作者:未玖 来源:科学网微信公众号 发布时间:2023/12/10 20:49:59
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《科学》(20231208出版)一周论文导读

 

Science, 8 DEC 2023, VOL 382, ISSUE 6675

《科学》2023年12月8日,第382卷,6675期

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天文学Astronomy

Element abundance patterns in stars indicate fission of nuclei heavier than uranium

恒星中的元素丰度模式表明比铀重的原子会发生核裂变

▲ 作者:Ian U. Roederer, Nicole Vassh, Erika M. Holmbeck, Matthew R. Mumpower, Rebecca Surman, John J. Cowan, et al.

▲ 链接:

https://www.science.org/doi/10.1126/science.adf1341

▲ 摘要:

最重的化学元素是在中子星合并或超新星爆发过程中由快速中子捕获过程(r-过程)自然产生的。人们对比铀重元素(超铀原子核)的r-过程产生知之甚少,尚无法进行实验,因此必须使用核合成模型进行推演。

研究组分析了r过程元素增强的恒星样本中的元素丰度。钌、铑、钯和银元素的丰度(原子序数Z = 44至47;质量数A = 99至110)与较重元素(63≤Z≤78,A > 150)的丰度相关。相邻元素(34≤Z≤42和48≤Z≤62)之间不存在相关性。

研究组将此解释为超铀原子核的裂变碎片对丰度有贡献的证据。该结果表明,在r过程事件中会产生质量数>260的富中子核。

▲ Abstract:

The heaviest chemical elements are naturally produced by the rapid neutron-capture process (r-process) during neutron star mergers or supernovae. The r-process production of elements heavier than uranium (transuranic nuclei) is poorly understood and inaccessible to experiments so must be extrapolated by using nucleosynthesis models. We examined element abundances in a sample of stars that are enhanced in r-process elements. The abundances of elements ruthenium, rhodium, palladium, and silver (atomic numbers Z = 44 to 47; mass numbers A = 99 to 110) correlate with those of heavier elements (63 ≤ Z ≤ 78, A > 150). There is no correlation for neighboring elements (34 ≤ Z ≤ 42 and 48 ≤ Z ≤ 62). We interpret this as evidence that fission fragments of transuranic nuclei contribute to the abundances. Our results indicate that neutron-rich nuclei with mass numbers >260 are produced in r-process events.

物理学Physics

On-demand entanglement of molecules in a reconfigurable optical tweezer array

可重构光镊阵列中分子的按需纠缠

▲ 作者:Connor M. Holland, Yukai Lu & Lawrence W. Cheuk

▲ 链接:

https://www.science.org/doi/10.1126/science.adf4272

▲ 摘要:

量子纠缠对于许多量子应用至关重要,包括量子信息处理、量子模拟和量子增强传感。由于其丰富的内部结构和相互作用,人们认为分子是量子科学颇有前景的平台。然而,单独控制分子的确定性纠缠一直是个长期存在的实验挑战。

研究组展示了单独制备分子的按需纠缠,利用可重构光镊阵列制备的分子对之间的电偶极相互作用,确定性地创建了贝尔分子对。该研究结果展示了量子应用所需的关键构建块,并有望推进利用捕获分子的量子增强基础物理测试。

▲ Abstract:

Entanglement is crucial to many quantum applications, including quantum information processing, quantum simulation, and quantum-enhanced sensing. Because of their rich internal structure and interactions, molecules have been proposed as a promising platform for quantum science. Deterministic entanglement of individually controlled molecules has nevertheless been a long-standing experimental challenge. We demonstrate on-demand entanglement of individually prepared molecules. Using the electric dipolar interaction between pairs of molecules prepared by using a reconfigurable optical tweezer array, we deterministically created Bell pairs of molecules. Our results demonstrate the key building blocks needed for quantum applications and may advance quantum-enhanced fundamental physics tests that use trapped molecules.

材料科学Materials Science

Self-enhancing sono-inks enable deep-penetration acoustic volumetric printing

自增强声纳油墨可实现深穿透声学立体打印

▲ 作者:Xiao Kuang, Qiangzhou Rong, Saud Belal, Tri Vu, Alice M. López López, Nanchao Wang, et al.

▲ 链接:

https://www.science.org/doi/10.1126/science.adi1563

▲ 摘要:

立体打印是一种新兴的增材制造技术,通过放弃逐步更新墨水的步骤,可提高生成对象的打印速度和表面质量。现有的立体打印技术几乎完全依靠光能来触发透明油墨中的光聚合,这限制了材料选择和构建尺寸。

研究组报道了一种用于深穿透声学立体打印(DAVP)的自增强超声油墨(或声纳油墨)设计及相应的聚焦超声书写技术。采用实验和声学建模的方法来研究频率和扫描速率相关的声学打印行为。

DAVP实现了低声流、快速声热聚合和大印刷深度的关键特性,可打印各种形状的体积水凝胶和纳米复合材料(无论其光学性质如何)。DAVP还在生物组织中实现了厘米深度的打印,为微创医学铺平了道路。

▲ Abstract:

Volumetric printing, an emerging additive manufacturing technique, builds objects with enhanced printing speed and surface quality by forgoing the stepwise ink-renewal step. Existing volumetric printing techniques almost exclusively rely on light energy to trigger photopolymerization in transparent inks, limiting material choices and build sizes. We report a self-enhancing sonicated ink (or sono-ink) design and corresponding focused-ultrasound writing technique for deep-penetration acoustic volumetric printing (DAVP). We used experiments and acoustic modeling to study the frequency and scanning rate–dependent acoustic printing behaviors. DAVP achieves the key features of low acoustic streaming, rapid sonothermal polymerization, and large printing depth, enabling the printing of volumetric hydrogels and nanocomposites with various shapes regardless of their optical properties. DAVP also allows printing at centimeter depths through biological tissues, paving the way toward minimally invasive medicine.

