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  • Comparative genomics reveal shared genomic changes in syngnathid fishes and signatures of genetic convergence with placental mammals
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2020-01-09
    Zhang Y, Ravi V, Qin G, et al.

    Syngnathids (seahorses, pipefishes and seadragons) exhibit an array of morphological innovations including loss of pelvic fins, a toothless tubular mouth and male pregnancy. They comprise two subfamilies: Syngnathinae and Nerophinae. Genomes of three Syngnathinae members have been analysed previously. In this study, we have sequenced the genome of a Nerophinae member, the Manado pipefish (Microphis manadensis), which has a semi-enclosed brood pouch. Comparative genomic analysis revealed that the molecular evolutionary rate of the four syngnathids is higher than that of other teleosts. The loss of all but one P/Q-rich SCPP genes in the syngnathids suggests a role for the lost genes in dentin and enameloid formation in teleosts. Genome-wide comparison identified a set of 118 genes with parallel identical amino acid substitutions in syngnathids and placental mammals. Association of some of these genes with placental and embryonic development in mammals suggests a role for them in syngnathid pregnancy.

  • Ultrafast Growth of Large Single Crystals of Monolayer WS2 and WSe2
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2020-01-08
    Zhang Z, Chen P, Yang X, et al.

    ABSTRACTMonolayer transition metal dichalcogenides (TMDs) have attracted considerable attention as atomically thin semiconductors for the ultimate transistor scaling. For practical applications in integrated electronics, large monolayer single crystals are essential for ensuring consistent electronic properties and high device yield. The TMDs available today are generally obtained by mechanical exfoliation or chemical vapor deposition (CVD) growth, and often plagued with a mixed layer thickness, a limited single crystal domain size or a very slow growth rate. Scalable and rapid growth of large single crystals of monolayer TMDs requires maximizing lateral growth rate while completely suppressing the vertical growth, which represents a fundamental synthetic challenge and has motivated considerable efforts. Herein we report a modified CVD approach with a controllable reverse flow for the rapid growth of large domain single crystals of monolayer TMDs. With the reverse flow to precisely control the chemical vapor supply in thermal CVD process, we can effectively prevent the undesired nucleation before reaching optimum growth temperature and enable rapid nucleation and growth of monolayer TMD single crystals at a high temperature that is difficult to access in a typical thermal CVD process. We show monolayer single crystals with 450 μm lateral size can be prepared in 10 s, with a highest lateral growth rate up to 45 μm/s. Electronic characterizations show the resulting monolayer WSe2 material exhibit excellent electronic properties with the carrier mobility up to 90 cm2V-1s-1, comparable to that of the best exfoliated monolayers. Our study provides a robust pathway for rapid growth of high-quality TMD single-crystals.

  • Land surface processes and summer cloud-precipitation characteristics in the Tibetan Plateau and their effects on downstream weather: a review and perspective
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2020-01-06
    Fu Y, Ma Y, Zhong L, et al.

    Correct understanding of the land surface processes and cloud-precipitation processes in the Tibetan Plateau (TP) is an important prerequisite for the study and forecast of the downstream activities of weather systems and one of the key points for understanding the global atmospheric movement. In order to show the achievements that have been made, this paper reviews the progresses on the observations for atmospheric boundary layer, land surface heat fluxes, cloud-precipitation distributions and vertical structures by using ground- and space-based multi-platform, multi-sensor instruments, and the effect of cloud system in the TP on the downstream weather. The results show that the form drag related to the topography, land-atmosphere momentum and scalar fluxes is an important part of the parameterization process. The sensible heat flux decreased especially in the central and northern TP caused by the decrease of wind speeds and the differences of the ground-air temperatures. Observations show that the cloud and precipitation over the TP has a strong diurnal variation. Studies also show the compressed air column in the troposphere by the higher altitude terrain of the TP makes particles inside clouds vary in shorter distance in the vertical direction than those in non-plateau area so that precipitation intensity over the TP is usually small with short duration, and the vertical structure of convective precipitation over the TP is obvious different from that in other regions. In addition, the influence of the TP on the severe weather in the downstream is preliminarily understood from the mechanism. It is necessary to use model simulations and observation techniques to reveal the difference between cloud precipitation in the TP and non-plateau areas in order to understand the cloud microphysical parameters over the TP, the processes of land boundary layer affecting cloud, precipitation and weather in the downstream regions.

  • Drone-based entanglement distribution towards mobile quantum networks
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2020-01-03
    Liu H, Tian X, Gu C, et al.

    Satellites have shown free-space quantum-communication ability, however, they are orbit-limited from full-time all-location coverage. Meanwhile, practical quantum networks require satellite constellations, which are complicate and expensive. Whereas the airborne mobile quantum may be a practical alternate to offer full-time all-location multi-weather coverage in a cost-effective way. Here we demonstrate the first mobile entanglement distribution based on drones, and realizes multi-weather operation including daytime and rainy night, with Clauser-Horne-Shimony-Holt S-parameter measured to be 2.41 ± 0.14 and 2.49 ± 0.06, respectively. Such system shows unparalleled mobility, flexibility and configurability compared to the existing satellite and fiber-based quantum communication, and reveals its potential to establish a multi-node quantum network, with scalable design using symmetric beam-aperture and single-mode-fiber coupling. All key technologies have been developed to pack quantum nodes into lightweight mobile platforms for local-area coverage, and arouses further technical improvements to establish wide-area quantum networks with high-altitude mobile communication.

  • Is graphite lithiophobic or lithiophilic?
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2020-01-03
    Duan J, Zheng Y, Luo W, et al.

    Graphite and lithium metal are two classic anode materials, and their composite has shown promising performance for rechargeable batteries. However, it is generally accepted that Li metal wets graphite poorly, causing its spreading and infiltration difficult. Here we show that graphite can either appear superlithiophilic or lithiophobic depending on the local redox potential. By comparing the wetting performance of HOPG, porous carbon paper (PCP), lithiated PCP and graphite powder, we demonstrate that the surface contaminants that pin the contact line motion and cause contact angle hysteresis have their own electrochemical stability windows. The surface contaminants can be either removed or reinforced in a time-dependent manner depending on whether the reducing agents (C6 → LiC6) or the oxidizing agents (air, moisture) dominate in the ambient environment, leading to bifurcating dynamics of either superfast or superslow wetting. Our findings enable new fabrication technology for Li-graphite composite with controllable Li metal/graphite ratio and present a great promise for mass production of Li-based anode used in high-energy-density batteries.

  • Experiments on Cu isotope fractionation between chlorine bearing fluid and silicate magma: implications for fluid exsolution and porphyry Cu deposits
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2020-01-02
    Guo H, Xia Y, Bai R, et al.

    Hydrothermal fluid is essential for transporting metals in the crust and mantle. To explore the potential of Cu isotopes as a tracer of hydrothermal-fluid activity, Cu isotope fractionation factors between Cl-bearing aqueous fluids and silicate magmas (andesite, dacite, rhyolite dacite, rhyolite, and haplogranite) were experimentally calibrated. Fluids containing 1.75 to 14 wt.% Cl were mixed together with rock powders in Au95Cu5 alloy capsules, which were equilibrated in cold-seal pressure vessels for 5 to 13 days at 800 to 850°C and 2 kbar. The elemental and Cu isotopic compositions of the recovered aqueous fluid and solid phases were analyzed by (LA-) ICP-MS and MC-ICP-MS, respectively. Our experimental results show that the fluid phases are consistently enriched in heavy Cu isotope (65Cu) relative to the coexisting silicates. The Cu isotope fractionation factor (Δ65CuFLUID-MELT) ranges from 0.08±0.01‰ to 0.69±0.02‰. The experimental results show that the Cu isotopic fractionation factors between aqueous fluids and silicates strongly depend on the Cu speciation in the fluids (e.g., CuCl(H2O), CuCl2– and CuCl32−) and silicate melts (CuO1/2), suggesting that the exsolved fluids may have higher δ65Cu than the residual magmas. Our results suggest the elevated δ65Cu values in Cu-enriched rocks could be produced by addition of aqueous fluids exsolved from magmas. Together with previous studies on Cu isotopes in the brine and vapor phases of porphyry deposits, our results are helpful for better understanding Cu mineralization processes.

  • Genes and speciation – Is it time to abandon the Biological Species Concept?
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-31
    Wang X, He Z, Shi S, et al.

