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  • The TanSat mission: preliminary global observations
    Sci. Bull. (IF 4.136) Pub Date : 2018-08-16
    Yi Liu, Jing Wang, Lu Yao, Xi Chen, Zhaonan Cai, Dongxu Yang, Zengshan Yin, Songyan Gu, Longfei Tian, Naimeng Lu, Daren Lv

    The Chinese global carbon dioxide monitoring satellite (TanSat) was launched successfully in December 2016 and has completed its on-orbit tests and calibration. TanSat aims to measure the atmospheric column-averaged dry air mole fractions of carbon dioxide (XCO2) with a precision of 4 ppm at the regional scale, and in addition, to derive global and regional CO2 fluxes. Progress towards these objectives is reviewed and the first scientific results from TanSat measurements are presented. TanSat on-orbit tests indicate that the Atmospheric Carbon dioxide Grating Spectrometer is in normal working status and is beginning to produce L1B products. The preliminary TanSat XCO2 products have been retrieved by an algorithm and compared to NASA Orbiting Carbon Observatory - 2 (OCO-2) measurements during an overlapping observation period. Furthermore, the XCO2 retrievals have been validated against eight ground-site measurement datasets from the Total Carbon Column Observing Network, for which the preliminary conclusion is that TanSat has met the precision design requirement, with an average bias of 2.11 ppm. The first scientific observations are presented, namely, the seasonal distributions of XCO2 over land on a global scale.

    更新日期:2018-08-17
  • Fast response CdS-CdSxTe1–x-CdTe core-shell nanobelt photodetector
    Sci. Bull. (IF 4.136) Pub Date : 2018-08-04
    Mingwei Tang, Pengfei Xu, Zhong Wen, Xing Chen, Chenlei Pang, Xuechu Xu, Chao Meng, Xiaowei Liu, He Tian, Nagarajan Raghavan, Qing Yang
    更新日期:2018-08-05
  • The global oxygen budget and its future projection
    Sci. Bull. (IF 4.136) Pub Date : 2018-08-03
    Jianping Huang, Jiping Huang, Xiaoyue Liu, Changyu Li, Lei Ding, Haipeng Yu

    Atmospheric Oxygen (O2) is the most crucial element on Earth for the aerobic organisms that depend on it to release energy from carbon-based macromolecules. This is the first study to systematically analyze the global O2 budget and its changes over the past 100 years. It is found that anthropogenic fossil fuel combustion is the largest contributor to the current O2 deficit, which consumed 2.0 Gt/a in 1900 and has increased to 38.2 Gt/a by 2015. Under the Representative Concentration Pathways (RCPs) RCP8.5 scenario, approximately 100Gt (gigatonnes) of O2 would be removed from the atmosphere per year until 2100, and the O2 concentration will decrease from its current level of 20.946% to 20.825%. Human activities have caused irreversible decline of atmospheric O2. It’s time to take actions to promote O2 production and reduce O2 consumption.

    更新日期:2018-08-03
  • Spontaneous T-symmetry breaking and exceptional points in cavity quantum electrodynamics systems
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-31
    Yu-Kun Lu, Pai Peng, Qi-Tao Cao, Da Xu, Jan Wiersig, Qihuang Gong, Yun-Feng Xiao
    更新日期:2018-07-31
  • Tip-induced or enhanced superconductivity: a way to detect topological superconductivity
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-29
    He Wang, Lei Ma, Jian Wang

    Topological materials, hosting topological nontrivial electronic band, have attracted widespread attentions. As an application of topology in physics, the discovery and study of topological materials not only enrich the existing theoretical framework of physics, but also provide fertile ground for investigations on low energy excitations, such as Weyl fermions and Majorana fermions, which have not been observed yet as fundamental particles. These quasiparticles with exotic physical properties make topological materials the cutting edge of scientific research and a new favorite of high tech. As a typical example, Majorana fermions, predicted to exist in the edge state of topological superconductors, are proposed to implement topological error-tolerant quantum computers. Thus, the detection of topological superconductivity has become a frontier in condensed matter physics and materials science. Here we review a way to detect topological superconductivity triggered by the hard point contact: tip-induced superconductivity (TISC) and tip-enhanced superconductivity (TESC). The TISC refers to the superconductivity induced by a non-superconducting tip at the point contact on non-superconducting materials. We take the elaboration of the chief experimental achievement of TISC in topological Dirac semimetal Cd3As2 and Weyl semimetal TaAs as key components of this article for detecting topological superconductivity. Moreover, we also briefly introduce the main results of another exotic effect, TESC, in superconducting Au2Pb single crystal and Sr2RuO4 single crystal, which are respectively proposed as the candidates of helical topological superconductor and chiral topological superconductor. Related results and the potential mechanism are conducive to improving the comprehension of how to induce and enhance the topological superconductivity.

