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  • Magnetic field-induced electronic phase transition in the Dirac semimetal state of black phosphorus under pressure
    Sci. Bull. (IF 4.136) Pub Date : 2018-11-16
    Zeliang Sun, Ziji Xiang, Zhongyi Wang, Jinglei Zhang, Long Ma, Naizhou Wang, Chao Shang, Fanbao Meng, Liangjian Zou, Yuanbo Zhang, Xianhui Chen

    Different instabilities have been confirmed to exist in the three-dimensional (3D) electron gas when it is confined to the lowest Landau level in the extreme quantum limit. The recently discovered 3D topological semimetals offer a good platform to explore these phenomena due to the small sizes of their Fermi pockets, which means the quantum limit can be achieved at relatively low magnetic fields. In this work, we report the high-magnetic-field transport properties of the Dirac semimetal state in pressurized black phosphorus. Under applied hydrostatic pressure, the band structure of black phosphorus goes through an insulator-semimetal transition. In the high pressure topological semimetal phase, anomalous behaviors are observed on both magnetoresistance and Hall resistivity beyond the relatively low quantum limit field, which is demonstrated to indicate the emergence of an exotic electronic state hosting a density wave ordering. Our findings bring the first insight into the electronic interactions in black phosphorus under intense field.

  • Cu(OH)2 supported on Fe(OH)3 as a synergistic and highly efficient system for the dehydrogenation of ammonia-borane
    Sci. Bull. (IF 4.136) Pub Date : 2018-11-12
    Cheng-Yun Peng, Chun-Chao Hou, Qian-Qian Chen, Chuan-Jun Wang, Xiao-Jun Lv, Jun Zhong, Wen-Fu Fu, Chi-Ming Che, Yong Chen

    Herein, we first describe the physical mixture of Cu(OH)2/Fe(OH)3 as a composite catalyst precursor for the dehydrogenation of ammonia borane (AB) in methanol. During the initial period of catalytic reaction, Cu nanoparticles were formed in-situ. The catalytic activity of Cu nanoparticles can be significantly enhanced with the assistance of Fe species and OH–. A maximum turnover frequency (TOF) of 50.3 molH2 moltotal metal–1 min–1 (135.6 molH2 molCu–1 min–1) was achieved at ambient temperature, which is superior to those of previously reported Fe or Cu based systems.

  • Solution evaporation processed high quality perovskite films
    Sci. Bull. (IF 4.136) Pub Date : 2018-11-12
    Aqiang Liu, Kang Liu, Huimin Zhou, Hongmei Li, Xiaoqing Qiu, Yang Yi, Min Liu

    Organic-inorganic hybrid perovskite solar cells (PSCs), due to their high photoelectric conversion efficiency (PCE) and low cost, have been considered as one of the most promising photovoltaic devices. Well-distributed large-grain perovskite crystals play an important role for light adsorption and charge transfer. While, high quality perovskite crystals closely relate to the preparation method. Generally, the preparation of perovskite films requires a nitrogen atmosphere and toxic anti-solvents, which hinder their practical applications. Here, we reported a novel and simple solution evaporation process followed with a methylammonium iodide (MAI) solution immersion to prepare high quality perovskite films. Porous lead iodide (PbI2) films were firstly formed by evaporation of PbI2 precursor solution. The obtained porous PbI2 films were completely transformed into well-distributed large-grain perovskite films after a quick MAI solution immersion. As a result, the corresponding PCE was enhanced by 30% compared to that prepared with a regular sequential deposition. This solution evaporation method provides a convenient and practical way for preparing high-quality perovskite films.

  • Precision mapping the topological bands of 2D Spin-Orbit Coupling with Microwave spin-injection Spectroscopy
    Sci. Bull. (IF 4.136) Pub Date : 2018-11-09
    Xiao-Tian Xu, Chang-Rui Yi, Bao-Zong Wang, Wei Sun, Youjin Deng, Xiong-Jun Liu, Shuai Chen, Jian-Wei Pan

    To investigate the band structure is one of the key approaches to study the fundamental properties of a novel material. We report here the precision band mapping of a 2-dimensional (2D) spin-orbit (SO) coupling in an optical lattice. By applying the microwave spin-injection spectroscopy, the band structure and spin-polarization distribution are achieved simultaneously. The band topology is also addressed with observing the band gap close and re-open at the Dirac points. Furthermore, the lattice depth and the Raman coupling strength are precisely calibrated with relative errors in the order of 10 - 3 . Our approach could also be applied for exploring the exotic topological phases with even higher dimensional system.