    The biological species concept (BSC) is the cornerstone of the neo-Darwinian thinking. In BSC, species do not exchange genes either during or after speciation. However, since a substantial literature has increasingly reported gene flow during speciation, it seems time to reassess the revered but often doubted BSC. Contrary to the common perception, BSC should expect substantial gene flow at the onset of speciation, not the least because geographical isolation develops gradually. Although BSC does not stipulate how speciation begins, it does require a sustained period of isolation for speciation to complete its course. Evidence against BSC needs to demonstrate that the observed gene flow does not merely happen at the onset of speciation but continues until its completion. Importantly, recent genomic analyses cannot reject this more realistic version of BSC, although future analyses may still prove it wrong. The ultimate acceptance or rejection of BSC is not merely about a historical debate; rather, it is about the fundamental nature of species - Are species (and, hence, divergent adaptations) driven by a relatively small number of genes, or by thousands of them? Many levels of biology, ranging from taxonomy to biodiversity, depend on this resolution.

  • A global-scale multidecadal variability driven by Atlantic Multidecadal Oscillation
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-24
    Yang Y, An S, Wang B, et al.

    Observational analysis shows that there is a predominant global-scale multidecadal variability (GMV) of sea surface temperature (SST). Its horizontal pattern resembles that of the Interdecadal Pacific Oscillation (IPO) in the Pacific and the Atlantic multidecadal oscillation (AMO) in the Atlantic Ocean, which could affect global precipitation and temperature over globe. Here, we demonstrate that the GMV could be driven by the Atlantic multidecadal oscillation (AMO) through atmospheric teleconnections and atmosphere-ocean coupling processes. Observations reveal a strong negative correlation when AMO leads GMV by approximately 4–8 yrs. Pacemaker experiments using a climate model driven by observed AMO signals reveal that the tropical Atlantic warm SST anomalies of AMO initiate anomalous cooling in the equatorial central-eastern Pacific through atmospheric teleconnections. Anticyclonic anomalies in the North and South Pacific induce equatorward winds along the coasts of North and South America, contributing to further cooling. The upper ocean dynamics plays a minor role in GMV formation but contributes to a delayed response of the IPO to the AMO forcing. The possible impact of the GMV on AMO was also tested by prescribing only Pacific SST in the model, however, the model could not reproduce the observed phase relationship between the AMO and GMV. These results support the hypothesis that the Atlantic Ocean plays a key role in the multidecadal variability of global SST.

  • Au23(CR)14 Nanocluster restores fibril Aβ’s Unfolded state with abolished cytotoxicity and dissolves endogenous Aβ Plaques
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-20
    Zhang W, Gao G, Ma Z, et al.

    The misfolding of amyloid-β (Aβ) peptides from natural unfolded state to β-sheet structure is a critical step, leading to abnormal fibrillation and formation of endogenous Aβ plaques in Alzheimer's disease (AD). Previous studies have reported inhibition of Aβ fibrillation or disassembly of exogenous Aβ fibrils in vitro. However, soluble Aβ oligomers have been reported with increased cytotoxicity; this might be part of the reasons why current clinical trials targeting disassembly of Aβ fibrils by anti-Aβ antibodies have failed so far. Here we show Au23(CR)14 (a new Au nanocluster modified by Cys-Arg (CR) dipeptide) is able to completely dissolve exogenous mature Aβ fibrils into monomers and restore the natural unfolded state of Aβ peptides from misfolded β-sheets. And the cytotoxicity of Aβ40 fibrils when dissolved by Au23(CR)14 has been fully abolished. More importantly, Au23(CR)14 is able to completely dissolve endogenous Aβ plaques in the brain slices from transgenic AD model mice. In addition, Au23(CR)14 have good biocompatibility and infiltration ability across the blood brain barrier. Taken together, this work presents a promising therapeutics candidate for AD treatment, and manifests the potential of nanotechnological approaches in the development of nanomedicines.

  • Neurosurgical treatment for addiction: Lessons from an untold story in China and a path forward
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-17
    Ma S, Zhang C, Yuan T, et al.

    Addiction is a major public health crisis associated with significant disability and mortality. Although various pharmacological and behavioral treatments are currently available, the clinical efficacy of these treatments is limited. Given this situation, there is a growing interest in finding an effective neurosurgical treatment for addiction. First, we discuss the use of ablative surgery in treating addiction. We focus on the rise and fall of nucleus accumbens ablation for addiction in China. Subsequently, we review recent studies that have explored the efficacy and safety of deep brain stimulation treatment for addiction. We conclude that neurosurgical procedures, particularly deep brain stimulation, have a potentially valuable role in the management of otherwise intractable addictive disorders. Larger well-controlled clinical trials, however, are needed to assess clinical efficacy and safety. We end by discussing several key issues involved in this clinical field, and identifying some areas of progress.

  • Evolution and distribution of medullary bone: evidence from a new Early Cretaceous enantiornithine bird
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-19
    Wang M, O’Connor J, Bailleul A, et al.

    Living birds are unique among vertebrates in the formation of a female-specific bone tissue called medullary bone (MB) that is strictly associated with reproductive activity. MB is a rapidly mobilized source of calcium and phosphorus for the production of eggshell. Among living taxa, its skeletal distribution can be highly extensive such that it even exists in the ribs of some species. Due to its ephemeral nature MB is rarely fossilized, little is understood with regards to the origin of MB and its skeletal distribution in early taxa. Here we describe a new Early Cretaceous enantiornithine bird, Mirusavis parvus, gen. et. sp. nov., indicating that skeleton-wide distribution of MB appeared early in avian evolution. We suggest that this represents the plesiomorphic condition for the Aves, and that the distribution of MB observed among extant neornithines is a product of increased pneumatization in this lineage and natural selection for more efficient distribution of MB.

  • Electron-hole Hybridization in Bilayer Graphene
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-19
    Wang S, Zhao M, Zhang C, et al.

    Band structure determines the motion of electrons in a solid, giving rise to exotic phenomena when properly engineered. Drawing an analogy between electrons and photons, artificially designed optical lattices indicate the possibility of a similar band modulation effect in graphene systems. Yet due to the fermionic nature of electrons, modulated electronic systems promise far richer categories of behaviors than those found in optical lattices. Here, we uncovered a strong modulation of electronic states in bilayer graphene subject to periodic potentials. We observed for the first time the hybridization of electron and hole sub-bands, resulting in local band gaps at both primary and secondary charge neutrality points. Such hybridization leads to the formation of flat bands, enabling the study of correlated effects in graphene systems. This work may provide a novel way to manipulate electronic states in layered systems, which is important to both fundamental research and application.

  • Convergent genomic signatures of high altitude adaptation among domestic mammals
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-19
    Wu D, Yang C, Wang M, et al.

    Abundant and diverse domestic mammals living on the Tibetan Plateau provide useful materials for investigating adaptive evolution and genetic convergence. Here, we utilized 327 genomes from horses, sheep, goats, cattle, pigs and dogs living at both high and low altitudes, including 73 genomes generated for this study, to disentangle the genetic mechanisms underlying local adaptation of domestic mammals. Although molecular convergence is comparatively rare at the DNA sequence level, we found convergent signature of positive selection at the gene level, particularly EPAS1 gene in these Tibetan domestic mammals. We also reported a potential function in response to hypoxia for the gene C10orf67, which underwent positive selection in three of the domestic mammals. Our data provides insight into adaptive evolution of high-altitude domestic mammals, and should facilitate the search for additional novel genes involved in the hypoxia response pathway.

  • Enantioselective Assembly of Multi-Layer 3D Chirality
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-16
    Wu G, Liu Y, Yang Z, et al.

    The first enantioselective assembly of sandwich-shaped organo molecules has been achieved by conducting dual asymmetric Suzuki-Miyaura couplings and nine other reactions. This work also presents the first fully C-C anchored multi-layer 3D chirality with optically pure enantiomers. As confirmed by X-ray diffraction analysis that this chiral framework is featured by a unique C2-symmetry in which a nearly parallel fashion consisting of three layers: top, middle and bottom aromatic rings. Unlike the documented planar or axial chirality, the present chirality shows its top and bottom layers restrict each other from free rotation, i.e., this multi-layer 3D chirality would not exist if either top or bottom layer is removed. Nearly all multi-layered compounds showed strong luminescence of different colors under UV irradiation, and several randomly selected samples displayed aggregation-induced emission (AIE) properties. This work is believed to have broad impacts on chemical, medicinal and material sciences including optoelectronic materials in future.

  • Surface superconductivity in the type II Weyl semimetal TaIrTe4
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-16
    Xing Y, Shao Z, Ge J, et al.