    更新日期:2018-07-30
  • High-temperature treatment induced carbon anode with ultrahigh Na storage capacity at low-voltage plateau
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-25
    Chenglong Zhao, Qidi Wang, Yaxiang Lu, Baohua Li, Liquan Chen, Yong-Sheng Hu
    更新日期:2018-07-26
  • Future biomass carbon sequestration capacity of Chinese forests
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-24
    Yitong Yao, Shilong Piao, Tao Wang

    Chinese forests, characterized by relatively young stand age, represent a significant biomass carbon (C) sink over the past several decades. Nevertheless, it is unclear how forest biomass C sequestration capacity in China will evolve as forest age, climate and atmospheric CO2 concentration change continuously. Here, we present a semi-empirical model that incorporates forest age and climatic factors for each forest type to estimate the effects of forest age and climate change on total forest biomass, under three different scenarios based on the fifth phase of the Coupled Model Intercomparison Project (CMIP5). We estimate that age-related forest biomass C sequestration to be 6.69 Pg C (∼0.17 Pg C yr-1) from the 2000s to the 2040s. Climate change induces a rather weak increase in total forest biomass C sequestration (0.52–0.60 Pg C by the 2040s). We show that rising CO2 concentrations could further increase the total forest biomass C sequestration by 1.68–3.12 Pg C in the 2040s across all three scenarios. Overall, the total forest biomass in China would increase by 8.89–10.37 Pg C by the end of 2040s. Our findings highlight the benefits of Chinese afforestation programs, continued climate change and increasing CO2 concentration in sustaining the forest biomass C sink in the near future, and could therefore be useful for designing more realistic climate change mitigation policies such as continuous forestation programs and careful choice of tree species.

    更新日期:2018-07-24
  • Enhanced piezo-response in copper halide perovskites based PVDF composite films
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-24
    Sheng Huang, Gang Tang, Hailong Huang, Xian-gang Wu, Puming Zhou, Lin Zou, Lei Xie, Jianming Deng, Xueyun Wang, Haizheng Zhong, Jiawang Hong
    更新日期:2018-07-24
  • Discovery of multi-drug resistant, MCR-1 and ESBL-coproducing ST117 Escherichia coli from diseased chickens in Northeast China
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-21
    Sijia Ding, Xiaohu Han, Jun Li, Weifan Gao, Zeliang Chen, Youjun Feng

    An endemic multi-drug resistant ST117 E. coli isolate coproducing MCR-1 and 3 ESBL loci was, for the first time, detected from diseased chicken, Liaoning Province, in Northeast China, from 2011-2012. Whole-genome sequencing revealed 5 unique plasmids, namely pHXH-1, pHXH-2, pHXH-3, pHXH-4 and pHXH-5). Among them, pHXH1 and pHXH4 encode ESBL, and pHXH-5 mediates MCR-1 colistin resistance. The results indicate that the potentially-national dissemination of MCR-1-positive pathogens with pan-drug resistance proceeds via food chains.

    更新日期:2018-07-22
  • Inter-valley spiral order in the Mott insulating state of a heterostructure of trilayer graphene-boron nitride
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-20
    Guo-Yi Zhu, Tao Xiang, Guang-Ming Zhang

    Recent experiment has shown that the ABC-stacked trilayer graphene-boron nitride Moire super-lattice at half-filling is a Mott insulator. Based on symmetry analysis and effective band structure calculation, we propose a valley-contrasting chiral tight-binding model with local Coulomb interaction to describe this Moire super-lattice system. By matching the positions of van Hove points in the low-energy effective bands, the valley-contrasting staggered flux per triangle is determined around . When the valence band is half-filled, the Fermi surfaces are found to be perfectly nested between the two valleys. Such an effect can induce an inter-valley spiral order with a gap in the charge excitations, indicating that the Mott insulating behavior observed in the trilayer graphene-boron nitride Moire super-lattice results predominantly from the inter-valley scattering.

    更新日期:2018-07-21
  • A systematic study of the determinants of protein abundance memory in cell lineage
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-19
    Zongmao Gao, Haoyuan Sun, Shanshan Qin, Xiaojing Yang, Chao Tang

    Proteins are essential players of life activities. Intracellular protein levels directly affect cellular functions and cell fate. Upon cell division, the proteins in the mother cell are inherited by the daughters. However, what factors and by how much they affect this epigenetic inheritance of protein abundance remains unclear. Using both computational and experimental approaches, we systematically investigated this problem. We derived an analytical expression for the dependence of protein inheritance on various factors and showed that it agreed with numerical simulations of protein production and experimental results. Our work provides a framework for quantitative studies of protein inheritance and for the potential application of protein memory manipulation.

    更新日期:2018-07-20
  • Spatiotemporal variations of aridity in China during 1961-2015: decomposition and attribution
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-19
    Chang Liu, Wei Huang, Song Feng, Jianhui Chen, Aifeng Zhou

    Changes in global climate intensify the hydrological cycle, directly influence precipitation, evaporation, runoff, and cause the re-distribution of water resources in time and space. The aridity index (AI), defined as the ratio of annual precipitation to annual potential evapotranspiration, is a widely used numerical indicator to quantify the degree of dryness at a given location. This study examined the effects of climate change on AI in China during 1961-2015. The results showed that the nationally averaged AI experienced a notable interdecadal transition in 1993, characterized by increasing AI (wetter) between 1961 and 1993, and decreasing AI (drier) after 1993. Overall, the decreased solar radiation (solar dimming) was the main factor affected the nationally averaged AI during 1961-1993, while the relative humidity dominated the variations of nationally averaged AI during 1993-2015. However, the roles of individual factors on the changes in AI vary in different subregions. Precipitation is one of the important contributing factors for the changes of AI in almost all subregions, except the Mid-Lower Yangtze and Huaihe basins. Solar radiation has been significantly decreased during 1961-1993 in South China, Southwest China, Mid-Lower Yangtze and Huaihe basins, and the Tibetan Plateau. Therefore, it dominated the trends of AI in these subregions. The relative humidity mainly affected the Mid-Lower Yangtze and Huaihe basins, Southwest China, and the Tibetan Plateau during 1993-2015, hence dominated the trends of AI in these subregions. The changes of temperature and wind speed, however, played a relatively weak role in the variations of AI.

