科研
科研
编译|未玖
Science, 4 OCT 2024, VOL 386, ISSUE 6717
《科学》，2024年10月4日，第386卷，6717期
天文学Astronomy
Observing the evolution of the Sun’s global coronal magnetic field over 8 months
观测全球日冕磁场在8个月内的演变
▲ 作者：ZIHAO YANG, HUI TIAN, STEVEN TOMCZYK, XIANYU LIU, SARAH GIBSON, RICHARD J. MORTON, ET AL.
▲ 链接：https://www.science.org/doi/10.1126/science.ado2993
▲摘要：日冕中的磁场储存着能量，这些能量可被释放出来加热等离子体并驱动太阳爆发。对全球日冕磁场的测量仅限于几次快照。
在这项工作中，研究组使用升级版日冕多通道偏振仪进行观测，提供了跨度为8个月的太阳翼上方全球日冕的114张磁场图。最终确定了日冕磁场随高度的分布，并监测了多次太阳自转过程中不同纬度的演变。
1.05~1.60太阳半径范围内的场强变化幅度为<1高斯至约20高斯。日冕磁场测量中也出现了活跃经度特征。日冕模型总体上与该观测结果一致，尽管在高纬度地区存在较大差异。
▲ Abstract：
The magnetic field in the Sun’s corona stores energy that can be released to heat plasma and drive solar eruptions. Measurements of the global coronal magnetic field have been limited to several snapshots. In this work, we present observations, using the Upgraded Coronal Multi-channel Polarimeter, that provide 114 magnetograms of the global corona above the solar limb spanning ~8 months. We determined the magnetic field distribution with altitude in the corona and monitored the evolution at different latitudes over multiple solar rotations. The field strength between 1.05 and 1.60 solar radii varies from <1 to ~20 gauss. A signature of active longitudes appears in the coronal magnetic field measurements. Coronal models are generally consistent with our observations, though they have larger discrepancies in high-latitude regions.
材料科学Materials Science
Grain rotation mechanisms in nanocrystalline materials: Multiscale observations in Pt thin films
纳米晶材料中的晶粒旋转机制：铂薄膜的多尺度观测
▲ 作者：YUAN TIAN, XIAOGUO GONG, MINGJIE XU, CAIHAO QIU, YING HAN, YUTONG BI, ET AL.
▲ 链接：https://www.science.org/doi/10.1126/science.adk6384
▲摘要：在纳米晶材料的晶粒生长、再结晶和塑性变形过程中，经常会观察到近刚体晶粒旋转。尽管经过了数十年的研究，晶粒旋转的主要机制仍然是个谜。
研究组提供了直接证据，表明在铂薄膜中，晶粒旋转通过沿晶界的断续运动（具有阶梯和位错特征的线缺陷）发生。最先进的原位四维扫描透射电子显微镜（4D-STEM）观测揭示了晶粒旋转与晶粒生长或收缩之间的统计相关性。
这种相关性源于通过断续运动发生的剪切耦合晶界迁移，与原位高角度环形暗场STEM观测和原子模拟辅助分析所证明的一致。该发现为纳米晶材料的结构动力学提供了定量见解。
▲ Abstract：
Near-rigid-body grain rotation is commonly observed during grain growth, recrystallization, and plastic deformation in nanocrystalline materials. Despite decades of research, the dominant mechanisms underlying grain rotation remain enigmatic. We present direct evidence that grain rotation occurs through the motion of disconnections (line defects with step and dislocation character) along grain boundaries in platinum thin films. State-of-the-art in situ four-dimensional scanning transmission electron microscopy (4D-STEM) observations reveal the statistical correlation between grain rotation and grain growth or shrinkage. This correlation arises from shear-coupled grain boundary migration, which occurs through the motion of disconnections, as demonstrated by in situ high-angle annular dark-field STEM observations and the atomistic simulation–aided analysis. These findings provide quantitative insights into the structural dynamics of nanocrystalline materials.
化学Chemistry
A chiral hydrogen atom abstraction catalyst for the enantioselective epimerization of meso-diols
手性氢原子提取催化剂助力内消旋二醇对映选择性差向异构化
▲ 作者：ANTTI S. K. LAHDENPER?, JYOTI DHANKHAR, DANIEL J. DAVIES, NELSON Y. S. LAM, P. DAVID BACO?, KAREN DE LA VEGA-HERNáNDEZ, ET AL.