    The search for unconventional superconductivity in Weyl semimetal materials is currently an exciting pursuit, since such superconducting phases could potentially be topologically nontrivial and host exotic Majorana modes. The layered material TaIrTe4 is a newly predicted time-reversal invariant type II Weyl semimetal with minimum number of Weyl points. Here, we report the discovery of surface superconductivity in Weyl semimetal TaIrTe4. Our scanning tunneling microscopy/spectroscopy (STM/S) visualizes Fermi arc surface states of TaIrTe4 that are consistent with the previous angle-resolved photoemission spectroscopy (ARPES) results. By a systematic study based on STS at ultralow temperature, we observe uniform superconducting gaps on the sample surface. The superconductivity is further confirmed by electrical transport measurements at ultralow temperature, with an onset transition temperature (Tc) up to 1.54 K being observed. The normalized upper critical field h*(T/Tc) behavior and the stability of the superconductivity against the ferromagnet indicate that the discovered superconductivity is unconventional with the p-wave pairing. The systematic STS, thickness and angular dependent transport measurements reveal that the detected superconductivity is quasi-one-dimensional (quasi-1D) and occurs in the surface states. The discovery of the surface superconductivity in TaIrTe4 provides a new novel platform to explore topological superconductivity and Majorana modes.

  • Two-dimensional Ferromagnetic Superlattices
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-16
    Liu S, Yang K, Liu W, et al.

    Mechanically-exfoliated two-dimensional ferromagnetic materials (2D FMs) were discovered to possess long-range ferromagnetic order and topologically nontrivial skyrmions in few-layers. However, owing to the dimensionality effect, such few-layer systems usually exhibit much lower Curie temperature (TC) compared to their bulk counterparts. It is therefore of great interest to explore effective approaches to enhance their TC, particularly in wafer-scale for practical applications. Here, we report an interfacial proximity-induced high-TC 2D FM Fe3GeTe2 (FGT) via A-type antiferromagnetic material CrSb (CS) which strongly couples to FGT. A superlattice structure of (FGT/CS)n, where n stands for the period of FGT/CS heterostructure, has been successfully produced with sharp interfaces by molecular-beam epitaxy on 2-inch wafers. By performing the elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally discovered that TC of 4-layer Fe3GeTe2 can be significantly enhanced from 140 K to 230 K because of the interfacial ferromagnetic coupling. In the meanwhile, an inverse proximity effect occurs in the FGT/CS interface, driving the interfacial antiferromagnetic CrSb into a ferrimagnetic state as evidenced by a double-switching behavior in hysteresis loops and the XMCD spectra. Density functional theory calculations show that the Fe-Te/Cr-Sb interface is strongly FM coupled and doping of the spin-polarized electrons by the interfacial Cr layer gives rise to the TC enhancement of the Fe3GeTe2 films, in accordance with our XMCD measurements. Strikingly, by introducing rich Fe in 4-layer FGT/CS superlattice, TC can be further enhanced to near room temperature. Our results provide a feasible approach in enhancing the magnetic order of few-layer 2D FMs in wafer-scale and render opportunities for realizing realistic ultra-thin spintronic devices.

  • Tianshanbeilu and the Isotopic Millet Road: reviewing the late Neolithic/Bronze Age radiation of human millet consumption from north China to Europe
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2017-02-24
    Wang T, Wei D, Chang X, et al.

    The westward expansion of human millet consumption from north China has important implications for understanding early interactions between the East and West. However, few studies have focused on the Xinjiang Uyghur Autonomous Region, the vast geographical area directly linking the ancient cultures of the Eurasian Steppe and the Gansu Corridor of China. In this study, we present the largest isotopic investigation of Bronze Age China (n = 110) on material from the key site of Tianshanbeilu, in eastern Xinjiang. The large range of δ13C values (–17.6‰ to –7.2‰; –15.5 ± 1.2‰) provides direct evidence of unique dietary diversity and consumption of significant C4 resources (millets). The high δ15N results (10.3‰ to 16.7‰; 14.7 ± 0.8‰) likely reflect sheep/goat and wild game consumption and the arid climate of the Taklamakan Desert. Radiocarbon dates from four individuals indicate Tianshanbeilu was in use between 1940 and 1215 cal bc. The Tianshanbeilu results are then analysed with respect to 52 Bronze Age sites from across Eurasia, to investigate the spread and chronology of significant human millet consumption and human migration. This isotopic survey finds novel evidence that the second millennium bc was a dynamic period, with significant dietary interconnectivity occurring between north China, Central Asia and Siberia. Further, we argue that this ‘Isotopic Millet Road’ extended all the way to the Mediterranean and Central Europe, and conclude that these C4 dietary signatures of millet consumption reflect early links (migration and/or resource transfer) between the Bronze Age inhabitants of modern-day China and Europe.

  • Evidence for diurnal periodicity of earthquakes from midnight to daybreak
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2018-10-08
    Hao J, Zhang J, Yao Z.

    Previously, inadequate earthquake catalogs and the lack of method made it challenging, if not impossible, to determine the dominant period of earthquake occurrence. With the advent of densely distributed seismic stations in Japan since 2002, 410 642 M1.0+ earthquakes have been cataloged under the mainland within 30-km depth, which provide a superb dataset to identify the periodicity of earthquakes. We processed this catalog using time-frequency analyses and daily stacking, which are powerful in extracting weak periodical signal from strong random noises. We concentrated on the time sector from 0:00 to 6:00 (i.e. from midnight to daybreak), which is a reliable time window for much higher detectability of weak earthquakes, since it has the lowest affects from cultural noises. We successfully observed two apparent periodicities of 12- and 24-hour, which are much smaller than the fortnightly periodicity presented previously in the literature. Synthetic earth tides, after intentionally ignoring the contribution from the Moon, present similar dominant periods as the earthquakes. This may indicate that the dominant period of earthquakes is statistically associated with the Sun rather than the Moon. The daily stacking number of earthquakes using a 15-minute or 1-hour interval shows a peak around 1:30, rather than usually expected 3:00 to 4:00. In addition, bigger earthquakes show more evident variations in the stacking results, and the trend is very consistent for various lower limits of earthquake magnitude from M1.0 to M4.0. These discoveries settled the disputes on the existence of the periodicity of earthquakes since 1886 and may open a window to unravel the mystery of earthquakes.

  • Applications of chemical imaging techniques in paleontology
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2018-10-10
    Pan Y, Hu L, Zhao T.

    Chemical imaging techniques, based on a combination of microscopy and spectroscopy, are designed to analyse the composition and spatial distribution of heterogeneous chemical complexes within a sample. Over the last few decades, it has become an increasingly popular tool for characterizing trace elements, isotopic information and organic biomarkers (molecular biosignatures) found in fossils. Here, we introduce the analytical principle of each technique and the interpretation of the chemical signals, followed by a review of the main applications of these techniques in paleontology. We also demonstrate that each technique is associated with pros and cons, and the current limitations and obstacles associated with the use of each specific technique should be taken into account before being applied to fossil samples. Finally, we propose that, due to the rapid advances in the available technology and overall trends towards more multi-disciplinary studies in paleontology, chemical imaging techniques can be expected to have broader applications in paleontology in the near future.

  • Totally homogeneous networks
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-04-09
    Shi D, Lü L, Chen G.

    In network science, the non-homogeneity of node degrees has been a concerning issue for study. Yet, with today's modern web technologies, the traditional social communication topologies have evolved from node-central structures into online cycle-based communities, urgently requiring new network theories and tools. Switching the focus from node degrees to network cycles could reveal many interesting properties from the perspective of totally homogenous networks or sub-networks in a complex network, especially basic simplexes (cliques) such as links and triangles. Clearly, compared with node degrees, it is much more challenging to deal with network cycles. For studying the latter, a new clique vector-space framework is introduced in this paper, where the vector space with a basis consisting of links has a dimension equal to the number of links, that with a basis consisting of triangles has the dimension equal to the number of triangles and so on. These two vector spaces are related through a boundary operator, for example mapping the boundary of a triangle in one space to the sum of three links in the other space. Under the new framework, some important concepts and methodologies from algebraic topology, such as characteristic number, homology group and Betti number, will play a part in network science leading to foreseeable new research directions. As immediate applications, the paper illustrates some important characteristics affecting the collective behaviors of complex networks, some new cycle-dependent importance indexes of nodes and implications for network synchronization and brain-network analysis.

  • Superior performance and high service stability for GeTe-based thermoelectric compounds
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-04-10
    Xing T, Song Q, Qiu P, et al.

    ABSTRACTGeTe-based compounds have been intensively studied recently due to their superior thermoelectric performance, but their real applications are still limited so far due to the drastic volume variation that occurs during the rhombohedral–cubic phase transition, which may break the material or the material/electrode interface during service. Here, superior performance and high service stability for GeTe-based thermoelectric compounds are achieved by co-doping Mg and Sb into GeTe. The linear coefficient of thermal expansion before phase transition is greatly improved to match that after phase transition, yielding smooth volume variation around the phase transition temperature. Likewise, co-doping (Mg, Sb) in GeTe successfully tunes the carrier concentration to the optimal range and effectively suppresses the lattice thermal conductivity. A peak zT of 1.84 at 800 K and an average zT of 1.2 in 300–800 K have been achieved in Ge0.85Mg0.05Sb0.1Te. Finally, a Ni/Ti/Ge0.85Mg0.05Sb0.1Te thermoelectric uni-leg is fabricated and tested, showing quite good service stability even after 450 thermal cycles between 473 K and 800 K. This study will accelerate the application of GeTe-based compounds for power generation in the mid-temperature range.