    更新日期:2018-07-20
  • Activation and counteraction of antiviral innate immunity by KSHV: an Update
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-19
    Xiaoqin Wei, Ke Lan

    The innate immune responses triggering production of type I interferons and inflammatory cytokines constitute a nonspecific innate resistance that eliminates invading pathogens including viruses. The activation of innate immune signaling through pattern recognition receptors (PRRs) is by sensing pathogen-associated molecular patterns derived from viruses. According to their distribution within cells, PRRs are classified into three types of receptors: membrane, cytoplasmic, and nuclear. Kaposi’s sarcoma-associated herpesvirus (KSHV), a large DNA virus, replicates in the nucleus. Its genome is protected by capsid proteins during transport in the cytosol. Multiple PRRs are involved in KSHV recognition. To successfully establish latent infection, KSHV has evolved to manipulate different aspects of the host antiviral innate immune responses. This review presents recent advances in our understanding about the activation of the innate immune signaling in response to infection of KSHV. It also reviews the evasion strategies used by KSHV to subvert host innate immune detection for establishing a persistent infection.

    更新日期:2018-07-20
  • Severe human infection with a novel avian-origin influenza A(H7N4) virus
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-19
    Xiang Huo, Lun-biao Cui, Cong Chen, Dayan Wang, Xian Qi, Ming-hao Zhou, Xiling Guo, Fengming Wang, William J. Liu, Weirong Kong, Daxin Ni, Ying Chi, Yiyue Ge, Haodi Huang, Feifei Hu, Chao Li, Xiang Zhao, Ruiqi Ren, Feng-Cai Zhu

    Human infections with influenza H7 subtypes, such as H7N9, have raised concerns worldwide. Here, we report a human infection with a novel influenza A(H7N4) virus. A 68 years-old woman with cardiovascular and cholecystic comorbidities developed rapidly progressed pneumonia with influenza-like-illness as initial symptom, recovered after 23 days-hospitalization including 8 days in ICU. Laboratory indicators for liver and blood coagulation dysfunction were observed. Oseltamivir phosphate, glucocorticoids and antibiotics were jointly implemented, with nasal catheterization of oxygen inhalation for this patient. We obtained the medical records and collected serial respiratory and blood specimens from her. We collected throat, cloacal and/or feces samples of poultry and wild birds from the patient’s backyard, neighborhood, local live poultry markets (LPMs) and the nearest lake. All close contacts of the patient were followed up and sampled with throat swabs and sera. Influenza viruses and other respiratory pathogens were tested by real-time RT-PCR, viral culturing and/or sequencing for human respiratory and bird samples. Micro-neutralizing assay was performed for sera. A novel reassortant wild bird-origin H7N4 virus is identified from the patient and her backyard poultry (chickens and ducks) by sequencing, which is distinct from previously-reported avian H7N4 and H7N9 viruses. At least four folds increase of neutralizing antibodies to H7N4 was detected in her convalescent sera. No samples from close contacts, wild birds or other poultry were tested positive for H7N4 by real-time RT-PCR.

    更新日期:2018-07-20
  • S, N co-doped carbon nanotube-encapsulated core-shelled CoS2@Co nanoparticles: efficient and stable bifunctional catalysts for overall water splitting
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-17
    Jing-Yu Wang, Ting Ouyang, Nan Li, Tianyi Ma, Zhao-Qing Liu

    Hydrogen, serving as a clean, sustainable energy source, may be mainly produced from electrolysis water. Herein, we report cobalt disulphide (CoS2) encapsulated in self-catalyzed carbon nanotubes serving as a bifunctional catalyst, which exhibits excellent hydrogen evolution reaction performance (10.0 mA cm−2 at 0.112 V, and low Tafel slope for 104.9 mV dec−1) and oxygen evolution reaction performance (10.0 mA cm−2 at 1.57 V, and low Tafel slope for 76.1 mV dec−1), meanwhile with a strong stability at various current densities. In-depth study reveals that the excellent catalytic properties can be mainly attributed to the increased catalytic sites induced by S, N co-doping, the improved electronic conductivity derived from the carbon nanotubes, and Mott-Schottky effect between the metal cobalt and semiconductive cobalt disulfide. Notably, the synthesized bifunctional catalysts apply into the overall water splitting process, a low potential of 1.633V at the current density of 10.0 mA cm−2 is achieved, which can compete with the precious metal catalyst benchmarks in alkaline media, demonstrating its promising practicability in the realistic water splitting application. This work elucidates a practicable way to the design of transition metal and nano-carbon composite catalysts for a broad application in the fields of energy chemistry.

