房地产论文_ 《自然》（20200123出版）一周论文导读_房地产金融论文

翻译 | 唐一尘

Nature, 23 January 2020, Volume 577 Issue7791

《自然》2020年1月23日，第577卷，7791期

材料科学Materials Science

Conversion of non-van der Waals solids to 2D transition-metal chalcogenides

非范德华固体向二维过渡金属硫族化合物的转化

作者：Zhiguo Du、Shubin Yang、Pulickel M. Ajayan，et al.

链接：

https://www.nature.com/articles/s41586-019-1904-x

摘要：

二维（2D）原子层晶体具有独特的物理化学性质，在电子、传感器、催化剂、电池等领域有广泛的应用，但获得相位控制的2D结构仍是挑战。

这里证明了一种有效的合成策略，通过将非范德华固体逐步转化为具有2H（三角棱柱）/1T（八面体）相的2D范德华（vdW）过渡金属硫族化物层。

研究人员通过将非vdw固态暴露在硫蒸汽中，可以利用反应产物的焓和蒸气压控制。

杂原子取代的（如钇和磷）过渡金属硫族化物也可以使用这种方式合成，以便一个通用的合成方法能够工程化选择2D过渡金属硫族化物结构，并在高温下具有良好的稳定性，实现高通量单层膜的生产。

研究人员预计这些2D过渡金属硫族化物将在电子、催化和储能领域有广泛的应用。

Abstract

Although two-dimensional (2D) atomic layers, such as transition-metal chalcogenides, have been widely synthesized using techniques such as exfoliation and vapour-phase growth, it is still challenging to obtain phase-controlled 2D structures. Here we demonstrate an effective synthesis strategy via the progressive transformation of non-van der Waals (non-vdW) solids to 2D vdW transition-metal chalcogenide layers with identified 2H (trigonal prismatic)/1T (octahedral) phases. The transformation, achieved by exposing non-vdW solids to chalcogen vapours, can be controlled using the enthalpies and vapour pressures of the reaction products. Heteroatom-substituted(such as yttrium and phosphorus) transition-metal chalcogenides can also be synthesized in this way, thus enabling a generic synthesis approach to engineering phase-selected 2D transition-metal chalcogenide structures withgood stability at high temperatures (up to 1,373 kelvin) and achieving high-throughput production of monolayers. We anticipate that these 2D transition-metal chalcogenides will have broad applications for electronics, catalysis and energy storage.

Superstructure control of first-cycle voltage hysteresis in oxygen-redox cathodes

氧氧化还原正极首圈电压滞后的超结构控制

作者：Robert A. House、Urmimala Maitra、Peter G. Bruce，et al.

链接：

https://www.nature.com/articles/s41586-019-1854-3

摘要：

在传统的插入式正极中，碱金属离子可以进出层状材料，而电荷可以通过过渡金属离子的可逆还原和氧化得到补偿。

如果锂离子或钠离子电池使用的正极材料是富含碱的，这可以通过将电荷储存在氧化物和过渡金属离子上，增加电池的能量密度。

但是，首次充电时与O^2-氧化有关的高压在放电时无法恢复，从而导致能量密度显著降低。

研究人员通过比较两个相关的插层正极Na_0.75[Li_0.25Mn_0.75]O₂和Na_0.6[Li_0.2Mn_0.8]O₂，发现首圈电压滞后由超结构决定，特别是过渡金属层中锂离子和过渡金属离子的局部顺序。

通过在该层中形成具有抑制过渡金属迁移超结构的材料，可以避免O^2-氧化还原正极的电压滞后。

Na_0.75[Li_0.25Mn_0.75]O₂中出现的超结构，几乎在所有的氧氧化还原化合物中都存在，而这种超结构在充电时会丢失，部分原因是形成了分子O₂。

Abstract

In conventional intercalation cathodes, alkali metal ions can move in and out of a layered material with the charge being compensated for by reversible reduction and oxidation of the transitionmetal ions. If the cathode material used in a lithium-ion or sodium-ion battery is alkali-rich, this can increase the battery’s energy density by storing charge on the oxide and the transition metal ions, rather than on the transition metal alone. There is a high voltage associated with oxidation of O^2-during the first charge, but this is not recovered on discharge, resulting in reduced energy density. Displacement of transition metal ions into the alkali metal layers has been proposed to explain the first-cycle voltage loss (hysteresis). By comparing two closely related intercalation cathodes, Na_0.75[Li_0.25Mn_0.75]O₂and Na_0.6[Li_0.2Mn_0.8]O₂, here we show that the first-cycle voltage hysteresis is determined by the superstructure in the cathode, specifically the localordering of lithium and transition metal ions in the transition metal layers. The honeycomb superstructure of Na_0.75[Li_0.25Mn_0.75]O₂, present in almost all oxygen-redox compounds, is lost on charging, driven in part by formation of molecular O₂inside the solid. The O₂molecules are cleavedon discharge, reforming O^2-, but the manganese ions have migrated within the plane, changing the coordination around O^2-and lowering the voltage on discharge. The ribbon superstructure in Na_0.6[Li_0.2Mn_0.8]O₂inhibits manganese disorder and hence O₂formation, suppressing hysteresis and promoting stable electron holes on O^2-that are revealed by X-ray absorption spectroscopy. The results show that voltage hysteresis can be avoided in oxygen-redox cathodes by forming materials with a ribbon superstructure in the transition metal layers that suppresses migration of the transition metal.