化学Chemistry

Kinetic and thermodynamic control of C(sp2)–H activation enables site-selective borylation

C(sp2)-H活化的动力学和热力学控制实现了位点选择性硼化反应

▲ 作者:Jose B. Roque, Alex M. Shimozono, Tyler P. Pabst, Gabriele Hierlmeier, Paul O. Peterson & Paul J. Chirik

▲ 链接:

https://www.science.org/doi/10.1126/science.adj6527

▲ 摘要:

在不依赖空间效应或定向基团的情况下区分电子上不同的碳氢键(C-H)的催化剂颇难设计。

在这项工作中,研究组描述了由N-烷基咪唑取代吡啶二卡宾(ACNC)螯合配体负载的钴预催化剂,可以实现氟代芳烃的非定向远程硼化,并将范围扩大到包括富电子芳烃、吡啶、三氟和二氟甲基化芳烃,从而解决了第一排过渡金属C-H官能化催化剂的主要限制之一。

尽管邻位C-H活化产生的钴芳基配合物在热力学上更优,但机制研究表明间位C-H活化在动力学上更优。因此,该研究使用单一预催化剂初步证明了C-H硼化反应中的可切换位点选择性可起到硼试剂的作用。

▲ Abstract:

Catalysts that distinguish between electronically distinct carbon-hydrogen (C–H) bonds without relying on steric effects or directing groups are challenging to design. In this work, cobalt precatalysts supported by N-alkyl-imidazole–substituted pyridine dicarbene (ACNC) pincer ligands are described that enable undirected, remote borylation of fluoroaromatics and expansion of scope to include electron-rich arenes, pyridines, and tri- and difluoromethoxylated arenes, thereby addressing one of the major limitations of first-row transition metal C–H functionalization catalysts. Mechanistic studies established a kinetic preference for C–H bond activation at the meta-position despite cobalt-aryl complexes resulting from ortho C–H activation being thermodynamically preferred. Switchable site selectivity in C–H borylation as a function of the boron reagent was thereby preliminarily demonstrated using a single precatalyst.

地球科学Earth Science

Drought sensitivity in mesic forests heightens their vulnerability to climate change

湿地森林的干旱敏感性加剧了其对气候变化的脆弱性

▲ 作者:Robert Heilmayr, Joan Dudney & Frances C. Moore

▲ 链接:

https://www.science.org/doi/10.1126/science.adi1071

▲ 摘要:

气候变化正在改变全球森林的结构和功能,因此迫切需要预测哪些森林最容易受到未来更热、更干燥气候的影响。

研究组分析了122个物种的660万个树木年轮,以评估树木对水和能量可用性的敏感性。结果发现生长在气候范围内湿润地区的树木表现出最大的干旱敏感性。为了测试这些干旱敏感性模式如何影响气候变化的脆弱性,还预测了至2100年的树木生长情况。

研究结果表明,干旱地区的干旱适应将部分缓冲树木免受气候变化的影响。相比之下,生长在气候范围内更潮湿、更热地区的树木,在气候变化下可能会遭受意想不到的巨大不利影响。

▲ Abstract:

Climate change is shifting the structure and function of global forests, underscoring the critical need to predict which forests are most vulnerable to a hotter and drier future. We analyzed 6.6 million tree rings from 122 species to assess trees’ sensitivity to water and energy availability. We found that trees growing in wetter portions of their range exhibit the greatest drought sensitivity. To test how these patterns of drought sensitivity influence vulnerability to climate change, we predicted tree growth through 2100. Our results suggest that drought adaptations in arid regions will partially buffer trees against climate change. By contrast, trees growing in the wetter, hotter portions of their climatic range may experience unexpectedly large adverse impacts under climate change.

Watershed sediment cannot offset sea level rise in most US tidal wetlands

美国大多数潮汐湿地的流域沉积物不能抵消海平面上升

▲ 作者:Scott H. Ensign, Joanne N. Halls & Erin K. Peck

▲ 链接:

https://www.science.org/doi/10.1126/science.adj0513

▲ 摘要:

流域沉积物可增加潮汐湿地的海拔,以对抗海平面上升,但流域沉积物在何处以及起到多大的作用尚不清楚。

通过结合美国4972条河流及其河口的沉积物负荷和潮汐湿地面积的连续数据集,研究组计算出,在72%的河流中,河流沉积物的增加不足以与海平面上升相抗衡,因为大多数流域太小(中值21平方千米),无法产生足够的沉积物。

近一半的潮汐湿地将需要10倍以上的河流沉积物来抵消海平面上升,这在某些地区,即使通过拆除大坝也无法实现。认识到流域沉积物对大多数潮汐湿地海拔几乎无影响后,人们应将研究重点转向对海拔变化影响最大的生物过程和海岸沉积物动力学。

▲ Abstract:

Watershed sediment can increase elevation of tidal wetlands struggling against rising seas, but where and how much watershed sediment helps is unknown. By combining contiguous US datasets on sediment loads and tidal wetland areas for 4972 rivers and their estuaries, we calculated that river sediment accretion will be insufficient to match sea level rise in 72% of cases because most watersheds are too small (median 21 square kilometers) to generate adequate sediment. Nearly half the tidal wetlands would require 10 times more river sediment to match sea level, a magnitude not generally achievable by dam removal in some regions. The realization that watershed sediment has little effect on most tidal wetland elevations shifts research priorities toward biological processes and coastal sediment dynamics that most influence elevation change.

 
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