    更新日期:2018-07-18
  • Electrochemical solid-state amorphization in the immiscible Cu-Li system
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-10
    Muhua Sun, Jiake Wei, Zhi Xu, Qianming Huang, Yu Zhao, Wenlong Wang, Xuedong Bai

    As a typical immiscible binary system, copper (Cu) and lithium (Li) show no alloying and chemical intermixing under normal circumstances. Here we show that, when decreasing Cu nanoparticle sizes into ultrasmall range, the nanoscale size effect can play a subtle yet critical role in mediating the chemical activity of Cu and therefore its miscibility with Li, such that the electrochemical alloying and solid-state amorphization will occur in such an immiscible system. This unusual observation was accomplished by performing in-situ studies of the electrochemical lithiation processes of individual CuO nanowires inside a transmission electron microscopy (TEM). Upon lithiation, CuO nanowires are first electrochemically reduced to form discrete ultrasmall Cu nanocrystals that, unexpectedly, can in turn undergo further electrochemical lithiation to form amorphous CuLix nanoalloys. Real-time TEM imaging unveils that there is a critical grain size (ca. 6 nm), below which the nanocrystalline Cu particles can be continuously lithiated and amorphized. The possibility that the observed solid-state amorphization of Cu-Li might be induced by electron beam irradiation effect can be explicitly ruled out; on the contrary, it was found that electron beam irradiation will lead to the dealloying of as-formed amorphous CuLix nanoalloys.

    更新日期:2018-07-12
  • Atomically dispersed Au1 catalyst towards efficient electrochemical synthesis of ammonia
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-10
    Xiaoqian Wang, Wenyu Wang, Man Qiao, Geng Wu, Wenxing Chen, Tongwei Yuan, Qian Xu, Min Chen, Yan Zhang, Xin Wang, Jing Wang, Jingjie Ge, Xun Hong, Yafei Li, Yuen Wu, Yadong Li

    Tremendous efforts have been devoted to explore energy-efficient strategies of ammonia synthesis to replace Haber-Bosch process which accounts for 1.4% of the annual energy consumption. In this study, atomically dispersed Au1 catalyst is synthesized and applied in electrochemical synthesis of ammonia under ambient conditions. A high NH4+ Faradaic efficiency of 11.1% achieved by our Au1 catalyst surpasses most of reported catalysts under comparable conditions. Benefiting from efficient atom utilization, an NH4+ yield rate of 1,305 μg h−1 mgAu−1 has been reached, which is roughly 22.5 times as high as that by supported Au nanoparticles. We also demonstrate that by employing our Au1 catalyst, NH4+ can be electrochemically produced directly from N2 and H2 with an energy utilization rate of 4.02 mmol kJ−1. Our study provides a possibility of replacing the Haber-Bosch process with environmentally benign and energy-efficient electrochemical strategies.

    更新日期:2018-07-12
  • On-chip silicon photonic signaling and processing: a review
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-12
    Jian Wang, Yun Long

    The arrival of the big data era has driven the rapid development of high-speed optical signaling and processing, ranging from long-haul optical communication links to short-reach data centers and high-performance computing, and even micro-/nano-scale inter-chip and intra-chip optical interconnects. On-chip photonic signaling is essential for optical data transmission, especially for chip-scale optical interconnects, while on-chip photonic processing is a critical technology for optical data manipulation or processing, especially at the network nodes to facilitate ultracompact data management with low power consumption. In this article, we review recent research progress in on-chip photonic signaling and processing on silicon photonics platforms. Firstly, basic key devices (lasers, modulators, detectors) are introduced. Secondly, for on-chip photonic signaling, we present recent works on on-chip data transmission of advanced multi-level modulation signals using various silicon photonic integrated devices (microring, slot waveguide, hybrid plasmonic waveguide, subwavelength grating slot waveguide). Thirdly, for on-chip photonic processing, we summarize recent works on on-chip data processing of advanced multi-level modulation signals exploiting linear and nonlinear effects in different kinds of silicon photonic integrated devices (strip waveguide, directional coupler, 2D grating coupler, microring, silicon-organic hybrid slot waveguide). Various photonic processing functions are demonstrated, such as photonic switch, filtering, polarization/wavelength/mode (de)multiplexing, wavelength conversion, signal regeneration, optical logic and computing. Additionally, we also introduce extended silicon+ photonics and show recent works on on-chip graphene-silicon photonic signal processing. The advances in on-chip silicon photonic signaling and processing with favorable performance pave the way to integrate complete optical communication systems on a monolithic chip and integrate silicon photonics and silicon nanoelectronics on a chip. It is believed silicon photonics will enable more and more emerging advanced applications even beyond silicon photonic signaling and processing.

    更新日期:2018-07-12
  • A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-05
    Funian Mo, Hongfei Li, Zengxia Pei, Guojin Liang, Longtao Ma, Qi Yang, Donghong Wang, Yan Huang, Chunyi Zhi

    Thermal runaway has been a long-standing safety issue impeding the development of high-energy-density batteries. Physical safety designs such as employing circuit-breakers and fuses to batteries are limited by small operating voltage windows and no resumption of original working condition when it is cooled down. Here we report a smart thermoresponsive polymer electrolyte that can be incorporated inside batteries to prevent thermal runaway via a fast and reversible sol-gel transition, and successfully combine this smart electrolyte with a rechargeable Zn/α-MnO2 battery system. At high temperature, battery operation is inhibited as a result of the increased internal resistance caused by the gelation of liquid electrolyte. After cooling down, the electrolyte is spontaneously reversed to sol state and the electrochemical performance of the battery is restored. More importantly, sol-gel transition enables the smart battery to experience different charge-discharge rates under various temperature levels, providing a smart and active strategy to achieve dynamic and reversible self-protection.

