編譯 | 馮維維
SCIENCE, Volume 383, Issue 6682, 2 February 2024
《科學(xué)》, 第383卷，6682期，2024年2月2日
化學(xué)Chemistry
通過動態(tài)共價聚合物網(wǎng)絡(luò)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(huán)回火被用于調(diào)整一系列材料的微觀結(jié)構(gòu)，包括許多金屬甚至巧克力。研究者將這一想法擴(kuò)展到單一聚合物體系中機(jī)械性能的可逆轉(zhuǎn)變。這種方法是通過包含相對較弱的thia-Michael鍵來實(shí)現(xiàn)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(wǎng)絡(luò)的交聯(lián)密度降低，導(dǎo)致材料的剛度降低，而在較低的溫度下回火會產(chǎn)生更硬的材料。由于結(jié)合和非結(jié)合交聯(lián)的變化引起的動態(tài)反應(yīng)誘導(dǎo)相分離，材料表現(xiàn)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(yīng)
▲ 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(yīng)作為一種替代許多原料化學(xué)品中大量不活潑的碳?xì)滏I的方法而出現(xiàn)。盡管如此，烷基鏈的位點(diǎn)選擇性仍然是一個挑戰(zhàn)。
研究者使用氯化鐵光催化劑來促進(jìn)可逆的氫原子轉(zhuǎn)移過程，對鏈上的位點(diǎn)進(jìn)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(tǒng)實(shí)現(xiàn)了多圖尺度下的高效反應(yīng)。
▲ 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(fā)生Pauson-khand型有機(jī)化學(xué)反應(yīng)
▲ 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(jī)化學(xué)反應(yīng)是近50年來化學(xué)中最常見的環(huán)加成反應(yīng)之一。將兩個不飽和鍵與一氧化碳偶聯(lián)，轉(zhuǎn)化仍然局限于一氧化碳作為C1構(gòu)建塊。研究者報告了類似的環(huán)加成反應(yīng)與亞硝基烯作為N1單元。
非共軛二烯與亞硝基前體的反應(yīng)產(chǎn)生常見飽和雜環(huán)的雙環(huán)生物異構(gòu)體，如哌啶、啉和哌嗪。實(shí)驗(yàn)和計算機(jī)制研究支持將三重態(tài)亞硝基的雙自由基性質(zhì)轉(zhuǎn)化為π系。研究展示了該反應(yīng)在藥物化合物后期功能化和可溶性環(huán)氧化物水解酶抑制劑的發(fā)現(xiàn)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(qū)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(qū)體中的雜質(zhì)和非化學(xué)計量限制了電池的功率轉(zhuǎn)換效率。研究者發(fā)現(xiàn)，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(jī)溶劑。
這條路線最大限度地減少雜質(zhì)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(rèn)證功率轉(zhuǎn)換效率，并且在50℃下連續(xù)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(tài)學(xué)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(jīng)經(jīng)歷了滅絕和衰退。外地引進(jìn)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(rèn)為對植物有不同尋常的負(fù)面影響。
通過對來自221項(xiàng)研究的3995個樣點(diǎn)尺度的植物豐度和多樣性響應(yīng)進(jìn)行薈萃分析，研究者發(fā)現(xiàn)沒有證據(jù)表明巨型動物的影響是由本土性、入侵性、野性、共同進(jìn)化史或功能和系統(tǒng)發(fā)育新穎性決定的。也沒有證據(jù)表明外來巨型動物比本土巨型動物更能促進(jìn)外來植物的生長。
相反，研究者發(fā)現(xiàn)了強(qiáng)有力的證據(jù)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(jìn)了植物的多樣性。研究表明，基于性狀的生態(tài)學(xué)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(jī)器學(xué)習(xí)Machine Learning
Grounded language acquisition through the eyes and ears of a single child
通過機(jī)器學(xué)習(xí)模仿幼兒眼睛和耳朵的基礎(chǔ)語言習(xí)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(lián)系起來。這些知識中有多少是可以通過相對通用的學(xué)習(xí)機(jī)制從感官輸入中學(xué)習(xí)的，又有多少需要更強(qiáng)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(jī)記錄，在61小時的相關(guān)視覺語言數(shù)據(jù)流上訓(xùn)練了一個相對通用的神經(jīng)網(wǎng)絡(luò)，學(xué)習(xí)基于特征的表示和跨模態(tài)關(guān)聯(lián)。研究模型獲得了兒童日常經(jīng)驗(yàn)中存在的許多詞指涉映射，實(shí)現(xiàn)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(tǒng)保持一致。
這些結(jié)果表明，基礎(chǔ)詞義的關(guān)鍵方面是如何通過一個孩子輸入的聯(lián)合表征和聯(lián)想學(xué)習(xí)來學(xué)習(xí)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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