  • Astronomical time scale for the lower Doushantuo Formation of early Ediacaran, South China
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-31
    Yu Sui, Chunju Huang, Rui Zhang, Zhixiang Wang, James Ogg, David B. Kemp

    Nearly 90% of the Ediacaran Period (635−541 Ma) of the Neoproterozoic is represented by the Doushantuo Formation (DST Fm) in South China. It is lowest Member I is a 3.7 m-thick cap carbonate deposited at the termination of the Cryogenian Marinoan glaciation. The DST Fm consists of alternating organic-rich black shale and thinly bedded dolostone, and it contains some of the oldest records of multi-cellular life and three pronounced negative carbon isotope excursions. The Jiulongwan (JLW) section is a well-studied reference section for these Ediacaran events. Spectral analysis of geochemical data through the lower DST Fm (22.3 m) shows 27 predominant ∼90 cm sedimentary cycles that correspond to 405-ka long eccentricity cycles. The power spectra of the 405-ka tuned Ca and Fe/Ti series show significant peaks at ∼1.2-Ma, 405-ka, 133-ka, 128-ka, 100-ka, 82-ka, ∼31-ka and 29-ka periods, respectively. A 11.16 Ma-long astronomical time scale has been constructed for the lower DST Fm and provide a duration of 1.6 Ma for the cap carbonate (Member I) based on the 405 -ka long eccentricity cycle tuning. Using the U-Pb age of 635.2 ± 0.6 Ma for the volcanic ash bed at the Member I /II boundary, we proposed a 636.8 Ma age for the base of the DST Fm. These ages and astronomical timescale provide important new constraints on the subdivision of Ediacaran strata, and have implications for understanding the character of the first negative δ13C excursion (EN1). Orbital forcing may have been played an important role for the climate changes and the evolution of Ediacaran multi-cellular life and the carbon cycle variations.

  • New radiocarbon and archaeobotanical evidence reveal the timing and route of southward dispersal of rice farming in south China
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-31
    Xiaoyan Yang, Qiuhe Chen, Yongchao Ma, Zhao Li, Hsiao-chun Hung, Qianglu Zhang, Zhiwei Jin, Suoqiang Liu, Zhenyu Zhou, Xianguo Fu

    The origins and spreads of rice agriculture have been enduring topics, yet the timing and southward dispersal from the Yangtze River Basin have been difficult to trace, due to the scarcity of archaeobotanical data, especially systematic macro-plant remains examination, combined with the poor preservation in the humid climate and acidic soils of China’s southern provinces. Here, we report new radiocarbon dating and preserved rice phytolith evidence, derived from three Late Neolithic archaeological sites in south China, dated about 5,000–4,100 cal a BP. Our results demonstrate that rice farming had spread southward through the mountainous regions of Wuyi and Nanling, then entered the areas of Western Fujian and North Guangdong by 5,000 cal a BP, followed by continued expansion into coastal areas of East China Sea and South China Sea, also crossing the Taiwan Strait, around 4,500-4,000 cal a BP. The North River, East River, Min River, and possibly other river systems likely were influential as pathways or conduits.

  • Optimal photonic indistinguishability tests in multimode networks
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-25
    Niko Viggianiello, Fulvio Flamini, Marco Bentivegna, Nicolò Spagnolo, Andrea Crespi, Daniel J. Brod, Ernesto F. Galvão, Roberto Osellame, Fabio Sciarrino
  • A general and simple method for evaluating the electrical transport performance of graphene by the van der Pauw-Hall measurement
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-18
    Fangzhu Qing, Yang Shu, Linsen Qing, Yuting Niu, He Guo, Shuyi Zhang, Chunlin Liu, Changqing Shen, Wanli Zhang, Samuel S. Mao, Wenjuan Zhu, Xuesong Li
  • Liquid metal fractals induced by synergistic oxidation
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-18
    Sen Chen, Lei Wang, Qinglei Zhang, Jing Liu
  • Insight into the catalytic activity of MXenes for hydrogen evolution reaction
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-13
    Xiaowan Bai, Chongyi Ling, Li Shi, Yixin Ouyang, Qiang Li, Jinlan Wang
  • Exploring facile strategies for high-oxidation-state metal nitride synthesis: carbonate-assisted one-step synthesis of Ta3N5 films for solar water splitting
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-12
    Tao Fang, Huiting Huang, Jianyong Feng, Yingfei Hu, Yongsheng Guo, Shiying Zhang, Zhaosheng Li, Zhigang Zou
  • Active greeting technique: a mother-and-child catheter based technique to facilitate retrograde wire externalization in recanalization of coronary chronic total occlusion
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-10
    Junbo Ge, Lei Ge, Bin Zhang, Xin Zhong, Jianying Ma, Leisheng Ru, Tao Hu, Juying Qian,

    Although retrograde approach has greatly improved the success rate of percutaneous coronary intervention (PCI) for coronary chronic total occlusion (CTO), retrograde wire externalization still remains challenging and time-consuming in some cases. Cases utilizing “Active Greeting Technique (AGT)”, a mother-and-child catheter based technique to facilitate retrograde wire externalization, were extracted from Chronic Total Occlusion Club, China (CTOCC) database. AGT was performed by deep intubation a mother-and-child catheter (GuidezillaTM extension, 4 or 5 Fr inner catheter, and etc.) in combination with either reverse controlled antegrade or retrograde subintimal tracking (CART) technique or retrograde wire crossing technique. A total of 111 patients with 112 CTO lesions treated with this technique were retrospectively analyzed. Reverse CART technique and retrograde wire crossing technique were performed in 90.2% and 9.8% of all procedures. The utilization of GuidezillaTM extension, 4 Fr, and 5 Fr inner catheter accounted for 94.6%, 3.6%, and 1.8%, respectively. Externalization of retrograde wire was successful in all cases. No procedural complications were adjudicated to AGT. Complications independent of AGT included two target vessel perforations and two collateral perforations. No in-hospital major adverse cardiac events were found. AGT is a feasible and safe technique that facilitates retrograde wire externalization.

