Chinese Academy of SciencesBeijing

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Chinese Academy of SciencesBeijing

Chinese, China
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Zeng Y.,Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular SciencesInstitute of Chemistry | Mahmood Q.,Chinese Academy of SciencesBeijing | Hao X.,Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular SciencesInstitute of Chemistry | Sun W.-H.,Chinese Academy of Engineering Physics
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2017

A series of 8-(arylimino)-5,6,7-trihydroquinolines ligand pendant fluorenyl group at N-aryl ring, and their nickel complexes (Ni1-Ni5) have been prepared and characterized. Once activated with Et2AlCl, the complexes Ni1, Ni2, and Ni3 bearing ligands from para-fluorenylaniline produced unimodal polyethylenes; on the contrary complexes Ni4 and Ni5 gave bimodal polyethylenes due to steric influence of ligands from ortho-fluorenyl anilines. With a increment of Et2Zn/Ni4 ratio from 0 to 400, the distinct bimodel polyethylenes were obtained with molecular weights shifted from 14.3 to 57.6 kg·mol-1; apart shiftment to higher molecular weights, the portion of low molecular weight decreased along with higher portion of high molecular weight. © 2017 Wiley Periodicals, Inc.

Zhai Q.,Chinese Academy of SciencesKunming | Zhai Q.,University of Chinese Academy of Sciences | Zhai Q.,CAS National Astronomical Observatories | Zhai Q.,Chinese Academy of SciencesBeijing
New Astronomy | Year: 2017

The El Niño No. 3 area index (5°S∼ 5°N, 150°W∼ 90°W) and yearly sunspot number (SSN) from 1408 to 1978 are used to investigate the influence of solar activity on the El Niño/Southern Oscillation (ENSO), through periodicity analysis, cross wavelet transform (XWT), cross correlation and ensemble empirical mode decomposition (EEMD) analyses. The solar activity period, the Hale period, and the Gleissberg period are determined in the El Niño index time series, but of weak statistical significance. Cross correlation analysis of the index with SSN, and that of its low-frequency components decomposed by EEMD clearly indicate that solar activity may take effect on the ENSO, and such an impact should undergo an accumulation procedure (phase delay). XWT also indicates the existence of the impact. It is found that the index is negatively correlated with SSN when SSN is large during a certain long-term interval, and positively when SSN is small. Strong El Niño is inferred to be taken place in decade(s) to come. © 2016 Elsevier B.V.

Huang C.,Chinese Academy of Sciences | Zeng Y.,Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular ScienceInstitute of Chemistry | Flisak Z.,Chinese Academy of SciencesBeijing | Zhao Z.,Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular ScienceInstitute of Chemistry | And 2 more authors.
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2017

A series of 8-(nitro/benzhydryl-substituted arylimino)-7,7-dimethyl-5,6-dihydroquinolines and the corresponding nickel halide complexes were synthesized and characterized. Molecular structures of representative nickel complexes were determined by single crystal X-ray diffraction, showing the dinuclear dimers with distorted square-pyramidal geometry around the nickel center. The binding energies determined by X-ray photoelectron spectroscopy (XPS) indicate the effective coordination between the sp2-nitrogen and nickel atoms as well as the influence of both the halogen ligands and the substituents within dihydroquinolines on the strength of the Ni-N bond. Ethylene polymerization with the nickel precatalysts in presence of either methylaluminoxane or diethylaluminum chloride was explored in detail. For the complexes containing the nitro substituent within the organic ligand, the catalytic activity is inversely proportional to the electron density around the nickel core determined by XPS; such phenomenon is consistent with the conclusion of the computational study stating that the activity of precatalysts is correlated with the net charge on the metal center. In the polymerization process, unimodal and branched polyethylenes containing vinyl or vinylene groups were obtained. The nickel precatalysts bearing bulky benzhydryl within the organic ligand as well as bromide rather than chloride attached to the nickel atom produce polymers with relatively large amount of vinylene groups. © 2017 Wiley Periodicals, Inc.

Wong G.,CAS Institute of Microbiology | Wong G.,Chinese Academy of SciencesBeijing | Liu W.,CAS Institute of Microbiology | Liu W.,Chinese Academy of SciencesBeijing | And 9 more authors.
Cell Host and Microbe | Year: 2015

Super-spreading occurs when a single patient infects a disproportionate number of contacts. The 2015 MERS-CoV, 2003 SARS-CoV, and to a lesser extent 2014-15 Ebola virus outbreaks were driven by super-spreaders. We summarize documented super-spreading in these outbreaks, explore contributing factors, and suggest studies to better understand super-spreading. © 2015 Elsevier Inc.

Ding R.,Peking University | Li T.,CAS Institute of Theoretical Physics | Li T.,University of Electronic Science and Technology of China | Staub F.,CERN | And 3 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We propose the supersymmetric Standard Models (SSMs) with a pseudo-Dirac gluino from hybrid F- and D-term supersymmetry (SUSY) breaking. Similar to the SSMs before the LHC, all the supersymmetric particles in the minimal SSM obtain the SUSY breaking soft terms from the traditional gravity mediation and have masses within about 1 TeV except gluino. To evade the LHC SUSY search constraints, the gluino also has a heavy Dirac mass above 3 TeV from D-term SUSY breaking. Interestingly, such a heavy Dirac gluino mass will not induce the electroweak fine-tuning problem. We realize such SUSY breaking via an anomalous U(1)X gauge symmetry inspired from string models. To maintain the gauge coupling unification and increase the Higgs boson mass, we introduce extra vectorlike particles. We study the viable parameter space which satisfies all the current experimental constraints and present a concrete benchmark point. This kind of model not only preserves the merits of pre-LHC SSMs such as naturalness, dark matter, etc., but also solves the possible problems in the SSMs with Dirac gauginos due to the F-term gravity mediation. © 2015 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "" Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Chen W.,National University of Singapore | Wang Y.,Chinese Academy of SciencesBeijing | Ji W.,National University of Singapore
Journal of Physical Chemistry C | Year: 2015

