Design and printing of proprioceptive three-dimensional architected robotic metamaterials
3D建筑机器人超材料的设计和打印
▲ 作者：HUACHEN CUI, DESHENG YAO, RYAN HENSLEIGH et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abn0090
▲ 摘要：
增材制造技术的进步使得刺激响应材料创造设计三维结构的成为可能。与生物系统将传感、驱动和控制功能紧密结合在一起的特性不同，很少有建筑材料具有类似的系统复杂性。
我们报告一种设计和制造方法，以制造一类能够进行多自由度运动、在电场的响应下在指定方向上放大应变（反之亦然）的机器人超材料，从而实现具有自感知和反馈控制的程序化运动。
这些机器人超材料由压电、导电和结构元素组成的网络组成一个3D晶格。由此产生的材料作为本体感知的微型机器人，积极地感知和移动。
▲ Abstract：
Advances in additive manufacturing techniques have enabled the creation of stimuli-responsive materials with designed three-dimensional (3D) architectures. Unlike biological systems in which functions such as sensing, actuation, and control are closely integrated, few architected materials have comparable system complexity. We report a design and manufacturing route to create a class of robotic metamaterials capable of motion with multiple degrees of freedom, amplification of strain in a prescribed direction in response to an electric field (and vice versa), and thus, programmed motions with self-sensing and feedback control. These robotic metamaterials consist of networks of piezoelectric, conductive, and structural elements interwoven into a designed 3D lattice. The resulting architected materials function as proprioceptive microrobots that actively sense and move.
A photonic integrated circuit–based erbium-doped amplifier
基于光子集成电路的掺铒放大器
▲ 作者：YANG LIU, ZHERU QIU, XINRU JI et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abo2631
▲ 摘要：
掺铒光纤放大器彻底改变了长途光通信和激光技术。铒离子可以为光子集成电路的高效光学放大提供基础，但由于输出功率不足，铒离子的应用仍不现实。
在此，我们展示了一种基于光子集成电路的掺铒放大器，其输出功率达到145毫瓦，小信号增益超过30分贝，与商业光纤放大器相当，超过了最先进的III-V异质集成半导体放大器。
我们将离子注入应用于超低损耗氮化硅（Si3N4）光子集成电路中，使孤子微梳输出功率提高100倍，实现了低噪声光子微波产生和波分复用光通信的功率需求。氮化硅光子集成电路增益使各种光纤器件小型化，如高脉冲能量飞秒锁模激光器。
▲ Abstract：
Erbium-doped fiber amplifiers revolutionized long-haul optical communications and laser technology. Erbium ions could provide a basis for efficient optical amplification in photonic integrated circuits but their use remains impractical as a result of insufficient output power. We demonstrate a photonic integrated circuit–based erbium amplifier reaching 145 milliwatts of output power and more than 30 decibels of small-signal gain—on par with commercial fiber amplifiers and surpassing state-of-the-art III-V heterogeneously integrated semiconductor amplifiers. We apply ion implantation to ultralow–loss silicon nitride (Si3N4) photonic integrated circuits, which are able to increase the soliton microcomb output power by 100 times, achieving power requirements for low-noise photonic microwave generation and wavelength-division multiplexing optical communications. Endowing Si3N4 photonic integrated circuits with gain enables the miniaturization of various fiber-based devices such as high–pulse-energy femtosecond mode-locked lasers.
Spin-charge separation in a one-dimensional Fermi gas with tunable interactions
可调谐相互作用的一维费米气体中自旋电荷分离
▲ 作者：RUWAN SENARATNE, DANYEL CAVAZOS-CAVAZOS, SHENG WANG et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abn1719
▲ 摘要：
局限于周期势的超冷原子已被证明是复杂多体系统量子模拟的有力工具。我们将费米子限制在一维，实现了描述费米子低能激发的高度集体性质的Tomonaga-Luttinger液体模型。
我们利用布拉格光谱学直接激发各种斥力相互作用强度的自旋波或电荷波。我们观察到自旋和电荷激发的速度随着相互作用的增加而向相反的方向移动，而这是自旋-电荷分离的标志。
激发光谱与Yang-Gaudin模型和Tomonaga-Luttinger液体理论的精确解在定量上一致。此外，我们确认了来自波段曲率和背散射的非线性修正对这一理论的影响。
▲ Abstract：
Ultracold atoms confined to periodic potentials have proven to be a powerful tool for quantum simulation of complex many-body systems. We confine fermions to one dimension to realize the Tomonaga-Luttinger liquid model, which describes the highly collective nature of their low-energy excitations. We use Bragg spectroscopy to directly excite either the spin or charge waves for various strengths of repulsive interaction. We observe that the velocity of the spin and charge excitations shift in opposite directions with increasing interaction, a hallmark of spin-charge separation. The excitation spectra are in quantitative agreement with the exact solution of the Yang-Gaudin model and the Tomonaga-Luttinger liquid theory. Furthermore, we identify effects of nonlinear corrections to this theory that arise from band curvature and back-scattering.