  • Scalable volumetric imaging for ultrahigh-speed brain mapping at synaptic resolution
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-04-24
    Wang H, Zhu Q, Ding L, et al.

    The speed of high-resolution optical imaging has been a rate-limiting factor for meso-scale mapping of brain structures and functional circuits, which is of fundamental importance for neuroscience research. Here, we describe a new microscopy method of Volumetric Imaging with Synchronized on-the-fly-scan and Readout (VISoR) for high-throughput, high-quality brain mapping. Combining synchronized scanning beam illumination and oblique imaging over cleared tissue sections in smooth motion, the VISoR system effectively eliminates motion blur to obtain undistorted images. By continuously imaging moving samples without stopping, the system achieves high-speed 3D image acquisition of an entire mouse brain within 1.5 hours, at a resolution capable of visualizing synaptic spines. A pipeline is developed for sample preparation, imaging, 3D image reconstruction and quantification. Our approach is compatible with immunofluorescence methods, enabling flexible cell-type specific brain mapping and is readily scalable for large biological samples such as primate brains. Using this system, we examined behaviorally relevant whole-brain neuronal activation in 16 c-Fos-shEGFP mice under resting or forced swimming conditions. Our results indicate the involvement of multiple subcortical areas in stress response. Intriguingly, neuronal activation in these areas exhibits striking individual variability among different animals, suggesting the necessity of sufficient cohort size for such studies.

  • Evolutionary transition between invertebrates and vertebrates via methylation reprogramming in embryogenesis
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-05-24
    Xu X, Li G, Li C, et al.

    ABSTRACTMajor evolutionary transitions are enigmas, and the most notable enigma is between invertebrates and vertebrates, with numerous spectacular innovations. To search for the molecular connections involved, we asked whether global epigenetic changes may offer a clue by surveying the inheritance and reprogramming of parental DNA methylation across metazoans. We focused on gametes and early embryos, where the methylomes are known to evolve divergently between fish and mammals. Here, we find that methylome reprogramming during embryogenesis occurs neither in pre-bilaterians such as cnidarians nor in protostomes such as insects, but clearly presents in deuterostomes such as echinoderms and invertebrate chordates, and then becomes more evident in vertebrates. Functional association analysis suggests that DNA methylation reprogramming is associated with development, reproduction and adaptive immunity for vertebrates, but not for invertebrates. Interestingly, the single HOX cluster of invertebrates maintains unmethylated status in all stages examined. In contrast, the multiple HOX clusters show dramatic dynamics of DNA methylation during vertebrate embryogenesis. Notably, the methylation dynamics of HOX clusters are associated with their spatiotemporal expression in mammals. Our study reveals that DNA methylation reprogramming has evolved dramatically during animal evolution, especially after the evolutionary transitions from invertebrates to vertebrates, and then to mammals.

  • What will robots be like in the future?
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-06-07
    Lu Y, Zhao W.

    Robots are changing our lives: sweeping robots patrol our living rooms; interactive robots accompany our children; industrial robots assemble vehicles; rescue robots search and save lives in catastrophes; medical robots perform surgeries in hospitals. To better understand robots' challenges and impact, National Science Review (NSR) interviewed Professor Toshio Fukuda, who is one of the world’s most representative robotics experts and has developed a number of bionic robots and micro/nano-robots.

  • Neolithic millet farmers contributed to the permanent settlement of the Tibetan Plateau by adopting barley agriculture
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-06-21
    Li Y, Tian J, Liu F, et al.

    ABSTRACTThe permanent human settlement of the Tibetan Plateau (TP) has been suggested to have been facilitated by the introduction of barley agriculture ∼3.6 kilo-years ago (ka). However, how barley agriculture spread onto the TP remains unknown. Given that the lower altitudes in the northeastern TP were occupied by millet cultivators from 5.2 ka, who also adopted barley farming ∼4 ka, it is highly possible that it was millet farmers who brought barley agriculture onto the TP ∼3.6 ka. To test this hypothesis, we analyzed mitochondrial DNA (mtDNA) from 8277 Tibetans and 58 514 individuals from surrounding populations, including 682 newly sequenced whole mitogenomes. Multiple lines of evidence, together with radiocarbon dating of cereal remains at different elevations, supports the scenario that two haplogroups (M9a1a1c1b1a and A11a1a), which are common in contemporary Tibetans (20.9%) and were probably even more common (40–50%) in early Tibetans prior to historical immigrations to the TP, represent the genetic legacy of the Neolithic millet farmers. Both haplogroups originated in northern China between 10.0–6.0 ka and differentiated in the ancestors of modern Tibetans ∼5.2–4.0 ka, matching the dispersal history of millet farming. By showing that substantial genetic components in contemporary Tibetans can trace their ancestry back to the Neolithic millet farmers, our study reveals that millet farmers adopted and brought barley agriculture to the TP ∼3.6–3.3 ka, and made an important contribution to the Tibetan gene pool.

  • Aging amorphous/crystalline heterophase PdCu nanosheets for catalytic reactions
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-07-05
    Cheng H, Yang N, Liu X, et al.

    ABSTRACTPhase engineering is arising as an attractive strategy to tune the properties and functionalities of nanomaterials. In particular, amorphous/crystalline heterophase nanostructures have exhibited some intriguing properties. Herein, the one-pot wet-chemical synthesis of two types of amorphous/crystalline heterophase PdCu nanosheets is reported, in which one is amorphous phase-dominant and the other one is crystalline phase-dominant. Then the aging process of the synthesized PdCu nanosheets is studied, during which their crystallinity increases, accompanied by changes in some physicochemical properties. As a proof-of-concept application, their aging effect on catalytic hydrogenation of 4-nitrostyrene is investigated. As a result, the amorphous phase-dominant nanosheets initially show excellent chemoselectivity. After aging for 14 days, their catalytic activity is higher than that of crystalline phase-dominant nanosheets. This work demonstrates the intriguing properties of heterophase nanostructures, providing a new platform for future studies on the regulation of functionalities and applications of nanomaterials by phase engineering.

  • A question of balance: weighing the options for controlling ammonia, sulfur dioxide and nitrogen oxides
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-07-16
    Ravishankara A.

    Acid precipitation, climate change and deteriorating air quality are some of the major environmental concerns of today, all caused by anthropogenic emissions of sulfur dioxide (SO2), carbon dioxide (CO2), hydrocarbons, nitrous oxide (N2O), nitrogen oxides (NOx), mercury and others. Societies have designed coping strategies by reducing specific emissions, depending on the environmental concerns of the times. The regulatory and management approaches for the different environmental issues have been formulated at different times. For example, acid precipitation was addressed as an environmental problem well before the anthropogenic climate change. In some countries, air-quality deterioration has been identified as an urgent problem only recently. Because of these reasons, there is incoherence in regulatory strategies and policies.

  • Measuring the Meissner effect at megabar pressures
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-07-17
    Semenok D, Oganov A.

    Since 2014, when the research group of Professor Tian Cui (Jilin University) predicted [1] (and experiments [2] confirmed) the existence of an unusual high-pressure compound, H3S, with superconductivity at 191–204 K, a new era in studies of superconductivity began. In 2019, a new record of high-temperature superconductivity was set, with LaH10 experimentally proven to be a superconductor with a nearly room-Tc of 250–260 K [3,4]. H3S and LaH10 cannot be used in practical applications, because they exist only at megabar pressures, but their study may hint at which compounds can be room-temperature superconductors at normal pressure. The unusually high electron–phonon coupling constants (λ > 2) of these materials also make them interesting from the physical point of view.

  • Bio-inspired untethered fully soft robots in liquid actuated by induced energy gradients
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-07-11
    Lyu L, Li F, Wu K, et al.

    Soft robotics with new designs, fabrication technologies and control strategies inspired by nature have been totally changing our view on robotics. To fully exploit their potential in practical applications, untethered designs are preferred in implementation. However, hindered by the limited thermal/mechanical performance of soft materials, it has been always challenging for researchers to implement untethered solutions, which generally involve rigid forms of high energy-density power sources or high energy-density processes. A number of insects in nature, such as rove beetles, can gain a burst of kinetic energy from the induced surface-energy gradient on water to return to their familiar habitats, which is generally known as Marangoni propulsion. Inspired by such a behavior, we report the agile untethered mobility of a fully soft robot in liquid based on induced energy gradients and also develop corresponding fabrication and maneuvering strategies. The robot can reach a speed of 5.5 body lengths per second, which is 7-fold more than the best reported, 0.69 (body length per second), in the previous work on untethered soft robots in liquid by far. Further controlling the robots, we demonstrate a soft-robot swarm that can approach a target simultaneously to assure a hit with high accuracy. Without employing any high energy-density power sources or processes, our robot exhibits many attractive merits, such as quietness, no mechanical wear, no thermal fatigue, invisibility and ease of robot fabrication, which may potentially impact many fields in the future.

