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《科学》（20220527出版）一周论文导读2022-05-29 21:39·科学网编译 | 李言Science,27 MAY 2022, Volume 376 Issue 6596《科学》2022年5月27日，第376卷，6596期材料科学Materials ScienceFerroelectricity in untwisted heterobilayers of transition metal dichalcogenides过渡金属二卤族化合物未扭曲异双层中的铁电性▲ 作者：LUKAS ROG?E, LVJIN WANG, YI ZHANG, SONGHUA CAI et al.▲ 链接：https://www.science.org/doi/10.1126/science.abm5734▲ 摘要：具有面外铁电和压电特性的二维材料是实现超薄铁和压电电子器件的理想材料。我们通过一步化学气相沉积法合成了未扭曲、相称和外延的MoS2/WS2异质双层材料，意外证明了OOP铁电性和压电性。我们得到的d33压电常数为1.95 ~ 2.09皮米/伏，比单层In2Se3的自然OOP压电常数大6倍。通过改变MoS2/WS2异质双层的极化状态，我们证明了相应铁电隧道结器件中隧穿电流可进行约三个数量级调制。我们的结果与密度泛函理论是一致的，这表明对称性破缺和层间滑动都产生了意想不到的性质，而不需要调用扭曲角或摩尔畴。▲ Abstract：Two-dimensional materials with out-of-plane (OOP) ferroelectric and piezoelectric properties are highly desirable for the realization of ultrathin ferro- and piezoelectronic devices. We demonstrate unexpected OOP ferroelectricity and piezoelectricity in untwisted, commensurate, and epitaxial MoS2/WS2 heterobilayers synthesized by scalable one-step chemical vapor deposition. We show d33 piezoelectric constants of 1.95 to 2.09 picometers per volt that are larger than the natural OOP piezoelectric constant of monolayer In2Se3 by a factor of ~6. We demonstrate the modulation of tunneling current by about three orders of magnitude in ferroelectric tunnel junction devices by changing the polarization state of MoS2/WS2 heterobilayers. Our results are consistent with density functional theory, which shows that both symmetry breaking and interlayer sliding give rise to the unexpected properties without the need for invoking twist angles or moiré domains.化学ChemistryHydrotrioxide (ROOOH) formation in the atmosphere在大气中形成的氢三氧化物（ROOOH）▲ 作者：TORSTEN BERNDT, JING CHEN, EVA R. KJ?RGAARD et al.▲ 链接：https://www.science.org/doi/10.1126/science.abn6012▲ 摘要：有机氢三氧化物（ROOOH）是用于有机合成的强氧化剂。此前，研究推测它们是在大气中通过有机过氧自由基（RO2）与氢氧自由基（OH）的气相反应形成的。在此，我们报告了从几个大气相关的RO2自由基中直接观察到ROOOH的形成。动力学分析证实RO2 + OH快速反应形成ROOOH，速率系数接近碰撞极限。对于氢氧自由基引发的异戊二烯降解，全球模型预测三氧化二氢摩尔生成率高达1%，这意味着每年约有1000万吨的ROOOH生成。ROOOH在大气中的寿命预计为几分钟到几小时。氢三氧化物是大气中先前被忽略的一类物质，其影响需要进一步研究。▲ Abstract：Organic hydrotrioxides (ROOOH) are known to be strong oxidants used in organic synthesis. Previously, it has been speculated that they are formed in the atmosphere through the gas-phase reaction of organic peroxy radicals (RO2) with hydroxyl radicals (OH). Here, we report direct observation of ROOOH formation from several atmospherically relevant RO2 radicals. Kinetic analysis confirmed rapid RO2 + OH reactions forming ROOOH, with rate coefficients close to the collision limit. For the OH-initiated degradation of isoprene, global modeling predicts molar hydrotrioxide formation yields of up to 1%, which represents an annual ROOOH formation of about 10 million metric tons. The atmospheric lifetime of ROOOH is estimated to be minutes to hours. Hydrotrioxides represent a previously omitted substance class in the atmosphere, the impact of which needs to be examined.Dynamic interplay between metal nanoparticles and oxide support under redox conditions氧化还原条件下金属纳米粒子和氧化物载体之间的动态相互作用▲ 作者：H. FREY, A. BECK, X. HUANG et al.