化学/地质学

Chemistry/Geology

Molecular tuning of CO₂-to-ethylene conversion

二氧化碳转化为乙烯的分子调谐

作者：Fengwang Li、Arnaud Thevenon、Edward H.Sargent，et al.

链接：

https://www.nature.com/articles/s41586-019-1782-2

摘要：

以可再生电力为动力的电催化能减少二氧化碳，以生产有价值的燃料和原料，为间歇性可再生能源的能源储存提供了一种可持续和碳中性方法。

然而，高选择性地从二氧化碳还原反应（CO₂RR）中制备理想的C2产品，如乙烯，仍然是一个挑战。

这里，研究人员提出一种分子调控策略，通过用有机分子对电催化剂表面进行修饰，从而稳定反应中间体，以提高CO₂RR转化为乙烯的选择性。

芳基取代联吡啶及其衍生物对Cu催化剂进行修饰后可明显提高乙烯的选择性。该类分子改善了CO中间体的稳定性，有利于进一步还原为乙烯。

结果显示，当局部电流密度为每平方厘米230毫安时，CO₂RR对乙烯的法拉第效率为72%。研究人员推测，该方法或能补充多相催化剂通过稳定中间体通过局部分子调谐。

Abstract

The electrocatalytic reduction of carbon dioxide, powered by renewable electricity, to produce valuable fuels and feedstocks provides a sustainable and carbon-neutral approach to the storage of energy produced by intermittent renewable sources. However, the highly selective generation of economically desirable products such as ethylene from the carbon dioxide reduction reaction (CO₂RR) remains a challenge. Tuning the stabilities of intermediates to favour a desired reaction pathway can improve selectivity, and this has recently been explored for the reaction on copper by controlling morphology, grain boundaries, facets, oxidation state and dopants. Unfortunately, the Faradaic efficiency for ethylene is still low in neutral media (60 per cent at a partial current density of 7 milliamperes per square centimetre in the best catalyst reported so far), resulting in a low energy efficiency. Here we present a molecular tuning strategy—the functionalization of the surface of electrocatalysts with organic molecules—that stabilizes intermediates for moreselective CO₂RR to ethylene. Using electrochemical, operando/in situ spectroscopic and computational studies, we investigate the influence of a library of molecules, derived by electro-dimerization of arylpyridiniums, adsorbed on copper. We find that the adhered molecules improve the stabilization of an ‘atop-bound’ CO intermediate (that is, an intermediate bound to a single copper atom), thereby favouring further reduction to ethylene. As a result of this strategy, wereport the CO₂RR to ethylene with a Faradaic efficiency of 72 per cent at a partial currentdensity of 230 milliamperes per square centimetre in a liquid-electrolyte flow cell in a neutral medium. We report stable ethylene electrosynthesis for 190 hours in a system based on a membrane-electrode assembly that provides a full-cell energy efficiency of 20 per cent. We anticipate that this may be generalized to enable molecular strategies to complement heterogeneous catalysts by stabilizing intermediates through local molecular tuning.

Global-scale human impact on delta morphology has led to net land area gain

全球范围内人类对三角洲形态的影响导致土地面积增加

作者：J. H. Nienhuis、A. D. Ashton、T. E. Törnqvist，etal.

