Beijing, China
Beijing, China

Beijing Normal University , colloqiually known as 北师大 or Beishida, is a public research university located in Beijing with strong emphasis on basic disciplines of humanities and science. It is one of the oldest and most prestigious universities in China.A normal school referred to an institution that aimed to train school teachers in the early twentieth century, and this terminology is preserved in the official names of such institutions in China. Wikipedia.

Time filter

Source Type

Wang H.-Y.,Beijing Normal University | Bao J.-D.,Beijing Normal University
Physica A: Statistical Mechanics and its Applications | Year: 2017

In the paper, we investigate the transport properties of coupled flashing ratchets in viscoelastic media. Using generalized Langevin equation, subvelocity Vα, subdiffusive coefficient Dα and generalized Peclet number Peα are calculated as functions of the temperature T and the flashing period τ with different subdiffusive exponents α. The results show that the transport of coupled flashing ratchets can be optimized in viscoelastic media. © 2017 Elsevier B.V.

Zhang J.-M.,Beijing Normal University | Bao J.-D.,Beijing Normal University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2017

We study a frequency-dependent damping model of hyperdiffusion within the generalized Langevin equation. The model allows for the colored noise defined by its spectral density, assumed to be proportional to ωδ-1 at low frequencies with 0<δ<1 (sub-Ohmic damping) or 1<δ<2 (super-Ohmic damping), where the frequency-dependent damping is deduced from the noise by means of the fluctuation-dissipation theorem. It is shown that for super-Ohmic damping and certain parameters, the diffusive process of the particle in a titled periodic potential undergos sequentially four time regimes: thermalization, hyperdiffusion, collapse, and asymptotical restoration. For analyzing transition phenomenon of multidiffusive states, we demonstrate that the first exist time of the particle escaping from the locked state into the running state abides by an exponential distribution. The concept of an equivalent velocity trap is introduced in the present model; moreover, reformation of ballistic diffusive system is also considered as a marginal situation but does not exhibit the collapsed state of diffusion. © 2017 American Physical Society.

Zhang X.,Beijing Normal University | Liu F.,Beijing Normal University | Zheng S.,Beijing Normal University
Bioresource Technology | Year: 2017

This is the first study to achieve a short HRT (∼2 h for the A/O reactor), high MLSS (∼10 g L−1), and high volumetric loading (∼3.7 kg COD m−3 d−1 and ∼0.6 kg NH4-N m−3 d−1) in the A/O process for sewage treatment by enhancing biomass retention in the secondary clarifier (∼4 h settling time), which we refer to as the high-performance A/O process (HP-A/O) in this paper. Over 258 days of continuous operation, with a decrease in HRT from 12 to 2 h, remarkable COD (95 ± 3%), NH4 +-N (98 ± 2%), TN (79 ± 5%), and TP (74 ± 10%) removals were stably achieved, while the air requirement significantly decreased by 22%. The HP-A/O process offers advantages over the conventional A/O process (6–8 h for A/O reactor, 3–5 g L−1 MLSS, and ∼1.0 kg COD m−3 d−1) for sewage treatment in terms of its lower energy consumption, smaller footprint and reactor requirements. © 2017 Elsevier Ltd

Lee C.-C.,Beijing Normal University | Lee C.-C.,National Sun Yat - sen University | Ning S.-L.,Beijing Normal University
Energy Economics | Year: 2017

This study investigates the dynamic relationship between oil price shocks and country risks using a Structural VAR framework for a sample of both net oil-exporting and net oil-importing countries over the period January 1994-December 2014. The results reveal that country risk is significantly affected by oil price shocks, but the impacts are different. Unanticipated positive oil price shocks trigger a reduction (addition) in country risk for net oil-exporting country (net oil-exporting countries). As to the responses of oil prices to country risk shock, evidence show that country risk shocks have a delayed significantly positive impacts on oil price for oil-exporting country. With respect to the effects of subcomponents of country risk, we find evidence that economic and political risk have a significant impact on supply-side shocks in net oil-exporting countries like Canada, while economic and political risk have a significant effect on supply-side shocks and oil specific demand shocks in net oil-importing countries like the US. These results are particularly important to policy makers and government. © 2017 Elsevier B.V.

