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《科学》(20190906出版)一周论文导读

作者:学术无界 / 关注公众号:xueshuwujie  发布:2019-11-03

编译 | 冯维维
Science,6 SEPTEMBER 2019, VOL 365, ISSUE6457
《科学》2019年9月6日,第365卷,第6457期
生态学Ecology
Breakdown in spawning synchrony: A silent threat to coral persistence
对珊瑚持续性的无声威胁
▲作者:Tom Shlesinger, Yossi Loya▲链接:https://science.sciencemag.org/content/365/6457/1002▲摘要:
不断变化的气候对珊瑚是一种威胁,导致曾经充满生命的珊瑚礁变形、白化和死亡。Shlesinger和Loya提醒人们,珊瑚还面临着同样危险但几乎看不见的威胁:繁殖不同步。
他们发现,环境的变化导致红海中几种产卵珊瑚配子释放时间的变化。全球可能也会发生类似的变化。这种产卵同步性的丧失可能导致繁殖失败,尽管它不明显,但对珊瑚礁的威胁同样严重。
▲Abstract
Our changing climate is a threat to corals, causing disfiguring bleaching and mortality to reefs that once teemed with life. Shlesinger and Loya alert us to an equally dangerous yet nearly invisible hazard to coral: loss of breeding synchrony . They found that environmental changes have resulted in shifts in the timing of gamete release in several species of broadcast-spawning corals in the Red Sea. Similar changes are likely occurring globally. Such a loss of spawning synchrony could result in reproductive failure, a much less obvious but no less insidious threat to coral reefs.
Kīlauea lava fuels phytoplankton bloom in the North Pacific Ocean
北太平洋基拉威厄火山熔岩使浮游植物大量繁殖
▲作者:Samuel T. Wilson, Nicholas J. Hawco, E. Virginia Armbrust, Benedetto Barone, etc.▲链接:
https://science.sciencemag.org/content/365/6457/1040
▲摘要:
从2018年6月到8月,夏威夷基拉威厄火山的爆发引发了以硅藻为主的浮游植物的爆发。Wilson等人通过航行对烟羽进行取样,他们还部署了水下滑翔机,并用卫星监测营养不良的太平洋地区这一罕见事件的动态。
他们发现了遥感无法观测到的地下叶绿素最大值,进行了转录组和N同位素标记分析,并测量了营养物质、生物量在不同生物体中的分配以及初级产量。
海洋动力学的物理模型证实了许多数据。作者得出的结论是,这些烟羽是由熔岩加热地下水并引发深水营养物上涌至地表的结果,而不是直接从熔岩中注入微量营养素。
▲Abstract
From June to August 2018, the eruption of Kīlauea volcano triggered a diatom-dominated phytoplankton bloom. Wilson et al. set sail to sample the plume, deploying subsea gliders and using satellite monitoring to measure the dynamics of this rare event in the nutrient-poor Pacific. They found subsurface chlorophyll maxima not visible by remote sensing, performed transcriptome and N isotope marker analysis, and measured nutrients, partitioning of biomass into different organisms, and primary production. Much of the data are corroborated by physical modeling of the ocean dynamics. The authors conclude that the plume was fed by the lava heating subsurface water and triggering upwelling of deepwater nutrients to the surface rather than by direct injection of micronutrients from lava.