    更新日期:2018-07-08
  • Sniffing with mass spectrometry
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-05
    Miao-Miao Chen, Hai-Feng Su, Ying Xie, Li-Fang He, Shui-Chao Lin, Mei-Lin Zhang, Cheng Wang, Su-Yuan Xie, Rong-Bin Huang, Lan-Sun Zheng

    Gaseous compounds are usually on-line detectable on sensors. The limitations of conventional sensors are suffering from incapability for exactly identifying multiple components as well as incompatibility to possible toxicants in every odor sample. Herein, we discuss an inlet modification to the laboratory standard mass spectrometer, inspired by the sensitive olfactory systems of animals, for direct sniffing, established by connecting a mini pump to the nebulizer gas tubing. The modified mass spectrometry method—sniffing-mass spectrometry (sniffing-MS)—can acquire detailed fingerprint spectra of mixed odors and shows high tolerance to toxicants. Furthermore, the method has a low limit of detection in the order of parts per trillion and is a ‘sampling-free’ technique for analyzing various gaseous compounds simultaneously, thus offering versatility for smelling daily commodities, tracking diffusion, and locating position of odors. Sniffing-MS can mimic or even surpass the olfaction of animals and is applicable for analyzing gaseous/volatile compounds, especially those polar compounds, in a simple manner depending on the intrinsic molecular mass-to-charge ratio.

    更新日期:2018-07-08
  • Generation of isogenic single and multiplex gene knockout mice by base editing-induced STOP
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-05
    Guang Yang, Tianyu Zhu, Zongyang Lu, Guanglei Li, Hao Zhang, Songjie Feng, Yajing Liu, Jianan Li, Yu Zhang, Jia Chen, Xuejiang Guo, Xingxu Huang

    Although CRISPR/Cas9 has been widely used to generate knockout mice, two major limitations remain: the founders usually carry a mixture of genotypes, and mosaicism harboring multiple genotypes. Therefore, it takes a long time to get homozygous mutants. Recently developed base editing (BE) system, which introduces C-to-T conversion without double strand DNA cleavage, has been used to introduce artificial stop codons (i-STOP) to prematurely terminate translation, providing a cleaner strategy for genome engineering. Using this strategy, we generated CD160 KO and VISTA/CD160 double KO mice by microinjection of a single sgRNA targeting CD160 and a mixture of sgRNAs targeting VISTA and CD160, respectively. The BE system induced STOP efficiently in mouse embryos and consequently in founder mice without detectable off-target. Most interestingly, the majority of the mutants harbor same genetic modifications, indicating we generated isogenic single and multiplex gene mutant mice by BE-induced STOP. We also obtained homozygous mutant mouse in F1 mice, demonstrating the accelerated strategy in generating animal models.

    更新日期:2018-07-08
  • Explicit Diagnosis of the Local Ozone Production Rate and the Ozone-NOx-VOC Sensitivities
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-05
    Zhaofeng Tan, Keding Lu, Huabin Dong, Min Hu, Xin Li, Yuhan Liu, Sihua Lu, Min Shao, Rong Su, Haichao Wang, Yusheng Wu, Andreas Wahner, Yuanhang Zhang

    In the troposphere, ozone is a harmful gas compound to both human health and vegetation. Ozone is produced from the reaction of NOx (=NO+NO2) and VOCs (volatile organic compounds) with light. Due to the highly nonlinear relationships between ozone and its precursors, proper ozone mitigation relies on the knowledge of chemical mechanisms. In this study, an observation-based method is used to simulate ozone formation and elucidate its controlling factors for a rural site on the North China Plain. The instantaneous ozone production rate is calculated utilizing a box model using the dataset obtained from the Wangdu campaign. First, the model was operated in a time-dependent mode to calculate the ozone production rate at each time stamp. The calculated ozone formation rate showed a diurnal average maximum value of 17 ppbv/h (1-h diurnal averaged). The contribution of individual peroxy radicals to ozone production was analyzed. In addition, the functional dependence of calculated P(O3) reveals that ozone production was in a NOx-limited regime during the campaign. Furthermore, the missing peroxy radical source will further extend NOx-limited conditions to earlier in the day, making NOx limitation dominate more of a day than the current chemical model predicts. Finally, a multiple scenarios mode, also known as EKMA (empirical kinetic modeling approach), was used to simulate the response of P(O3) to the imaginary change in precursor concentrations. We found that ozone production was in the NOx-limited region. However, the use of NO2 measured by the molybdenum converter and/or the absence of a peroxy radical source in the current chemical model could over-emphasize the VOC-limited effect on ozone production.

    更新日期:2018-07-08
  • Simultaneous observation of quantum contextuality and quantum nonlocality
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-06
    Xiao-Min Hu, Bi-Heng Liu, Jiang-Shan Chen, Yu Guo, Yu-Chun Wu, Yun-Feng Huang, Chuan-Feng Li, Guang-Can Guo

    Quantum nonlocality and quantum contextuality are the most curious properties that change our understanding of nature, and were observed independently in recent decades. One important question is whether both properties can be observed simultaneously. In this letter, we show that in a qutrit-qutrit system we can observe quantum nonlocality and quantum contextuality at the same time. From the perspective of quantum information, our experiment proves in principle that the two resources, quantum nonlocality and quantum contextuality, can be utilized simultaneously.

