科学小论文350字左右四年级

编译 | 李言
Science, 30 SEP 2022, VOL 377, ISSUE 6614
《科学》2022年9月30日，第377卷， 6614期

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材料科学Material Sciences

Promotion of superconductivity in magic-angle graphene multilayers
磁角石墨烯多层膜中超导性的提升
▲ 作者：YIRAN ZHANG, ROBERT POLSKI, CYPRIAN LEWANDOWSKI et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abn8585
▲ 摘要：
石墨烯摩尔超晶格显示出丰富的相关绝缘、拓扑和超导相。尽管强相关性和非平凡拓扑的起源可以直接与平坦带联系起来，但超导性的特质仍然是个谜团。
我们证明了，将扭曲三层、四层和五层石墨烯置于单层二烯化钨上的后产生的魔角装置表现出极化和超导性。我们还观察到三层和四层石墨烯在有限电位移场下产生了绝缘态。
随着层数的增加，超导性在一个增强的填充因子范围内出现，在五层石墨烯中，它扩展到每个摩尔的4个电子的填充。我们的结果突出了扁平带和更分散带之间的相互作用在石墨烯摩尔超晶格中延伸超导区域的角色。
▲ Abstract：
Graphene moiré superlattices show an abundance of correlated insulating, topological, and superconducting phases. Whereas the origins of strong correlations and nontrivial topology can be directly linked to flat bands, the nature of superconductivity remains enigmatic. We demonstrate that magic-angle devices made of twisted tri-, quadri-, and pentalayer graphene placed on monolayer tungsten diselenide exhibit flavor polarization and superconductivity. We also observe insulating states in the tril- and quadrilayer arising at finite electric displacement fields. As the number of layers increases, superconductivity emerges over an enhanced filling-factor range, and in the pentalayer it extends well beyond the filling of four electrons per moiré unit cell. Our results highlight the role of the interplay between flat and more dispersive bands in extending superconducting regions in graphene moiré superlattices.

化学Chemistry

Inefficient and unlit natural gas flares both emit large quantities of methane
低效和未点燃的天然气火炬都会释放大量的甲烷
▲ 作者：GENEVIEVE PLANT, ERIC A. KORT, ADAM R. BRANDT et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.abq0385
▲ 摘要：
火炬被化石燃料工业广泛用于处理天然气。工业界和政府通常认为，火炬保持燃烧，同时以98%的效率消耗甲烷——天然气的主要成分。然而，这两种想法都不是基于现实世界的观察。我们通过对三个占美国燃烧的80%的盆地的空中采样计算燃烧效率，并将这些观测结果与未点燃的火炬覆盖率调查相结合。
我们发现，未点燃的火炬和低效燃烧对无效甲烷破坏的贡献都相当大，火炬只能有效破坏91.1%的甲烷。
这意味着甲烷排放量比目前的假设增加了5倍，占美国油气甲烷排放总量的4%至10% 。这一发现强调了此前未被重视的甲烷来源和减排机会。
▲ Abstract：
Flaring is widely used by the fossil fuel industry to dispose of natural gas. Industry and governments generally assume that flares remain lit and destroy methane, the predominant component of natural gas, with 98% efficiency. Neither assumption, however, is based on real-world observations. We calculate flare efficiency using airborne sampling across three basins responsible for >80% of US flaring and combine these observations with unlit flare prevalence surveys. We find that both unlit flares and inefficient combustion contribute comparably to ineffective methane destruction, with flares effectively destroying only 91.1% (90.2, 91.8; 95% confidence interval) of methane. This represents a fivefold increase in methane emissions above present assumptions and constitutes 4 to 10% of total US oil and gas methane emissions, highlighting a previously underappreciated methane source and mitigation opportunity.

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