編譯 | 馮維維
SCIENCE, Volume 383, Issue 6682, 2 February 2024
《科學》, 第383卷，6682期，2024年2月2日
化學Chemistry
通過動態共價聚合物網絡回火獲得多能材料
▲ 作者：NICHOLAS R. BOYNTON, JOSEPH M. DENNIS, NEIL D. DOLINSKI, CHARLIE A. LINDBERG, ANTHONY P. KOTULA, GARRETT L. GROCKE, STEPHANIE L. VIVOD, JOSEPH L. LENHART, SHRAYESH N. PATEL, AND STUART J. ROWAN
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adi5009
▲ 摘要：
通過控制加熱和冷卻循環回火被用于調整一系列材料的微觀結構，包括許多金屬甚至巧克力。研究者將這一想法擴展到單一聚合物體系中機械性能的可逆轉變。這種方法是通過包含相對較弱的thia-Michael鍵來實現的，與聚合物中的共價鍵相比，thia-Michael鍵能夠在較低的溫度下重組。
在較高的回火溫度下，thia-Michael網絡的交聯密度降低，導致材料的剛度降低，而在較低的溫度下回火會產生更硬的材料。由于結合和非結合交聯的變化引起的動態反應誘導相分離，材料表現出形狀記憶特性。
▲ Abstract：
Tempering through controlled heating and cooling cycles is used to adjust the microstructure of a range of materials, including many metals and even chocolate. Boynton et al. extended this idea to reversible transformations of the mechanical properties in a single polymer system. This method was achieved through the inclusion of thia-Michael bonds that are relatively weak and capable of reshuffling at lower temperatures compared with the covalent bonds in the polymer. At higher tempering temperatures, the cross-link density of the thia-Michael network decreases, resulting in a lower stiffness of the material, whereas tempering at lower temperatures creates a stiffer material. The material exhibits shape memory properties attributed to the dynamic reaction–induced phase separation caused by the change in bound and unbound cross-links.
Terminal C(SP3)–H borylation through intermolecular radical sampling
分子間自由基取樣的末端硼化反應
▲ 作者：MIAO WANG, YAHAO HUANG, AND PENG HU
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adj9258
▲ 摘要：
在過去的二十年里，硼化反應作為一種替代許多原料化學品中大量不活潑的碳氫鍵的方法而出現。盡管如此，烷基鏈的位點選擇性仍然是一個挑戰。
研究者使用氯化鐵光催化劑來促進可逆的氫原子轉移過程，對鏈上的位點進行采樣，并最終以高選擇性將硼酯附加到末端碳上。流動系統實現了多圖尺度下的高效反應。
▲ Abstract：
Borylation has emerged in the past two decades as a - means of substituting the otherwise unreactive carbon–hydrogen bonds abundant in many feedstock chemicals. Nonetheless, site selectivity in alkyl chains remains a challenge. Wang et al. used an iron chloride photocatalyst to prompt a reversible hydrogen atom transfer process that samples sites along the chain and ultimately appends boronic esters to the end carbon with high selectivity. A flow system enabled efficient reactivity at multigram scale.
Photosensitization enables Pauson-Khand–type reactions with nitrenes
光敏化促使與亞胺發生Pauson-khand型有機化學反應
▲ 作者：FANG LI, W. FELIX ZHU, CLAIRE EMPEL, OLEKSANDR DATSENKO, ADARSH KUMAR, YAMENG XU, JOHANNA H. M. EHRLER, IULIANA ATODIRESEI, STEFAN KNAPP, AND RENE M. KOENIGS
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adm8095
▲ 摘要：
Pauson-Khand有機化學反應是近50年來化學中最常見的環加成反應之一。將兩個不飽和鍵與一氧化碳偶聯，轉化仍然局限于一氧化碳作為C1構建塊。研究者報告了類似的環加成反應與亞硝基烯作為N1單元。
非共軛二烯與亞硝基前體的反應產生常見飽和雜環的雙環生物異構體，如哌啶、啉和哌嗪。實驗和計算機制研究支持將三重態亞硝基的雙自由基性質轉化為π系。研究展示了該反應在藥物化合物后期功能化和可溶性環氧化物水解酶抑制劑的發現中的效用。
▲ Abstract：
The Pauson-Khand reaction has in the past 50 years become one of the most common cycloaddition reactions in chemistry. Coupling two unsaturated bonds with carbon monoxide, the transformation remains limited to CO as a C1 building block. Herein we report analogous cycloaddition reactions with nitrenes as an N1 unit. The reaction of a nonconjugated diene with a nitrene precursor produces bicyclic bioisosteres of common saturated heterocycles such as piperidine, morpholine, and piperazine. Experimental and computational mechanistic studies support relaying of the diradical nature of triplet nitrene into the π-system. We showcase the reaction’s utility in late-stage functionalization of drug compounds and discovery of soluble epoxide hydrolase inhibitors.
