科研
科研
编译|李言
Science, 16 AUG 2024, Volume 385 Issue 6710
《科学》2024年8月16日，第385卷，6710期
化学Chemistry
Decoupling the air sensitivity of Na-layered oxides
解耦钠层氧化物的空气稳定性
▲ 作者：YANG YANG, ZAIFA WANG et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adm9223
▲ 摘要：
空气稳定性仍然是钠层状氧化物（NLOs）商业化的一大障碍。在此，我们表明了水蒸气只有分别与二氧化碳或氧气耦合时，在NLOs的破坏性酸降解和氧化降解中起关键作用。
定量分析表明，降低离子电位和钠含量综合影响的阳离子竞争系数(η)和增大粒径可以增强聚合物的抗酸侵蚀能力，而使用高电位氧化还原对可以消除氧化降解。这些发现阐明了潜在的空气恶化机制，并使空气稳定NLOs的设计合理化。
▲ Abstract：
Air sensitivity remains a substantial barrier to the commercialization of sodium (Na)–layered oxides (NLOs). We show here that water vapor plays a pivotal role in initiating destructive acid and oxidative degradations of NLOs only when coupled with carbon dioxide or oxygen, respectively. Quantification analysis revealed that reducing the defined cation competition coefficient (η), which integrates the effects of ionic potential and sodium content, and increasing the particle size can enhance the resistance to acid attack, whereas using high-potential redox couples can eliminate oxidative degradation. These findings elucidate the underlying air deterioration mechanisms and rationalize the design of air-stable NLOs.
天文学Astronomy
Ruthenium isotopes show the Chicxulub impactor was a carbonaceous-type asteroid
钌同位素表明希克苏鲁伯陨石是一颗碳质小行星
▲ 作者：MARIO FISCHER-G?DDE, JONAS TUSCH et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adk4868
▲ 摘要：
6600万年前发生在墨西哥希克苏鲁伯的一次陨石撞击，产生了一个标志着白垩纪和古近纪分界线的地层。这一地层含有高浓度的铂族元素，包括钌。
我们测量了三个白垩纪—古近纪边界地点的样品中的钌同位素，另外五个发生在3600万到4.7亿年前的撞击，以及35亿到32亿年前的撞击球体层。我们的数据表明，希克苏鲁伯撞击物是一颗形成于木星轨道之外的碳质小行星。
另外五个撞击结构的同位素特征与形成于离太阳更近的地方的硅质小行星更一致。太古宙球粒层样品与地球吸积最后阶段含碳小行星的撞击相一致。
▲ Abstract：
An impact at Chicxulub, Mexico, occurred 66 million years ago, producing a global stratigraphic layer that marks the boundary between the Cretaceous and Paleogene eras. That layer contains elevated concentrations of platinum-group elements, including ruthenium. We measured ruthenium isotopes in samples taken from three Cretaceous-Paleogene boundary sites, five other impacts that occurred between 36 million to 470 million years ago, and ancient 3.5-billion- to 3.2-billion-year-old impact spherule layers. Our data indicate that the Chicxulub impactor was a carbonaceous-type asteroid, which had formed beyond the orbit of Jupiter. The five other impact structures have isotopic signatures that are more consistent with siliceous-type asteroids, which formed closer to the Sun. The ancient spherule layer samples are consistent with impacts of carbonaceous-type asteroids during Earth’s final stages of accretion.
物理学Physics
Quantum state tracking and control of a single molecular ion in a thermal environment
热环境中单个分子离子的量子态跟踪与控制
▲ 作者：YU LIU, JULIAN SCHMIDT et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.ado1001
▲ 摘要：
在此，我们报告单个分子在不同状态（“跳跃”）之间的热辐射驱动转换的实时观察。我们通过微波驱动的转变逆转了这些“跳跃”，使得分子停留在选定状态的时间延长了20倍。
测量的跃迁速率在热环境中显示出各向异性，这表明使用单分子作为环境场强度的原位探针是可能的。我们的状态检测和操纵方法应用广泛，促进它们在量子科学、分子物理和离子中性化学等领域的应用。
▲ Abstract：
Here, we report real-time observations of thermal radiation–driven transitions between individual states (“jumps”) of a single molecule. We reversed these jumps through microwave-driven transitions, which resulted in a 20-fold improvement in the time the molecule dwells in a chosen state. The measured transition rates showed anisotropy in the thermal environment, pointing to the possibility of using single molecules as in situ probes for the strengths of ambient fields. Our approaches for state detection and manipulation could apply to a wide range of species, facilitating their uses in fields including quantum science, molecular physics, and ion-neutral chemistry.