    更新日期:2018-07-08
  • A secret key distribution technique based on semiconductor superlattice chaos devices
    Sci. Bull. (IF 4.136) Pub Date : 2018-07-02
    Wei Liu, Zhizhen Yin, Xiaoming Chen, Zhenyun Peng, Helun Song, Peihua Liu, Xinhai Tong, Yaohui Zhang
    更新日期:2018-07-02
  • Seismological challenges in earthquake hazard reductions: reflections on the 2008 Wenchuan earthquake
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-30
    Yong Chen, Jiupeng Hu, Fei Peng

    The Wenchuan earthquake is a natural disaster. Its occurrence and aftermath have demonstrated the critical roles of seismology and earthquake engineering in reducing seismic hazards and damages. However, their existing limitations should also be underscored. This article summarized and reviewed the current scientific understanding of earthquake ruptures, and new insights gained since the Wenchuan event. This study focused on the related challenges to seismology and earthquake engineering as follows: (1) The under-estimation of earthquake risks before occurrences; (2) The current limited data regarding large earthquakes in continental thrust fault systems; (3) The causal relationship between the Wenchuan earthquake and the reservoir impoundment in its vicinity; (4) The identification of low-velocity zone in the crust and its seismogenical role; and (5) The casualties and economic losses from a cascade of diverse natural hazards triggered by the ruptures, and the excellent earthquake resistance associated with tunnels in mountainous terrain.

    更新日期:2018-07-01
  • Oxygen-deficient bismuth tungstate and bismuth oxide composite photoanode with improved photostability
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-27
    Hoi Ying Chung, Weijian Chen, Xiaoming Wen, Judy N. Hart, Hao Wu, Yuekun Lai, Rose Amal, Yun Hau Ng

    A homogeneous layer of Bi2O3-Bi14WO24 composite (BWO/Bi2O3) thin film was fabricated using a combination of electrodeposition and thermal treatment. The evenly distributed Bi14WO24 component within the Bi2O3 layer was found to be important in stabilising the photoelectrochemical performances of Bi2O3 photoanode by promoting the photoelectron transport. The unmodified Bi2O3 suffered from severe photocorrosion as proven by X-ray diffraction (XRD) and inductively coupled plasma (ICP) analyses while the composite thin film was active without noticeable activity decay for at least 3 h of illumination. This strategy might be applicable to other photocatalysts with stability issues.

    更新日期:2018-06-27
  • 64-qubit quantum circuit simulation
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-20
    Zhao-Yun Chen, Qi Zhou, Cheng Xue, Xia Yang, Guang-Can Guo, Guo-Ping Guo
    更新日期:2018-06-22
  • Superconductivity at 10.4 K in a novel quasi-one-dimensional ternary molybdenum pnictide K2Mo3As3
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-22
    Qing-Ge Mu, Bin-Bin Ruan, Kang Zhao, Bo-Jin Pan, Tong Liu, Lei Shan, Gen-Fu Chen, Zhi-An Ren
    更新日期:2018-06-22
  • Enhanced photoresponsivity and hole mobility of MoTe2 phototransistors by using an Al2O3 high-κ gate dielectric
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-15
    Wenjie Chen, Renrong Liang, Jing Wang, Shuqin Zhang, Jun Xu
    更新日期:2018-06-15
  • A possible family of Ni-based high temperature superconductors
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-15
    Congcong Le, Jinfeng Zeng, Yuhao Gu, Guang-Han Cao, Jiangping Hu
    更新日期:2018-06-15
  • Hierarchically porous carbon/red phosphorus composite for high-capacity sodium-ion battery anode
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-12
    Meng Li, Na Feng, Mengmeng Liu, Zifeng Cong, Jiangman Sun, Chunhua Du, Quanbin Liu, Xiong Pu, Weiguo Hu
    更新日期:2018-06-13
  • Tuning radical reactivity for selective radical/radical cross-coupling
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-07
    Shengchun Wang, Shan Tang, Aiwen Lei
    更新日期:2018-06-08
  • Toxicity of silicon dioxide nanoparticles with varying sizes on the cornea and protein corona as a strategy for therapy
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-08
    Dayu Sun, Linji Gong, Jing Xie, Xianliang Gu, Yijian Li, Qinglin Cao, Qiyou Li, A. Luodan, Zhanjun Gu, Haiwei Xu
    更新日期:2018-06-08
  • PEGylated mBPEI-rGO nanocomposites facilitate hepotocarcinoma treatment combining photothermal therapy and chemotherapy
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-07
    Chunyi Tong, Xizhi Zhang, Jialong Fan, Bin Li, Bin Liu, Muhammad Daniyal, Wei Wang
    更新日期:2018-06-07
  • Enhanced catalysis of ultrasmall Au-MoS2 clusters against reactive oxygen species for radiation protection
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-07
    Peixian Bian, Jinxuan Zhang, Junying Wang, Jiang Yang, Jingya Wang, Haile Liu, Yuanming Sun, Meixian Li, Xiao-Dong Zhang
    更新日期:2018-06-07
  • Calcium-catalyzed reactions of element-H bonds
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-05
    Lei Yu, Rongrong Qian, Xin Deng, Fang Wang, Qing Xu
    更新日期:2018-06-05
  • Thermoelectric properties of metal-(Z)-1,2-dihydroselenoethene-1,2-dithiol coordination polymers
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-05
    Yutao Cui, Jie Yan, Yue Sun, Ye Zou, Yimeng Sun, Wei Xu, Daoben Zhu
    更新日期:2018-06-05
  • 更新日期:2018-06-03
  • A vicinal effect for promoting catalysis of Pd1/TiO2: Supports of atomically dispersed catalysts play more roles than simply serving as ligands
    Sci. Bull. (IF 4.136) Pub Date : 2018-03-10
    Pengxin Liu, Yun Zhao, Ruixuan Qin, Lin Gu, Peng Zhang, Gang Fu, Nanfeng Zheng
    更新日期:2018-06-03
  • Atomic scale electronic structure of the ferromagnetic semiconductor Cr2Ge2Te6
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-01
    Zhenqi Hao, Haiwei Li, Shunhong Zhang, Xintong Li, Gaoting Lin, Xuan Luo, Yuping Sun, Zheng Liu, Yayu Wang
    更新日期:2018-06-01
  • Origin of symmetry breaking in the seed-mediated growth of bi-metal nano-heterostructures
    Sci. Bull. (IF 4.136) Pub Date : 2018-06-01
    Guifen Du, Jun Pei, Zhiyuan Jiang, Qiaoli Chen, Zhenming Cao, Qin Kuang, Zhaoxiong Xie, Lansun Zheng
    更新日期:2018-06-01
  • Ultraviolet/ozone and oxygen plasma treatments for improving the contact of carbon nanotube thin film transistors
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-30
    Qi Huang, Jiye Xia, Jie Zhao, Guodong Dong, Fang Liu, Hu Meng, Xuelei Liang