  • A forum on innovative fusion approaches: will there be a SpaceX for fusion energy?
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-07-22
    Zhao W.

    Among all the clean-energy approaches, fusion energy is generally considered to be the best option: fusion fuels such as deuterium (D) can be extracted from sea water while lithium for breeding tritium (T) is an abundant mineral and almost infinite in reserve; the fusion reaction is completely carbon-emission-free and generates no waste except for a small and manageable amount of radioactivity; fusion power plants are failsafe, free of potential nuclear disasters. However, fusion reaction occurs at extremely high temperature and pressure, so it is not easy to reach the ignition point and to have a container that confines the reaction. People have been pursuing fusion energy for more than six decades, but no fusion power plants have been built.

  • Physical modeling and validation of porpoises’ directional emission via hybrid metamaterials
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-07-22
    Dong E, Zhang Y, Song Z, et al.

    ABSTRACTIn wave physics and engineering, directional emission sets a fundamental limitation on conventional simple sources as their sizes should be sufficiently larger than their wavelength. Artificial metamaterial and animal biosonar both show potential in overcoming this limitation. Existing metamaterials arranged in periodic microstructures face great challenges in realizing complex and multiphase biosonar structures. Here, we proposed a physical directional emission model to bridge the gap between porpoises’ biosonar and artificial metamaterial. Inspired by the anatomical and physical properties of the porpoise's biosonar transmission system, we fabricated a hybrid metamaterial system composed of multiple composite structures. We validated that the hybrid metamaterial significantly increased directivity and main lobe energy over a broad bandwidth both numerically and experimentally. The device displayed efficiency in detecting underwater target and suppressing false target jamming. The metamaterial-based physical model may be helpful to achieve the physical mechanisms of porpoise biosonar detection and has diverse applications in underwater acoustic sensing, ultrasound scanning, and medical ultrasonography.

  • Intermingled fates of the South China Sea and Philippine Sea plate
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-07-31
    Zhao M, Sibuet J, Wu J.

    Recent studies have shown the extent and nature of the South China Sea (SCS) at the end of spreading by unfolding (i.e. structurally restoring) the Manila slab, which is the subducted part of the SCS, and by identifying the nature of the crust-lithosphere (oceanic or thinned continental) from mid-slab P-wave velocity perturbations (dVp) [1,2]. The objective of this paper is to propose a reconstruction of the SCS at the end of seafloor spreading and to discuss its geodynamic consequences in the context of the SCS and Philippine Sea plate (PSP) evolution. Reasonably accurate PSP paleo-latitudes and poorly defined paleo-declinations were primarily used to establish the kinematic evolution of the PSP through time (e.g. [3,4]) until 2016, when Wu et al. [1] introduced new kinematic constraints based on the unfolding and restoration of Southeast Asian slabs. Here, we propose to better constrain the relationship between the SCS, the Huatung basin (HB) and the PSP. Our main target is to bring new light on the challenging problem of SCS subduction initiation along a major shear-plate boundary. For that, we build on the new kinematic constraints provided by Wu et al. [1] and consider that the HB was not formed during Tertiary (e.g. [5,6]), but during the early Cretaceous (e.g. [7]).

  • New insights into marine basin opening
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-08-05
    Wang P.

    Break-up of continental lithosphere and opening of marine basins are one of the fundamental issues in geology, known as passive margin geodynamics. Its significance goes far beyond the academic interest as passive margin basins host nearly two-thirds of the discovered hydrocarbons worldwide. Our knowledge of the geodynamic evolution of passive margin originated largely from the northern Atlantic, resulting from multiple expeditions of international ocean drilling in the 1980s and 1990s. As a standard hypothesis of rifting and rupturing, the Atlantic model of passive margin has been applied widely to paleo- and modern basins from the Alps to Pacific; yet, its universal applicability needs to be tested by drilling in other basins, as recently done in the northern South China Sea (SCS).

  • Immobilization of functional nano-objects in living engineered bacterial biofilms for catalytic applications
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-07-30
    Wang X, Pu J, Liu Y, et al.

    Nanoscale objects feature very large surface-area-to-volume ratios and are now understood as powerful tools for catalysis, but their nature as nanomaterials brings challenges including toxicity and nanomaterial pollution. Immobilization is considered a feasible strategy for addressing these limitations. Here, as a proof-of-concept for the immobilization of nanoscale catalysts in the extracellular matrix of bacterial biofilms, we genetically engineered amyloid monomers of the Escherichia coli curli nanofiber system that are secreted and can self-assemble and anchor nano-objects in a spatially precise manner. We demonstrated three scalable, tunable and reusable catalysis systems: biofilm-anchored gold nanoparticles to reduce nitro aromatic compounds such as the pollutant p-nitrophenol, biofilm-anchored hybrid Cd0.9Zn0.1S quantum dots and gold nanoparticles to degrade organic dyes and biofilm-anchored CdSeS@ZnS quantum dots in a semi-artificial photosynthesis system for hydrogen production. Our work demonstrates how the ability of biofilms to grow in scalable and complex spatial arrangements can be exploited for catalytic applications and clearly illustrates the design utility of segregating high-energy nano-objects from injury-prone cellular components by engineering anchoring points in an extracellular matrix.

  • Potential role of strike-slip faults in opening up the South China Sea
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-08-20
    Huang C, Wang P, Yu M, et al.

    Radiometric dates of key rock units indicate that a remnant Late Mesozoic ocean of the Huatung Basin is still preserved today east of the South China Sea (SCS). We integrate regional geology with a Cretaceous oceanic basement in the vicinity of the Huatung Basin to reconstruct the Huatung Plate east of the Eurasian continent. Results of geophysical investigations, four expeditions of deep-sea drilling and a renaissance of regional geology allow us to propose a hypothesis that the mechanism responsible for the SCS opening was raised from strike-slip fault on the east. The hypothesis suggests that the SCS opening could highly relate to the strike-slip faults inherited from Late Mesozoic structures onshore–offshore the SE Cathaysia Block to develop rhombic-shaped extensional basins en echelon on the thinned Eurasian continental crust in the Early Cenozoic. It was followed by sinistral strike-slip movements along the boundary between the Eurasian Plate and the Huatung Plate driven by oblique subduction of the Huatung Plate to the northwest coupled with slab-pull force by southward subduction of the Proto-SCS to open up the triangle-shaped oceanic East Sub-basin in the Early Oligocene (33/34 Ma). The spreading ridge then propagated southwestward in the step-over segment between the Zhongnan-Lile and the Red River strike-slip fault systems to open the triangle-shaped oceanic Southwest Sub-basin by 23 Ma. The plate boundary fault was subsequently converted into the Manila Trench when the Eocene Sierra Madre arc of the Huatung Plate had moved from the south to its present latitude by the Middle Miocene.

  • Log-periodic quantum magneto-oscillations and discrete-scale invariance in topological material HfTe5
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-08-06
    Wang H, Liu Y, Liu Y, et al.

    Discrete-scale invariance (DSI) is a phenomenon featuring intriguing log-periodicity that can be rarely observed in quantum systems. Here, we report the log-periodic quantum oscillations in the longitudinal magnetoresistivity (ρxx) and the Hall traces (ρyx) of HfTe5 crystals, which reveal the DSI in the transport-coefficients matrix. The oscillations in ρxx and ρyx show the consistent logB-periodicity with a phase shift. The finding of the logB oscillations in the Hall resistance supports the physical mechanism as a general quantum effect originating from the resonant scattering. Combined with theoretical simulations, we further clarify the origin of the log-periodic oscillations and the DSI in the topological materials. This work evidences the universality of the DSI in the Dirac materials and provides indispensable information for a full understanding of this novel phenomenon.

  • Long march for healthy research ecology
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-09-25
    Yang W.

    In recent years, the research community in China has launched five campaigns against research misconduct. The first one started at the turn of this century and enabled whistleblowers to flag fabrication, falsification and plagiarism violations during promotions and in talent reviews. Investigations would proceed when the allegation contained verifiable details. Clear signals were sent to researchers, who took the chance of ‘not getting caught’. The second campaign started around 2005 and sought to eliminate duplicate submissions for publication in a different language. In 2007, the Chinese Medical Association established the rule of no duplicate publication in a different language. The copyright law in China also was revised. The third campaign involved the engagement of similarity checks for dissertations, grants and journal submissions. Universities began to perform a full check on all theses submitted for degrees. The National Natural Science Foundation of China installed similarity check software in their system for all submitted grant proposals. All similarities were classified according to their severity and earmarked during the subsequent peer reviews.