链接：

https://www.nature.com/articles/s41586-019-1905-9

摘要：

河流三角洲是地球上最具经济和生态价值的环境之一。

即使海平面没有上升，三角洲也越来越容易受到沿海灾害的影响，因为沉积物供应的减少和气候变化改变了其沉积物获得，影响了三角洲的形态，并可能导致侵蚀。

然而，三角洲沉积物分布、波浪和潮汐等力以及三角洲形态之间的关系至今仍未得到很好量化。

在这里，研究人员展示了世界范围内大约11000个沿海三角洲的形态，从小河口三角洲到巨型三角洲，是如何受到筑坝和砍伐森林的影响的。

研究模型显示，当今三角洲的形态受波浪（约80%）、潮汐（约10%）和河流（约10%）主导的连续影响，但大多数大型三角洲的变化是潮汐和河流主导的。

在过去30年里，尽管海平面上升，全球三角洲每年净增加土地54±12平方公里，其中最大的1%三角洲占净土地面积增加的30%。

人类是这些土地净收益的一个重要驱动因素——25%的三角洲增长可以归因于森林砍伐导致的河流沉积物供应的增加。

然而，在近1000个三角洲地区，河流筑坝导致人为沉积物流量严重减少（超过50%），迫使三角洲地区每年损失12±3.5平方公里。

研究人员表示，理解波浪和潮汐对沉积物的重新分布，对于成功预测人类对三角洲的影响至关重要。

Abstract

River deltas rank among the most economically and ecologically valuable environments on Earth. Even in the absence of sea-level rise, deltas are increasingly vulnerable to coastal hazards as declining sediment supply and climate change alter their sediment budget, affecting delta morphology and possibly leading to erosion. However, the relationship between deltaic sediment budgets, oceanographic forces of waves and tides, and delta morphology has remained poorly quantified. Here we show how the morphology of about 11,000 coastal deltas worldwide, ranging from small bayhead deltas to mega-deltas, has been affected by river damming and deforestation. We introduce a model that shows that present-day deltamorphology varies across a continuum between wave (about 80 per cent), tide(around 10 per cent) and river (about 10 per cent) dominance, but that most large deltas are tide- and river-dominated. Over the past 30 years, despite sea-level rise, deltas globally have experienced a net land gain of 54 ± 12 square kilometres per year (2 standard deviations), with the largest 1 per cent of deltas being responsible for 30 per cent of all net land area gains. Humans are a considerable driver of these net land gains—25 percent of delta growth can be attributed to deforestation-induced increases influvial sediment supply. Yet for nearly 1,000 deltas, river damming has resulted in a severe(more than 50 per cent) reduction in anthropogenic sediment flux, forcing acollective loss of 12 ± 3.5 square kilometres per year (2 standard deviations) of deltaic land. Not all deltas lose land in response to river damming: deltas transitioning towards tide dominance are currently gaining land, probably through channel infilling. With expected accelerated sea-level rise, however, recent land gains are unlikely to be sustained throughout the twenty-first century. Understanding the redistribution of sediments by waves and tides will be critical for successfully predicting human-driven change to deltas, both locally and globally.

神经学Neuroscience

Decoding the development of the human hippocampus

解码人类海马体的发育

作者：Suijuan Zhong、Wenyu Ding、Qian Wu、Xiaoqun Wang

链接：

https://www.nature.com/articles/s41586-019-1917-5

摘要：

海马体是由端脑的内侧区域发育而来，是大脑边缘系统的一部分，在信息编码、短时记忆、长时记忆、空间导航等方面发挥着重要作用，另外，海马体和癫痫、智力障碍、阿尔茨海默病等多种病理的发病机制密切相关。

虽然海马体是脊椎动物大脑中一个进化上保守的器官，但人们对发育中的人类海马体的细胞和分子特征仍缺乏了解。

这里，研究人员首次通过高通量单细胞转录组技术对人类胚胎期16周到27周海马体关键发育期的30416个单细胞进行了测序，并利用了经典tSNE分析把细胞划分为8大类，47个不同的细胞亚型。

他们对其中关键的神经干细胞的动态发育进行了系统的功能研究，深入阐明人脑海马在动态变化的发育过程以及记忆功能环路的形成的细胞基础和分子机制。

同时，该研究结合跨物种平台，多角度比较在海马的进化过程中，人类与啮齿类动物海马的关键差异，全方位多层次地揭示海马发育的重要关键时间节点以及关键基因，为相关疾病临床应用和治疗提供了前期基础。

Abstract

The hippocampus is an important part of the limbic system in the human brain that has essential roles in spatial navigation and the consolidation of information from short-term memory to long-term memory. Here we use single-cell RNA sequencing and assay for transposase-accessible chromatin using sequencing (ATAC–seq) analysis toillustrate the cell types, cell linage, molecular features and transcriptional regulation of the developing human hippocampus. Using the transcriptomes of 30,416 cells from the human hippocampus at gestational weeks 16–27, we identify 47 cell subtypes and their developmental trajectories. We also identify the migrating paths and cell lineages of PAX6⁺and HOPX⁺hippocampal progenitors, and regional markers of CA1, CA3 and dentate gyrus neurons. Multiomic data have uncovered transcriptional regulatory networks of the dentate gyrus marker PROX1. We also illustrate spatiallyspecific gene expression in the developing human prefrontal cortex and hippocampus. The molecular features of the human hippocampus at gestational weeks 16–20 are similar to those of the mouse at postnatal days 0–5 and revealgene expression differences between the two species. Transient expression of the primate-specific geneNBPF1leads to a marked increase in PROX1⁺cells in the mouse hippocampus. These data provides a blueprint for understanding human hippocampal development and a tool for investigating related diseases.

Nearest neighbours reveal fast and slow components of motor learning

邻居或揭示运动学习的快慢组成