作者:李言 来源:科学网微信公众号 发布时间:2023/9/10 20:56:14
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《科学》(20230908出版)一周论文导读

 

编译 | 李言

Science, 8 SEP 2023, Volume 381 Issue 6662

《科学》,2023年9月8日,第381卷,6662期

 

化学Chemistry

Cross-coupling by a noncanonical mechanism involving the addition of aryl halide to Cu(II)

涉及将芳基卤化物加入Cu(II)的非规范机制的交叉偶联

▲ 作者:CONNOR P. DELANEY, EVA LIN et al.

▲ 链接:https://www.science.org/doi/full/10.1126/science.adi9226

▲ 摘要:

铜配合物广泛用于催化杂原子亲核试剂与芳基卤化物偶联的精细化学品和材料的合成。我们发现,一些最活跃的催化剂催化的交叉偶联发生的机制以前没有被考虑过。通过将芳基卤化物协同氧化加成到Cu(II)上,形成高价物质,以及草酰胺配体上的自由基特性进行稳定,草酰胺配体的Cu(II)配合物催化乌尔曼偶联反应在芳基醚中形成C-O键。

这种机制不同于那些已被假定为其他乌尔曼型耦合、涉及Cu(I)和Cu(III)中间体的机制。Cu(II)态的稳定性促成了苯氧化合物与芳氯亲电试剂大于1000的高周转率,以及在空气中进行反应的能力。

▲ Abstract:

Copper complexes are widely used in the synthesis of fine chemicals and materials to catalyze couplings of heteroatom nucleophiles with aryl halides. We show that cross-couplings catalyzed by some of the most active catalysts occur by a mechanism not previously considered. Copper(II) [Cu(II)] complexes of oxalamide ligands catalyze Ullmann coupling to form the C–O bond in aryl ethers by concerted oxidative addition of an aryl halide to Cu(II) to form a high-valent species that is stabilized by radical character on the oxalamide ligand. This mechanism diverges from those involving Cu(I) and Cu(III) intermediates that have been posited for other Ullmann-type couplings. The stability of the Cu(II) state leads to high turnover numbers, >1000 for the coupling of phenoxide with aryl chloride electrophiles, as well as an ability to run the reactions in air.

Carbon-doped metal oxide interfacial nanofilms for ultrafast and precise separation of molecules

碳掺杂金属氧化物界面纳米膜用于超快速和精确地分离分子

▲ 作者:BRATIN SENGUPTA, QIAOBEI DONG et al.

▲ 链接:https://www.science.org/doi/full/10.1126/science.adh2404

▲ 摘要:

我们报告了一种超快界面工艺,可以生成无机纳米多孔碳掺杂金属氧化物(CDTO)纳米膜,用于精确的分子分离。对于给定的孔径,这些纳米膜的孔密度比已有的有机溶剂纳滤膜高2到10倍,也能产生超高的溶剂渗透率,即使后者更厚。

由于优异的机械、化学和热稳定性,具有可设计的刚性纳米孔的CDTO纳米膜在严苛的条件下也能表现出长期稳定和高效的有机分离。

▲ Abstract:

We report an analogous ultrafast interfacial process to generate inorganic, nanoporous carbon-doped metal oxide (CDTO) nanofilms for precise molecular separation. For a given pore size, these nanofilms have 2 to 10 times higher pore density (assuming the same tortuosity) than reported and commercial organic solvent nanofiltration membranes, yielding ultra-high solvent permeance, even if they are thicker. Owing to exceptional mechanical, chemical, and thermal stabilities, CDTO nanofilms with designable, rigid nanopores exhibited long-term stable and efficient organic separation under harsh conditions.

地球科学Geoscience

Fast and destructive density currents created by ocean-entering volcanic eruptions

进入海洋的火山喷发形成的快速且具有破坏性的密度流

▲ 作者:MICHAEL A. CLARE, ISOBEL A. YEO et al.

▲ 链接:

https://www.science.org/doi/full/10.1126/science.adi3038

▲ 摘要:

我们展示了大量喷发的物质如何迅速进入陡峭的淹没斜坡,引发了极快(每小时122公里)和长距离(>100公里)的海底洋流。这些高密度海流比地震、洪水或风暴引发的海流要快,它们破坏了海底电缆,切断了一个国家与世界其他地方的联系。

这些水流挖掘出的深层冲刷物与许多水下火山周围的冲刷物相似,为世界上其他地方的大规模喷发提供了证据。

▲ Abstract:

We show how the rapid emplacement of large volumes of erupted material onto steep submerged slopes triggered extremely fast (122 kilometers per hour) and long-runout (>100 kilometers) seafloor currents. These density currents were faster than those triggered by earthquakes, floods, or storms, and they broke seafloor cables, cutting off a nation from the rest of the world. The deep scours excavated by these currents are similar to those around many submerged volcanoes, providing evidence of large eruptions at other sites worldwide.

