编译 |渭九
science, 26 jan 2024, vol 383, issue 6681
《科学》，2024年1月26日，第383卷，第6681期
天文学
acceleration and transport of relativistic electrons in the jets of the microquasar ss 433
相对论电子在微类星体SS 433的射流中的加速和传输
作者： He.s.s. collaboration
链接：
总结：
SS 433是一个微类星体和双星系统，发射准直的相对论性喷流。
研究小组使用了高能立体系统（h.）。e.s.s.观测到来自SS 433的伽马射线，发现伽马射线发射在瞬间尺度射流中的表观位置与能量有关。 这些观测结果追踪了高能电子的数量，并表明逆康普顿散射是伽马射线的发射机制。
该团队对能量依赖性伽马射线形态的建模限制了粒子可以加速的地方，并且需要射流突然减速。 他们推断，在双星系统两侧的25到30秒差距之间存在一个冲击波，进动射流的自准直形成了一个冲击波，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
super-tetragonal sr4al2o7 as a sacrificial layer for high-integrity freestanding oxide membranes
超四方相SR4Al2O7用作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：
总结：
确定合适的水溶性牺牲层对于制造大规模、独立的氧化膜至关重要，这些氧化膜具有有吸引力的功能，并与先进的半导体技术相结合。
研究小组引入了一种水溶性牺牲层，即“超四方”SR4Al2O7（SAOT）。 低对称晶体结构使其具有维持外延应变的卓越能力，从而实现了晶格常数的广泛可调性。 钙钛矿ABO3 SAOT异质结构中的共晶格结构和无缺陷界面有效抑制了独立氧化膜释放过程中裂纹的形成。
对于各种非铁电氧化物薄膜，无裂纹区域可达 1 毫米。 这一引人注目的特性，加上其固有的高水溶性，使SAOT成为一种多功能且可行的牺牲层，可用于生产高质量、独立的氧化膜，从而增加其在创新器件应用方面的潜力。
▲ 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
automated self-optimization, intensification, and scale-up of photocatalysis in flow
流动光催化的自动自我优化、强化和放大
作者：Aidan Slattery、Zhenghui 温、Pauline Tenblad、Jesús Sanjosé-Orduna、Diego Pintossi、Tim den Hartog 等
链接：
总结：
在主要面向热化学的制造环境中，光化学过程的优化、强化和放大构成了特殊的挑战。
该研究小组提出了一个多功能的、基于流程的机器人平台，通过集成现有硬件和定制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、可调谐连续流式反应器、廉价的物联网设备和台式核磁共振波谱仪，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无需编程或机器学习专业知识的化学家能够轻松检测、分析和改进连续和离散变量上的光催化反应。 通过提高总反应产率和提高时空产率，该系统的有效性明显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 **ailable 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： Guotting Zhang， Matthew D wodrich & nicolai cramer
链接：
总结：
对映选择性催化的一个重要挑战是如何准确合成相邻的致密全碳季碳立构中心。 [3,3]- 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方式。
该研究小组报告了手性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。 这种发育转变能够完全控制两个新形成的无环立构中心，从而形成具有相邻的全碳季铵盐-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
machine learning predicts which rivers, streams, and wetlands the clean water act regulates
机器学***《清洁水法》规范了河流、溪流和湿地
作者： Simon Greenhill， Hannah Druckenmiller， Sherrie Wang， D**ID A keiser, manuela girotto, jason k. moore, et al.
链接：
总结：
研究小组评估了哪些水域受到《清洁水法》的保护，以及最高法院和白宫的规则如何改变这一规定。 利用航空图像和地球物理数据，对美国陆军工程兵团的 150,000 个管辖决定进行了深度学习模型的训练，每个决定都对应于一项水法规。
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 2020 年白宫的一项规定，《清洁水法》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 690,000 英里河流、3500 万英亩湿地和 30% 饮用水源周围水域的监管。
该研究框架支持许可、政策设计和机器学习在监管实施问题中的使用。
▲ 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差距
作者： Megan He， Jenna C ditto, lexie gardner, jo machesky, tori n. hass-mitchell, christina chen, et al.
链接：
总结：
人为有机碳排放报告主要局限于挥发性有机化合物的化学指定子集。 然而，新的基于飞机的测量表明，气相有机碳排放总量比油砂行业报告的要高出1,900%至6,300%以上，其中大部分归因于未说明的中间和半挥发性有机化合物。
设施区域内的测量排放量约占开采石油的 1%，导致有机碳排放总量相当于加拿大所有其他排放量的总和。 这些真实世界的观察表明，总有机碳测量是一种检测未知或低于报告碳排放量的手段，而不管化学特征如何。
由于报告差距可能包括有害、反应性或二次空气污染物，因此全面限制人为排放的影响需要常规、全面的总有机碳监测，作为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.