法学是一门科学论文（科学一周论文导读）

编译 | 唐一尘

Science, 01 MAY 2020, VOL 368, ISSUE 6490

《科学》2020年5月1日，第368卷，6490期

物理学Physics

The Sun is less active than other solar-like stars

太阳不如其他类太阳恒星活跃

▲ 作者：Timo Reinhold、Alexander I. Shapiro、Sami K. Solanki，et al.

▲ 链接：https://science.sciencemag.org/content/368/6490/518

▲ 摘要

太阳拥有强大的磁场，会产生昏暗的太阳黑子、明亮的太阳耀斑和其他可见的特征。这些磁性印记会随时间而变化，并会一时性地影响该恒星光输出的可变性，导致太阳经历周期为11年的活动增高或降低。

了解太阳的磁场对预测该恒星的未来至关重要，但科学家对太阳的活动是否会减弱或磁性可能变得更活跃存在争议。

本文将太阳的亮度变化与所观察到的有着相似质量、温度、组成和旋转特性的369颗恒星进行了比较，这些数据选自开普勒太空望远镜为期4年的观测，并与来自盖亚航天器的数据相结合。

通过量化这些恒星的亮度变化，研究人员发现，大多数的恒星比太阳更为活跃；在过去的140年中，它们的可变性常常比太阳高5倍。

▲ Abstract

The magnetic activity of the Sun and other stars causes their brightness to vary. We investigated how typical the Sun’s variability is compared with other solar-like stars, i.e., those with near-solar effective temperatures and rotation periods. By combining 4 years of photometric observations from the Kepler space telescope with astrometric data from the Gaia spacecraft, we were able to measure photometric variabilities of 369 solar-like stars. Most of those with well-determined rotation periods showed higher variability than the Sun and are therefore considerably more active. These stars appear nearly identical to the Sun except for their higher variability. Therefore, we speculate that the Sun could potentially also go through epochs of such high variability.

Ferromagnetic order beyond the superconducting dome in a cuprate superconductor

铜酸盐超导体中超出超导圆顶的铁磁序

▲ 作者：Tarapada Sarkar、D. S. Wei、J. Zhang，et al.

▲ 链接：https://science.sciencemag.org/content/368/6490/532

▲ 摘要

根据传统观点，铜高温超导体的非凡性能是由于掺杂了一种强烈相关的反铁磁绝缘体而产生的。高掺杂的铜被认为是传统的费米液体金属。

研究人员报告了在掺杂电子的La2–xCexCuO4 (LCCO)薄膜中，超导圆顶外的掺杂出现了低于4开尔文的流动铁磁序。负的、各向异性的、滞后磁阻、滞后磁化和极克尔效应证明了铁磁序的存在，这些都是金属中流动铁磁性的标准标志。

这一令人惊讶的结果表明，过量的铜酸盐受到电子关联的强烈影响。

▲ Abstract

According to conventional wisdom, the extraordinary properties of the cuprate high-temperature superconductors arise from doping a strongly correlated antiferromagnetic insulator. The highly overdoped cuprates—whose doping lies beyond the dome of superconductivity—are considered to be conventional Fermi liquid metals. We report the emergence of itinerant ferromagnetic order below 4 kelvin for doping beyond the superconducting dome in thin films of electron-doped La2–xCexCuO4 (LCCO). The existence of this ferromagnetic order is evidenced by negative, anisotropic, and hysteretic magnetoresistance, hysteretic magnetization, and the polar Kerr effect, all of which are standard signatures of itinerant ferromagnetism in metals. This surprising result suggests that the overdoped cuprates are strongly influenced by electron correlations.

生物学Biology

A noncanonical inhibitory circuit dampens behavioral sensitivity to light

非典型抑制回路抑制了对光行为敏感性

▲ 作者：Takuma Sonoda、Jennifer Y. Li、Nikolas W. Hayes，et al.

▲ 链接：https://science.sciencemag.org/content/368/6490/527

▲ 摘要

以前，研究人员认为眼睛只发出兴奋信号。本文发现视网膜神经元的一个子集能向大脑发送抑制信号。通常，兴奋性信号使神经元更加兴奋，抑制性信号使神经元活动减弱。

研究人员在小鼠模型中阻断了负责抑制信号传导的视网膜神经元。结果显示，当这种信号被阻断时，昏暗的光线能更有效地改变小鼠的昼夜节律。

研究人员表示，这部分视网膜神经元与潜意识行为有关，比如昼夜节律与亮/暗周期的同步，以及瞳孔对强光的收缩。通过更好地理解这些神经元如何运作，研究人员可以探索光影响人们行为的新途径。

▲ Abstract

Retinal ganglion cells (RGCs) drive diverse, light-evoked behaviors that range from conscious visual perception to subconscious, non–image-forming behaviors. It is thought that RGCs primarily drive these functions through the release of the excitatory neurotransmitter glutamate. We identified a subset of melanopsin-expressing intrinsically photosensitive RGCs (ipRGCs) in mice that release the inhibitory neurotransmitter γ-aminobutyric acid (GABA) at non–image-forming brain targets. GABA release from ipRGCs dampened the sensitivity of both the pupillary light reflex and circadian photoentrainment, thereby shifting the dynamic range of these behaviors to higher light levels. Our results identify an inhibitory RGC population in the retina and provide a circuit-level mechanism that contributes to the relative insensitivity of non–image-forming behaviors at low light levels.