Gao C.,China Academy of Engineering Physics | Lu J.,Beijing Normal University
Mathematical Methods in the Applied Sciences | Year: 2017

In this paper, we study the global well-posedness and scattering theory of the solution to the Cauchy problem of a generalized fourth-order wave equation [[EQUATION1]] where 1+4/d

Zeng X.,Beijing Normal University
Journal of religion and health | Year: 2015

Goenka's Vipassana meditation (GVM), a widely applied mindfulness training system rooted in Buddhism, is currently widely used. Although the two abilities cultivated in GVM, awareness and equanimity, exhibit certain similarities with the mindfulness cultivated in mindfulness-based psychotherapies (MBTs), they are not major concerns in MBTs. While many mindfulness scales have been created to measure different aspects of mindfulness constructs and certain scales and items can indeed reflect the basic abilities of awareness and equanimity, none of them can adequately capture the way in which those abilities and related ideas are applied in GVM. This paper presents a critical examination of the problems associated with the concepts and measurement of awareness and equanimity and presents potential solutions for achieving better measurement of these concepts in the future.

Huang H.,Beijing Normal University
Differential Geometry and its Application | Year: 2017

We show that no exotic R4 admits a complete Riemannian metric with uniformly positive isotropic curvature and with bounded geometry. This is essentially a corollary of the main result in [7], and was stated in [8] without proof. In the process of the proof we also show that the diffeomorphism type of an infinite connected sum of some connected smooth n-manifolds (n≥2) according to a locally finite graph does not depend on the gluing maps used. © 2017 Elsevier B.V.

Long R.,Beijing Normal University | Prezhdo O.V.,University of Southern California | Fang W.,Beijing Normal University
Wiley Interdisciplinary Reviews: Computational Molecular Science | Year: 2017

The review describes recent research into the nonequilibrium phenomena in nanoscale materials, with focus on charge separation and recombination, that form the basis for photovoltaic and photocatalytic devices. Nonadiabatic molecular dynamics combined with ab initio real-time time-dependent density functional theory enable us to model time-resolved laser experiments at the atomistic level, emphasizing realistic aspects of the materials, such as defects, dopants, boundaries, chemical bonding, etc. A variety of systems have been considered, including bulk semiconductors sensitized by semiconducting/metallic nanoparticles and graphene, nanocrystal/molecule junctions, polymer interfaces with carbon nanotubes and nanoclusters, van der Waals heterojunctions, black phosphorus, and hybrid organic-inorganic perovskites. The detailed atomistic knowledge obtained from the explicit time-domain modeling generates comprehensive understanding of electron-vibrational dynamics in complex multi-component systems, provides critical insights into quantum mechanical transport of energy and charge, and leads to valuable guidelines for improvement of solar-to-electric power conversion in photovoltaic and photocatalytic applications and for efficient performance of transport devices. For further resources related to this article, please visit the WIREs website. © 2017 Wiley Periodicals, Inc.

Towards the goal of establishing kinetic database for low-temperature combustion (T < 1000 K) of mid-sized biodiesel surrogates, the study uses quantum chemistry and statistical kinetic methods to investigate three primary unimolecular reaction pathways of methyl octanoate peroxy radicals, including dissociation, isomerization and concerted elimination. We calculate kinetic barriers and pressure-dependent rate constants at 500–1000 K. The comparison between our computed and previously estimated rate constants offers further insight into how transition state structures and molecular mechanics are correlated with reaction kinetics. In the branching ratio analysis, we investigate the proposed unimolecular reactions and factors affecting these kinetic characteristics. For the first time, the previously measured oxidation rates of methyl octanoate under the cool flame regime (560–1000 K) are computationally verified by kinetic modeling that reflects the contribution of the present submodel to an existing detailed mechanism of methyl octanoate. Consequently, the rate-of-production analysis reveals the significance of newly proposed reaction pathways. © 2017 The Combustion Institute

Xu L.,Beijing Normal University | Zhang Y.,Beijing Normal University
Advances in Intelligent Systems and Computing | Year: 2017

The risk caused by the rapid development of online P2P lending attracts more and more attention from the public. This paper mainly establishes a credit rating model for online P2P lending based on Analytic Hierarchy Process. Among lots of qualitative and quantitative indices focused by lenders, we screened out 39 indices and then established a model for calculating the weight of each index group based on Analytic Hierarchy Process. Finally we got a comprehensive score for each online lending project, and investors can evaluate the advantages and disadvantages of each P2P platform based on this model. At the same time, the model can help investors to make a rational choice considering the balance between risk and return according to their personal preferences. © Springer Science+Business Media Singapore 2017.

