkylations of not only oxygen nucleophiles but also nitrogen nucleophiles, giving support for the potential of transition-metal catalysts to provide a solution to the pivotal challenge of achieving enantioselective alkylations of heteroatom nucleophiles.
人工智能Artificial Intelligence
Faster sorting algorithms discovered using deep reinforcement learning
使用深度强化学习发现更快的排序算法
▲ 作者：Daniel J. Mankowitz, Andrea Michi, Anton Zhernov et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06004-9
▲ 摘要：
在此，我们将展示人工智能如何通过发现未知的规律来超越当前的状态。为了实现这一点，我们制定了一个挑战，以单人游戏的方式寻找更好的排序算法。然后我们训练了一个新的深度强化学习代理AlphaDev来玩这个游戏。
AlphaDev从零开始发现了小型排序算法，且优于已知的人类基准。这些算法已集成到LLVM标准C++排序库中。排序库的这一变化代表了可使用深度强化学习自动发现的算法组成。我们还提供了其他领域的结果，以展示该方法的通用性。
▲ Abstract：
Here we show how artificial intelligence can go beyond the current state of the art by discovering hitherto unknown routines. To realize this, we formulated the task of finding a better sorting routine as a single-player game. We then trained a new deep reinforcement learning agent, AlphaDev, to play this game. AlphaDev discovered small sorting algorithms from scratch that outperformed previously known human benchmarks. These algorithms have been integrated into the LLVM standard C++ sort library. This change to this part of the sort library represents the replacement of a component with an algorithm that has been automatically discovered using reinforcement learning. We also present results in extra domains, showcasing the generality of the approach.
地理学Geography
Tree islands enhance biodiversity and functioning in oil palm landscapes
树岛增强了油棕景观的生物多样性和功能
▲ 作者：Delphine Clara Zemp, Nathaly Guerrero-Ramirez et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06086-5
▲ 摘要：
在此，我们展示了一项为期5年的大规模生态系统恢复实验的结果。这项实验在一个拥有52个树岛的油棕景观地进行，包括10个生物多样性指标和19个生态系统功能指标的评估。
总体而言，与传统管理的油棕地相比，人工岛的生物多样性和生态系统功能指标更高。较大的树岛通过植被结构的变化导致更大的多样性增益。此外，树木富集没有降低景观尺度油棕产量。研究结果表明，以油棕为主的人工岛是一种很有前景的生态恢复策略，但不应以此取代对剩余森林的保护。
▲ Abstract：
Here, we present findings from a large-scale, 5-year ecosystem restoration experiment in an oil palm landscape enriched with 52 tree islands, encompassing assessments of ten indicators of biodiversity and 19 indicators of ecosystem functioning. Overall, indicators of biodiversity and ecosystem functioning, as well as multidiversity and ecosystem multifunctionality, were higher in tree islands compared to conventionally managed oil palm. Larger tree islands led to larger gains in multidiversity through changes in vegetation structure. Furthermore, tree enrichment did not decrease landscape-scale oil palm yield. Our results demonstrate that enriching oil palm-dominated landscapes with tree islands is a promising ecological restoration strategy, yet should not replace the protection of remaining forests.
信息技术Information Technology
Users choose to engage with more partisan news than they are exposed to on Google Search
用户主动选择有偏向性的新闻多于被搜索引擎推送
▲ 作者：Ronald E. Robertson, Jon Green, Damian J. Ruck et al.
▲ 链接：
https://www.nature.com/articles/s41586-023-06078-5
▲ 摘要：
涉及媒体生态暴露的研究很少，而且主要局限于社交媒体平台，这给网络搜索引擎留下了疑问。为了解决这些问题，我们进行了一项双线研究，将调查与2018年和2020年美国大选期间谷歌搜索的曝光率和参与度的有效测量相结合。
在两条线中，我们在参与者的选择中发现了更多与身份一致的不可靠新闻来源，无论是在谷歌搜索中还是网络整体，都比他们在谷歌搜索结果中接触到的要多。这些结果表明，在谷歌搜索中，对不可靠新闻的曝光和参与主要不是由算法管理驱动的，而是由用户自己的选择驱动的。
▲ Abstract：
Studies involving ecological exposure have therefore been rare, and largely limited to social media platforms, leaving open questions about web search engines. To address these gaps, we conducted a two-wave study pairing surveys with ecologically valid measures of both exposure and engagement on Google Search during the 2018 and 2020 US elections. In both waves, we found more identity-congruent and unreliable news sources in participants’ engagement choices, both within Google Search and overall, than they were exposed to in their Google Search results. These results indicate that exposure to and engagement with partisan or unreliable news on Google Search are driven not primarily by algorithmic curation but by users’ own choices.
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