  • The South China Sea is not a mini-Atlantic: plate-edge rifting vs intra-plate rifting
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-09-12
    Wang P, Huang C, Lin J, et al.

    The South China Sea, as ‘a non-volcanic passive margin basin’ in the Pacific, has often been considered as a small-scale analogue of the Atlantic. The recent ocean drilling in the northern South China Sea margin found, however, that the Iberian model of non-volcanic rifted margin from the Atlantic does not apply to the South China Sea. In this paper, we review a variety of rifted basins and propose to discriminate two types of rifting basins: plate-edge type such as the South China Sea and intra-plate type like the Atlantic. They not only differ from each other in structure, formation process, lifespan and geographic size, but also occur at different stages of the Wilson cycle. The intra-plate rifting occurred in the Mesozoic and gave rise to large oceans, whereas the plate-edge rifting took place mainly in the mid-Cenozoic, with three-quarters of the basins concentrated in the Western Pacific. As a member of the Western Pacific system of marginal seas, the South China Sea should be studied not in isolation on its origin and evolution, but in a systematic context to include also its neighboring counterparts.

  • 17% efficiency organic photovoltaic cell with superior processability
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-05
    Cui Y, Yao H, Hong L, et al.

    The development of organic photoactive materials, especially the new-emerging non-fullerene electron acceptors (NFAs), has enabled rapid progress in organic photovoltaic (OPV) cells in recent years. Although the power conversion efficiencies (PCEs) of the top-performance OPV cells have surpassed 16%, the devices are usually fabricated via a spin-coating method and are not suitable for large-area production. Here, we demonstrate that the fine-modification of the flexible side chains of NFAs can yield 17% PCE for OPV cells. More crucially, as the optimal NFA has a suitable solubility and thus a desirable morphology, the high efficiencies of spin-coated devices can be maintained when using the scalable blade-coating processing technology. Our results suggest that the optimization of the chemical structures of the OPV materials can improve the device performance. This has great significance in larger-area production technologies that provide important scientific insights for the commercialization of OPV cells.

  • A green, efficient and precise hydrogen therapy of cancer based on in-vivo electrochemistry
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-05
    Qi G, Wang B, Song X, et al.

    By combined use of traditional Chinese acupuncture Fe needle electrode and in-vivo electrochemistry, we achieve in-vivo H2 generation in tumors in a controllable manner and exploited it for effective and green therapy of tumor for the first time. The cathodic acupuncture electrodes working under the applied voltage of ~ 3 volt (with minimal damage to the living body) undergo effectively electrochemical reactions in the acidic tumor area to produce sufficient H2 locally, causing cancer cells to burst and die. Due to puncture positioning, acidic tumor microenvironment and gas diffusion effect, the developed H2 generation electrochemotherapy (H2-ECT) strategy enables precise and large-scale tumor therapy, as demonstrated by in vivo treatment of diseased mice (glioma and breast cancers). Such green H2-ECT is simple, highly efficient and minimally invasive, requiring no expensive medical equipment or (nano)materials and medication, and is therefore very promising for potential clinic applications.

  • Large dipole moment induced efficient bismuth chromate photocatalysts for wide-spectrum driven water oxidation and complete mineralization of pollutants
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-12-02
    Chen X, Xu Y, Ma X, et al.

    Herein, a wide-spectrum (~678 nm) responsive Bi8(CrO4)O11 photocatalyst with a theoretical solar spectrum efficiency of 42.0% was successfully constructed. Bi8(CrO4)O11 showed highly efficient and stable photocatalytic water oxidation activity with a notable apparent quantum efficiency of 2.87% (420 nm), superior to many reported wide-spectrum driven photocatalysts. Most remarkably, its strong oxidation ability also enables the simultaneous degradation and complete mineralization for phenol, and its excellent performance is about 23.0 and 2.9 times higher than CdS and P25-TiO2, respectively. And its high activity ascribes to the giant internal electric field induced by its large crystal dipole, which accelerates the rapid separation of photogenerated electron-hole pairs. Briefly, the discovery of wide-spectrum bismuth chromate and the mechanism of exponentially enhanced photocatalytic performance by increasing crystal dipole throw light on improving solar energy conversion.

  • Single-atom Sn-Zn Pairs in CuO Catalyst Promote Dimethyldichlorosilane Synthesis
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-28
    Shi Q, Ji Y, Chen W, et al.

    Single-atom catalysts (SACs) are of great interest because they can maximize the atom-utilization efficiency and generate unique catalytic properties; however, much attention has paid to single-site active components, rarely to catalyst promoters. Promoters can significantly affect the activity and selectivity of a catalyst, even at their low concentrations in catalysts. In this work, we designed and synthesized CuO catalysts with atomically dispersed co-promoters of Sn and Zn. When used as the catalyst in the Rochow reaction for the synthesis of dimethyldichlorosilane, this catalyst exhibited much-enhanced activity, selectivity, and stability as compared with the conventional CuO catalysts with promoters in the form of nanoparticles. Density functional theory calculations demonstrate that single-atomic Sn substitution in CuO surface can enrich surface Cu vacancies and promote dispersion of Zn to its atomic levels. The obtained both Sn and Zn single-sites as the co-promoters cooperatively generate electronic interaction with the CuO support, which further facilitates the adsorption of the reactant molecules on the surface, thereby leading to the superior catalytic performance.

  • Information Theory of Metasurfaces
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-27
    Wu H, Bai G, Liu S, et al.

    We propose a theory to characterize the information and information processing abilities of metasurfaces, and demonstrate the relation between the information of metasurface and its radiation pattern in the far-field region. By incorporating a general aperture model with uncertainty relation in L2-space, we propose a theory to predict the upper bound of information contained in the radiation pattern of a metasurface, and reveal the theoretical upper limit of orthogonal radiation states that can be realized. The proposed theory also provides guidance for inverse design of the metasurface with respect to given functionalities. Through investigating the information of disordered-phase modulated metasurfaces, we find the information invariance (1-γ) of chaotic radiation patterns. That is to say, the information of the disordered-phase modulated radiation patterns is always equal to 1-γ (γ is the Euler’s constant), no matter how the size, the number of elements, and the phase pattern of metasurface vary. This value might be the lower bound of radiation-pattern information of the metasurface, which can provide theoretical limit for information modulation applications, including computational imaging, stealth technologies and wireless communications.

  • Experimental measurement of the quantum geometric tensor using coupled qubits in diamond
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-27
    Yu M, Yang P, Gong M, et al.

    Geometry and topology are fundamental concepts, which underlie a wide range of fascinating physical phenomena such as topological states of matter and topological defects. In quantum mechanics, the geometry of quantum states is fully captured by the quantum geometric tensor. Using a qubit formed by an NV center in diamond, we perform the first experimental measurement of the complete quantum geometric tensor. Our approach builds on a strong connection between coherent Rabi oscillations upon parametric modulations and the quantum geometry of the underlying states. We then apply our method to a system of two interacting qubits, by exploiting the coupling between the NV center spin and a neighboring 13C nuclear spin. Our results establish coherent dynamical responses as a versatile probe for quantum geometry, and they pave the way for the detection of novel topological phenomena in solid state.

  • A Stage-Specific Cell Manipulation Platform for On-demand Inducing Endothelialization
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-21
    Zhao Q, Wang J, Wang Y, et al.

    Endothelialization is of great significance for vascular remodeling, as well as for the success of implanted vascular grafts/stents in cardiovascular disease treatment. However, desirable endothelialization on synthetic biomaterials remains greatly challenging owing to extreme difficulty in offering dynamic guidance on endothelial cell (EC) functions resembling the native extracellular matrix (ECM)-mediated effects. Here, we demonstrate a bilayer platform with near infrared (NIR)-triggered transformable topographies, which can alter the geometries and functions of human ECs by tunable topographical cues in a remote-controlled manner, yet bring no damage on cell viability. The migration and the adhesion/spreading of human ECs are respectively promoted by the temporary anisotropic and permanent isotropic topographies of the platform in turn, which appropriately meet the requirements of stage-specific EC manipulation for endothelialization. In addition to the potential of promoting the development of new generation of vascular grafts/stents enabling rapid endothelialization, this stage-specific cell manipulation platform also holds promise in various biomedical fields since the needs of stepwise control over different cell functions are common in wound healing and various tissue regeneration processes.

  • A General End-to-end Diagnosis Framework for Manufacturing Systems
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-21
    Yuan Y, Ma G, Cheng C, et al.