Wang X.,Beijing Normal University | Feng J.,CAS Institute of Atmospheric Physics
Atmospheric Science Letters | Year: 2017

A 1D air-sea interactive model that couples an atmospheric column model with a slab ocean model was introduced. The model simulated an exact balance between radiative cooling and convective heating in the free troposphere. Within the planet boundary layer, the turbulent mixing produces cooling in the upper part and warming in the lower part, which is compensated by radiative and convective heating together. The model was then used to explore the equilibrium response of sea surface temperature (SST) and precipitation to carbon dioxide (CO2) and aerosol forcing changes. Results show a warming or cooling signal owning to increased CO2 or aerosols can be well captured by the ocean, leading to an increasing or decreasing of the SST, and hence the precipitation. Cutting off the interactions between atmosphere and ocean however renders different results. By applying the relaxed weak temperature gradient (WTG) approximation, the local response to aerosol forcing perturbations was investigated, which was shown to be largely different from the global response in spite of the same forcing. To understand the nonlinear interactions among different forcings, the equilibrium responses to multiple combinations of CO2 and aerosol forcings are analyzed. © 2017 Royal Meteorological Society.

Wen L.-N.,Capital Medical University | Xie M.-X.,Beijing Normal University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2017

KRAS promoter can form G-quadruplex structure and regulate gene transcription. The drugs which can bind with G-quadruplex of KRAS promoter may be potential remedy for treatment of cancers associated with KRAS mutation. The interaction mechanism between the G-quadruplex of KRAS promoter and three isoquinoline alkaloids (jatrorrhizine, berberine and sanguinarine) has been investigated by UV-visible, fluorescence and circular dichroism spectroscopic methods. The results showed that the three alkaloids can form complexes with G-quadruplex KRAS promoter with the molecular ratio of 1:1, and the binding constants were (0.90 ± 0.16) × 106 L mol− 1, (0.93 ± 0.21) × 106 L mol− 1 and (1.16 ± 0.45) × 106 L mol− 1 for jatrorrhizine, berberine and sanguinarine. The absorption spectra, KI quenching and fluorescence anisotropy and polarization studies suggested jatrorrhizine and berberine interacted with G-quadruplex by not only end-stacking binding mode but also grooves or loops binding mode, while sanguinarine by end-stacking binding mode. Sanguinarine was more beneficial to maintain the stability and parallel conformation of KRAS promoter G-quadruplex. MTT assay was performed to evaluate antiproliferation effects of the three isoquinoline alkaloids on SW620 cells, and the antiproliferation effects of the three alkaloids were sanguinarine > berberine > jatrorrhizine. All the three alkaloids can bind with KRAS promoter G-quadruplex, and sanguinarine had the better binding property and antiproliferation effects on SW620 cells. The results obtained are meaningful to explore potential reagents targeting the parallel G-quadruplex structure of KRAS promoter for gene theraphy of colorectal carcinomas. © 2016 Elsevier B.V.

Tumor cells preferentially adopt aerobic glycolysis for their energy supply, a phenomenon known as the Warburg effect. It remains a matter of debate as to how the Warburg effect is regulated during tumor progression. Here, we show that CHIP (carboxyl terminus of Hsc70-interacting protein), a U-box E3 ligase, suppresses tumor progression in ovarian carcinomas by inhibiting aerobic glycolysis. While CHIP is downregulated in ovarian carcinoma, induced expression of CHIP results in significant inhibition of the tumor growth examined by in vitro and in vivo experiments. Reciprocally, depletion of CHIP leads to promotion of tumor growth. By a SiLAD proteomics analysis, we identified pyruvate kinase isoenzyme M2 (PKM2), a critical regulator of glycolysis in tumors, as a target that CHIP mediated for degradation. Accordingly, we show that CHIP regulates PKM2 protein stability and thereafter the energy metabolic processes. Depletion or knockout of CHIP increased the glycolytic products in both tumor and mouse embryonic fibroblast cells. Simultaneously, we observed that CHIP expression inversely correlated with PKM2 levels in human ovarian carcinomas. This study reveals a mechanism that the Warburg effect is regulated by CHIP through its function as an E3 ligase, which mediates the degradation of PKM2 during tumor progression. Our findings shed new light into understanding of ovarian carcinomas and may provide a new therapeutic strategy for ovarian cancer.Oncogene advance online publication, 27 March 2017; doi:10.1038/onc.2017.31. © 2017 Macmillan Publishers Limited, part of Springer Nature.