天文学Astronomy

Evidence for a radiation belt around a brown dwarf

褐矮星周围存在辐射带的证据

▲ 作者:J. B. CLIMENT, J. C. GUIRADO et al.

▲ 链接:

https://www.science.org/doi/full/10.1126/science.adg6635

▲ 摘要:

超冷矮星(UCDs)是一类包括褐矮星和非常低质量恒星的天文天体。对超冷矮星的射电观测测量了它们的亮度作为时间(光曲线)和光谱能量分布的函数,从而深入了解了它们的磁场。我们利用超长基线干涉测量法对褐矮星LSR J1835+3259进行空间分辨射电观测,结果显示出扩展的射电发射。

我们探测到的形态与辐射带的存在相一致。与模型的比较表明,辐射带中含有受磁镜像约束的高能粒子。我们认为,射电发射的超冷矮星具有偶极有序的磁场,具有类似木星的辐射带状形态和极光。

▲ Abstract:

Ultracool dwarfs (UCDs) are a category of astronomical objects that includes brown dwarfs and very-low-mass stars. Radio observations of UCDs have measured their brightness as a function of time (light curves) and spectral energy distributions, providing insight into their magnetic fields. We present spatially resolved radio observations of the brown dwarf LSR J1835+3259 using very-long-baseline interferometry showing extended radio emission. The detected morphology is consistent with the presence of a radiation belt. Comparison with models indicates that the radiation belt contains energetic particles confined by magnetic mirroring. We contend that radio-emitting UCDs have dipole-ordered magnetic fields with radiation belt–like morphologies and aurorae that are similar to those of Jupiter.

生态学Ecology

Widespread shifts in body size within populations and assemblages

在种群和组合中体型的广泛变化

▲ 作者:INS S. MARTINS, FRANZISKA SCHROD et al.

▲ 链接:https://www.science.org/doi/full/10.1126/science.adg6006

▲ 摘要:

在此,我们评估了1960年至2020年的5025个组合时间序列中6个分类群体型变化的流行程度。通过利用普莱斯公式将这种变化划分为种内体型变化和组成变化,我们发现,随着时间的推移,体型的变小主要表现在鱼类中,其他类群的变化模式更多。

我们发现,群落组成的变化对体型变化的贡献大于种内趋势,但两者在幅度和方向上都表现出实质性的变化。当体型变小与丰度的增加相平衡时,组合的生物量保持比较稳定。

▲ Abstract:

Here, we assessed the prevalence of body size change in six taxon groups across 5025 assemblage time series spanning 1960 to 2020. Using the Price equation to partition this change into within-species body size versus compositional changes, we detected prevailing decreases in body size through time driven primarily by fish, with more variable patterns in other taxa. We found that change in assemblage composition contributes more to body size changes than within-species trends, but both components show substantial variation in magnitude and direction. The biomass of assemblages remains quite stable as decreases in body size trade off with increases in abundance.

环境科学Environmental Science

Reducing single-use cutlery with green nudges: Evidence from China’s food-delivery industry

用“绿色助推”减少一次性餐具使用:来自中国外卖行业的证据

▲ 作者:GUOJUN HE, YUHANG PAN et al.

▲ 链接:https://www.science.org/doi/full/10.1126/science.add9884

▲ 摘要:

消费者对外卖的需求不断增长,增加了一次性餐具的消费数量,导致了全球范围内的塑料污染。在这项研究中,我们调查了“绿色助推”对中国一次性餐具消费的影响。

通过与阿里巴巴的外卖平台“饿了么”合作,我们分析了详细的客户数据,发现“绿色助推”——将默认设置改为“不使用餐具”,并奖励消费者“绿色积分”——让不使用餐具的订单比例增加了648%。

这样产生的环境效益是巨大的:如果在全中国推行“绿色助推”,每年可节省超过217.5亿套一次性餐具,相当于避免产生326万吨塑料垃圾,少砍伐544万棵树。

▲ Abstract:

Rising consumer demand for online food delivery has increased the consumption of disposable cutlery, leading to plastic pollution worldwide. In this work, we investigate the impact of green nudges on single-use cutlery consumption in China. In collaboration with Alibaba’s food-delivery platform, Eleme (which is similar to Uber Eats and DoorDash), we analyzed detailed customer-level data and found that the green nudges—changing the default to “no cutlery” and rewarding consumers with “green points”—increased the share of no-cutlery orders by 648%. The environmental benefits are sizable: If green nudges were applied to all of China, more than 21.75 billion sets of single-use cutlery could be saved annually, equivalent to preventing the generation of 3.26 million metric tons of plastic waste and saving 5.44 million trees.

 
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