编译 | 未玖
Science, 26 JAN 2024, VOL 383, ISSUE 6681
《科学》2024年1月26日，第383卷，6681期
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天文学Astronomy
Acceleration and transport of relativistic electrons in the jets of the microquasar SS 433
微类星体SS 433喷流中相对论电子的加速和输运
▲ 作者：H.E.S.S. Collaboration
▲ 链接：
https://www.science.org/doi/10.1126/science.adi2048
▲ 摘要：
SS 433是一个微类星体，也是一个可发射准直相对论性喷流的双星系统。
研究组利用高能立体系统（H.E.S.S.）观测了SS 433的伽马射线，发现了秒差距尺度喷流中伽马射线发射的表观位置发生了能量依赖偏移。这些观测追踪了高能电子布居数，并表明逆康普顿散射是伽马射线的发射机制。
研究组对能量依赖伽马射线形态的建模限制了粒子加速的位置，且需要喷流突然减速。他们推断在双星系统两侧距离为25到30秒差距之间存在激波，且进动射流的自准直形成了激波，然后有效地加速了电子。
▲ Abstract：
SS 433 is a microquasar, a stellar binary system that launches collimated relativistic jets. We observed SS 433 in gamma rays using the High Energy Stereoscopic System (H.E.S.S.) and found an energy-dependent shift in the apparent position of the gamma-ray emission from the parsec-scale jets. These observations trace the energetic electron population and indicate that inverse Compton scattering is the emission mechanism of the gamma rays. Our modeling of the energy-dependent gamma-ray morphology constrains the location of particle acceleration and requires an abrupt deceleration of the jet flow. We infer the presence of shocks on either side of the binary system, at distances of 25 to 30 parsecs, and that self-collimation of the precessing jets forms the shocks, which then efficiently accelerate electrons.
材料科学Materials Science
Super-tetragonal Sr4Al2O7 as a sacrificial layer for high-integrity freestanding oxide membranes
超四方相Sr4Al2O7作为高完整性独立氧化膜的牺牲层
▲ 作者：Jinfeng Zhang, Ting Lin, Ao Wang, Xiaochao Wang, Qingyu He, Huan Ye, et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adi6620
▲ 摘要：
确定合适的水溶性牺牲层对于制造大规模独立氧化膜至关重要，可提供吸引人的功能并与先进半导体技术相结合。
研究组介绍了一种水溶性牺牲层，即“超四方相”Sr4Al2O7（SAOT）。低对称晶体结构使其具有维持外延应变的优越能力，从而实现晶格常数的广泛可调性。钙钛矿ABO3/SAOT异质结构中的共格结构和无缺陷界面有效地抑制了独立氧化膜释水放过程中裂纹的形成。
对于各种非铁电氧化膜，无裂纹区域范围可达一毫米。这一引人注目的特性联合其固有的高水溶性，助力SAOT成为一种多功能且可行的牺牲层，可用于制备高质量的独立氧化膜，从而提高其在创新设备应用中的潜力。
▲ Abstract：
Identifying a suitable water-soluble sacrificial layer is crucial to fabricating large-scale freestanding oxide membranes, which offer attractive functionalities and integrations with advanced semiconductor technologies. Here, we introduce a water-soluble sacrificial layer, “super-tetragonal” Sr4Al2O7 (SAOT). The low-symmetric crystal structure enables a superior capability to sustain epitaxial strain, allowing for broad tunability in lattice constants. The resultant structural coherency and defect-free interface in perovskite ABO3/SAOT heterostructures effectively restrain crack formation during the water release of freestanding oxide membranes. For a variety of nonferroelectric oxide membranes, the crack-free areas can span up to a millimeter in scale. This compelling feature, combined with the inherent high water solubility, makes SAOT a versatile and feasible sacrificial layer for producing high-quality freestanding oxide membranes, thereby boosting their potential for innovative device applications.
化学Chemistry
Automated self-optimization, intensification, and scale-up of photocatalysis in flow
流动光催化的自动自优化、强化和放大
▲ 作者：Aidan Slattery, Zhenghui Wen, Pauline Tenblad, Jesús Sanjosé-Orduna, Diego Pintossi, Tim den Hartog, et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adj1817
▲ 摘要：
在主要面向热化学的制造环境中，光化学过程的优化、强化和放大构成了一个特殊挑战。
研究组提出了一个多功能、基于流动的机器人平台，通过集成现有硬件和自定义软件来解决这些挑战。该开源平台结合了液体处理器、注射泵、可调连续流光反应器、廉价物联网设备和在线台式核磁共振光谱仪，通过闭环贝叶斯优化策略实现自动化、数据丰富的优化。
用户友好的图形界面使没有编程或机器学习专业知识的化学家也能够轻松检测、分析和改进关于连续和离散变量的光催化反应。通过提高总反应产率和改善时空产率，该系统的有效性显著优于先前报道的工艺。
▲ Abstract：
The optimization, intensification, and scale-up of photochemical processes constitute a particular challenge in a manufacturing environment geared primarily toward thermal chemistry. In this work, we present a versatile flow-based robotic platform to address these challenges through the integration of readily available hardware and custom software. Our open-source platform combines a liquid handler, syringe pumps, a tunable continuous-flow photoreactor, inexpensive Internet of Things devices, and an in-line benchtop nuclear magnetic resonance spectrometer to enable automated, data-rich optimization with a closed-loop Bayesian optimization strategy. A user-friendly graphical interface allows chemists without programming or machine learning expertise to easily monitor, analyze, and improve photocatalytic reactions with respect to both continuous and discrete variables. The system's effectiveness was demonstrated by increasing overall reaction yields and improving space-time yields compared with those of previously reported processes.