Yan G.,Beijing Normal University | Hu R.,Beijing Normal University | Wang Y.,Beijing Normal University | Ren H.,Peking University | And 3 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2016

Scale effect, which is caused by a combination of model nonlinearity and surface heterogeneity, has been of interest to the remote sensing community for decades. However, there is no current analysis of scale effect in the ground-based indirect measurement of leaf area index (LAI), where model nonlinearity and surface heterogeneity also exist. This paper examines the scale effect on the indirect measurement of LAI. We built multiscale data sets based on realistic scenes and field measurements. We then implemented five representative methods of indirect LAI measurement at scales (segment lengths) that range from meters to hundreds of meters. The results show varying degrees of deviation and fluctuation that exist in all five methods when the segment length is shorter than 20 m. The retrieved LAI from either Beer's law or the gap-size distribution method shows a decreasing trend with increasing segment lengths. The length at which the LAI values begin to stabilize is about a full period of row in row crops and 100 m in broadleaf or coniferous forests. The impacts of segment length on the finite-length averaging method, the combination of gap-size distribution and finite-length methods, and the path-length distribution method are relatively small. These three methods stabilize at the segment scale longer than 20 m in all scenes. We also find that computing the average LAI of all of the short segment lengths, which is commonly done, is not as good as merging these short segments into a longer one and computing the LAI value of the merged one. © 2015 IEEE.

Tian B.,Beijing Normal University | Yuan R.,Beijing Normal University
Nonlinear Analysis: Real World Applications | Year: 2017

This paper is devoted to the existence of the traveling waves of the equations describing a diffusive SEIR model with non-local reaction between the infected and the susceptible. The existence of traveling waves depends on the minimal speed c∗ and basic reproduction rate β/γ. We use the Laplace transform and the Schauder fixed point theorem to get the existence and non-existence of traveling waves in our paper. We also give some numerical results of the minimal wave speed. © 2017 Elsevier Ltd

Sun M.,Beijing Normal University | Mao J.,Beijing Normal University
Journal of Industrial Ecology | Year: 2017

To meet human needs, the geographical location of lead changes during the process of mining lead ore to produce lead products for use by humans. These changes reveal the influence of human activities on lead distribution on the surface of Earth. In this study, a framework was built to analyze changes in lead distribution. Lead was traced through its life cycle using this framework. The provincial administrative unit in mainland of China was defined as the unit of space. The process of anthropogenic spatial transfer of lead was quantitatively analyzed by comparing lead distribution between different areas during each stage of its life cycle in 2010. The results showed that in 2010, around 60% of domestic lead resources were distributed in the Inner Mongolia Autonomous Region, Yunnan Province, and other locations in China. Nearly 80% of the refined lead was produced in Henan, Anhui, Hunan, Yunnan, and Jiangsu provinces. More than 50% of lead products were fabricated and manufactured in Zhejiang, Jiangsu, Shandong, and Hebei provinces. The distribution of lead usage and scrap recovery was relatively uniform (approximately 21 provinces accounted for 1% to 6% of all scrap in the country), although lead products and scrap were mainly distributed in Guangdong, Shandong, Jiangsu, and Zhejiang provinces, which together accounted for nearly 40% of the total. The recycling of lead scrap was mainly concentrated in Anhui (around 57% of the total). Overall, during the whole process, from the mining lead ore from the lithosphere to each stage of the product life cycle, lead was gradually transferred from the south and north of China to the central area and, finally, to the eastern coastal areas. © 2017, Yale University.

Ma F.,Beijing Normal University | Ye A.,Beijing Normal University | Duan Q.,Beijing Normal University
Climate Dynamics | Year: 2017

An experimental seasonal drought forecasting system is developed based on 29-year (1982–2010) seasonal meteorological hindcasts generated by the climate models from the North American Multi-Model Ensemble (NMME) project. This system made use of a bias correction and spatial downscaling method, and a distributed time-variant gain model (DTVGM) hydrologic model. DTVGM was calibrated using observed daily hydrological data and its streamflow simulations achieved Nash–Sutcliffe efficiency values of 0.727 and 0.724 during calibration (1978–1995) and validation (1996–2005) periods, respectively, at the Danjiangkou reservoir station. The experimental seasonal drought forecasting system (known as NMME-DTVGM) is used to generate seasonal drought forecasts. The forecasts were evaluated against the reference forecasts (i.e., persistence forecast and climatological forecast). The NMME-DTVGM drought forecasts have higher detectability and accuracy and lower false alarm rate than the reference forecasts at different lead times (from 1 to 4 months) during the cold-dry season. No apparent advantage is shown in drought predictions during spring and summer seasons because of a long memory of the initial conditions in spring and a lower predictive skill for precipitation in summer. Overall, the NMME-based seasonal drought forecasting system has meaningful skill in predicting drought several months in advance, which can provide critical information for drought preparedness and response planning as well as the sustainable practice of water resource conservation over the basin. © 2017 Springer-Verlag Berlin Heidelberg

