roaming文件夹是干嘛的 roaming文件夹( 二 ) _云知道

通过无监督机器学习加速双核钯催化剂识别
▲ 作者：JULIAN A. HUEFFEL, THERESA SPERGER, IGNACIO FUNES-ARDOIZ, JAS S. WARD, KARI RISSANEN AND FRANZISKA SCHOENEBECK
▲ 链接：
https://www.science.org/doi/10.1126/science.abj0999
▲ 摘要
机器学习在加速同质催化的发展方面具有巨大潜力，但频繁地需要大量的实验数据可能成为瓶颈。作者报告了一个无监督机器学习工作流，只使用了5个实验数据点。它利用了广义参数数据库，并辅以在硅数据采集和聚类中针对特定问题的数据库。
他们展示了该策略在钯（Pd）催化剂形态形成的挑战性问题上的力量，目前缺乏一个机械原理。从348个配体的总空间中，该算法预测并通过实验验证了一些膦配体（包括以前从未合成的配体) ，它们在更常见的Pd（0）和Pd（II）物种上产生双核Pd（I）配合物。
▲ Abstract
Although machine learning bears enormous potential to accelerate developments in homogeneous catalysis, the frequent need for extensive experimental data can be a bottleneck for implementation. Here, we report an unsupervised machine learning workflow that uses only five experimental data points. It makes use of generalized parameter databases that are complemented with problem-specific in silico data acquisition and clustering. We showcase the power of this strategy for the challenging problem of speciation of palladium (Pd) catalysts, for which a mechanistic rationale is currently lacking. From a total space of 348 ligands, the algorithm predicted, and we experimentally verified, a number of phosphine ligands (including previously never synthesized ones) that give dinuclear Pd(I) complexes over the more common Pd(0) and Pd(II) species.
Orbiting resonances in formaldehyde reveal coupling of roaming, radical, and molecular channels
甲醛轨道共振揭示漫游、自由基和分子通道的耦合
▲ 作者：CASEY D. FOLEY, CHANGJIAN XIE, HUA GUO, AND ARTHUR G. SUITS
▲ 链接：
https://www.science.org/doi/10.1126/science.abk0634
▲ 摘要
漫游化学反应机制是指受电分子对自由基的接近解离，在较长距离重新定向后发生分子内反应。令人惊讶的是，尽管漫游事件具有量子性质，但到目前为止还没有观察到清晰的漫游量子特征。
作者在漫游阈值附近发现了甲醛光解离的量子动力学证据。这归因于与H+HCO（Ka = 1）相关的共振，它对CO的旋转和平动能量分布有深刻的影响，并导致漫游分数在10厘米- 1的能量范围内变化了2倍。
漫游路径用于调节和报道受激分子衰变成产物时复杂的振动动力学和三种解离路径之间的耦合。
▲ Abstract
The roaming chemical reaction mechanism involves near-dissociation of an energized molecule to radicals that leads instead to intramolecular reaction after reorientation at long range. Surprisingly, no clear quantum signatures of roaming have been observed to date, despite the quantum nature of the roaming event. We found evidence of quantum dynamics in the photodissociation of formaldehyde near the roaming threshold. This is ascribed to resonances associated to H+HCO(Ka = 1) that have a profound impact on the CO rotational and translational energy distributions and cause the roaming fraction to vary by a factor of 2 over an energy range of 10 cm–1. The roaming pathway serves both to modulate and report on the complex vibrational dynamics and coupling among the three dissociation pathways in the excited molecule as it decays to products.
地质和生物Geology & biology
Global response of fire activity to late Quaternary grazer extinctions
野火对晚第四纪食草动物灭绝的全球响应
▲ 作者：ALLISON T. KARP, X J. TYLER FAITH, JENNIFER R. MARLONAND A. CARLA STAVER

roaming文件夹是干嘛的 roaming文件夹( 二 )

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