编译 | 李言
Science, 11 DECEMBER 2020, VOL 370, ISSUE 6522
《科学》2020年12月11日，第370卷，6522期
环境科学Environmental Science
Recent global decline of CO2 fertilization effects on vegetation photosynthesis
最近全球CO2施肥效应下降对植被光合作用的影响
▲ 作者：Songhan Wang, Yongguang Zhang, Weimin Ju, Jing M. Chen, et al.
▲ 链接：
https://science.sciencemag.org/content/370/6522/1295
▲ 摘要
由二氧化碳浓度增加所驱动的增强的植被生产力，例如CO2施肥效应（CFE），对气候变暖具有重要的负反馈作用，但CFE的时间动态仍不清楚。通过长期使用多个卫星和地面数据集。
我们发现，从1982年到2015年，全球CFE在全球大多数陆地地区都呈下降趋势，这与养分浓度和土壤水分可用性的变化密切相关。目前的碳循环模型也显示出CFE的下降趋势，尽管比全球观测结果要弱得多。
大气中二氧化碳的增加迫使陆地碳汇下降的趋势，意味着气候系统的负反馈减弱，社会对缓解气候变暖的未来策略依赖增加。
▲ Abstract
The enhanced vegetation productivity driven by increased concentrations of carbon dioxide (CO2) [i.e., the CO2 fertilization effect (CFE)] sustains an important negative feedback on climate warming, but the temporal dynamics of CFE remain unclear. Using multiple long-term satellite- and ground-based datasets, we showed that global CFE has declined across most terrestrial regions of the globe from 1982 to 2015, correlating well with changing nutrient concentrations and availability of soil water. Current carbon cycle models also demonstrate a declining CFE trend, albeit one substantially weaker than that from the global observations. This declining trend in the forcing of terrestrial carbon sinks by increasing amounts of atmospheric CO2 implies a weakening negative feedback on the climatic system and increased societal dependence on future strategies to mitigate climate warming.
Indian monsoon derailed by a North Atlantic wavetrain
北大西洋波列使印度季风偏离轨道
▲ 作者：P. J. Borah, V. Venugopal, J. Sukhatme, P. Muddebihal, B. N. Goswami
▲ 链接：
https://science.sciencemag.org/content/370/6522/1335
▲ 摘要
对印度季风干旱的预测是基于一种长期降雨不足的概念，这种概念与温暖的赤道太平洋有关。在此，我们发现，在过去的一个世纪里，几乎有一半的干旱与这一模式不同。
因为它们（1）发生在太平洋温度接近中性的时候，（2）是亚季节性现象，特征是后期降雨的突然减少。这种严重的次季节性降雨不足可能与来自中纬度的罗斯比波有关。
具体地说，我们发现高层风与北大西洋涡旋异常的相互作用导致了向东亚弯曲的波列，并扰乱了季风。这种大气远距联系为提高干旱的可预测性提供了一种途径，特别是在太平洋缺乏明显信号的情况下。
▲ Abstract
The forecast of Indian monsoon droughts has been predicated on the notion of a season-long rainfall deficit linked to a warm equatorial Pacific. Here we show that nearly half of all droughts over the past century differ from this paradigm in that they (i) occur when Pacific temperatures are near-neutral and (ii) are subseasonal phenomena, characterized by an abrupt decline in late-season rainfall. This severe subseasonal rainfall deficit can be associated with a Rossby wave from mid-latitudes. Specifically, we find that the interaction of upper-level winds with an episodic North Atlantic vorticity anomaly results in a wavetrain that curves toward East Asia, disrupting the monsoon. This atmospheric teleconnection offers an avenue for improved predictability of droughts, especially in the absence of telltale signatures in the Pacific.
材料科学Materials Science
Monolithic perovskite/silicon tandem solar cell with >29% efficiency by enhanced hole extraction
通过增强空穴提取，单晶钙钛矿/硅串联太阳能电池的效率能高于 29％
▲ 作者：Amran Al-Ashouri, Eike Köhnen, Bor Li, Artiom Magomedov, Hannes Hempel, et al.
▲ 链接：
https://science.sciencemag.org/content/370/6522/1300
▲ 摘要
串联太阳能电池将硅和金属卤化物钙钛矿配对，对于超越单电池的效率限制是一个很有前途的选择。我们报告一个认证功率转换效率为29.15%的单片钙钛矿/硅串联太阳能电池。
带隙为1.68电子伏特的钙钛矿吸收剂，通过快速空穴提取和空穴选择界面的最小化非辐射复合，在光照下保持相稳定。
这些特征是由于自组装的甲基取代咔唑单层作为钙钛矿电池的空穴选择层。加速的空穴提取与1.26的低理想系数和84%的单结填充系数有关，同时使串联开路电压高达1.92伏特。在空气中没有封装时，300小时的运行后串联仍保持95%的初始效率。
▲ Abstract
Tandem solar cells that pair silicon with a metal halide perovskite are a promising option for surpassing the single-cell efficiency limit. We report a monolithic perovskite/silicon tandem with a certified power conversion efficiency of 29.15%. The perovskite absorber, with a bandgap of 1.68 electron volts, remained phase-stable under illumination through a combination of fast hole extraction and minimized nonradiative recombination at the hole-selective interface. These features were made possible by a self-assembled, methyl-substituted carbazole monolayer as the hole-selective layer in the perovskite cell. The accelerated hole extraction was linked to a low ideality factor of 1.26 and single-junction fill factors of up to 84%, while enabling a tandem open-circuit voltage of as high as 1.92 volts. In air, without encapsulation, a tandem retained 95% of its initial efficiency after 300 hours of operation.