▲ 链接：https://www.science.org/doi/10.1126/science.adq8029
▲摘要：氢原子提取是一个重要的基础化学过程，但很难对映选择性地进行。
研究组开发了较易从金鸡纳生物碱家族天然产物中提取的催化剂，凭借其手性胺结构可实现这一目标。该催化剂在单电子氧化后，通过选择性地从一个碳中心提取一个氢原子，之后再从硫醇中提取来重新获得一个氢原子，使内消旋二醇脱对称。这导致一个对映选择性差向异构化过程，形成具有高对映体过量的手性非对映体。
环状和非环状的1,2-二醇是相容的，非环状的1,3-二醇亦是如此。研究组还证明了将该方法与Giese加成中的碳-碳键形成相结合的可行性。鉴于涉及氢原子转移步骤的合成方法越来越多，预期该工作将在对映选择性自由基化学领域产生广泛的影响。
▲ Abstract：
Hydrogen atom abstraction is an important elementary chemical process but is very difficult to carry out enantioselectively. We have developed catalysts, readily derived from the Cinchona alkaloid family of natural products, which can achieve this by virtue of their chiral amine structure. The catalyst, following single-electron oxidation, desymmetrizes meso-diols by selectively abstracting a hydrogen atom from one carbon center, which then regains a hydrogen atom by abstraction from a thiol. This results in an enantioselective epimerization process, forming the chiral diastereomer with high enantiomeric excess. Cyclic and acyclic 1,2-diols are compatible, as are acyclic 1,3-diols. Additionally, we demonstrate the viability of combining our approach with carbon-carbon bond formation in Giese addition. Given the increasing number of synthetic methods involving hydrogen atom transfer steps, we anticipate that this work will have a broad impact in the field of enantioselective radical chemistry.
Photocatalytic furan-to-pyrrole conversion
光催化呋喃转化为吡咯
▲ 作者：DONGHYEON KIM, JAEHYUN YOU, DA HYE LEE, HOJIN HONG, DONGWOOK KIM AND YOONSU PARK
▲ 链接：https://www.science.org/doi/10.1126/science.adq6245
▲摘要：芳香环内杂原子的性质影响该杂环化合物的化学性质。然而，由于原子交换过程中的热力学失配，系统地评估单个原子的影响带来了合成挑战。
研究组提出了一种光催化策略，将呋喃的氧原子与氮基团交换，在单个分子间反应中将呋喃直接转化为吡咯类似物。
结果观测到与药物发现中常用的各种呋喃衍生物和氮亲核试剂具有很高的相容性，并且后期官能化成功制备了从天然存在的高分子复杂性呋喃中难以获得的吡咯。机理分析表明，通过单电子转移的极性反转引发了室温下氧化还原—中性原子交换过程。
▲ Abstract：
The identity of a heteroatom within an aromatic ring influences the chemical properties of that heterocyclic compound. Systematically evaluating the effect of a single atom, however, poses synthetic challenges, primarily as a result of thermodynamic mismatches in atomic exchange processes. We present a photocatalytic strategy that swaps an oxygen atom of furan with a nitrogen group, directly converting the furan into a pyrrole analog in a single intermolecular reaction. High compatibility was observed with various furan derivatives and nitrogen nucleophiles commonly used in drug discovery, and the late-stage functionalization furnished otherwise difficult-to-access pyrroles from naturally occurring furans of high molecular complexity. Mechanistic analysis suggested that polarity inversion through single electron transfer initiates the redox-neutral atom exchange processes at room temperature.
地球科学Earth Science
ENSO affects the North Atlantic Oscillation 1 year later
ENSO在1年后影响北大西洋涛动
▲ 作者：ADAM A. SCAIFE, NICK DUNSTONE, STEVEN HARDIMAN, SARAH INESON, CHAOFAN LI, RIYU LU, ET AL.