Lu S.,Beijing Normal University
Pure and Applied Geophysics | Year: 2017

The magnitude–frequency relationship is a fundamental statistic in seismology. Customarily, the temporal variations of b values in the magnitude–frequency distribution are demonstrated via “sliding-window” approach. However, the window size is often only tuned empirically, which may cause difficulties in interpretation of b value variability. In this study, a continuous-time hidden Markov model (HMM) is applied to characterize b value variations of New Zealand shallow earthquakes over decades. HMM-based approach to the b value estimation has some appealing properties over the popular sliding-window approach. The estimation of b value is stable over a range of magnitude thresholds, which is ideal for the interpretation of b value variability. The overall b values of medium and large earthquakes across North Island and northern South Island in New Zealand vary roughly at a decade scale. It is noteworthy that periods of low b values are typically associated with the occurrences of major large earthquakes. The overall temporal variations of b values seem prevailing over many grids in space as evidenced by a comparison of spatial b values in many grids made between two periods with low or high b values, respectively. We also carry out a pre-seismic b value analysis for recent Darfield earthquake and Cook Strait swarm. it is suggested that the mainshock rupture is nucleated at the margin of or right at low b value asperities. In addition, short period of pre-seismic b value decrease is observed in both cases. The overall time-varying behavior of b values over decades is an indication of broad scale of time-varying behavior associated with subduction process, probably related to the convergence rate of the plates. The advance in the method of b value estimation will enhance our understanding of earthquake occurrence and may lead to improved risk forecasting. © 2017, Springer International Publishing.

Zhang X.-T.,Beijing Normal University | Wang S.,CAS Institute of Chemistry | Xing G.-W.,Beijing Normal University
ACS Applied Materials and Interfaces | Year: 2017

Ginsenoside is a large family of triterpenoid saponins from Panax ginseng, which possesses various important biological functions. Due to the very similar structures of these complex glycoconjugates, it is crucial to develop a powerful analytic method to identify ginsenosides qualitatively or quantitatively. We herein report an eight-channel fluorescent sensor array as artificial tongue to achieve the discriminative sensing of ginsenosides. The fluorescent cross-responsive array was constructed by four boronlectins bearing flexible boronic acid moieties (FBAs) with multiple reactive sites and two linear poly(phenylene-ethynylene) (PPEs). An "on-off-on" response pattern was afforded on the basis of superquenching of fluorescent indicator PPEs and an analyte-induced allosteric indicator displacement (AID) process. Most importantly, it was found that the canonical distribution of ginsenoside data points analyzed by linear discriminant analysis (LDA) was highly correlated with the inherent molecular structures of the analytes, and the absence of overlaps among the five point groups reflected the effectiveness of the sensor array in the discrimination process. Almost all of the unknown ginsenoside samples at different concentrations were correctly identified on the basis of the established mathematical model. Our current work provided a general and constructive method to improve the quality assessment and control of ginseng and its extracts, which are useful and helpful for further discriminating other complex glycoconjugate families. © 2017 American Chemical Society.

Guo X.,Beijing Normal University | Zhao K.,Beijing Normal University
Journal of Physics Condensed Matter | Year: 2017

We report here a dielectric study on three kinds of anionic spherical polyelectrolyte brush (SPBs, consisting of a polystyrene (PS) core and three different poly (acrylic acid) chains grafted onto the core) suspensions over a frequency ranging from 40 Hz to 110 MHz. The relaxation behavior of the SPB suspensions shows significant changes in the brush-layer properties when the mass fraction of SPBs and the pH of the suspensions change. Two definite relaxations related to the interfacial polarization are observed around 100 kHz and 10 MHz. A single-layer spherical-shell model is applied to describe the SPB suspensions wherein the suspended SPB is modeled as a spherical-shell composite particle in which an insulated PS sphere is surrounded by a conducting ion-permeable shell (the polyelectrolyte chain layer). We developed the curve-fitting procedure to analyze the dielectric spectrum in order to obtain the dielectric properties of the components of the SPBs, especially the properties of the polyelectrolyte brush. Based on this method and model, the permittivity and conductivity of the brush layer, ζ potential, etc are calculated. The ordered orientation of the water molecules in the layer leads to an additional electrical dipole moment; increasing pH causes the brush layer to swell. In addition, the repulsive force between the SPB particles are evaluated using the brush-layer thickness, which is obtained by fitting dielectric spectra, combined with relative theoretical formulas. Increasing PH values or SPB concentration would improve the stability of the SPBs dispersion. © 2016 IOP Publishing Ltd.

