編譯 | 未玖
Science, 26 JAN 2024, VOL 383, ISSUE 6681
《科學》2024年1月26日，第383卷，6681期
天文學Astronomy
Acceleration and transport of relativistic electrons in the jets of the microquasar SS 433
微類星體SS 433噴流中相對論電子的加速和輸運
▲ 作者：H.E.S.S. Collaboration
▲ 連結：
https://www.science.org/doi/10.1126/science.adi2048
▲ 摘要：
SS 433是一個微類星體，也是一個可發射準直相對論性噴流的雙星系統。
研究組利用高能立體系統（H.E.S.S.）觀測了SS 433的伽馬射線，發現了秒差距尺度噴流中伽馬射線發射的表觀位置發生了能量依賴偏移。這些觀測追蹤了高能電子布居數，并表明逆康普頓散射是伽馬射線的發射機制。
研究組對能量依賴伽馬射線形态的模組化限制了粒子加速的位置，且需要噴流突然減速。他們推斷在雙星系統兩側距離為25到30秒差距之間存在激波，且進動射流的自準直形成了激波，然後有效地加速了電子。
▲ 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.
材料科學Materials Science
Super-tetragonal Sr4Al2O7 as a sacrificial layer for high-integrity freestanding oxide membranes
超四方相Sr4Al2O7作為高完整性獨立氧化膜的犧牲層
▲ 作者：Jinfeng Zhang, Ting Lin, Ao Wang, Xiaochao Wang, Qingyu He, Huan Ye, et al.
▲ 連結：
https://www.science.org/doi/10.1126/science.adi6620
▲ 摘要：
确定合适的水溶性犧牲層對于制造大規模獨立氧化膜至關重要，可提供吸引人的功能并與先進半導體技術相結合。
研究組介紹了一種水溶性犧牲層，即“超四方相”Sr4Al2O7（SAOT）。低對稱晶體結構使其具有維持外延應變的優越能力，進而實作晶格常數的廣泛可調性。鈣钛礦ABO3/SAOT異質結構中的共格結構和無缺陷界面有效地抑制了獨立氧化膜釋水放過程中裂紋的形成。
對于各種非鐵電氧化膜，無裂紋區域範圍可達一毫米。這一引人注目的特性聯合其固有的高水溶性，助力SAOT成為一種多功能且可行的犧牲層，可用于制備高品質的獨立氧化膜，進而提高其在創新裝置應用中的潛力。
▲ 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.
化學Chemistry
Automated self-optimization, intensification, and scale-up of photocatalysis in flow
流動光催化的自動自優化、強化和放大
▲ 作者：Aidan Slattery, Zhenghui Wen, Pauline Tenblad, Jesús Sanjosé-Orduna, Diego Pintossi, Tim den Hartog, et al.
▲ 連結：
https://www.science.org/doi/10.1126/science.adj1817
▲ 摘要：
在主要面向熱化學的制造環境中，光化學過程的優化、強化和放大構成了一個特殊挑戰。
研究組提出了一個多功能、基于流動的機器人平台，通過內建現有硬體和自定義軟體來解決這些挑戰。該開源平台結合了液體處理器、注射泵、可調連續流光反應器、廉價物聯網裝置和線上台式核磁共振光譜儀，通過閉環貝葉斯優化政策實作自動化、資料豐富的優化。
使用者友好的圖形界面使沒有程式設計或機器學習專業知識的化學家也能夠輕松檢測、分析和改進關于連續和離散變量的光催化反應。通過提高總反應産率和改善時空産率，該系統的有效性顯著優于先前報道的工藝。
▲ 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
催化對映選擇性還原Eschenmoser-Claisen重排
▲ 作者：Guoting Zhang, Matthew D. Wodrich & Nicolai Cramer
▲ 連結：
https://www.science.org/doi/10.1126/science.adl3369
▲ 摘要：
對映選擇性催化的一個重要挑戰是如何精确合成相鄰密集的全碳季碳立體中心。[3,3]-σ遷移重排的明确過渡态及其潛在的立體特異性使其成為合成此類陣列的有力工具。然而，這種類型的周環反應仍然極難催化，尤其是以對映選擇性的方式。
研究組報道了手性1,3,2-二氮雜環磷烯氫化物催化的對映選擇性還原Eschenmoser-Claisen重排。這種發展轉化能夠完全控制兩個新形成的無環立體中心，進而生成具有鄰近全碳季—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.
地球科學Earth Science
Machine learning predicts which rivers, streams, and wetlands the Clean Water Act regulates
機器學習預測《清潔水法》監管的河流、溪流和濕地
▲ 作者：Simon Greenhill, Hannah Druckenmiller, Sherrie Wang, David A. Keiser, Manuela Girotto, Jason K. Moore, et al.
▲ 連結：
https://www.science.org/doi/10.1126/science.adi3794
▲ 摘要：
研究組評估了《清潔水法》保護哪些水域，以及最高法院和白宮的規則如何改變這一規定。使用航空圖像和地球實體資料訓練了一個深度學習模型，以預測來自美國陸軍工程兵團的15萬個管轄權決定，每個決定對應一種水資源監管。
根據2006年最高法院的一項裁決，《清潔水法》保護了美國三分之二的河流和一半以上的濕地。根據白宮2020年的一項規定，《清潔水法》隻保護了不到一半的河流和四分之一的濕地，這意味着放松了對69萬英裡河流、3500萬英畝濕地和30%飲用水水源周圍水域的管制。
該研究架構可在監管實施問題中支援許可、政策設計和使用機器學習。
▲ 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
總有機碳測量揭示了石化排放報告的重大漏洞
▲ 作者：Megan He, Jenna C. Ditto, Lexie Gardner, Jo Machesky, Tori N. Hass-Mitchell, Christina Chen, et al.
▲ 連結：
https://www.science.org/doi/10.1126/science.adj6233
▲ 摘要：
人為有機碳排放報告在很大程度上僅限于化學指定的揮發性有機化合物子集。然而，新的基于飛機的測量顯示，氣相有機碳總排放量比油砂行業報告的值高出1900%至6300%以上，其中大部分歸因于未計算在内的中間揮發性和半揮發性有機化合物。
設施範圍内的實測排放約占開采石油的1%，導緻有機碳排放總量相當于加拿大所有其他來源的總和。這些真實世界的觀測結果表明，無論化學特征如何，總有機碳測量都是檢測未知或低于報告的碳排放的一種手段。
由于報告漏洞可能包括有害、反應性的或二次空氣污染物，全面限制人為排放的影響需要進行正常、全面的總有機碳監測，并将其作為對大規模關閉的固定檢查。
▲ 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.