▲ 链接：https://www.science.org/doi/10.1126/science.abm3371▲ 摘要：贵金属颗粒和可还原金属氧化物载体之间的动态相互作用依赖于与周围气体的氧化还原反应。透射电子显微镜显示，当系统暴露在含氧和氢的氧化还原反应环境中，在还原条件下观察到的、包裹在二氧化钛上的金属-载体强相互作用（SMSI）诱导的铂颗粒在1 bar 压力下消失了。金属氧化物的不稳定和氧化还原介导的二氧化钛重构导致了依赖于纳米粒子取向的粒子动力学和定向迁移。当转回纯氧化条件时，SMSI静态状态被重新建立。这项研究强调了反应态和非反应态之间的差异，并表明金属-载体相互作用的表现强烈地依赖于化学环境。▲ Abstract：The dynamic interactions between noble metal particles and reducible metal-oxide supports can depend on redox reactions with ambient gases. Transmission electron microscopy revealed that the strong metal-support interaction (SMSI)–induced encapsulation of platinum particles on titania observed under reducing conditions is lost once the system is exposed to a redox-reactive environment containing oxygen and hydrogen at a total pressure of ~1 bar. Destabilization of the metal–oxide interface and redox-mediated reconstructions of titania lead to particle dynamics and directed particle migration that depend on nanoparticle orientation. A static encapsulated SMSI state was reestablished when switching back to purely oxidizing conditions. This work highlights the difference between reactive and nonreactive states and demonstrates that manifestations of the metal-support interaction strongly depend on the chemical environment.地球科学Earth SciencePersistent influence of precession on northern ice sheet variability since the early Pleistocene早更新世以来岁差对北部冰盖变化的持续影响▲ 作者：STEPHEN BARKER, AIDAN STARR, JEROEN VAN DER LUBBE et al.▲ 链接：https://www.science.org/doi/10.1126/science.abm4033▲ 摘要：100万年前，全球冰量的变化主要是倾角的变化；然而，岁差产生何种作用的问题仍然没有解决。通过过去170万年的北大西洋冰漂流记录，我们发现特定冰川周期（反映了冰盖的扩张）中冰漂流起始通常持续在倾角较少而大规模冰消融事件都与岁差的最小值相关。此外，我们的研究结果表明，在中-晚更新世时期，由岁差驱动的大规模消融事件与冰消期之间普遍存在关联。在增加发生前，倾角本身就足以结束一次冰期循环，在约100万年以后，随着北半球冰原的南延，倾角失去了对冰川消退的主导作用。▲ Abstract：Prior to ~1 million years ago (Ma), variations in global ice volume were dominated by changes in obliquity; however, the role of precession remains unresolved. Using a record of North Atlantic ice rafting spanning the past 1.7 million years, we find that the onset of ice rafting within a given glacial cycle (reflecting ice sheet expansion) consistently occurred during times of decreasing obliquity whereas mass ice wasting (ablation) events were consistently tied to minima in precession. Furthermore, our results suggest that the ubiquitous association between precession-driven mass wasting events and glacial termination is a distinct feature of the mid to late Pleistocene. Before then (increasing), obliquity alone was sufficient to end a glacial cycle, before losing its dominant grip on deglaciation with the southward extension of Northern Hemisphere ice sheets since ~1 Ma.Where rivers jump course河流“跳跃”的地方▲ 作者：SAM BROOKE, AUSTIN J. CHADWICK, JOSE SILVESTRE et al.▲ 链接：https://www.science.org/doi/10.1126/science.abm1215▲ 摘要：在罕见的河流冲裂事件中，河流会突然改道，导致灾难性的洪水。由于数据稀少，对冲裂位置的控制知之甚少。我们分析了近50年来的卫星图像，并记录了全球113起冲裂事件，发现了三种不同的冲裂位置控制。扇体的冲裂作用与谷限变化相吻合，而三角洲的冲裂作用主要集中在回水带内，表明洪水期间受空间流的减速或加速控制。