Yang W.,Beijing Normal University | Tian Z.,Peking University
Astrophysical Journal | Year: 2017

Recent investigations have shown that the extended main-sequence turnoffs (eMSTOs) are a common feature of intermediate-age star clusters in the Magellanic Clouds. The eMSTOs are also found in the color magnitude diagram of young-age star clusters. The origin of the eMSTOs is still an open question. Moreover, asteroseismology shows that the value of the overshooting parameter dov of the convective core is not fixed for the stars with an approximatelly equal mass. Thus the MSTO of star clusters may be affected by the overshooting of the convective core (OVCC). We calculated the effects of the OVCC with different α μ on the MSTO of youngand intermediate-age star clusters. If α μ varies between stars in a cluster, the observed eMSTOs of young- and intermediate-age star clusters can be explained well by the effects. The equivalent age spreads of MSTO caused by the OVCC are related to the age of star clusters and are in good agreement with observed results of many clusters. Moreover, the observed eMSTOs of NGC 1856 are reproduced by the coeval populations with different α μ. The eMSTOs of star clusters may be relevant to the effects of the OVCC. The effects of the OVCC are similar to that of rotation in some respects. However, the effects cannot result in a significant split of the main sequence of young star clusters at mU ≲ 21. The presence of a rapid rotation can make the split of the main sequence of young star clusters more significant. © 2017. The American Astronomical Society. All rights reserved.

Zhang Y.,Beijing Normal University
Xitong Gongcheng Lilun yu Shijian/System Engineering Theory and Practice | Year: 2016

This paper presents some concepts of the information-components and replica economy, studies the market characteristics and behavioral characteristic of network economies based on the Internet, and reveals the inner relationships between the information-components and matter-element, information flow and logistics, virtual economy and real economy. It finds the inner relationship among network replication economy, effect of endogenous economic scale, and Moore's law (namely the network information aggregation-synergy effects), which makes a huge improvement for the research of network externality, information asymmetry and other major issues. It not only makes an essential correction (the equivalence conditions of individual and the overall optimization) for well-known Moore's law and network effect, but reveals its origin. Furthermore, this finding is also significant for the theoretical research and practical application regarding modern network and information economy. The network cooperation-replica economic model built in this paper provides an important analysis for the research and application regarding information and Internet economy. © 2016, Editorial Board of Journal of Systems Engineering Society of China. All right reserved.

Li L.,University of Southern California | Long R.,Beijing Normal University | Long R.,University College Dublin | Prezhdo O.V.,University of Southern California
Chemistry of Materials | Year: 2017

With applications in high performance electronics, photovoltaics and catalysis, two-dimensional transition metal dichalcogenides (TMDs) attract strong attention. Isolated TMDs, which are already remarkably complex, can stack in sequence to make even more complex heterostructures. Surprisingly, charge separation is ultrafast in layered TMD heterostructures, even though the interlayer interaction is weak. Also surprisingly, the charge separated state is long-lived, despite the close proximity of electron and hole. Using real-time time-dependent density functional theory combined with nonadiabatic (NA) molecular dynamics, we model hole and electron transfer, and electron-hole recombination at a MoS2/WS2 heterojunction. Hole transfer is ultrafast, in excellent agreement with the experiment, due to significant delocalization of the photoexcited state between the donor and acceptor materials. Electron transfer is 1 order of magnitude longer, due to weaker donor-acceptor and NA couplings, lower density of acceptor states, and shorter quantum coherence. The electron-hole recombination is 3-4 orders of magnitude slower than the charge separation, because the initial and final states are localized strongly within different materials, rationalizing the long-lived charge separation. The computed recombination time scale agrees with the experimental data on the closely related MoSe2/WSe2 system. All electronic processes are coupled to the characteristic out-of-plane 400 cm-1 motion of the MoS2 and WS2 layers. The atomistic, time-domain methodology provides theoretical insights into the photoinduced electron-phonon dynamics in two-dimensional TMD heterostructures, and can be used for in silico design of novel functional materials operating under nonequilibrium conditions. © 2016 American Chemical Society.