Aqueous synthesis of perovskite precursors for highly efficient perovskite solar cells
高效鈣鈦礦太陽能電池鈣鈦礦前驅體的水合成
▲ 作者：PEIDE ZHU, DENG WANG, YONG ZHANG , ZHENG LIANG, JINGBAI LI, JIE ZENG, JIYAO ZHANG, YINTAI XU, SIYING WU, AND BAOMIN XU
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adj7081
▲ 摘要：
鈣鈦礦太陽能電池具有較高的缺陷容忍度，但薄膜前驅體中的雜質和非化學計量限制了電池的功率轉換效率。研究者發現，水法制備甲脒碘化鉛微晶為制備高純度前體提供了一種低成本途徑，且無需使用有機溶劑。
這條路線最大限度地減少雜質離子，如形成電荷載流子陷阱的鈣。對于倒置太陽能電池，獲得了25.3%的認證功率轉換效率，并且在50℃下連續工作1000小時后仍保持該效率的94%。
▲ Abstract：
Perovskite solar cells have a high defect tolerance, but impurities and nonstoichiometries in the film precursor have limited power conversion efficiency. Zhu et al. report that the aqueous synthesis of microcrystals of formamidinium lead iodide provides a low-cost route to highly pure precursors without the use of organic solvents. This route minimizes impurity ions such as calcium that form charge carrier traps. For inverted solar cells, a certified power conversion efficiency of 25.3% was obtained, and 94% of this efficiency was retained after 1000 hours of continuous operation at 50℃.
生態學Ecology
Functional traits—not nativeness—shape the effects of large mammalian herbivores on plant communities
大型食草哺乳動物對植物群落的影響是由功能特征而非原生特征決定的
▲ 作者：ERICK J. LUNDGREN, JURAJ BERGMAN, JONAS TREPEL, SOPHIE MONSARRAT, JEPPE AAGAARD KRISTENSEN, RASMUS ?STERGAARD PEDERSEN, PATRICIO PEREYRA, MELANIE TIETJE, AND JENS-CHRISTIAN SVENNING
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adh2616
▲ 摘要：
史前以來，大型食草哺乳動物已經經歷了滅絕和衰退。外地引進的巨型動物在一定程度上抵消了這些損失，但與本土巨型動物相比，它們被認為對植物有不同尋常的負面影響。
通過對來自221項研究的3995個樣點尺度的植物豐度和多樣性響應進行薈萃分析，研究者發現沒有證據表明巨型動物的影響是由本土性、入侵性、野性、共同進化史或功能和系統發育新穎性決定的。也沒有證據表明外來巨型動物比本土巨型動物更能促進外來植物的生長。
相反，研究者發現了強有力的證據表明，功能特征塑造了巨型動物的影響，體型更大、攝食量更大的巨型動物促進了植物的多樣性。研究表明，基于性狀的生態學比原生的概念更能洞察巨型動物和植物之間的相互作用。
▲ Abstract：
Large mammalian herbivores (megafauna) have experienced extinctions and declines since prehistory. Introduced megafauna have partly counteracted these losses yet are thought to have unusually negative effects on plants compared with native megafauna. Using a meta-analysis of 3995 plot-scale plant abundance and diversity responses from 221 studies, we found no evidence that megafauna impacts were shaped by nativeness,“invasiveness,” “feralness,” coevolutionary history, or functional and phylogenetic novelty. Nor was there evidence that introduced megafauna facilitate introduced plants more than native megafauna. Instead, we found strong evidence that functional traits shaped megafauna impacts, with larger-bodied and bulk-feeding megafauna promoting plant diversity. Our work suggests that trait-based ecology provides better insight into interactions between megafauna and plants than do concepts of nativeness.
機器學習Machine Learning
Grounded language acquisition through the eyes and ears of a single child
通過機器學習模仿幼兒眼睛和耳朵的基礎語言習得
▲ 作者：WAI KEEN VONG, WENTAO WANG, A. EMIN ORHAN, AND BRENDEN M. LAKE
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adi1374
▲ 摘要：
從6到9個月大的時候開始，幼兒開始掌握第一個單詞，將口頭單詞與視覺單詞聯系起來。這些知識中有多少是可以通過相對通用的學習機制從感官輸入中學習的，又有多少需要更強的歸納偏見？
研究者使用一個6到25個月大的孩子的縱向頭戴式攝像機記錄，在61小時的相關視覺語言數據流上訓練了一個相對通用的神經網絡，學習基于特征的表示和跨模態關聯。研究模型獲得了兒童日常經驗中存在的許多詞指涉映射，實現了對新的視覺指涉的零射擊泛化，并使其視覺和語言概念系統保持一致。
這些結果表明，基礎詞義的關鍵方面是如何通過一個孩子輸入的聯合表征和聯想學習來學習的。
▲ Abstract：
Starting around 6 to 9 months of age, children begin acquiring their first words, linking spoken words to their visual counterparts. How much of this knowledge is learnable from sensory input with relatively generic learning mechanisms, and how much requires stronger inductive biases? Using longitudinal head-mounted camera recordings from one child aged 6 to 25 months, we trained a relatively generic neural network on 61 hours of correlated visual-linguistic data streams, learning feature-based representations and cross-modal associations. Our model acquires many word-referent mappings present in the child’s everyday experience, enables zero-shot generalization to new visual referents, and aligns its visual and linguistic conceptual systems. These results show how critical aspects of grounded word meaning are learnable through joint representation and associative learning from one child’s input.
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