然而，三角洲上38%的冲裂发生在回水效应的上游。这些事件发生在热带和沙漠环境里陡峭、富含沉积物的河流中。我们的研究结果表明，三角洲上的冲裂位置是由上游的洪水侵蚀程度决定的，这种侵蚀通常局限于回水区，但在陡峭的含沙河流中可以向上游延伸。我们的研究发现阐明了冲裂灾害可能如何响应土地使用和气候变化。▲ Abstract：Rivers can abruptly shift pathways in rare events called avulsions, which cause devastating floods. The controls on avulsion locations are poorly understood as a result of sparse data on such features. We analyzed nearly 50 years of satellite imagery and documented 113 avulsions across the globe that indicate three distinct controls on avulsion location. Avulsions on fans coincide with valley-confinement change, whereas avulsions on deltas are primarily clustered within the backwater zone, indicating a control by spatial flow deceleration or acceleration during floods. However, 38% of avulsions on deltas occurred upstream of backwater effects. These events occurred in steep, sediment-rich rivers in tropical and desert environments. Our results indicate that avulsion location on deltas is set by the upstream extent of flood-driven erosion, which is typically limited to the backwater zone but can extend far upstream in steep, sediment-laden rivers. Our findings elucidate how avulsion hazards might respond to land use and climate change.Models predict planned phosphorus load reduction will make Lake Erie more toxic模型预测计划中的磷负荷减少将使伊利湖的毒性更大▲ 作者：FERDI L. HELLWEGER, ROBBIE M. MARTIN, FALK EIGEMANN et al.▲ 链接：https://www.science.org/doi/10.1126/science.abm6791▲ 摘要：有害的蓝藻菌是一个全球性的环境问题，但我们缺乏对有毒与非有毒的菌株生态和毒素生产的可操作的了解。我们进行了一项包含103篇论文的大规模荟萃分析，并利用它开发了一个微囊藻生长和微囊藻毒素产生的机械性代理人基模型。对伊利湖的模拟表明，在2014年托莱多饮用水危机期间，观察到的产毒素到非产毒素的菌株演替是由不同的细胞氧化应激缓解策略（微囊藻毒素保护vs酶降解）和这些机制对氮的不同易感度所控制的。这个模型以及一个更简单的经验模型，都预测计划中的磷负荷减少将降低生物量，但使氮和光更容易获得，这将增加毒素的产生，有利于产毒细胞，并增加毒素浓度。▲ Abstract：Harmful cyanobacteria are a global environmental problem, yet we lack actionable understanding of toxigenic versus nontoxigenic strain ecology and toxin production. We performed a large-scale meta-analysis including 103 papers and used it to develop a mechanistic, agent-based model of Microcystis growth and microcystin production. Simulations for Lake Erie suggest that the observed toxigenic-to-nontoxigenic strain succession during the 2014 Toledo drinking water crisis was controlled by different cellular oxidative stress mitigation strategies (protection by microcystin versus degradation by enzymes) and the different susceptibility of those mechanisms to nitrogen limitation. This model, as well as a simpler empirical one, predicts that the planned phosphorus load reduction will lower biomass but make nitrogen and light more available, which will increase toxin production, favor toxigenic cells, and increase toxin concentrations.
2024年11月30日，值得注意的是，根据巴克莱的数据，已经在进行的项目产生的额外容量将足以为现有的互联网服务，再加上1.2万个具有颁丑补迟骋笔罢用户基础和输入需求的新应用程序。这表明，超大型公司建造新数据中心的计划超出了预期需求。
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而这样的情绪也让她迟迟走不出来当然这也造成了一种现象那就是在大家每个人在舞台上唱歌的时候张提纳爱完全没控制好自己的情绪
据该理财公司官方资料介绍，青银理财面对波动强化产物运作，成功保持“零破净”，理财产物和理财资产余额同时突破两千亿元。但在2023年，山东银保监局曾先后公布两张罚单，对青岛银行“理财产物相互交易调节收益违法违规行为”进行处罚。在拍摄过程中，不给别人添麻烦，不损人利己，做个安静的美阿姨。