物理学Physics
A measurement of the atomic hydrogen Lamb shift and the proton charge radius
解开质子之谜:对氢原子兰姆位移和质子电荷半径的测量▲作者:N. Bezginov, T. Valdez, M. Horbatsch, A. Marsman, A. C. Vutha, E. A. Hessels▲链接:https://science.sciencemag.org/content/365/6457/1007▲摘要:近十年来,物理学家一直困惑于从μ介子氢的兰姆位移推导出的质子大小与以普通(电子)氢为基础的教科书平均值之间的差异。一种可能的解决方案是,电子与质子的相互作用方式与介子不同,这将需要“新的物理学”。Bezginov等人测量了电子氢中的兰姆位移,这使得直接比较介子氢中的兰姆位移成为可能。这两个结果是一致的,但与平均值的差异仍然存在。▲AbstractThe discrepancy between the proton size deduced from the Lamb shift in muonic hydrogen and the average, textbook value based on regular (electronic) hydrogen has puzzled physicists for nearly a decade. One possible resolution could be that electrons interact with protons in a different way than muons do, which would require “new physics.” Bezginov et al. measured the Lamb shift in electronic hydrogen, which allowed for a direct comparison to the Lamb shift measured in muonic hydrogen. The two results agreed, but the discrepancy with the averaged value remains.
Radio emission from a pulsar’s magnetic pole revealed by general relativity
广义相对论揭示脉冲星磁极射电辐射
▲作者:Gregory Desvignes, Michael Kramer, Kejia Lee, Joeri van Leeuwen, Ingrid Stairs, etc.
▲链接:
https://science.sciencemag.org/content/365/6457/1013
▲摘要:
脉冲星是一种旋转的中子星,它沿着磁极发射无线电波,如果光束指向地球,就会被视为有规律的脉冲。
Desvignes等人对一个脉冲星进行了十多年的监测,以观察其射电脉冲如何变化。由于受双星伴星的影响,广义相对论导致旋转轴的进动。
2005年,它的每一次旋转可以看到两次脉冲,每个脉冲来自一个磁极,但到2018年,其中一个脉冲从视线中消失了。将射电辐射映射到磁极上决定了光束的角度,也就是射电观测者可以探测到脉冲星的角度区域。
▲Abstract
Pulsars are rotating neutron stars that emit beams of radio waves along their magnetic poles, seen as regular pulses if the beam points toward Earth. Desvignes et al. monitored a pulsar for more than a decade, observing how its radio pulses vary. General relativity causes precession of the rotation axis, because of the influence of a binary companion. In 2005, two pulses per rotation were visible, one from each magnetic pole, but by 2018 one had precessed out of our line of sight and disappeared. Mapping the radio emission across the magnetic pole determines the beaming angle, the angular region in which a radio observer can detect a pulsar.
化学Chemistry
Single-nanowire spectrometers
小型化光谱仪
▲作者:Zongyin Yang, Tom Albrow-Owen, Hanxiao Cui, Jack Alexander-Webber, Tawfique Hasan, etc.
▲链接:
https://science.sciencemag.org/content/365/6457/1017
▲摘要:
光谱仪是一种无处不在的表征工具,涵盖了大多数科学和许多工业学科。大多数手持光谱仪都是基于桌面光学元件,这就限制了这些光谱仪可以缩小的规模。
为了满足对微米级(和更小的)微型光谱仪的需求,作者开发了一种基于单根合成纳米线的微型光谱仪。
这一结果为其他光敏纳米材料在超小型化光谱学平台上的应用提供了实用的进展。
▲Abstract
Spectroscopy is a ubiquitous characterization tool spanning most scientific and many industrial disciplines. Most handheld spectrometers are based on tabletop optical components, which limits the scale to which these spectrometers can be shrunk. To address the desire for miniaturized spectrometers with a micrometer-scale (and smaller) footprint, Yang et al. developed such a microspectrometer based on single, compositionally engineered nanowire. This result is a practical step forward for the use of other light-sensitive nanomaterials for such ultra-miniaturized spectroscopy platforms.
Atomically precise, custom-design origami graphene nanostructures
精确折叠石墨烯纳米结构
▲作者:Hui Chen, Xian-Li Zhang, Yu-Yang Zhang, Dongfei Wang, De-Liang Bao, Hong-Jun Gao, etc.
