编译 | 李言

Science, 1 DEC 2023, Volume 382 Issue 6674

《科学》2023年12月1日，第382卷，6674期

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生物学Biology

Two teosintes made modern maize

两种大刍草为现代玉米的祖先

▲ 作者：NING YANG, YUEBIN WANG et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.adg8940

▲ 摘要：

玉米的起源是近一个世纪以来激烈争论的话题，但目前的遗传模型和早期的考古模型都不能解释现有的全部数据，近期的一些研究强调了野生近亲墨西哥高原大刍草亚种的潜在贡献。

我们的群体遗传分析表明，现代玉米的起源可以追溯到古代玉米和大刍草亚种之间的混合，这一过程始于驯化开始4000年后的墨西哥高地。我们发现，无论是在个体位点还是在农艺性状基础上的加性遗传变异上，基因渗透都是玉米多样性的关键组成部分。

我们的研究结果澄清了现代玉米的起源，并提出了关于在玉米在整个美洲扩散的人为机制的新问题。

▲ Abstract：

The origins of maize were the topic of vigorous debate for nearly a century, but neither the current genetic model nor earlier archaeological models account for the totality of available data, and recent work has highlighted the potential contribution of a wild relative, Zea mays ssp. mexicana. Our population genetic analysis reveals that the origin of modern maize can be traced to an admixture between ancient maize and Zea mays ssp. mexicana in the highlands of Mexico some 4000 years after domestication began. We show that variation in admixture is a key component of maize diversity, both at individual loci and for additive genetic variation underlying agronomic traits. Our results clarify the origin of modern maize and raise new questions about the anthropogenic mechanisms underlying dispersal throughout the Americas.

Nesting chinstrap penguins accrue large quantities of sleep through seconds-long microsleeps

筑巢的帽带企鹅能通过几秒钟的微睡眠积累大量的睡眠

▲ 作者：P.-A. LIBOUREL, W. Y. LEE et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.adh0771

▲ 摘要：

我们研究了野生帽带企鹅在海上和在南极洲筑巢时，不断暴露于蛋捕食者和其他企鹅的攻击下的脑电图显示的睡眠情况。这些企鹅每天打盹超过1万次，双脑和单脑慢波睡眠都有，平均持续时间仅为4秒，但累积的睡眠时间超过11小时。

成功繁殖的企鹅在微睡眠的表现表明，睡眠的好处是可以逐渐积累的。

▲ Abstract：

We investigated electroencephalographically defined sleep in wild chinstrap penguins, at sea and while nesting in Antarctica, constantly exposed to an egg predator and aggression from other penguins. The penguins nodded off >10,000 times per day, engaging in bouts of bihemispheric and unihemispheric slow-wave sleep lasting on average only 4 seconds, but resulting in the accumulation of >11 hours of sleep for each hemisphere. The investment in microsleeps by successfully breeding penguins suggests that the benefits of sleep can accrue incrementally.

天文学Astronomy

A Neptune-mass exoplanet in close orbit around a very low-mass star challenges formation models

一颗海王星大小的系外行星在一颗质量极低的恒星的近轨道上运行，挑战了形成模型

▲ 作者：GUDMUNDUR STEFáNSSON, SUVRATH MAHADEVAN et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.abo0233

▲ 摘要：

我们利用径向速度观测发现了一颗海王星质量的系外行星，它围绕着LHS 3154运行，这颗恒星的质量比太阳小9倍。这颗系外行星的轨道周期为3.7天，其最小质量是地球质量的13.2倍。

我们通过模拟表明，高行星—恒星质量比（>3.5 × 10⁻³）不是核心吸积理论或行星形成引力不稳定性理论的预期结果。在核心吸积模拟中，我们表明，只有当原行星盘的尘埃质量比通常在非常低质量的恒星周围观察到的大一个数量级时，才会形成海王星质量等级的近距离行星。

▲ Abstract：

We used radial velocity observations to detect a Neptune-mass exoplanet orbiting LHS 3154, a star that is nine times less massive than the Sun. The exoplanet’s orbital period is 3.7 days, and its minimum mass is 13.2 Earth masses. We used simulations to show that the high planet-to-star mass ratio (>3.5 × 10⁻³) is not an expected outcome of either the core accretion or gravitational instability theories of planet formation. In the core-accretion simulations, we show that close-in Neptune-mass planets are only formed if the dust mass of the protoplanetary disk is an order of magnitude greater than typically observed around very low-mass stars.