  • Timing the termination of the Doushantuo negative carbon isotope excursion: evidence from U-Pb ages from the Dengying and Liuchapo formations, South China
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-10
    Mingzhong Zhou, Taiyi Luo, Warren D. Huff, Zhiqing Yang, Guanghong Zhou, Tian Gan, Hua Yang, Di Zhang

    The Doushantuo negative carbon isotope excursion (DOUNCE) is the largest known marine inorganic carbon isotope anomaly. The origin of this pronounced negative excursion is still an enigmatic issue that attracts geologists. Time constraints on the excursion are the critical information that would provide insight into its genesis. In previous decades, the timing of its termination has been constrained by the widely cited zircon U-Pb age of 550.5 ± 0.8 Ma for the tuff at the top of the Miaohe Member at the Jiuqunao section in the Yangtze Gorges area, South China. However, results of recent studies indicate that the reliability of this time constraint needs to be re-evaluated. Here, a geochronological study was carried out using two K-bentonites from Fanglong in South China. A K-bentonite in the lower Dengying Formation yielded a U-Pb age of 557 ± 3 Ma, while a K-bentonite in the basal Liuchapo Formation yielded an age of 550 ± 3 Ma. Based on regional correlations between the Ediacaran successions in South China, the age data from the present study for the K-bentonite in the lower Dengying Formation may serve as a second critical timing constraint for the ending of the DOUNCE. Combined with available estimates of the DOUNCE duration, our new data indicate that the DOUNCE has a maximum onset age ∼570 Ma.

  • Retrieval of global terrestrial solar-induced chlorophyll fluorescence from TanSat satellite
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-10
    Shanshan Du, Liangyun Liu, Xinjie Liu, Xiao Zhang, Xingying Zhang, Yanmeng Bi, Lianchong Zhang
  • Observation of two-times self-focusing of femtosecond laser beam in ZnO crystal by two-photon luminescence
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-10
    Xiaorui Wang, Honggang Ye, Zhicheng Su, Dapeng Yu, Shijie Xu
  • Subsurface reconstruction and saturation of surface bonds
    Sci. Bull. (IF 4.136) Pub Date : 2018-10-05
    Linhan Liu, Yonghao Sun, Zhiying Cheng, Jing Zhu, Rong Yu

    Surface reconstructions and stabilization mechanisms have been great challenges for insulators. Based on accurate determination of the long-sought atomic structure of the spinel (111) surface, here we show that the surface is stabilized by an unconventional mechanism. In general, solid surfaces have unsaturated chemical bonds and are prone to atomic reconstruction to saturate them. The spinel (111) surface, however, has the surface bonds fully saturated, while the unsaturated bonds remain only in the subsurface. It undergoes a reconstruction that keeps the topmost atomic layer unchanged, but has the subsurface atoms completely rearranged. Such a reconstruction results in a perfect compensation of the surface polarity and a large reduction in the surface energy. This work provides surprising insights into the surface stability and physical and chemical behaviors of complex oxides and insulators.

  • Transient deformation during the Milashan Tunnel construction in northern Sangri-Cuona Rift, southern Tibet, China observed by Sentinel-1 Satellites
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-29
    Yunfeng Tian, Jing Liu-Zeng, Yi Luo, Yongsheng Li, Yingshun Hu, Bin Gong, Lizheng Liu, Ping Guo, Jingfa Zhang

    Using 3-year Sentinel-1 C-band synthetic aperture radar (SAR) data, we observed prominent ground subsidence around the construction site of the Milashan Tunnel, which is on top of the northern Sangri-Cuona Rift (SCR) in southern Tibet. The most deformed area extends ∼7 km in the north-south direction and ∼6 km in the east-west direction, with a peak subsidence rate of over 10 mm/a in the line of sight direction of both the descending and ascending satellites. Aside from the long-term ground subsidence arising directly from underground water outflow and rock excavation, a regional aseismic fault slip episode is also evident. The aseismic slip event began in May 2016 and ended in July 2016. The surface aseismic displacements can be explained by normal faulting with mainly down-dip movement and a modest right-lateral strike-slip component on a nearly north-south trending fault. The aseismic deformation triggered by the Milashan Tunnel construction demonstrates the sensitive response of crustal-scale tectonics to human activity, which poses high seismic hazards for the heavily populated region.