▲ 链接：https://www.science.org/doi/10.1126/science.adk4671
▲ 摘要：研究组在观测分析和气候模型中证明了厄尔尼诺—南方涛动（ENSO）的1年滞后温带响应。这种响应映射到北极涛动，在北大西洋最为强烈，与北大西洋涛动（NAO）相似。
出乎意料的是，这些滞后1年的遥相关至少与众所周知的冬季同步相关一样强。然而，滞后1年的响应在迹象上与同期响应相反，即1年后，厄尔尼诺现象之后是一个正相NAO，而拉尼娜现象之后是一个负相NAO。滞后响应也可能干扰同时发生的ENSO遥相关。
研究组表明，这些影响不太可能由ENSO循环的残余混叠引起；相反，缓慢移动的大气角动量异常解释了温带响应的迹象和时间。该研究结果对理解ENSO遥相关、解释观测到的温带气候变率以及解释季节到年际气候预测具有重要意义。
▲ Abstract：
We demonstrate a 1-year lagged extratropical response to the El Ni?o–Southern Oscillation (ENSO) in observational analyses and climate models. The response maps onto the Arctic Oscillation and is strongest in the North Atlantic, where it resembles the North Atlantic Oscillation (NAO). Unexpectedly, these 1-year lagged teleconnections are at least as strong as the better-known simultaneous winter connections. However, the 1-year lagged response is opposite in sign to the simultaneous response such that 1 year later, El Ni?o is followed by a positive NAO, whereas La Ni?a is followed by a negative NAO. The lagged response may also interfere with simultaneous ENSO teleconnections. We show here that these effects are unlikely to be caused by residual aliasing of ENSO cycles; rather, slowly migrating atmospheric angular momentum anomalies explain both the sign and the timing of the extratropical response. Our results have implications for understanding ENSO teleconnections, explaining observed extratropical climate variability and interpreting seasonal to interannual climate predictions.
医学Medicine
Cancer immunotherapy by γδ T cells
γδ T细胞助力肿瘤免疫治疗
▲ 作者：ADRIAN HAYDAY, JULIE DECHANET-MERVILLE, JAMIE ROSSJOHN AND BRUNO SILVA-SANTOS
▲ 链接：https://www.science.org/doi/10.1126/science.abq7248
▲摘要：癌症免疫疗法的前提是健康自我耐受的免疫系统可明显识别癌症。癌症免疫治疗的前景是免疫效应机制和免疫记忆可共同根除癌症和无法手术的转移，并事实上接种预防复发的疫苗。对于一些转移性黑色素瘤等迄今无法治愈的疾病，这一希望正在通过基于αβT细胞改变游戏规则的免疫疗法来实现。
今天的挑战是针对更多癌症类型使更多不同种族的患者受益，并在减少不良事件的同时实现治愈。在应对这些挑战时，γδT细胞有望提供特定的益处，它构成了第二种T细胞谱系，具有独特的识别能力和功能特征，可连接先天免疫和适应性免疫。
基于包括现成过继细胞疗法和激动剂抗体的γδT细胞临床试验，人们正在产生有希望的结果，尽管仍然存在可识别的问题。在解决这些问题时，研究组主张免疫疗法以γδT细胞的独特生物学为指导，这与正在进行的研究所阐明的一致。
▲ Abstract：
The premise of cancer immunotherapy is that cancers are specifically visible to an immune system tolerized to healthy self. The promise of cancer immunotherapy is that immune effector mechanisms and immunological memory can jointly eradicate cancers and inoperable metastases and de facto vaccinate against recurrence. For some patients with hitherto incurable diseases, including metastatic melanoma, this promise is being realized by game-changing immunotherapies based on αβ T cells. Today’s challenges are to bring benefit to greater numbers of patients of diverse ethnicities, target more cancer types, and achieve a cure while incurring fewer adverse events. In meeting those challenges, specific benefits may be offered by γδ T cells, which compose a second T cell lineage with distinct recognition capabilities and functional traits that bridge innate and adaptive immunity. γδ T cell–based clinical trials, including off-the-shelf adoptive cell therapy and agonist antibodies, are yielding promising results, although identifiable problems remain. In addressing those problems, we advocate that immunotherapies be guided by the distinctive biology of γδ T cells, as elucidated by ongoing research.
本文链接：http://knowith.com/news-3-1035.html《科学》（20241004出版）一周论文导读
声明：本网页内容由互联网博主自发贡献，不代表本站观点，本站不承担任何法律责任。天上不会到馅饼，请大家谨防诈骗！若有侵权等问题请及时与本网联系，我们将在第一时间删除处理。