环境科学Environmental Science

State dependence of CO₂ forcing and its implications for climate sensitivity

二氧化碳作用力的状态依赖性及其对气候敏感性的影响

▲ 作者：HAOZHE HE, RYAN J. KRAMER et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.abq6872

▲ 摘要：

在此，我们表明IRF2×CO₂不是常数，而是取决于气候基础状态，二氧化碳每增加一倍，IRF2×CO₂就增加约25%。并且，由于平流层上部的冷却，IRF2×CO₂自工业化前时代以来增加了约10%，这意味着气候敏感性的比例增加。

这种对基本状态的依赖也解释了IRF2×CO₂中大约一半的模式间传播问题，这一问题在气候模型中持续争论了近30年。

▲ Abstract：

Here, we show that the IRF2×CO₂ is not constant, but rather depends on the climatological base state, increasing by about 25% for every doubling of CO₂, and has increased by about 10% since the preindustrial era primarily due to the cooling within the upper stratosphere, implying a proportionate increase in climate sensitivity. This base-state dependence also explains about half of the intermodel spread in IRF2×CO₂, a problem that has persisted among climate models for nearly three decades.

化学Chemistry

Boryl radical catalysis enables asymmetric radical cycloisomerization reactions

硼自由基催化使不对称环异构化反应成为可能

▲ 作者：CHANG-LING WANG, JIE WANG et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.adg1322

▲ 摘要：

在这项研究中，我们报告了一个手性氮杂环卡宾（NHC）连接的硼基自由基家族作为催化剂，可以催化不对称自由基环异构化反应。自由基催化剂可以由易于制备的手性硼烷配合物生成，并且手性NHC组分的广泛可用性为立体化学控制提供了帮助。

该机理研究支持一个由硼基自由基加成、氢原子转移、环化和消除硼基自由基催化剂组成的催化循环，其中手性NHC亚基决定了自由基环化的对映选择性。这种催化作用允许从简单的起始材料不对称构造有价值的手性杂环产物。

▲ Abstract：

In this work, we report a family of chiral N-heterocyclic carbene (NHC)–ligated boryl radicals as catalysts that enable catalytic asymmetric radical cycloisomerization reactions. The radical catalysts can be generated from easily prepared NHC-borane complexes, and the broad availability of the chiral NHC component provides substantial benefits for stereochemical control. Mechanistic studies support a catalytic cycle comprising a sequence of boryl radical addition, hydrogen atom transfer, cyclization, and elimination of the boryl radical catalyst, wherein the chiral NHC subunit determines the enantioselectivity of the radical cyclization. This catalysis allows asymmetric construction of valuable chiral heterocyclic products from simple starting materials.

材料科学Materials Science

3D microscopy at the nanoscale reveals unexpected lattice rotations in deformed nickel

纳米级三维显微镜揭示了变形镍中意外的晶格旋转

▲ 作者：QIONGYAO HE, SØREN SCHMIDT et al.

▲ 链接：

https://www.science.org/doi/10.1126/science.adj2522

▲ 摘要：

在原位纳米力学测试之前和之后，我们都通过透射电子显微镜的三维定向映射来跟踪纳米镍中单个晶粒的旋转。许多较大尺寸的颗粒经历了意外的晶格旋转，我们认为这是由于卸载过程中的旋转逆转。

这种固有的可逆旋转源于背应力驱动的位错滑移过程，较大的晶粒在其中更为活跃。研究结果为纳米颗粒金属的基本变形机制提供了见解，并将有助于指导材料设计和工程应用策略。

▲ Abstract：

We tracked the rotations of individual grains in nanograined nickel by using three-dimensional orientation mapping in a transmission electron microscope before and after in situ nanomechanical testing. Many of the larger-size grains underwent unexpected lattice rotations, which we attributed to a reversal of rotation during unloading. This inherent reversible rotation originated from a back stress–driven dislocation slip process that was more active for larger grains. These results provide insights into the fundamental deformation mechanisms of nanograined metals and will help to guide strategies for material design and engineering applications.