Chronic oiling in global oceans
全球海洋长期石油污染情况
▲ 作者：YANZHU DONG, YONGXUE LIU, CHUANMIN HU et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abm5940
▲ 摘要：
海面浮油来自自然渗漏或人为排放。迄今为止，它们的全球分布以及相对的自然和人为影响仍不清楚。
在此，通过分析2014-2019年的563705张哨兵1号图像，我们提供了第一份全球浮油地图，以及一份来源（自然渗漏、平台和管道）的详细清单。约90%的浮油分布在160公里的海岸线内，21条高密度浮油带与航道吻合。
根据浮油面积的量化，人为排放的比例比自然渗漏的比例大一个数量级（94%比6%），与1990-1999年期间根据体积量化的预估（54%比46%）则相反。我们的研究结果表明，当今人类活动对海洋石油污染的影响可能被大大低估了。
▲ Abstract：
Ocean oil slicks can be attributed to natural seepages or to anthropogenic discharges. To date, the global picture of their distribution and relative natural and anthropogenic contributions remains unclear. Here, by analyzing 563,705 Sentinel-1 images from 2014–2019, we provide the first global map of oil slicks and a detailed inventory of static-and-persistent sources (natural seeps, platforms, and pipelines). About 90% of oil slicks were within 160 kilometers of shorelines, with 21 high-density slick belts coinciding well with shipping routes. Quantified by slick area, the proportion of anthropogenic discharges was an order of magnitude greater than natural seepages (94 versus 6%), in contrast to the previous estimate quantified by volume during 1990–1999 (54 versus 46%). Our findings reveal that the present-day anthropogenic contribution to marine oil pollution may have been substantially underestimated.
Glacial ice supports a distinct and undocumented polar bear subpopulation persisting in late 21st-century sea-ice conditions
冰川冰使得一个没有记录的北极熊亚种群能在21世纪后期生存
▲ 作者：KRISTIN L. LAIDRE, MEGAN A. SUPPLE, ERIK W. BORN et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abk2793
▲ 摘要：
北极熊很容易受到气候变暖的影响，因为它们依赖海冰，而海冰正在迅速减少。我们提供了格陵兰东南部存在一群基因独特、独立生活的北极熊的首个证据。
这些北极熊所处的海冰环境类似于21世纪后期高纬度北极地区的情况，每年无冰期比该物种估计的禁食阈值要长100天。大部分住在北极地区的北极熊依靠每年的海冰来捕捉海豹，而格陵兰东南部的北极熊则有一个由淡水冰川组成的全年捕食环境。
这表明海洋冰川虽然数量有限，但可能依然是未被承认过的气候避难所。格陵兰东南部北极熊是世界上第20个北极熊亚种群，为了保护该物种的遗传多样性和进化潜力，有必要对该族群进行保护。
▲ Abstract：
Polar bears are susceptible to climate warming because of their dependence on sea ice, which is declining rapidly. We present the first evidence for a genetically distinct and functionally isolated group of polar bears in Southeast Greenland. These bears occupy sea-ice conditions resembling those projected for the High Arctic in the late 21st century, with an annual ice-free period that is >100 days longer than the estimated fasting threshold for the species. Whereas polar bears in most of the Arctic depend on annual sea ice to catch seals, Southeast Greenland bears have a year-round hunting platform in the form of freshwater glacial mélange. This suggests that marine-terminating glaciers, although of limited availability, may serve as previously unrecognized climate refugia. Conservation of Southeast Greenland polar bears, which meet criteria for recognition as the world’s 20th polar bear subpopulation, is necessary to preserve the genetic diversity and evolutionary potential of the species.
Droughts and societal change: The environmental context for the emergence of Islam in late Antique Arabia
干旱和社会变化：伊斯兰教在古代阿拉伯地区出现的环境背景
▲ 作者：DOMINIK FLEITMANN, JOHN HALDON, RAYMOND S. BRADLEY et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abg4044
▲ 摘要：
在阿拉伯地区，公元6世纪上半叶以希米叶尔王国的灭亡为标志。希米叶尔王国在公元525年之前一直是阿拉伯地区的统治性力量。
随后发生了重要的社会和政治变化，促进了阿拉伯政体的解体。在此，我们展示了阿拉伯南部附近的水文气候记录，包括来自阿曼北部的一份新的高分辨率石笋记录。
这些记录清楚地表明，该地区在公元6世纪发生了前所未有的干旱，最严重的时期发生在公元500年至530年之间。我们认为，这样的干旱破坏了希米叶尔王国的恢复力，从而促成了使伊斯兰教出现的社会变革。
▲ Abstract：
In Arabia, the first half of the sixth century CE was marked by the demise of Himyar, the dominant power in Arabia until 525 CE. Important social and political changes followed, which promoted the disintegration of the major Arabian polities. Here, we present hydroclimate records from around Southern Arabia, including a new high-resolution stalagmite record from northern Oman. These records clearly indicate unprecedented droughts during the sixth century CE, with the most severe aridity persisting between ~500 and 530 CE. We suggest that such droughts undermined the resilience of Himyar and thereby contributed to the societal changes from which Islam emerged.
如有侵权，请联系本站删除！