  • The construction of drug-resistant cancer cell lines by CRISPR/Cas9 system for drug screening
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-29
    Lingmin Zhang, Ying Li, Qinghua Chen, Yong Xia, Wenfu Zheng, Xingyu Jiang

    Cancer therapy is often hampered by the rapid emergence of drug resistance. Drug-resistant cellular models are essential for understanding the drug resistance and developing new therapeutics. The low efficiency and long time required in creating these models are major obstacles hindering drug resistance research and drug screening. Herein, we report an approach that can accelerate (shortening the time from years to 3 weeks) the establishment of cancer cell line-based, inheritable drug resistance models by specific knockout of MED12 gene using CRISPR/Cas9 system. The resultant MED12KO A375 (melanoma) cell line was resistant to inhibitors of B-Raf proto-oncogene, serine/threonine kinase (BRAF), whereas the resultant MED12KO PC9 (non-small cell lung cancer) cell line was resistant to inhibitors of epidermal growth factor receptor (EGFR). Evaluation of anti-cancer drugs and their combinations shows that certain combinations of BRAF inhibitors and TGF-β receptor (TGF- βR) inhibitors are active in suppressing the growth of MED12KO A375 cells, and a few combinations of EGFR inhibitors and TGF- βR inhibitors were active in suppressing the growth of MED12KO PC9 cells. The drug-resistant models will be useful in screening novel drugs and drug combinations for multi-drug-resistant cancer therapy.

  • Dynamical classification of topological quantum phases
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-29
    Lin Zhang, Long Zhang, Sen Niu, Xiong-Jun Liu
  • Effects of annealing and cold roll-bonded interface on the microstructure and mechanical properties of the embedded aluminum-steel composite sheet
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-29
    Chunyang Wang, Xinhua Liu, Yanbin Jiang, Jianxin Xie, Xiaojun Zhang, Dejing Zhou

    Embedded aluminum-steel composite sheets used in heat exchanger were produced by cold roll bonding (CRB). The influences of annealing temperature and annealing time on the microstructure and the bonding strength of the composite sheet were investigated. The recrystallization of the steel layer began at 525 °C and finished at 600 °C. With the increase of the annealing temperature, the peel strength of the composite sheet whose original steel sheet surface was treated by scratch brush initially increased and then decreased, which was resulted from the competition of the mechanical locking and metallurgical bonding. After annealing, the cracks which formed between the broken work-hardened steel surface layer and its matrix during cold roll bonding remained. The composite sheet produced by CRB with the steel surface treatment of flap disc had less interfacial defects, higher bonding quality, higher diffusion rate of Al and Fe atoms at the interface and larger metallurgical bonding extent than the composite sheet produced by CRB with the steel surface treatment of scratch brush under the same conditions of annealing, which was helpful to shorten annealing time, reduce energy consumption and improve production efficiency.

  • Fe5C2 nanoparticles as low-cost HER electrocatalyst: the importance of Co substitution
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-22
    Siwei Li, Pengju Ren, Ce Yang, Xi Liu, Zhen Yin, Weizhen Li, Hanjun Yang, Jian Li, Xiaoping Wang, Yi Wang, Ruochen Cao, Lili Lin, Siyu Yao, Xiaodong Wen, Ding Ma
  • Antimicrobial peptide LL-37 forms complex with bacterial DNA to facilitate blood translocation of bacterial DNA and aggravate ulcerative colitis
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-22
    Zilei Duan, Yaqun Fang, Yang Sun, Ning Luan, Xue Chen, Mengrou Chen, Yajun Han, Yizhu Yin, James Mwangi, Junkun Niu, Kunhua Wang, Yinglei Miao, Zhiye Zhang, Ren Lai

    Bacterial DNA (bacDNA) is frequently found in serum of patient with ulcerative colitis (UC) and Crohn’s disease, even blood bacterial culture is negative. How bacDNA evades immune elimination and is translocated into blood remain unclear. Here, we showed that bacDNA avoids elimination and disables bacteria-killing function of antimicrobial peptide LL-37 (Cramp in mice) by forming complex with LL-37, which is inducible after culture with bacteria or bacterial products. Elevated LL-37-bacDNA complex was found in plasma and lesions of patients with UC. LL-37-bacDNA promoted inflammation by inducing Th1, Th2 and Th17 differentiation and activating toll-like receptor-9 (TLR9). The complex also increased paracellular permeability, which possibly combines its inflammatory effects to promote local damage and bacDNA translocation into blood. Cramp-bacDNA aggravated mouse colitis severity while interference with the complex ameliorated the disease. The study identifies that inflammatogenic bacDNA utilizes LL-37 as a vehicle for blood translocation and to evade immune elimination. Additionally, bacteria may make a milieu by releasing bacDNA to utilize and resist host antimicrobial peptides as a ‘trojan horse’.

  • A conifer-dominated Early Triassic flora from Southwest China
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-17
    Zhuo Feng, Hai-Bo Wei, Yun Guo, Benjamin Bomfleur
  • Ligand-Accelerated, Branch-Selective Oxidative Cyanation of Alkenes
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-18
    Jun Yang, Huan Li, Jian Qin, Fan Song, Jian Zhang, Feng-Ling Qing, Lingling Chu
  • Measurement-device-independent quantum communication without encryption
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-15
    Peng-Hao Niu, Zeng-Rong Zhou, Zai-Sheng Lin, Yu-Bo Sheng, Liu-Guo Yin, Gui-Lu Long
  • Scanning tunneling microscopic observation of enhanced superconductivity in epitaxial Sn islands grown on SrTiO3 substrate
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-13
    Zhibin Shao, Zongyuan Zhang, Hui Yuan, Haigen Sun, Yan Cao, Xin Zhang, Shaojian Li, Habakubaho Gedeon, Tao Xiang, Qi-Kun Xue, Minghu Pan
  • Predicting Diamond-like Co-based Chalcogenides as Unconventional High Temperature Superconductors
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-11
    Jiangping Hu, Yuhao Gu, Congcong Le
  • Tauroursodeoxycholic acid (TUDCA) inhibits influenza A viral infection by disrupting viral proton channel M2
    Sci. Bull. (IF 4.136) Pub Date : 2018-09-01
    Ning Li, Yanxu Zhang, Shuangxiu Wu, Ruodan Xu, Zhiqing Li, Jindong Zhu, Hongliang Wang, Xiao Li, Mingyao Tian, Huijun Lu, Ningyi Jin, Chengyu Jiang