    Carbon nanotube thin film transistor (CNT-TFT) is an emerging technology for future macroelectronics, such as chemical and biological sensors, optical detectors, and the backplane driving circuits for flat panel displays. The mostly reported fabrication method of CNT-TFT is a lift-off based photolithography process. In such fabrication process, photoresist (PR) residue contaminates the interface of tube-metal contact and deteriorates the device performance. In this paper, ultraviolet ozone (UVO) and oxygen plasma treatments were employed to remove the PR contamination. Through our well-designed experiments, the UVO treatment is confirmed an effective way of cleaning contamination at the tube-metal interface, while oxygen plasma treatment is too reactive and hard to control, which is not appropriate for CNT-TFTs. It is determined that 2-6 min UVO treatment is the preferred window, and the best optimized treatment time is 4 min, which leads to 15% enhancement of device performance.

    更新日期:2018-05-31
  • 更新日期:2018-05-31
  • Identification and functional analysis of heterogeneous FOXP3+ Treg cell subpopulations in human pancreatic ductal adenocarcinoma
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-30
    Gang Yi, Shiwei Guo, Wenyu Liu, Huan Wang, Rendong Liu, Andy Tsun, Gang Jin, Bin Li

    CD4+ CD25+ regulatory T (Treg) cells express the transcription factor FOXP3 and play an essential role in preventing autoimmunity. Abundant Treg cell accumulation in tumors and tumor draining lymph nodes (TDLNs) has been reported to correlate with both poor and favorable prognosis in various cancers, which suggests that Tregs may have multiple effects on antitumor immunity. However, the heterogeneity of tumor- and TDLN-infiltrating Treg cells remains unclear. Here we provide heterogeneity analysis of tumor infiltrating human CD4+ Treg cells and their matched adjacent tissues and TDLNs. We defined three different subpopulations of tumor- and TDLN-infiltrating Treg cells by Helios and CCR8 expression in pancreatic ductal adenocarcinoma (PDAC) and confirmed their functional heterogeneity. Helios+ CCR8+ Treg cells with potent suppressor function and limited IL-2 and IFN-γ secretion were identified in tumors and TDLNs. On the contrary, Helios- CCR8- Treg cells have impaired suppressive activity, and elevated expression of pro-inflammatory cytokines. More advanced grades of PDAC have predominantly Helios+ CCR8+ Treg cells and few Helios- CCR8- Treg cells both in tumors and TDLNs that suggests poor prognosis. These data could help further define the role of Treg cells and their functional role in tumors and TDLNs.

    更新日期:2018-05-31
  • Activation of parvalbumin interneurons in anterior cingulate cortex impairs observational fear
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-31
    Chunran Zhou, Zheng Zhou, Yushui Han, Zhuogui Lei, Lei Li, Quentin Montardy, Xuemei Liu, Fuqiang Xu, Liping Wang

