科技論文范文3000字、科技論文范文3000字高中
編譯 | 馮維維
Science, VOLUME 381, ISSUE 6661, 1 SEP 2023
《科學》，第381卷，6661期，2023年9月1日
物理學
Physics
Observations of a black hole -ray binary indicate formation of a magnetically arrested disk
黑洞X射線雙星或能形成磁性圓盤
▲ 作者：BEI YOU, XINWU CAO, ZHEN YAN, JEAN-MARIE HAMEURY, BOZENA CZERNY, YUE WUTIANYU XIA, MAREK SIKORA, SHUANG-NAN ZHANG, AND PIOTR T. ZYCKI
▲ 鏈接：https://www.science.org/doi/full/10.1126/science.abo4504
▲ 摘要：
黑洞中物質的吸積會將磁場向內拖曳，從而增強磁場的強度。理論預測，足夠強的磁場可以阻止吸積流，產生磁阻盤（MAD）。
研究者分析了2018年黑洞X射線雙星MAXI J1820+070爆發的多波長觀測檔案。與X射線通量相比，射電通量和光通量分別延遲了約8天和17天。
他們將此解釋為MAD形成的證據。在這種情況下，磁場被不斷膨脹的日冕放大，在射電峰值前后形成一個磁極。研究者認為光延遲是由于外盤的熱粘性不穩定性造成的。
▲ Abstract：
Accretion of material onto a black hole drags any magnetic fields present inwards, increasing their strength. Theory predicts that sufficiently strong magnetic fields can halt the accretion flow, producing a magnetically arrested disk (MAD). We analyzed archival multiwavelength observations of an outburst from the black hole x-ray binary MAXI J1820+070 in 2018. The radio and optical fluxes were delayed compared with the x-ray flux by about 8 and 17 days, respectively. We interpret this as evidence for the formation of a MAD. In this scenario, the magnetic field is amplified by an expanding corona, forming a MAD around the time of the radio peak. We propose that the optical delay is due to thermal viscous instability in the outer disk.
化學
Chemistry
A machine-learning tool to predict substrate-adaptive conditions for Pd-catalyzed C–N couplings
預測鈀催化碳氮偶聯的底物自適應條件的機器學習工具
▲ 作者：N. IAN RINEHART, RAKESH K. SAUNTHWAL, JO?L WELLAUER, ANDREW F. ZAHRT, LUKAS SCHLEMPER, ALEXANDER S. SHVED, RAPHAEL BIGLER, SERENA FANTASIA , AND SCOTT E. DENMARK
▲ 鏈接：https://www.science.org/doi/full/10.1126/science.adg2114
▲ 摘要：
機器學習方法在加速識別化學轉化的反應條件方面具有很大的潛力。研究者提出了一種工具，給出了鈀（Pd）催化碳氮（C-N）偶聯的底物自適應條件。該工具的設計和構建需要生成一個實驗數據集，該數據集可以在一系列反應條件下探索不同的反應物配對網絡。
通過系統的實驗設計過程，研究者利用神經網絡模型主動學習大范圍的碳氮耦合。模型在實驗驗證中表現出良好的性能：從一系列與樣品外反應物的耦合中分離出10個產品，產率超過85%。重要的是，隨著數據量的增長，開發的工作流可不斷提高工具的預測能力。
▲ Abstract：
Machine-learning methods have great potential to accelerate the identification of reaction conditions for chemical transformations. A tool that gives substrate-adaptive conditions for palladium (Pd)–catalyzed carbon-nitrogen (C–N) couplings is presented. The design and construction of this tool required the generation of an experimental dataset that explores a diverse network of reactant pairings across a set of reaction conditions. A large scope of C–N couplings was actively learned by neural network models by using a systematic process to design experiments. The models showed good performance in experimental validation: Ten products were isolated in more than 85% yield from a range of couplings with out-of-sample reactants designed to challenge the models. Importantly, the developed workflow continually improves the prediction capability of the tool as the corpus of data grows.
Ring-opening polymerization of cyclic oligosiloxanes without producing cyclic oligomers
不產生環低聚物的環低聚硅氧烷開環聚合
▲ 作者：LIMIAO SHI, AURéLIE BOULèGUE-MONDIèRE, DELPHINE BLANC, ANTOINE BACEIREDO, VICEN? BRANCHADELL, AND TSUYOSHI KATO
▲ 鏈接：
https://www.science.org/doi/full/10.1126/science.adi1342
▲ 摘要：
硅氧鏈的穩定增長促進了有機硅的大規模生產。然而，這些鏈中有一小部分在反應后期不可避免地反咬自己，產生循環雜質。作者報道稱，苯甲醇可通過氫鍵與鏈端絡合，抑制咬背過程。
他們還描述了一種磷反離子，也被酒精穩定，但在沒有酒精的情況下會分解，以抑制鏈的生長，同樣防止副產物的形成。
▲ Abstract：
Mass production of silicones proceeds by the steady growth of silicon–oxygen chains. However, there is a small fraction of these chains that inevitably bite back on themselves late in the reaction to produce cyclic impurities. Shi et al. report that benzyl alcohol can complex with the chain end through hydrogen bonding and inhibit the back-biting process. Moreover, they describe a phosphonium counterion that is also stabilized by the alcohol but decomposes in its absence to deactivate chain growth, likewise preventing the by-product formation.