    Influenza is a persistent threat to human health and there is a continuing requirement for updating anti-influenza strategies. Initiated by observations of different endoplasmic reticulum (ER) responses of host to seasonal H1N1 and highly pathogenic avian influenza (HPAI) A H5N1 infections, we identified an alternative antiviral role of tauroursodeoxycholic acid (TUDCA), a clinically available ER stress inhibitor, both in vitro and in vivo. Rather than modulating ER stress in host cells, TUDCA abolished the proton conductivity of viral M2 by disrupting its oligomeric states, which induces inefficient viral infection. We also showed that M2 penetrated cells, whose intracellular uptake depended on its proton channel activity, an effect observed in both TUDCA and M2 inhibitor amantadine. The identification and application of TUDCA as an inhibitor of M2 proton channel will expand our understanding of IAV biology and complement current anti-IAV arsenals.

  • A novel PDZ domain-containing gene is essential for male sex differentiation and maintenance in yellow catfish (Pelteobagrus fulvidraco)
    Sci. Bull. (IF 4.136) Pub Date : 2018-08-31
    Cheng Dan, Qiaohong Lin, Gaorui Gong, Tianyi Yang, Shuting Xiong, Yang Xiong, Peipei Huang, Jian-Fang Gui, Jie Mei

    The sex-determining genes are found to be variable among different fish species. Yellow catfish (Pelteobagrus fulvidraco) is an important aquaculture fish species in China with XX/XY sex-determining type. Recently, YY super-male yellow catfish has been successfully produced by combining hormonal-induced sex reversal method with sex chromosome-linked markers. Here, we identified a novel PDZ domain-containing gene in yellow catfish designated as pfpdz1, in whose intron the sex-linked marker was located. The coding sequence of pfpdz1 in Y chromosome was identical to that in X chromosome except a missense SNP (A/T) that changes an amino acid (E8V) in the N-terminal region. Pfpdz1 displayed male-specific expression during sex differentiation. Overexpression of pfpdz1 using additive transgenesis induces XX ovary to differentiate into testis-like tissue, while the targeted inactivation of pfpdz1 in Y chromosome using CRISPR/Cas9-mediated mutagenesis triggers ovarian differentiation. Furthermore, we demonstrated that pfpdz1 initiates testicular differentiation through upregulating expression of amh, dmrt1 and sox9a1, as well as downregulating expression of cyp19a1, foxl2 and wnt4. Our data provide functional evidence that pfpdz1 is significant for male differentiation and maintenance in yellow catfish.

  • H2/CO/air Premixed and Partially Premixed Flame Structure at Different Pressures Based on Reaction Limit Analysis
    Sci. Bull. (IF 4.136) Pub Date : 2018-08-28
    Zaigang Liu, Wenjun Kong, Jean-Louis Consalvi, Wenhu Han
  • Structural insights into the CRISPR-Cas-associated ribonuclease activity of Staphylococcus epidermidis Csm3 and Csm6
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-03
    Yanqun Zhao, Jinjing Wang, Qiu Sun, Chao Dou, Yijun Gu, Chunlai Nie, Xiaofeng Zhu, Yuquan Wei, Wei Cheng

    The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-CRISPR-associated (Cas) system is an adaptive immune system in bacteria and archaea that resists exogenous invasion through nucleicacid-mediated cleavage. In the type III-A system, the Csm complex contains five effectors and a CRISPR RNA, which edits both single stranded RNA and double stranded DNA. It has recently been demonstrated that cyclic oligoadenylates (cOAs), which are synthesized by the Csm complex, act as second messengers that bind and activate Csm6. Here, we report the crystal structures of Staphylococcus epidermidis Csm3 (SeCsm3) and an N-terminally truncated Csm6 (SeCsm6ΔN) at 2.26 and 2.0Å, respectively. The structure of SeCsm3 highly resembled previously reported Csm3 structures from other species; however, it provided novel observations allowing further enzyme characterization. The homodimeric SeCsm6ΔN folds into a compact structure. The dimerization of the HEPN domain leads to the formation of the ribonuclease active site, which is consistent with the reported Csm6 structures. Altogether, our studies provide a structural view of the ribonuclease activity mediated by Csm3 and Csm6 of the type III-A CRISPR-Cas system.