▲链接:
https://science.sciencemag.org/content/365/6457/1036
▲摘要:
据预测,折叠或轧制石墨烯单层或双层结构所产生的石墨烯纳米结构具有许多有趣的电子特性,但对这种折叠过程的控制却存在限制。
作者使用扫描隧道显微镜尖端,在低温下(4开尔文)折叠和打开蚀刻在石墨表面的石墨烯纳米岛。
这种折叠角度可以精确控制,在双层石墨烯中产生不同的扭转角,并在折叠石墨烯中产生管状边缘。
他们还折叠了5 - 7环的缺损,并用扫描隧穿光谱技术研究了这种异质结。
▲Abstract
Graphene nanostructures that would result from folding or rolling graphene monolayers or bilayers have been predicted to have a number of interesting electronic properties, but control over such folding processes has been limited. Chen et al. used a scanning tunneling microscope tip to fold and unfold graphene nanoislands etched on graphite surfaces at low temperatures (4 kelvin). The fold angle could be precisely controlled to create different twist angles in bilayer graphene and a tubelike edge in folded graphene. They also folded 5 ring–7 ring defects and explored this heterojunction with scanning tunneling spectroscopy.
人类学Anthropology
The formation of human populations in South and Central Asia
南亚和中亚人口的形成
▲作者:Vagheesh M. Narasimhan, Nick Patterson, Priya Moorjani, Nadin Rohland, etc.
▲链接:
https://science.sciencemag.org/content/365/6457/eaat7487
▲摘要:
古DNA让我们能够追踪全球人类活动的历史。Narasimhan等人通过对生活在过去8000年里的500多人进行基因分析,发现了南亚和中亚地区复杂的人类迁徙和混合事件模式。
他们建立了欧亚史前人口的关键阶段,包括近东农耕民族的扩展,包括向西和向东的迁移。
青铜时代的亚姆纳亚民族也从黑海北部的一个焦点地区向西和向东迁移。遗传序列的总体模式反映了南亚和欧洲相似和平行的模式。
▲Abstract
Ancient DNA has allowed us to begin tracing the history of human movements across the globe. Narasimhan et al. identify a complex pattern of human migrations and admixture events in South and Central Asia by performing genetic analysis of more than 500 people who lived over the past 8000 years (see the Perspective by Schaefer and Shapiro). They establish key phases in the population prehistory of Eurasia, including the spread of farming peoples from the Near East, with movements both westward and eastward. The people known as the Yamnaya in the Bronze Age also moved both westward and eastward from a focal area located north of the Black Sea. The overall patterns of genetic clines reflect similar and parallel patterns in South Asia and Europe.
计算学Computing
Boltzmann generators: Sampling equilibrium states of many-body systems with deep learning
利用深度学习对多体系统的平衡态进行采样
▲作者:Frank Noe, Simon Olsson, Jonas Köhler, Hao Wu
▲链接:
https://science.sciencemag.org/content/365/6457/eaaw1147
▲摘要
分子动力学或蒙特卡罗方法可以用来采样平衡态,但对于复杂系统,这些方法的计算成本很高,因为从一种平衡态到另一种平衡态的转变可能只会通过罕见的事件发生。
Noe等人利用神经网络和深度学习,在平衡状态下生成独立的软凝聚物质样本的分布。作者利用监督训练,构造了复杂兴趣系统坐标与相同维数的简单高斯坐标之间的可逆变换。
因此,可以在这个更简单的坐标系中对构造进行采样,然后使用正确的统计加权将其转换到复杂坐标系。
▲Abstract
Molecular dynamics or Monte Carlo methods can be used to sample equilibrium states, but these methods become computationally expensive for complex systems, where the transition from one equilibrium state to another may only occur through rare events. Noé et al. used neural networks and deep learning to generate distributions of independent soft condensed-matter samples at equilibrium. Supervised training is used to construct invertible transformations between the coordinates of the complex system of interest and simple Gaussian coordinates of the same dimensionality. Thus, configurations can be sampled in this simpler coordinate system and then transformed back into the complex one using the correct statistical weighting.
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