    The manufacturing sector is envisioned to be heavily influenced by artificial intelligence-based technologies with the extraordinary increases in computational power and data volumes [1,2]. A central challenge in manufacturing sector lies in the requirement of a general framework to ensure satisfied diagnosis and monitoring performances in different manufacturing applications. Here we propose a general data-driven, end-to-end framework for the monitoring of manufacturing systems. This framework, derived from deep learning techniques, evaluates fused sensory measurements to detect and even predict faults and wearing conditions. This work exploits the predictive power of deep learning to automatically extract hidden degradation features from noisy, time-course data. We have experimented the proposed framework on ten representative data sets drawn from a wide variety of manufacturing applications. Results reveal that the framework performs well in examined benchmark applications and can be applied in diverse contexts, indicating its potential use as a critical corner stone in smart manufacturing.

  • Attribution of the Tibetan Plateau to Northern Drought
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-21
    Liu Y, Li Y, Huang J, et al.

    The Tibetan Plateau (TP), which is located in Asia and has an average elevation of over 4000 m, acts as a raised source of heat and an isolated region of humidity in the atmosphere. Previous studies have found that the eastward outflow of water vapor and clouds away from the TP contributes significantly to precipitation over downstream regions. However, the dynamic mechanism behind these observations is still unclear. Here, we propose a dynamic mechanism of the northern drought attributable to the TP in summer. The TP, similar to a very large engine, drives the nearby movement of water vapor, clouds, and aerosols. This “strengthening effect” controls precipitation near the TP and can trigger flooding or droughts in downstream regions. The northern drought is driven by the collocation of the subtropical westerly jet (SWJ) position and the TP strengthening effect. The meridional shift in the SWJ is the determining factor of the northern drought in summer. When the SWJ shifts northward, the upper-level westerly wind is weakened; thus, the water vapor, clouds or dusty clouds over the TP are transported to north less often, reducing precipitation and causing more frequent droughts. In contrast, when the SWJ shifts southward, the northern area of China experiences increased precipitation in summer. A new index established according to above dynamic mechanism can be used to improve the predictability of precipitation over the northern area and decadal climate prediction over the same area under a warming climate background.

  • Double-frequency Aharonov-Bohm effect and non-Abelian braiding properties of Jackiw-Rebbi zero-mode
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-22
    Wu Y, Liu H, Liu J, et al.

    Ever since its first proposal in 1976, Jackiw-Rebbi zero-mode has been drawing extensive attention for its charming properties including charge fractionalization, topologically protected zero-energy and possible non-Abelian statistics. We investigate these properties through the Jackiw-Rebbi zero-modes in quantum spin Hall insulators. Though charge fractionalization is not manifested, Jackiw-Rebbi zero-mode’s zero-energy nature leads to a double-frequency Aharonov-Bohm effect, implying that it can be viewed as a special case of Majorana zero-mode without particle-hole symmetry. Such relation is strengthened for Jackiw-Rebbi zero-modes also exhibiting non-Abelian properties in the absence of superconductivity. Furthermore, in the condition that the degeneracy of Jackiw-Rebbi zero-modes is lifted , we demonstrate a novel non-Abelian braiding with continuously tunable fusion rule, which is a generalization of Majorana zero-modes’ braiding properties.

  • Stomatocyte structural color barcode micromotors for multiplex assays
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-21
    Cai L, Wang H, Yu Y, et al.

    Artificial micromotors have a demonstrated value in biomedical area. Attempts to develop this technology tend to impart micromotors novel functions to improve the values. Herein, we present novel structural color barcode micromotors for the multiplex assays. We found that by rapid extracting solvent and assembling monodispersed nanoparticles in droplets, it could form stomatocyte colloidal crystal clusters, which not only showed striking structural colors and characteristic reflection peaks due to their ordered nanoparticles arrangement, but also provided effective cavities for the integration of functional elements. Thus, the micromotors with catalyst or magnetic elements in their cavities, as well as with corresponding structural color coding, could be achieved by using the platinum and ferric oxide dispersed pre-gel to fill and duplicate the stomatocyte colloidal crystal clusters. We have demonstrated that the self-movement of these structural color barcode micromotors could efficiently accelerate the mixing speed of the detection sample and greatly increase the probe-target interactions towards faster and more sensitive single or multiplex detection, and the magnetism of these barcode micromotors enables the flexible collection of the micromotors, which could facilitate the detection processes. These features make the stomatocyte structural color barcode micromotors ideal for biomedical applications.

  • Sin1-mediated mTOR Signaling in Cell Growth, Metabolism and Immune Response
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-19
    Ruan C, Ouyang X, Liu H, et al.

    The mammalian target of rapamycin (mTOR) is an evolutionarily conserved Ser/Thr protein kinase with essential cellular function via processing various extracellular and intracellular inputs. Two distinct multi-protein mTOR complexes (mTORC), mTORC1 and mTORC2, have been identified and well characterized in eukaryotic cells from yeast to human. Sin1, stands for Sty1/Spc1-interacting protein1, also known as mitogen-activated protein kinase (MAPK) associated protein (MAPKAP)1, is an evolutionarily conserved adaptor protein. Mammalian Sin1 interacts with many cellular proteins but it has been widely studied as an essential component of mTORC2, and it is crucial not only for the assemble of mTORC2 but also for the regulation of its substrate specificity. In this review, we summarize our current knowledge of the structure and functions of Sin1, focusing specifically on its protein interaction network and its roles in the mTOR pathway that could account for various cellular functions of mTOR in growth, metabolism, immunity, and cancer.

  • Olivine-norite rock detected by the lunar rover Yutu-2 likely crystallized from the SPA impact melt pool
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-14
    Lin H, He Z, Yang W, et al.

    Chang’E-4 landed in the South Pole-Aitken (SPA) Basin, providing a unique chance to probe the composition of the lunar interior. Its landing site is located on ejecta strips in Von Kármán crater that possibly originate from the neighboring Finsen crater. A surface rock and the lunar regolith at 10 sites along the rover Yutu-2 track were measured by the onboard Visible and Near-Infrared Imaging Spectrometer in the first three lunar days of mission operations. In-situ spectra of the regolith have peak band positions at 1 and 2 μm, similar to the spectral data of Finsen ejecta from the Moon Mineralogy Mapper, which confirms that the regolith’s composition of the landing area is mostly similar to that of Finsen ejecta. The rock spectrum shows similar band peak positions, but stronger absorptions, suggesting relatively fresh exposure. The rock may consist 38.1 ± 5.4% low-Ca pyroxene, 13.9 ± 5.1% olivine and 48.0 ± 3.1% plagioclase, referred to as olivine-norite. The plagioclase-abundant and olivine-poor modal composition of the rock is inconsistent with the origin of the mantle, but representative of the lunar lower crust. Alternatively, the rock crystallized from the impact-derived melt pool formed by the SPA impact event via mixing the lunar crust and mantle materials. This scenario is consistent with fast cooling thermal conditions of a shallow melt pool, indicated by the fine- to medium-sized texture (<3 mm) of the rock, and the SPA impact melting model [1].

  • Algorithm-improved high speed and non-invasive confocal Raman imaging of two-dimensional materials
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-13
    Nair S, Gao J, Yao Q, et al.

    Confocal Raman microscopy is important for characterizing two dimensional (2D) materials, but its low throughput significantly hinders its applications. For metastable materials such as graphene oxide (GO), the low throughput is aggravated by the requirement of extremely low laser dose to avoid sample damage. Here we introduce algorithm-improved Confocal Raman Microscopy (ai-CRM), which increases the Raman scanning rate by one to two orders of magnitude with respect to state-of-the-art works for a variety of 2D materials. Meanwhile, GO can be imaged at a laser dose that is 2 to 3 orders of magnitude lower than previously reported, such that laser-induced variations of the material properties can be avoided. ai-CRM also enables fast and spatially resolved quantitative analysis, and is readily extended to three-dimensional mapping of composite materials. Since ai-CRM is based on general mathematical principles, it is cost-effective, facile-to-implement and universally applicable to other hyperspectral imaging methods.

  • Functional Requirement of Terminal Inverted Repeats for Efficient ProtoRAG Activity Reveals the Early Evolution of V(D)J Recombination
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-13
    Tao X, Yuan S, Chen F, et al.