  • Widening and weakening of the Hadley circulation under global warming
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-28
    Yongyun Hu, Han Huang, Chen Zhou

    The Hadley circulation is one of the most important atmospheric circulations. Widening of the Hadley circulation has drawn extensive studies in the past decade. The key concern is that widening of the Hadley circulation would cause poleward shift of the subtropical dry zone. Various metrics have been applied to measure the widening of the tropics. What are responsible for the observed widening trends of the Hadley circulation? How anthropogenic and natural forcings caused the widening? How the widening results in regional climatic effects? These are the major questions in studies of the Hadley circulation. While both observations and simulations all show widening of the Hadley circulation in the past few decades, there are no general agreements of changes in the strength of the Hadley circulation. Although some reanalysis datasets show strengthening of the Hadley circulation, it was shown that the strengthening trend could be due to artificial reasons, and simulations show weakening of the Hadley circulation for global greenhouse warming. In the present paper, we shall briefly review the major progresses of studies in trends in width and strength of the Hadley circulation. We address answers to these questions, clarify inconsistent results, and propose ideas for future studies.

  • Evidence for a Dirac nodal-line semimetal in SrAs3
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-26
    Shichao Li, Zhaopeng Guo, Dongzhi Fu, Xing-Chen Pan, Jinghui Wang, Kejing Ran, Song Bao, Zhen Ma, Zhengwei Cai, Rui Wang, Rui Yu, Jian Sun, Fengqi Song, Jinsheng Wen

    Dirac nodal-line semimetals with the linear bands crossing along a line or loop, represent a new topological state of matter. Here, by carrying out magnetotransport measurements and performing first-principle calculations, we demonstrate that such a state has been realized in high-quality single crystals of SrAs3. We obtain the nontrivial ππ Berry phase by analysing the Shubnikov-de Haas quantum oscillations. We also observe a robust negative longitudinal magnetoresistance induced by the chiral anomaly. Accompanying first-principles calculations identifies that a single hole pocket enclosing the loop nodes is responsible for these observations.

  • Impact of 1.5°C and 2.0°C Global Warming on Aircraft Takeoff Performance in China
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-25
    Tianjun Zhou, Liwen Ren, Haiwen Liu, Jingwen Lu

    Associated with global warming, climate extremes such as extreme temperature will significantly increase. Understanding how climate change will impact the airflights is important to the planning of future flight operations. In this study, the impacts of 1.5 and 2 degree’s global warming on the aircraft takeoff performance in China are investigated using a unique climate projection data from an international collaboration project named HAPPI. It is found that the mean summer daily maximum temperature, which is a major factor that affects the flight through changing the aircraft’s takeoff weight, will increase significantly with magnitude less than 1.5°C over most parts of China except for the Tibetan Plateau. The half a degree additional global warming will lead to higher extreme temperature in the arid and semi arid western China, the Tibetan Plateau and the northeastern China, while the change in eastern China is weak. Five airports including Beijing, Shanghai, Kunming, Lasa and Urumqi will see ∼1.0°-2.0°C (1.4°-3.0°C) higher daily maximum temperature under 1.5°C (2.0°C) scenario. The half-degree additional warming will lead to a shift toward higher extreme temperature in these five sites. For both 1.5° and 2.0°C scenarios, the number of weight-restriction days will increase significantly at 3 airports including Beijing, Shanghai, and Lasa. Urumqi will witness an increase of weight-restriction days only in 2.0°C future.

  • Realization of non-equilibrium process for high thermoelectric performance Sb-doped GeTe
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-25
    Evariste Nshimyimana, Xianli Su, Hongyao Xie, Wei Liu, Rigui Deng, Tingting Luo, Yonggao Yan, Xinfeng Tang

    Pristine GeTe shows inferior thermoelectric properties around unit due to the large carrier concentration induced by the presence of intrinsic high concentration of Ge vacancy. In this study, we report a thermoelectric figure of merit ZT of 1.56 at 700 K, realized in Sb-doped GeTe based thermoelectric (TE) materials via combined effect of suppression of intrinsic Ge vacancy and Sb doping. The non-equilibrium nature during melt spinning process plays very important role. For one thing, it promotes the homogeneity in Ge1–xSbxTe samples and refines the grain size of the product. Moreover the persistent Ge precipitated as impurity phase in the traditional synthesis process were found to be dissolved back into the GeTe sublattice, accompanying with a drastic suppression of Ge vacancies concentration which in combination with Sb electron doping significantly reduced the inherent carrier concentration in GeTe. Low carrier concentration, approaching the optimum carrier concentration ∼3.74 × 10–20 cm–3 and a high power factor of 4.01 × 10–3 W m–1 K–2 at 750 K were achieved for Ge0.98Sb0.02Te sample. In addition, the enhanced grain boundary phonon scattering by refining the grain size through melt spinning (MS) process, coupled with the intensified alloying phonon scattering via Sb doping leads to low thermal conductivity of 1.53 W m−1 K−1 at 700 K for Ge0.94Sb0.06Te sample. All those contribute to a high ZT value, representing over 50% improvement in the ZT value compared to the Sb free samples, which provides an alternative way for ultrafast synthesis of high performance GeTe based thermoelectric material.