Interleukin-13 drives metabolic conditioning of muscle to endurance exercise

白介素-13驱动肌肉代谢调节以进行耐力运动

▲ 作者：Nelson H. Knudsen、Kristopher J. Stanya、Alexander L. Hyde，et al.

▲ 链接：https://science.sciencemag.org/content/368/6490/eaat3987

▲ 摘要

重复运动使肌肉线粒体能适应增加的能量需求，这是一种与改善代谢健康相关的适应性反应。

这里，研究人员发现，2型细胞因子白介素-13 (IL-13)在运动肌肉中被诱导。在肌肉运动中，它协调代谢重编程，以保留有利于脂肪酸氧化和线粒体呼吸的糖原。

在Il13–/– 小鼠模型中，运动训练介导的线粒体生物发生、跑步耐力和有益的血糖生成作用均消失。相比之下，增强肌肉IL-13信号足以增加跑步距离、葡萄糖耐量和与运动训练效果相似的线粒体活动。研究人员表示，协调的免疫和生理反应介导了运动引起的代谢适应，最大限度地提高了肌肉的燃料经济性。

▲ Abstract

Repeated bouts of exercise condition muscle mitochondria to meet increased energy demand—an adaptive response associated with improved metabolic fitness. We found that the type 2 cytokine interleukin-13 (IL-13) is induced in exercising muscle, where it orchestrates metabolic reprogramming that preserves glycogen in favor of fatty acid oxidation and mitochondrial respiration. Exercise training–mediated mitochondrial biogenesis, running endurance, and beneficial glycemic effects were lost in Il13–/– mice. By contrast, enhanced muscle IL-13 signaling was sufficient to increase running distance, glucose tolerance, and mitochondrial activity similar to the effects of exercise training. In muscle, IL-13 acts through both its receptor IL-13Rα1 and the transcription factor Stat3. The genetic ablation of either of these downstream effectors reduced running capacity in mice. Thus, coordinated immunological and physiological responses mediate exercise-elicited metabolic adaptations that maximize muscle fuel economy.

材料学/化学

Materials Science/ chemistry

A general method to synthesize and sinter bulk ceramics in seconds

短时间合成和烧结大块陶瓷的一般方法

▲ 作者：Chengwei Wang、Weiwei Ping、Qiang Bai，et al.

▲ 链接：https://science.sciencemag.org/content/368/6490/521

▲ 摘要

陶瓷是一类应用广泛的重要材料，具有良好的热稳定性、机械稳定性和化学稳定性。计算预测可能成为加速材料发现和改进陶瓷的重要工具，但用实验证实这些预测的材料特性是必要的。

然而，传统的陶瓷烧结工艺由于加工时间长，以及挥发性元素损失导致对成分的控制较差，使材料的筛选率受到限制。为了克服这些限制，研究人员开发了一种超快高温烧结（UHS）工艺——在惰性气体环境下通过辐射加热制备陶瓷材料。

研究人员提供了几个UHS过程案例，展示了其潜在的功效和应用，包括在固态电解质、多组分结构和高通量材料筛选方面的进展。

▲ Abstract

Ceramics are an important class of materials with widespread applications because of their high thermal, mechanical, and chemical stability. Computational predictions based on first principles methods can be a valuable tool in accelerating materials discovery to develop improved ceramics. It is essential to experimentally confirm the material properties of such predictions. However, materials screening rates are limited by the long processing times and the poor compositional control from volatile element loss in conventional ceramic sintering techniques. To overcome these limitations, we developed an ultrafast high-temperature sintering (UHS) process for the fabrication of ceramic materials by radiative heating under an inert atmosphere. We provide several examples of the UHS process to demonstrate its potential utility and applications, including advancements in solid-state electrolytes, multicomponent structures, and high-throughput materials screening.

Antimicrobial peptides: Application informed by evolution

抗菌肽：应用的演变

▲ 作者：Brian P. Lazzaro、Michael Zasloff、Jens Rolff

▲ 链接：https://science.sciencemag.org/content/368/6490/eaau5480

▲ 摘要

抗菌肽（AMP）是多细胞生物免疫防御的重要组成部分，目前正作为抗感染药物开发。传统上认为AMP具有广谱活性和简单的动力学，但最近的证据表明其具有意想不到的特异性和很高的协同能力。科学家对AMP的深入研究，揭示了其多态性的自适应维持，以及活性的自适应丧失的更多证据。

研究人员表示，AMP还表现出药效学特性，可减少目标微生物耐药性的演变，而且其可以与其他抗生素和常规抗生素协同作用。

然而，如果AMP要用于临床，了解它们的自然生物学是至关重要的，以便减少副作用风险，并避免目前传统抗生素的耐药性危机。

▲ Abstract

Antimicrobial peptides (AMPs) are essential components of immune defenses of multicellular organisms and are currently in development as anti-infective drugs. AMPs have been classically assumed to have broad-spectrum activity and simple kinetics, but recent evidence suggests an unexpected degree of specificity and a high capacity for synergies. Deeper evaluation of the molecular evolution and population genetics of AMP genes reveals more evidence for adaptive maintenance of polymorphism in AMP genes than has previously been appreciated, as well as adaptive loss of AMP activity. AMPs exhibit pharmacodynamic properties that reduce the evolution of resistance in target microbes, and AMPs may synergize with one another and with conventional antibiotics. Both of these properties make AMPs attractive for translational applications. However, if AMPs are to be used clinically, it is crucial to understand their natural biology in order to lessen the risk of collateral harm and avoid the crisis of resistance now facing conventional antibiotics.

合作事

,