We report our observation of two-photon absorption (2PA) in graphene enhanced by the excitonic Fano resonance at the saddle point with femtosecond laser pulses in the spectral range from 1.8 to 2.9 eV (or, from 435 to 700 nm). On the basis of the second-order, time-dependent perturbation theory on interband transitions among three states near the saddle point of two-dimensional systems (used in the Bassani-Hassan theoretical model), we develop a semiempirical model to take excitons in graphene into consideration. We find that the model is in agreement with the photon-energy dependence of the observed 2PA spectrum with a scaling factor of B = (1-5) × 102 cm/MW/eV5. © 2015 American Chemical Society.

Wang J.,CAS Institute of Process Engineering | Zhao B.,Chinese Academy of SciencesBeijing | Li J.,CAS Institute of Process Engineering
AIChE Journal | Year: 2016

Mesoscience has recently been proposed as a possible general concept for describing complex systems far from equilibrium, however, concrete formulations are needed, and particularly, a statistical mechanics foundation of mesoscience remains to be explored. To this end, the mathematical theory of stochastic geometry is combined with the energy minimization multi-scale (EMMS) principle under the concept of mesoscience to propose a statistical mechanics framework. An EMMS-based particle velocity distribution function is then derived as an example to show how the proposed framework works, and more importantly, as a first key step toward a generalized kinetic theory for heterogeneous gas-solid flow. It was shown that the resultant EMMS-based distribution is bimodal, instead of the widely-used Maxwellian distribution, but it reduces to the Maxwellian distribution when the gas-solid system is homogeneous. The EMMS-based distribution is finally validated by comparing its prediction of the variance of solid concentration fluctuation and granular temperature with experimental data available in literature. © 2016 American Institute of Chemical Engineers.

Liu X.,Chinese Academy of SciencesBeijing | Wang L.,CAS Institute of Process Engineering | Ge W.,CAS Institute of Process Engineering
AIChE Journal | Year: 2016

Statistical properties of particles in heterogeneous gas-solid flow were numerically investigated based on the results of a three-dimensional large-scale direct numerical simulation (DNS). Strong scale-dependence and local non-equilibrium of these properties, especially the particle fluctuating velocity (PFV) or granular temperature, were observed to be related to the effect of meso-scale structures formed by the compromise in competition between fluid and particle dominated mechanisms. To quantify such effects, the heterogeneous structures were partitioned into a gas-rich dilute phase and a solid-rich dense phase according to the particle-scale voidage defined through the Voronoi tessellation. Non-equilibrium features, such as the deviation of PFV from Gaussian distribution and anisotropy, were found even in phase-specific properties. A new distribution function for the PFV well characterizing these features was obtained by fitting the DNS results, which takes a typical bi-disperse mode, with phase-specific granular temperatures. The implications of these findings to the kinetic theory of granular flow and traditional continuum models of gas-solid flow were also discussed. © 2016 American Institute of Chemical Engineers AIChE J, 2016 © 2016 American Institute of Chemical Engineers.

Zhang W.,Beijing National Laboratory for Molecular SciencesInstitute of Chemistry | Yu G.,Chinese Academy of SciencesBeijing
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2016

Constructing planar, rigid, and high electronically delocalized π-conjugated molecular system is the most basic requirements of obtaining high-performance polymeric semiconductors for organic field-effect transistors (OFETs). In this regard, diarylethylene (DAE)-based polymers show great potential because many substantive progresses related to polymer field-effect transistors had been achieved from the kind of polymer materials in recent years. In the brief review, series of DAE-based polymer are highlighted, based on which several design strategies have been summarized by the way of comparative research method. These strategies have important guiding significance not only for further developing new DAE-based and other polymeric semiconductors for OFETs but also for developing specific polymeric semiconductors for other organic electronics, such as organic photovoltaics and organic light-emitting diodes. © 2016 Wiley Periodicals, Inc.

Gu Y.,U.S. Geological Survey | Wylie B.K.,U.S. Geological Survey | Zhang L.,Chinese Academy of SciencesBeijing | Gilmanov T.G.,South Dakota State University
Biomass and Bioenergy | Year: 2012

This study evaluates the carbon fluxes and trends and examines the environmental sustainability (e.g., carbon budget, source or sink) of the potential biofuel feedstock sites identified in the Greater Platte River Basin (GPRB). A 9-year (2000-2008) time series of net ecosystem production (NEP), a measure of net carbon absorption or emission by ecosystems, was used to assess the historical trends and budgets of carbon flux for grasslands in the GPRB. The spatially averaged annual NEP (ANEP) for grassland areas that are possibly suitable for biofuel expansion (productive grasslands) was 71-169 g C m-2 year-1 during 2000-2008, indicating a carbon sink (more carbon is absorbed than released) in these areas. The spatially averaged ANEP for areas not suitable for biofuel feedstock development (less productive or degraded grasslands) was -47 to 69 g C m-2 year-1 during 2000-2008, showing a weak carbon source or a weak carbon sink (carbon emitted is nearly equal to carbon absorbed). The 9-year pre-harvest cumulative ANEP was 1166 g C m-2 for the suitable areas (a strong carbon sink) and 200 g C m-2 for the non-suitable areas (a weak carbon sink). Results demonstrate and confirm that our method of dynamic modeling of ecosystem performance can successfully identify areas desirable and sustainable for future biofuel feedstock development. This study provides useful information for land managers and decision makers to make optimal land use decisions regarding biofuel feedstock development and sustainability. © 2012 Elsevier Ltd.

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