氣候和古人類學
Climate and Paleoanthropology
Fluctuating Atlantic inflows modulate Arctic atlantification
波動大西洋流入調節北極“大西洋化”
▲ 作者：IGOR V. POLYAKOV, RANDI B. INGVALDSEN, ANDREY V. PNYUSHKOV, UMA S. BHATT, JENNIFER A. FRANCIS, MARKUS JANOUT, RONALD KWOK, AND ?YSTEIN SKAGSETH
▲ 鏈接：
https://www.science.org/doi/10.1126/science.adh5158
▲ 摘要：
過去幾十年，北極海冰一直在消失，原因之一是來自大西洋的溫水正越來越多地平流到高緯度的海洋中，這一過程被稱為“大西洋化”。
是什么推動了這個過程呢？作者研究表明，被稱為北極偶極子的大尺度天氣模式導致大氣風模式，這種模式調節穿過弗拉姆海峽和巴倫支海的北大西洋流入，導致北冰洋環流、流入亞美亞盆地的淡水通量、海洋分層和熱通量的變化。
▲ Abstract：
One of the reasons that Arctic sea ice has been disappearing over the past decades is that warm water from the Atlantic is being advected into the high-latitude ocean in increasing amounts, a process called “atlantification.” But what drives this process? Polyakov et al. show that the large-scale weather pattern called the Arctic Dipole causes atmospheric wind patterns that modulate North Atlantic inflows across the Fram Strait and within the Barents Sea, resulting in variations in Arctic Ocean circulation, freshwater fluxes into the Amerasian Basin, ocean stratification, and heat fluxes.
Genomic inference of a severe human bottleneck during the Early to Middle Pleistocene transition
早更新世到中更新世過渡時期嚴重人類瓶頸的基因組推斷
▲ 作者：WANGJIE HU, ZIQIAN HAO, PENGYUAN DU, FABIO DI VINCENZO, GIORGIO MANZI, JIALONG CUI, YUN-XIN FU, YI-HSUAN PAN , AND HAIPENG LI
▲ 鏈接：https://www.science.org/doi/full/10.1126/science.abq7487
▲ 摘要：
今天，地球上有80多億人，主宰著地球。但在80萬到90萬年前，情況大不相同。研究者使用一種新開發的凝聚模型，從3000多個現代人類基因組中預測過去人類的人口規模。
該模型發現，人類祖先的規模曾從大約10萬人減少到大約1000人，這種情況持續了大約10萬年。這種下降似乎與主要的氣候變化和隨后的物種形成事件同時發生。
▲ Abstract：
Today, there are more than 8 billion human beings on the planet. We dominate Earth’s landscapes, and our activities are driving large numbers of other species to extinction. Had a researcher looked at the world sometime between 800,000 and 900,000 years ago, however, the picture would have been quite different. Hu et al. used a newly developed coalescent model to predict past human population sizes from more than 3000 present-day human genomes. The model detected a reduction in the population size of our ancestors from about 100,000 to about 1000 individuals, which persisted for about 100,000 years. The decline appears to have coincided with both major climate change and subsequent speciation events.
計量學Metrology
Establishing a new standard of care for calculus using trials with randomized student allocation
利用隨機分配學生試驗建立微積分學習新標準
▲ 作者：LAIRD KRAMER, EDGAR FULLER, CHARITY WATSON, ADAM CASTILLO, PABLO DURAN OLIVA
▲ 鏈接：https://www.science.org/doi/full/10.1126/science.ade9803
▲ 摘要：
在美國高校，微積分是獲得STEM學位的入門課程。在所有最初攻讀STEM學位的學生中，超過一半的人畢業時沒有獲得學位，通常是在努力完成課程之后。
教師默認采用傳統的以講座為基礎的教學方式，加劇了不合格率的差異；這對女性、西班牙裔和黑人學生的影響尤為嚴重，剝奪了勞動力中來自不同群體的人才和見解。
作者進行了一項大型試驗，將學生隨機分配到微積分教室，教師積極地與學生合作（治療），或者依賴傳統的授課方式，將他們視為被動的學習者（對照）。在不同的人口統計群體中，這種治療更有效，因為參與培養了對微積分的更深理解，提高了成績，并促進了代表性不足的學生的融入。這表明微積分教學的新標準和完成STEM學位的機會增加。
▲ Abstract：
Across US universities, calculus is a gateway course for STEM degrees. Of all students who initially pursue STEM degrees, more than half graduate without one, often after struggling through coursework. Instructors defaulting to traditional lecture-based instruction exacerbates disparities in failure rates; this disproportionately affects women, Hispanic, and Black students, depriving the workforce of talent and insights from diverse groups. Kramer et al. conducted a large trial that randomized students into calculus classrooms where instructors actively engaged students collaboratively (treatment) or relied on traditional lecture styles that treated them as passive learners (control). Across demographic groups, the treatment was more effective, as engagement fostered a deeper understanding of calculus, improved grades, and promoted the inclusion of underrepresented students.