    The discovery of ProtoRAG in amphioxus indicated that vertebrate RAG recombinases originated from an ancient transposon. However, the sequences of ProtoRAG TIRs were obviously dissimilar to the consensus sequence of mouse 12/23RSS, and recombination mediated by ProtoRAG or RAG made them incompatible with each other. Thus, it is difficult to determine whether or how 12/23RSS persisted in the vertebrate RAG system that evolved from the TIRs of ancient RAG transposons. Here, we found that the activity of ProtoRAG is highly dependent on its asymmetric 5’TIR and 3’TIR, which are composed of conserved TR1 and TR5 elements and a partially conserved TRsp element of 27/31 bp to separate them. Similar to the requirements for the RSSs of RAG recombinase, the first CAC in TR1, the three dinucleotides in TR5 and the specific length of the partially conserved TRsp are important for the efficient recombination activity of ProtoRAG. In addition, the homologous sequences flanking the signal sequences facilitate ProtoRAG- but not RAG-mediated recombination. In addition to the diverged TIRs, two differentiated functional domains in BbRAG1L were defined to coordinate with the divergence between TIRs and RSSs. One of these is the CTT* domain, which facilitates the specific TIR recognition of the BbRAGL complex, and the other is NBD*, which is responsible for DNA binding and the protein stabilization of the BbRAGL complex. Thus, our findings reveal that the functional requirement for ProtoRAG TIRs is similar to that for RSS in RAG-mediated recombination, which not only supports the common origin of ProtoRAG TIRs and RSSs from the asymmetric TIRs of ancient RAG transposons but also reveals the development of RAG and RAG-like machineries during chordate evolution.

  • Dynamics and manipulation of ferroelectric domain walls in bismuth ferrite thin films
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-08
    Xiao S, Jin Y, Lu X, et al.

    Ferroelectric domain walls differ from domains not only in crystalline and discrete symmetry, but also in electronic, magnetic, and mechanical properties. Although domain wall provides a degree of freedom to regulate the physical properties at nanoscale, the relatively less controllability holds off its practical applications in nano-devices. In this work, with the advantages of 3D domain configuration detection based on piezoresponse force microscopy, we find that the mobility of three types of domain walls [tail-to-tail, head-to-tail, head-to-head] in (001) BiFeO3 films varies with the applied electrical field. Under low voltages, head-to-tail domain walls are more mobile than other domain walls, while under high voltages, tail-to-tail domain walls become rather active and possess relatively long average length. This is due to the high nucleation energy and relative low growth energy for charged domain walls. Finally, we demonstrate the manipulation of domain walls through successive electric writings, which result in well-aligned conduction path as designed, paving the way for their application in advanced spintronic, memory and communication nano-devices.

  • Encapsulating metal organic framework into hollow mesoporous carbon sphere as efficient oxygen bifunctional electrocatalyst
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-11
    Xiong W, Li H, You H, et al.

    Applying metal organic frameworks (MOFs) in electrochemical systems is a currently emerging field owning to the rich metal nodes and high specific surface area of MOFs. However, the problems for MOFs that need to be solved urgently are poor electrical conductivity and low ion transport. Herein, we present a facile in-situ growth method for the rational synthesis of MOFs@hollow mesoporous carbon spheres (HMCS) yolk-shell structured hybrid material for the first time. The size of the encapsulated ZIF-67 is well controlled to 100 nm due to the spatial confinement effect of HMCS and electrical conductivity of ZIF-67 is also increased significantly. The obtained ZIF@HMCS-25% hybrid material exhibits a highly efficient ORR activity with 0.823 V (vs. RHE) half-wave potential and even a higher kinetic current density (Jk = 13.8 mA cm−2) than commercial Pt/C. ZIF@HMCS-25% also displays excellent OER performance and the overpotential of ZIF@HMCS-25% at 10 mA cm-2 is 407 mV. In addition, ZIF@HMCS-25% is further employed as an air electrode for a rechargeable Zn-air battery, exhibiting a high power density (120.2 mW cm-2 at 171.4 mA cm-2) and long-term charge/discharge stability (80 h at 5 mA cm-2). Such MOFs@HMCS yolk-shell design provides a versatile method for the application of MOFs as electrocatalysts directly.

  • Voltage Induced Penetration Effect in Liquid Metals at Room Temperature
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-05
    Yun F, Yu Z, He Y, et al.

    Room temperature liquid metal is discovered to be capable of penetrating through macro- and microporous materials by applying a voltage. The liquid metal penetration effects are demonstrated in various porous materials such as tissue paper, thick and fine sponges, fabrics, and meshes. The underlying mechanism is that the high surface tension of liquid metal can be significantly reduced to near-zero due to the voltage induced oxidation of the liquid metal surface in a solution. It is the extremely low surface tension and gravity that cause the liquid metal to superwet the solid surface, leading to the penetration phenomena. These findings offer new opportunities for novel microfluidic applications and could promote further discovery of more exotic fluid states of liquid metals.

  • Hierarchically porous metal–organic frameworks: synthetic strategies and applications
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-05
    Feng L, Wang K, Lv X, et al.

    Despite numerous advantages, applications of conventional microporous MOFs are hampered by their limited pore sizes, such as in heterogeneous catalysis and guest delivery which usually involves large molecules. Construction of hierarchically porous metal–organic frameworks (HP-MOFs) is vital to achieve the controllable augmentation of MOF pore size to mesopores or even macropores, which can enhance the diffusion kinetics of guests and improve the storage capacity. This review article focuses on recent methodology advances of HP-MOF synthesis, covering preparation of HP-MOFs with intrinsic hierarchical pores, and modulated, templated and template-free synthetic strategies for HP-MOFs. The key factors which affect the formation of HP-MOF architectures are summarized and discussed, which is followed by a brief review of their applications in heterogeneous catalysis and guest encapsulation. Overall, this review shall present a roadmap that guides the future design and development of HP-MOF materials with molecular precision and mesoscopic complexity.

  • Room-Temperature Multiferroicity and Diversified Magnetoelectric Couplings in Two-Dimensional Materials
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-05
    Zhong T, Li X, Wu M, et al.

    Multiferroics are rare in nature due to the mutual exclusive origins of magnetism and ferroelectricity. The simultaneous coexistence of robust magnetism/ferroelectricity and strong magnetoelectric coupling in single multiferroics is hitherto unreported, which may also be attributed to their potential conflictions. In this paper, we show the first-principles evidence of such desired coexistence in ultrathin-layer CuCrS2 and CuCrSe2. The vertical ferroelectricity is neither induced by empty d-shell nor spin-driven, giving rise to an alternative possibility of resolving those intrinsic exclusions and contradictions. Compared with their bulk phases, the ferromagnetism in the thin-layer structures (2–6 layers) can be greatly stabilized due to the enhanced carrier density and orbital shifting by the vertical polarization, and the Curie temperatures of both ferromagnetism and ferroelectricity can be above room-temperature. Moreover, a considerable net magnetization can be reversed upon a ferroelectric switching, where the change in spin-resolved band structure also renders efficient “magnetic reading + electrical writing”. The thickness-different layers may even exhibit diversified types of magnetoelectric coupling, which both enriches the physics of multiferroics and facilitates their practical applications.

  • Visually Constructing the Chemical Structure of a Single Molecule by Scanning Raman Microscopy
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-08
    Zhang Y, Yang B, Ghafoor A, et al.

    The strong spatial confinement of a nanocavity plasmonic field has made it possible to visualize the inner structure of a single molecule and even to distinguish its vibrational modes in real space. With such ever-improved spatial resolution, it is anticipated that full vibrational imaging of a molecule could be achieved to reveal molecular structural details. Here we demonstrate full Raman images of individual vibrational modes on the Ångström level for a single Mg-porphine molecule, revealing distinct characteristics of each vibrational mode in real space. Furthermore, by exploiting the underlying interference effect and Raman fingerprint database, we propose a new methodology for structural determination, coined as scanning Raman microscopy, to show how such ultrahigh-resolution spectromicroscopic vibrational images can be used to visually assemble the chemical structure of a single molecule through a simple Lego-like building process.

  • Practical High-Performance Lead-Free Piezoelectrics: Structural Flexibility Beyond Utilizing Multiphase Coexistence
    Natl. Sci. Rev. (IF 13.222) Pub Date : 2019-11-05
    Liu Q, Zhang Y, Gao J, et al.

    Due to growing concern for the environment and human health, searching for high-performance lead-free piezoceramics has been a hot topic of scientific and industrial research. Despite the significant progress achieved toward enhancing piezoelectricity, further effort should be devoted to the synergistic improvement of piezoelectricity and its thermal stability. This study provides new insight into these topics. A new KNN-based lead-free ceramic material is presented, which features a large piezoelectric coefficient (d33) exceeding 500 pC/N and a high Curie temperature (Tc) of ~200 °C. The superior piezoelectric response strongly relies on the increased composition-induced structural flexibility due to lattice softening and decreased unit cell distortion. In contrast to piezoelectricity anomalies induced via polymorphic transition, this piezoelectricity enhancement is effective within a broad temperature range rather than a specific small range. Especially, the hierarchical domain architecture composed by nano-sized domains along the submicron domains was detected in this material system, which further contributes to the high piezoelectricity.

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