    The ability to detect conspecific’s distress is crucial for animal survival. In rodent models, observational fear (OF) occurs when one animal perceives another’s fear related negative emotions and emotions, which may model certain behaviors caused by witnessing traumatic experiences in humans. Anterior cingulate cortex (ACC) has been showed to play a crucial role in OF. However, cellular and neural circuit basis relating to ACC governing OF are poorly understood. Here, we used Designer Receptor Exclusively Activated by a Designer Drug (DREADD) system to demonstrate the cell type specific circuit mechanism of ACC in OF. Firstly, inhibitory hM4D (Gi) designer receptor together with clozapine N-oxide (CNO) injection was applied to inactivate ACC neurons in the observer mice. We found that, chemogenetic inhibition of ACC resulted in a decreased freezing response in the observer mice. Next, combining PV-ires-Cre mice and Cre-dependent DREADD system, we selectively targeted the ACC parvalbumin (PV) interneurons with the excitatory hM3D (Gq) designer receptor. Activation of ACC PV interneurons following CNO injection reduced freezing response in the observer mice, while had no effect on freezing response in the demonstrator mice. Finally, monosynaptic rabies retrograde tracing revealed that ACC PV interneurons receive inputs from the mediodorsal thalamic nucleus (MD) and the ventromedial thalamic nucleus (VM), both known for their roles in OF. Taken together, these findings reveal that ACC activation is important for OF, during which PV interneurons in ACC play an important regulatory role. Abnormal function of ACC PV interneurons might contribute to the pathology of empathy- deficits related diseases, such as autism and schizophrenia.

    更新日期:2018-05-31
  • Bright and pure single-photons from quantum dots in micropillar cavities under up-converted excitation
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-29
    Rongling Su, Shunfa Liu, Yuming Wei, Ying Yu, Jin Liu, Siyuan Yu, Xuehua Wang
    更新日期:2018-05-30
  • A novel superhard tungsten nitride predicted by machine-learning accelerated crystal structure search
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-29
    Kang Xia, Hao Gao, Cong Liu, Jianan Yuan, Jian Sun, Hui-Tian Wang, Dingyu Xing
    更新日期:2018-05-30
  • In-situ electrochemical activation designed hybrid electrocatalysts for water electrolysis
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-29
    Xiao Shang, Bin Dong, Yong-Ming Chai, Chen-Guang Liu
    更新日期:2018-05-29
  • Predicting lifetime risk for developing atherosclerotic cardiovascular disease in Chinese population: the China-PAR project
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-25
    Fangchao Liu, Jianxin Li, Jichun Chen, Dongsheng Hu, Ying Li, Jianfeng Huang, Xiaoqing Liu, Xueli Yang, Jie Cao, Chong Shen, Ling Yu, Zhendong Liu, Xianping Wu, Liancheng Zhao, Xigui Wu, Dongfeng Gu, Xiangfeng Lu

    Evidence on the lifetime risk for atherosclerotic cardiovascular disease (ASCVD) is insufficient; yet, estimating an individual’s lifetime risk allows for a comprehensive assessment of ASCVD burden. We developed and validated lifetime risk prediction equations for ASCVD using four large and ongoing prospective cohorts of Chinese, the China-PAR project (Prediction for ASCVD Risk in China). Sex-specific equations were developed using two cohorts (as the derivation cohort) of 21,320 participants. Two other independent cohorts with 14,123 and 70,838 participants were used for their external validation, respectively. We evaluated both calibration and discrimination measures for model performance. Furthermore, we estimated ASCVD-free years lost or excess absolute risk attributable to high 10-year risk (≥10.0%) and/or high lifetime risk (≥32.8%). After 12.3 years’ follow-up of the derivation cohort, 1,048 ASCVD events and 1,304 non-ASCVD deaths were identified. Our sex-specific equations had good internal validation, with discriminant C statistics of 0.776 (95% confidence interval [CI]: 0.757-0.794) and 0.801 (95% CI: 0.778-0.825), and calibration χ2 χ 2 of 9.2 (P = 0.418) and 5.6 (P = 0.777) for men and women, respectively. Good external validation was also demonstrated with predicted rates closely matched to the observed ones. Compared with men having both low 10-year and low lifetime risk, men would develop ASCVD 3.0, 4.6 and 8.6 years earlier if they had high 10-year risk alone, high lifetime risk alone, or both high 10-year and high lifetime risk at the index age of 35 years, respectively. We developed well-performed lifetime risk prediction equations that will help to identify those with the greatest potential to avert ASCVD burden after implementation of innovative clinical and public health interventions in China.

    更新日期:2018-05-25
  • Synthesis of amphiphilic poly(fluorene) derivatives for selective imaging of Staphylococcus aureus
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-24
    Ping He, Fengting Lv, Libing Liu, Shu Wang
    更新日期:2018-05-24
  • Symmetry protected topological Luttinger liquids and the phase transition between them
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-17
    Hong-Chen Jiang, Zi-Xiang Li, Alexander Seidel, Dung-Hai Lee
    更新日期:2018-05-17
  • High precision nuclear mass predictions towards a hundred kilo-electron-volt accuracy
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-17
    Zhongming Niu, Haozhao Liang, Baohua Sun, Yifei Niu, Jianyou Guo, Jie Meng
    更新日期:2018-05-17
  • Long-term surface water changes and driving cause in Xiong’an, China: from dense Landsat time series images and synthetic analysis
    Sci. Bull. (IF 4.136) Pub Date : 2018-05-10
    Chunqiao Song, Linghong Ke, Hang Pan, Shengan Zhan, Kai Liu, Ronghua Ma
    更新日期:2018-05-10
  • 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.

    更新日期:2018-05-03
  • 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.

    更新日期:2018-04-28
  • 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 π π 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.

    更新日期:2018-04-26
  • 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.

    更新日期:2018-04-25
  • 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.

    更新日期:2018-04-25
  • 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.

    更新日期:2018-04-25
  • 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.

    更新日期:2018-04-25
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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