编译 | 唐一尘
Science, 23 AUGUST 2019, VOL 365, ISSUE 6455
《科学》2019年8月23日,第365卷6455期
材料学 Materials
Ultrafast laser welding of ceramics
陶瓷超快激光焊接
▲ 作者:E. H. Penilla、L. F. Devia-Cruz、A. T. Wieg, et al
▲ 链接:
https://science.sciencemag.org/content/365/6455/803
▲ 摘要:
陶瓷焊接是现代制造业中一个重要的缺失环节。目前的方法不能将陶瓷与温度敏感材料,如聚合物和电子元件,结合在一起。
本研究介绍了一种超快脉冲激光焊接方法,该方法将光聚焦在界面上,以确保陶瓷上的光相互作用范围,从而刺激非线性吸收过程,导致局部熔化而不是烧蚀。其关键是线性和非线性光学特性与激光能量—材料耦合的相互作用。
焊接陶瓷组件具有高真空,以及剪切强度可与金属—陶瓷扩散接合相媲美。激光焊接可以在恶劣环境的设备中制造陶瓷整体组件,也可以在光电子和/或需要可见射频透明度的电子封装中制造陶瓷整体组件。
▲ Abstract
Welding of ceramics is a key missing component in modern manufacturing. Current methods cannot join ceramics in proximity to temperature-sensitive materials like polymers and electronic components. We introduce an ultrafast pulsed laser welding approach that relies on focusing light on interfaces to ensure an optical interaction volume in ceramics to stimulate nonlinear absorption processes, causing localized melting rather than ablation. The key is the interplay between linear and nonlinear optical properties and laser energy–material coupling. The welded ceramic assemblies hold high vacuum and have shear strengths comparable to metal-to-ceramic diffusion bonds. Laser welding can make ceramics integral components in devices for harsh environments as well as in optoelectronic and/or electronic packages needing visible-radio frequency transparency.
Programmable CRISPR-responsive smart materials
可编程的CRISPR-反应性智能材料
生物地球化学/物理学 Biogeochemistry/ physics
The global soil community and its influence on biogeochemistry
全球土壤群落及其对生物地球化学的影响
Observation of a symmetry-protected topological phase of interacting bosons with Rydberg atoms
用里德伯原子观察玻色子相互作用的对称保护拓扑相
The concept of topological phases is a powerful framework for characterizing ground states of quantum many-body systems that goes beyond the paradigm of symmetry breaking. Topological phases can appear in condensed-matter systems naturally, whereas the implementation and study of such quantum many-body ground states in artificial matter require careful engineering.Here, we report the experimental realization of a symmetry-protected topological phase of interacting bosons in a one-dimensional lattice and demonstrate a robust ground state degeneracy attributed to protected zero-energy edge states. The experimental setup is based on atoms trapped in an array of optical tweezers and excited into Rydberg levels, which gives rise to hard-core bosons with an effective hopping generated by dipolar exchange interaction.
地球和行星科学 Earth and Planetary Science
Images from the surface of asteroid Ryugu show rocks similar to carbonaceous chondrite meteorites
龙宫表面图像显示其岩石类似于碳质球粒陨石
▲ 作者:R. Jaumann、N. Schmitz、T.-M. Ho、S. E. Schröder, et al
▲ 链接:
https://science.sciencemag.org/content/365/6455/817
▲ 摘要:
隼鸟2号计划对龙宫的岩石进行采样并将它们送返地球,这能帮助科学家了解太阳系是如何形成的。
隼鸟2号携带着一个被称作“移动式小行星表面侦察器”的着陆器,后者在2018年10月被投放到了龙宫的表面。当该着陆器靠近龙宫表面时,它的相机为龙宫拍摄了照片。
本研究分析了这些图像,结果显示,该小行星覆盖着岩石和巨石,它们分为两类:黑暗粗糙类或明亮光滑类。这两种类型的岩石几乎均匀分布于龙宫的表面。
研究人员表示,这支持这样一种理论,即龙宫是由碎石形成的,这些碎石在某颗母星遭撞击后重新聚拢,从而导致了两类岩石材料。
此外,许多岩石还含有类似于在碳质球粒陨石中所见的小型有色包含物,表明它们可能含有橄榄石这种矿物。
而且,这些图像显示,龙宫表面没有细小的颗粒或尘埃,而这些颗粒或尘埃的积聚预计会见于太空风化之后。
研究人员认为,有一种尚未发现的物理机制能有效清除小行星表面尘埃。
The near-Earth asteroid (162173) Ryugu is a 900-m-diameter dark object expected to contain primordial material from the solar nebula. The Mobile Asteroid Surface Scout (MASCOT) landed on Ryugu’s surface on 3 October 2018. We present images from the MASCOT camera (MASCam) taken during the descent and while on the surface. The surface is covered by decimeter- to meter-sized rocks, with no deposits of fine-grained material. Rocks appear either bright, with smooth faces and sharp edges, or dark, with a cauliflower-like, crumbly surface. Close-up images of a rock of the latter type reveal a dark matrix with small, bright, spectrally different inclusions, implying that it did not experience extensive aqueous alteration. The inclusions appear similar to those in carbonaceous chondrite meteorites.
The slow earthquake spectrum in the Japan Trench illuminated by the S-net seafloor observatories
S网海底观测站探知日本海沟的慢地震
通过对这些及其他相关观测资料的整理,包括重复地震和地震群资料,研究人员发现缓慢地震分布与日本东北部地震破裂是互补的。
研究人员利用这些观测资料,将日本海沟的巨型逆断层划分为3个具有不同滑动特性的部分。
研究人员发现,东北—冲绳地震的断裂(形成于断裂带中部)是被两个相邻的断裂带终止的。
Investigating slow earthquake activity in subduction zones provides insight into the slip behavior of megathrusts, which can provide important clues about the rupture extent of future great earthquakes. Using the S-net ocean-bottom seismograph network along the Japan Trench, we mapped a detailed distribution of tectonic tremors, which coincided with very-low-frequency earthquakes and a slow slip event. Compiling these and other related observations, including repeating earthquakes and earthquake swarms, we found that the slow earthquake distribution is complementary to the Tohoku-Oki earthquake rupture. We used our observations to divide the megathrust in the Japan Trench into three along-strike segments characterized by different slip behaviors. We found that the rupture of the Tohoku-Oki earthquake, which nucleated in the central segment, was terminated by the two adjacent segments.
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