  • Density gradient ultracentrifugation for colloidal nanostructures separation and investigation
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-25
    Pengsong Li, Anuj Kumar, Jun Ma, Yun Kuang, Liang Luo, Xiaoming Sun

    In this article, we review the advancement in nanoseparation and concomitant purification of nanoparticles (NPs) by using density gradient ultracentrifugation technique (DGUC) and demonstrated by taking several typical examples. Study emphasizes the conceptual advances in classification, mechanism of DGUC and synthesis-structure-property relationships of NPs to provide the significant clue for the further synthesis optimization. Separation, concentration, and purification of NPs by DGUC can be achieved at the same time by introducing the water/oil interfaces into the separation chamber. We can develop an efficient method “lab in a tube” by introducing a reaction zone or an assembly zone in the gradient to find the surface reaction and assembly mechanism of NPs since the reaction time can be precisely controlled and the chemical environment change can be extremely fast. Finally, to achieve the best separation parameters for the colloidal systems, we gave the mathematical descriptions and computational optimized models as a new direction for making practicable and predictable DGUC separation method. Thus, it can be helpful for an efficient separation as well as for the synthesis optimization, assembly and surface reactions as a potential cornerstone for the future development in the nanotechnology and this review can be served as a plethora of advanced notes on the DGUC separation method.

  • Bifunctional 3D n-doped porous carbon materials derived from paper towel for oxygen reduction reaction and supercapacitor
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-25
    Xinyu Gao, Xueyan Li, Zhuang Kong, Guozheng Xiao, Ying Zhu

    Designing and fabricating cheap and active bifunctional materials is crucial for the development of renewable energy technologies. In this article, three-dimensional nitrogen-doped porous carbon materials (NDPC-X, in which X represents the pyrolysis temperature) were fabricated by simultaneous carbonization and activation of polypyrrole-coated paper towel protected by a silica layer followed by acid etching. The material had a high specific surface area (1,123.40 m2/g). The as-obtained NDPC-900 displayed outstanding activity as a catalyst for the oxygen reduction reaction (ORR) as well as an electrode with a high specific capacitance in a supercapacitor in an alkaline medium. The NDPC-900 catalyst for the ORR exhibited a more positive reduction peak potential of –0.068 V (vs. Hg|HgCl2) than that of Pt/C (–0.121 V), as well as better cycling stability and stronger methanol tolerance. Moreover, the NDPC-900 had a high specific capacitance of 379.50 F/g at a current density of 1 A/g, with a retention rate of 94.5% after 10,000 cycles in 6 mol/L KOH electrolyte when used as an electrode in a supercapacitor. All these results were attributed to the effect of a large surface area, which provided electrochemically active sites. This work introduces an effective way to use biomass-derived materials for the synthesis of promising bifunctional carbon material for electrochemical energy conversion and storage devices.

  • Emergent symmetry at superradiance transition of a Bose condensate in two crossed beam cavities
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-19
    Zhigang Wu, Yu Chen, Hui Zhai

    Recently an experiment on superradiant transition of a Bose condensate in two crossed beam cavities has been reported by Léonard et al. in Nature 543, 87 (2017). The surprise is they find that across the superradiant transition, the cavity light can be emitted in any superposition of these two cavity modes. This indicates an additional U(1)U(1) symmetry that does not exist in the full Hamiltonian. In this paper we show that this symmetry is an emergent symmetry in the vicinity of the phase transition. We identify all the necessary conditions that are required for this emergent U(1)U(1) symmetry and show that the this experiment is a special case that satisfies these conditions. We further show that the superradiant transition in this system can also be driven to a first order one when the system is tuned away from the point having the emergent symmetry.

  • Highly enhanced visible-light photocatalytic NOx purification and conversion pathway on self-structurally modified g-C3N4 nanosheets
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-19
    Yuhan Li, Yanjuan Sun, Wingkei Ho, Yuxin Zhang, Hongwei Huang, Qiang Cai, Fan Dong

    The unmodified graphitic carbon nitride (g-C3N4) suffers from low photocatalytic activity because of the unfavourable structure. In the present work, we reported a simple self-structural modification strategy to optimize the microstructure of g-C3N4 and obtained graphene-like g-C3N4 nanosheets with porous structure. In contrast to traditional thermal pyrolysis preparation of g-C3N4, the present thermal condensation was improved via pyrolysis of thiourea in an alumina crucible without a cover, followed by secondary heat treatment. The popcorn-like formation and layer-by-layer thermal exfoliation of graphene-like porous g-C3N4 was proposed to explain the formation mechanism. The photocatalytic removal performance of both NO and NO2 with the graphene-like porous g-C3N4 for was significantly enhanced by self-structural modification. Trapping experiments and in-situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) measurement were conducted to detect the active species during photocatalysis and the conversion pathway of g-C3N4 photocatalysis for NOx purification was revealed. The photocatalytic activity of graphene-like porous g-C3N4 was highly enhanced due to the improved charge separation and increased oxidation capacity of the ∙O2− radicals and holes. This work could not only provide a novel self-structural modification for design of highly efficient photocatalysts, but also offer new insights into the mechanistic understanding of g-C3N4 photocatalysis.