Protein condensates as aging Maxwell fluids
蛋白质凝结形成老化的麦克斯韦体液
▲ 作者：Louise Jawerth, Elisabeth Fischer-Friedrich, Suropriya Saha, et al.
▲ 链接：
https://science.sciencemag.org/content/370/6522/1317
▲ 摘要
蛋白质凝聚物是一种复杂的液体，可以随时间改变其物质性质。然而，仍然缺失对这些流体的适当流变学描述。我们使用激光镊为基础的主动流变学和微珠为基础的被动流变学来表征体外蛋白凝聚物的时间依赖性材料特性。
对于不同的蛋白质，冷凝物在各个年龄阶段都表现为粘弹性的麦克斯韦流体。粘度随时间增长而增大，弹性模量变化较小。
电镜观察到早期和晚期在结构上无明显差异。我们的结论是，蛋白质凝聚物可以是柔软的玻璃状材料，我们称之为具有年龄依赖性材料属性的麦克斯韦玻璃。我们讨论了玻璃化行为对调节细胞生物化学的可能优势。
▲ Abstract
Protein condensates are complex fluids that can change their material properties with time. However, an appropriate rheological description of these fluids remains missing. We characterize the time-dependent material properties of in vitro protein condensates using laser tweezer–based active and microbead-based passive rheology. For different proteins, the condensates behave at all ages as viscoelastic Maxwell fluids. Their viscosity strongly increases with age while their elastic modulus varies weakly. No significant differences in structure were seen by electron microscopy at early and late ages. We conclude that protein condensates can be soft glassy materials that we call Maxwell glasses with age-dependent material properties. We discuss possible advantages of glassy behavior for modulation of cellular biochemistry.
物理学Physics
Resonant collisional shielding of reactive molecules using electric fields
反应分子在电场中的共振碰撞屏蔽
▲ 作者：Kyle Matsuda, Luigi De Marco, Jun-Ru Li, William G. Tobias, et al.
▲ 链接：
https://science.sciencemag.org/content/370/6522/1324
▲ 摘要
完全控制分子间的相互作用，包括反应性损耗，将为量子科学开辟新的前沿。我们证明了超低温化学反应速率的极端可调性，通过诱导共振偶极相互作用的外部电场。
我们制备了费米离子钾铷分子的第一个激发态，并观察到化学反应速率的三个数量级的变化，因为我们调整了几个百分点的共振电场强度。
在准二维几何中，我们准确地确定了碰撞的三个主要角动量投影的贡献。利用谐振特性，我们屏蔽了分子的损耗，并将反应速率抑制在背景值以下一个数量级，从而实现了在大电场中极性分子的长期样本。
▲ Abstract
Full control of molecular interactions, including reactive losses, would open new frontiers in quantum science. We demonstrate extreme tunability of ultracold chemical reaction rates by inducing resonant dipolar interactions by means of an external electric field. We prepared fermionic potassium-rubidium molecules in their first excited rotational state and observed a modulation of the chemical reaction rate by three orders of magnitude as we tuned the electric field strength by a few percent across resonance. In a quasi–two-dimensional geometry, we accurately determined the contributions from the three dominant angular momentum projections of the collisions. Using the resonant features, we shielded the molecules from loss and suppressed the reaction rate by an order of magnitude below the background value, thereby realizing a long-lived sample of polar molecules in large electric fields.
Optically addressable molecular spins for quantum information processing
用于量子信息处理的光学寻址分子自旋
▲ 作者：S. L. Bayliss, D. W. Laorenza, P. J. Mintun1, B. D. Kovos, D. E. Freedman, et al.
▲ 链接：
https://science.sciencemag.org/content/370/6522/1309
▲ 摘要
带有自旋的分子是量子技术很有前途的构建模块，因为它们可以通过化学方式进行调整，组装成可伸缩的阵列，并容易地整合到不同的器件架构中。
在分子系统中，光学寻址基态自旋将使量子信息科学的广泛应用成为可能，正如固态缺陷所证明的那样。
然而，对于分子来说，这个重要的功能仍然是难以捉摸的。在此，我们在一系列合成的有机金属铬（IV）分子中证明了这种光学寻址能力。这些化合物显示出一种基态自旋，可以用光进行初始化和读出，并用微波进行相干操纵。
此外，通过对分子结构的原子化修饰，我们改变了这些化合物的自旋和光学性质，这预示了自下而上合成设计量子系统的前景。
▲ Abstract
Spin-bearing molecules are promising building blocks for quantum technologies as they can be chemically tuned, assembled into scalable arrays, and readily incorporated into diverse device architectures. In molecular systems, optically addressing ground-state spins would enable a wide range of applications in quantum information science, as has been demonstrated for solid-state defects. However, this important functionality has remained elusive for molecules. Here, we demonstrate such optical addressability in a series of synthesized organometallic, chromium(IV) molecules. These compounds display a ground-state spin that can be initialized and read out using light and coherently manipulated with microwaves. In addition, through atomistic modification of the molecular structure, we vary the spin and optical properties of these compounds, indicating promise for designer quantum systems synthesized from the bottom-up.
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