Yang X.,Beijing Normal University | Yan D.,Beijing Normal University | Yan D.,Beijing University of Chemical Technology
Chemical Communications | Year: 2017

Zeolitic imidazolate framework-8 directly exhibits unexpected white-light emission and near-infrared (NIR) phosphorescence, due to the host-guest interaction and the alternation of electron-density distribution, as confirmed by both experimental and computational studies. © The Royal Society of Chemistry.

Long R.,Beijing Normal University | Fang W.-H.,Beijing Normal University | Prezhdo O.V.,University of Southern California
Journal of Physical Chemistry C | Year: 2017

Interfacial electron transfer (ET) plays a key role in the operation of solar cells based on TiO2 sensitized with organohalide perovskites, since it leads to separation of the photogenerated electrons and holes into different materials. The reported experimental ET times range by over 3 orders of magnitude, from sub-200 fs to over 300 ps. Using nonadiabatic molecular dynamics combined with ab initio time-domain density functional theory, we demonstrate that ET at a CH3NH3PbI3/TiO2 interface can be complete within 100 fs, indicating that the longer time scales reflect other processes, such as charge and exciton diffusion in perovskite bulk. The electron injection is fast because the interaction between the donor and acceptor species is strong at ambient conditions. Photoexcitation directly at the interface can create a charge-separated state. Electrons generated farther away inject by a combination of adiabatic and nonadiabatic mechanisms. Thermally activated low frequency vibrational motions at the interface modulate the CH3NH3PbI3/TiO2 separation, creating opportunities for chemical bonding and generating channels for adiabatic ET. Higher-frequency modes create large nonadiabatic coupling. The interaction between perovskite and TiO2 is purely van der Waals at 0 K, whereas at ambient temperatures I-Ti covalent bonds can form transiently at the interface. The covalent bonding is particularly important for photoexcitation of charge-separated states and adiabatic ET. The ET occurs prior to nonradiative electronic energy losses that can lead to charge trapping and recombination. The ultrafast interfacial charge separation contributes to the high efficiencies of perovskite-sensitized TiO2 solar cells. The reported simulations provide a detailed time-domain atomistic description of the interfacial ET and advance our understanding of carrier dynamics in perovskite solar cells. (Figure Presented). © 2017 American Chemical Society.

Hua Y.,Beijing Normal University | Cui B.,Beijing Normal University
Ecological Indicators | Year: 2017

Assessment of suitable environmental flows (EFs) and its satisfaction degree is significant for water resources management. We presented a forecasting framework for EFs, IFA and EF satisfaction degree to assess suitable EFs (minimum or threshold) and forecast EF satisfaction degree over the next 20 years. First, we investigated the temporal and spatial distribution characteristics of IFA using statistical analysis and Morlet wavelet analysis of the hydrologic series from 1919 to 2013. Second, forecasting models of IFA were established using hydrologic stochastic simulation based on wavelet analysis. Then, abrupt shifts of baseflow index (BI) were identified based on Mann-Kendall trend detection test. Subsequently, regressions models were developed between a normalized BI and the effect size (ES) of zoobenthos and fish species richness. Accordingly, EFs were calculated. Finally, the IFA and EF satisfaction degree for the forecasting years were calculated. Results show that thresholds of BI, with 0.8 and 0.4 as the lower limit, and 2.3 and 1.1 as the upper limit, were recommended as the limit percentage of the EFs standard during flood and non-flood seasons, respectively. An overall decreasing tendency of IFA was observed in all the seven stations from the 1910s to 2010s, which is especially particularly significant in the lower reaches in the past two or three decades. One major EFs deficit spell occurred throughout the river beginning in the 1990s. Forecasting results indicate that the IFA will satisfy the EFs for the stations located in the upper and middle reaches by 2020 and 2030, except for the stations in the lower reaches. Contradictions of EFs and IFA will be even graver in the future. The results will have important implications for the water management of the riverine ecosystem. © 2017 Elsevier Ltd.

Cheng Z.,Beijing Normal University | Bai F.,Beijing Normal University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2017

There are a lot of actual application scenarios of head pose estimation, such as live detection, human interaction, gesture-based equipment, VR devices. This paper proposes a method based on linear regression to get the pose angle. The method utilizes supervised gradient descent method to get the facial feature points, and estimates the head pose by least square regression. In regression modeling, we only use seven feature point positions, which decrease the model size and the computing load. A data normalization technique is employed to eliminate the effect of the camera imaging parameters on pose estimation. Moreover, the training data set is derived from a group of 3D face models according to the camera imaging model, which can provide precise pose parameters. Experiments validate the proposed method, and show it can be run in real time. The algorithm can be easily transplanted to the mobile terminals. We have released our source code at © Springer International Publishing AG 2017.