公共卫生Public Health
Mapping safe drinking water use in low- and middle-income countries
绘制低收入和中等收入国家安全饮用水使用情况地图
▲ 作者：ESTHER E. GREENWOOD, THOMAS LAUBER et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.adh9578
▲ 摘要：
获得安全饮用水是一项人权，但全球一半以上人口安全管理饮用水服务（SMDWS）的数据是缺失的。
我们利用地理空间建模方法，结合现有的家庭调查数据和现有的全球地理空间数据集，估算了135个低收入和中等收入国家（LMICs）在次国家级的SMDWS使用情况。我们估计，在2020年，中低收入国家中只有三分之一的人可以使用SMDWS，粪便污染是影响近一半LMICs人口的主要限制因素。
我们的研究结果有助于提高人们对当前全球监测方法的挑战和局限性的认识，并展示如何利用全球可用的地理空间数据来填补数据空白，确定LMICs的优先区域。
▲ Abstract：
Safe drinking water access is a human right, but data on safely managed drinking water services (SMDWS) is lacking for more than half of the global population. We estimate SMDWS use in 135 low- and middle-income countries (LMICs) at subnational levels with a geospatial modeling approach, combining existing household survey data with available global geospatial datasets. We estimate that only one in three people used SMDWS in LMICs in 2020 and identified fecal contamination as the primary limiting factor affecting almost half of the population of LMICs. Our results are relevant for raising awareness about the challenges and limitations of current global monitoring approaches and demonstrating how globally available geospatial data can be leveraged to fill data gaps and identify priority areas in LMICs.
生物学Biology
Structure and repair of replication-coupled DNA breaks
复制偶联DNA断裂的结构和修复
▲ 作者：Raphael Pavani, Veenu Tripathi, Kyle B. Vrtis et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.ado3867
▲ 摘要：
通过使用CRISPR-Cas9切割酶，我们研究了复制机制与单链断裂（最常见的内源性DNA损伤形式之一）之间的相互作用。我们表明了在前导链刻痕处的复制叉崩溃会产生切除的单端双链断裂（seDSBs），并通过同源重组（HR）修复。
如果这些seDSBs不能及时修复，相邻分叉的到来会产生双端DSB（deDSB），这可能会在HR缺陷癌症中驱动基因组瘢痕。当复制叉绕过滞后链缺口时，也会直接产生deDSB。
与独立于复制产生的dedsb不同，缺口诱导的se/deDSB的末端切除是不依赖于BRCA1的。然而，BRCA1拮抗53BP1对RAD51丝形成的抑制。这些结果突出了维持复制叉稳定性的独特机制。
▲ Abstract：
Using CRISPR-Cas9 nicking enzymes, we examined the interaction between the replication machinery and single-strand breaks, one of the most common forms of endogenous DNA damage. We show that replication fork collapse at leading-strand nicks generates resected single-ended double-strand breaks (seDSBs) that are repaired by homologous recombination (HR). If these seDSBs are not promptly repaired, arrival of adjacent forks creates double-ended DSBs (deDSBs), which could drive genomic scarring in HR-deficient cancers. deDSBs can also be generated directly when the replication fork bypasses lagging-strand nicks. Unlike deDSBs produced independently of replication, end resection at nick-induced seDSBs and deDSBs is BRCA1-independent. Nevertheless, BRCA1 antagonizes 53BP1 suppression of RAD51 filament formation. These results highlight distinctive mechanisms that maintain replication fork stability.
A hippocampal circuit mechanism to balance memory reactivation during sleep
睡眠中平衡记忆再激活的海马回路机制
▲ 作者：LINDSAY A. KARABA, HEATH L. ROBINSON et al.
▲ 链接：
https://www.science.org/doi/10.1126/science.ado5708
▲ 摘要：
记忆巩固涉及在睡眠锐波波纹（SWRs）中活跃的海马细胞的同步再激活。如何在学习后平衡这种放电率和同步性的增加以保持网络的稳定性尚不明确。
我们发现了一个由CA2锥体细胞亚群与胆囊收缩素（CCK+）篮细胞形成的海马内回路产生的网络事件，该回路在非快速眼动睡眠期间发射一系列动作电位（BARR）。在学习过程中增加活动的CA1神经元和组件在SWRs期间被重新激活，但在BARR期间会被抑制。
在SWRs期间，最初的再激活增加通过睡眠恢复到基线水平。通过在BARRs期间沉默CCK+篮细胞来消除这种趋势，导致CA1组装的更高同步性和记忆巩固受损。通过在BARRs期间沉默CCK+篮细胞来消除这种趋势，导致CA1的更高同步性和记忆巩固受损。
▲ Abstract：
Memory consolidation involves the synchronous reactivation of hippocampal cells active during recent experience in sleep sharp-wave ripples (SWRs). How this increase in firing rates and synchrony after learning is counterbalanced to preserve network stability is not understood. We discovered a network event generated by an intrahippocampal circuit formed by a subset of CA2 pyramidal cells to cholecystokinin-expressing (CCK+) basket cells, which fire a barrage of action potentials (“BARR”) during non–rapid eye movement sleep. CA1 neurons and assemblies that increased their activity during learning were reactivated during SWRs but inhibited during BARRs. The initial increase in reactivation during SWRs returned to baseline through sleep. This trend was abolished by silencing CCK+ basket cells during BARRs, resulting in higher synchrony of CA1 assemblies and impaired memory consolidation.
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