  • Towards the manipulation of topological states of matter: a perspective from electron transport
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-18
    Cheng Zhang, Hai-Zhou Lu, Shun-Qing Shen, Yong P. Chen, Faxian Xiu

    The introduction of topological invariants, ranging from insulators to metals, has provided new insights into the traditional classification of electronic states in condensed matter physics. A sudden change in the topological invariant at the boundary of a topological nontrivial system leads to the formation of exotic surface states that are dramatically different from its bulk. In recent years, significant advancements in the exploration of the physical properties of these topological systems and regarding device research related to spintronics and quantum computation have been made. Here, we review the progress of the characterization and manipulation of topological phases from the electron transport perspective and also the intriguing chiral/Majorana states that stem from them. We then discuss the future directions of research into these topological states and their potential applications.

  • N-doped defective carbon with trace Co for efficient rechargeable liquid electrolyte- /all-solid-state Zn-air batteries
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-18
    Zhiyan Chen, Qichen Wang, Xiaobin Zhang, Yongpeng Lei, Wei Hu, Yao Luo, Yaobing Wang

    Simple synthesis of multifunctional electrocatalysts with plentiful active sites from earth-abundant materials is especially fascinating. Here, N-doped defective carbon with trace Co (1.5 wt.%) was prepared via a scalable one pot solid pyrolysis process. The sample exhibits efficient bifunctional OER/ORR activity in alkaline, mainly ascribed to the unique micro-mesoporous structure (1−3 nm), high population of graphitic-N doping (up to 49.0%), abundant defects and the encapsulated Co nanoparticles with graphitized carbon. The according rechargeable liquid Zn-air batteries showed excellent performance (maximum power density of 154.0 mW cm−2; energy density of 773 Wh kg−1 at 5 mA cm−2 and charging-discharging cycling stability over 100 cycles). As a proof-of-concept, the flexible, rechargeable all-solid-state Zn-air batteries were constructed, and displayed a maximum power density as high as 45.9 mW cm−2, among the top level of those reported previously.

  • Enhancing photocatalytic performance by constructing ultrafine TiO2 nanorods/g-C3N4 nanosheets heterojunction for water treatment
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-12
    Shiliang Luan, Dan Qu, Li An, Wenshuai Jiang, Xiang Gao, Shixin Hua, Xiang Miao, Yuanjing Wen, Zaicheng Sun

    Photocatalysis is treated as a clean, green and efficient way to water purification. In this report, we first developed a highly efficient ultrafine TiO2 nanorods/g-C3N4 nanosheets (TiO2 NR/CN NS) composites via a simple hydrothermal method. Tiny TiO2 nanorods (diameter: ∼1.5 nm and length: ∼8.3 nm) were first in situ loaded on the CN NS by adding g-C3N4 into the reaction solution. The TiO2 NR/CN NS composites present high charge separation efficiency and broader light absorbance than P25 TiO2. Furthermore, we illustrate that TiO2 NR/CN NS catalyst possesses high performance for the photocatalytic degradation of the common and stubborn pollutants in the water, such as the rhodamine B (RhB) and the phenol. Under the visible light (λ > 420 nm) irradiation, the apparent rate of the TiO2 NR/CN NR is 172 and 41 times higher than that of the P25 TiO2, and TiO2 NR, respectively. As well as, we have speculated that the heterojunction formed between TiO2 NR and CN NS, the basis for the experiments we have designed and the corresponding results. That is, the reactive oxidative species like superoxide anion radical and holes play critical roles in the degradation, the hydroxyl radical has no contribution to the degradation.

  • A large-sized basal ankylopollexian from East Asia, shedding light on early biogeographic history of Iguanodontia
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-12
    Xing Xu, Qingwei Tan, Yilong Gao, Zhiqiang Bao, Zhigang Yin, Bin Guo, Junyou Wang, Lin Tan, Yuguang Zhang, Hai Xing

    A presumably mostly quadrupedal ankylopollexian iguanodontian, Bayannurosaurus perfectus gen. et sp. nov., is reported here, and is represented by an excellently well-preserved skeleton from the Lower Cretaceous Bayingebi Formation of Inner Mongolia, China. The diagnosis of the taxon includes several autapomorphies, notably a dorsally directed, strap-like posterodorsal process of the jugal and a horizontally oriented preacetabular process of the ilium. The nearly complete caudal series retains eight posterior-most caudals with procoelous, trapezoidal centra in dorsal view, and the last three caudals are fully fused. The discovery of B. perfectus opens a critical new window on the early evolution and intercontinental dispersal of Iguanodontia. The skeleton displays a transitional morphology between non-hadrosauriform ankylopollexians and Hadrosauriformes. A phylogenetic analysis indicates that Bayannurosaurus is positioned higher on the tree than Hypselospinus, but below Ouranosaurus just outside of Hadrosauriformes. The tree topology of Iguanodontia with temporal and spatial constraints reveals a possible biogeographic scenario supported by the statistical dispersal-vicariance analysis: around the J/K boundary, non-hadrosauriform ankylopollexians experienced multiple dispersal events from Europe to Asia, accompanying the coeval fall of the global sea level.

  • Astronomical tuning and magnetostratigraphy of Neogene biogenic reefs in Xisha Islands, South China Sea
    Sci. Bull. (IF 4.136) Pub Date : 2018-04-12
    Liang Yi, Zhimin Jian, Xinyu Liu, Youhua Zhu, Daojun Zhang, Zhenfeng Wang, Chenglong Deng
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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