Catalytic enantioselective reductive Eschenmoser-Claisen rearrangements
催化对映选择性还原Eschenmoser-Claisen重排
▲ 作者：Guoting Zhang, Matthew D. Wodrich & Nicolai Cramer
▲ 链接：
https://www.science.org/doi/10.1126/science.adl3369
▲ 摘要：
对映选择性催化的一个重要挑战是如何精确合成相邻密集的全碳季碳立体中心。[3,3]-σ迁移重排的明确过渡态及其潜在的立体特异性使其成为合成此类阵列的有力工具。然而，这种类型的周环反应仍然极难催化，尤其是以对映选择性的方式。
研究组报道了手性1,3,2-二氮杂环磷烯氢化物催化的对映选择性还原Eschenmoser-Claisen重排。这种发展转化能够完全控制两个新形成的无环立体中心，从而生成具有邻近全碳季—叔碳或季—季碳原子的酰胺。
▲ Abstract：
An important challenge in enantioselective catalysis is developing strategies for the precise synthesis of neighboring congested all-carbon quaternary stereocenters. The well-defined transition states of [3,3]-sigmatropic rearrangements and their underlying stereospecificity render them powerful tools for the synthesis of such arrays. However, this type of pericyclic reaction remains notoriously difficult to catalyze, especially in an enantioselective fashion. Herein, we describe an enantioselective reductive Eschenmoser-Claisen rearrangement catalyzed by chiral 1,3,2-diazaphospholene-hydrides. This developed transformation enables full control of the two newly formed acyclic stereogenic centers, leading to amides with vicinal all-carbon quaternary-tertiary or quaternary-quaternary carbon atoms.
地球科学Earth Science
Machine learning predicts which rivers, streams, and wetlands the Clean Water Act regulates
机器学习预测《清洁水法》监管的河流、溪流和湿地
▲ 作者：Simon Greenhill, Hannah Druckenmiller, Sherrie Wang, David A. Keiser, Manuela Girotto, Jason K. Moore, et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adi3794
▲ 摘要：
研究组评估了《清洁水法》保护哪些水域，以及最高法院和白宫的规则如何改变这一规定。使用航空图像和地球物理数据训练了一个深度学习模型，以预测来自美国陆军工程兵团的15万个管辖权决定，每个决定对应一种水资源监管。
根据2006年最高法院的一项裁决，《清洁水法》保护了美国三分之二的河流和一半以上的湿地。根据白宫2020年的一项规定，《清洁水法》只保护了不到一半的河流和四分之一的湿地，这意味着放松了对69万英里河流、3500万英亩湿地和30%饮用水水源周围水域的管制。
该研究框架可在监管实施问题中支持许可、政策设计和使用机器学习。
▲ Abstract：
We assess which waters the Clean Water Act protects and how Supreme Court and White House rules change this regulation. We train a deep learning model using aerial imagery and geophysical data to predict 150,000 jurisdictional determinations from the Army Corps of Engineers, each deciding regulation for one water resource. Under a 2006 Supreme Court ruling, the Clean Water Act protects two-thirds of US streams and more than half of wetlands; under a 2020 White House rule, it protects less than half of streams and a fourth of wetlands, implying deregulation of 690,000 stream miles, 35 million wetland acres, and 30% of waters around drinking-water sources. Our framework can support permitting, policy design, and use of machine learning in regulatory implementation problems.
Total organic carbon measurements reveal major gaps in petrochemical emissions reporting
总有机碳测量揭示了石化排放报告的重大漏洞
▲ 作者：Megan He, Jenna C. Ditto, Lexie Gardner, Jo Machesky, Tori N. Hass-Mitchell, Christina Chen, et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adj6233
▲ 摘要：
人为有机碳排放报告在很大程度上仅限于化学指定的挥发性有机化合物子集。然而，新的基于飞机的测量显示，气相有机碳总排放量比油砂行业报告的值高出1900%至6300%以上，其中大部分归因于未计算在内的中间挥发性和半挥发性有机化合物。
设施范围内的实测排放约占开采石油的1%，导致有机碳排放总量相当于加拿大所有其他来源的总和。这些真实世界的观测结果表明，无论化学特征如何，总有机碳测量都是检测未知或低于报告的碳排放的一种手段。
由于报告漏洞可能包括有害、反应性的或二次空气污染物，全面限制人为排放的影响需要进行常规、全面的总有机碳监测，并将其作为对大规模关闭的固定检查。
▲ Abstract：
Anthropogenic organic carbon emissions reporting has been largely limited to subsets of chemically speciated volatile organic compounds. However, new aircraft-based measurements revealed total gas-phase organic carbon emissions that exceed oil sands industry–reported values by 1900% to over 6300%, the bulk of which was due to unaccounted-for intermediate-volatility and semivolatile organic compounds. Measured facility-wide emissions represented approximately 1% of extracted petroleum, resulting in total organic carbon emissions equivalent to that from all other sources across Canada combined. These real-world observations demonstrate total organic carbon measurements as a means of detecting unknown or underreported carbon emissions regardless of chemical features. Because reporting gaps may include hazardous, reactive, or secondary air pollutants, fully constraining the impact of anthropogenic emissions necessitates routine, comprehensive total organic carbon monitoring as an inherent check on mass closure.
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