Li X.,Beijing Normal University
Journal of Hypertension | Year: 2017

BACKGROUND:: Hypertension is related with cognitive decline in the elderly. The frontal–parietal executive system plays an important role in cognitive aging and is also vulnerable to damage in elderly patients with hypertension. Examination of the brainʼs functional characteristics in frontal–parietal regions of hypertension is likely to be important for understanding the neural mechanisms of hypertensionʼs effect on cognitive aging. METHODS:: We address this issue by comparing hypertension and control-performers in a functional MRI study. Twenty-eight hypertensive patients and 32 elderly controls were tested with n-back task with two load levels. RESULTS:: The hypertensive patients exhibited worse executive and memory abilities than control subjects. The patterns of brain activation changed under different working memory loads in the hypertensive patients, who exhibited reduced activation only in the precentral gyrus under low loads and reduced activation in the middle frontal gyrus, left medial superior frontal gyrus and right precuneus under high loads. Thus, more regions of diminished activation were observed in the frontal and parietal regions with increasing task difficulty. More importantly, we found that lower activation in changed frontal and parietal regions was associated with worse cognitive function in high loads. CONCLUSION:: The results demonstrate the relationship between cognitive function and frontoparietal functional activation in hypertension and their relevance to cognitive aging risk. Our findings provide a better understanding of the mechanism of cognitive decline in hypertension and highlight the importance of brain protection in hypertension. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.

Gao H.,Beijing Normal University | Zhang B.,University of Nevada, Las Vegas | Zhang B.,Peking University
Astrophysical Journal Letters | Year: 2017

A γ-ray transient, Swift J0644.5-5111, has been claimed to be associated with FRB 131104. However, a long-term radio imaging follow-up observation only placed an upper limit on the radio afterglow flux of Swift J0644.5-5111. Applying the external shock model, we perform a detailed constraint on the afterglow parameters for the FRB 131104/Swift J0644.5-5111 system. We find that for the commonly used microphysics shock parameters (e.g., , , and p = 2.3), if the fast radio burst (FRB) is indeed cosmological as inferred from its measured dispersion measure (DM), the ambient medium number density should be , which is the typical value for a compact binary merger environment but disfavors a massive star origin. Assuming a typical ISM density, one would require that the redshift of the FRB be much smaller than the value inferred from DM (), implying a non-cosmological origin of DM. The constraints are much looser if one adopts smaller and values, as observed in some gamma-ray burst afterglows. The FRB 131104/Swift J0644.5-5111 association remains plausible. We critically discuss possible progenitor models for the system. © 2017. The American Astronomical Society. All rights reserved..

Zhang F.,Beijing Normal University | Zhang F.,West Virginia University
Astronomy and Astrophysics | Year: 2017

The canonical pulsar magnetosphere contains a bubble of closed magnetic field lines that is separated from the open lines by current sheets, and different branches of such sheets intersect at a critical line on the light cylinder (LC). The LC is located far away from the neutron star, and the pulsar's intrinsic magnetic field at that location is much weaker than the commonly quoted numbers applicable to the star surface. The magnetic field surrounding supermassive black holes that reside in galactic nuclei is of comparable or greater strength. Therefore, when the pulsar travels inside such regions, a non-negligible Lorentz force is experienced by the current sheets, which tends to pull them apart at the critical line. As breakage occurs, instabilities ensue that burst the bubble, allowing closed field lines to snap open and release large amounts of electromagnetic energy, sufficient to power fast radio bursts (FRBs). This process is necessarily associated with an environment of a strong magnetic field and thus might explain the large rotation measures recorded for the FRBs. We sketch a portrait of the process and examine its compatibility with several other salient features of the FRBs. © ESO, 2017.

Hu R.,Beijing Normal University | Li L.,Beijing Normal University | Jin W.J.,Beijing Normal University
Carbon | Year: 2017

The speciation of doped-nitrogen (pyridinic N, pyrrolic N, graphitic N and amino N) was controlled by ferric ion catalysis for improving fluorescence of nitrogen-doped carbon dots (NCDs). Comparing to the synthesis of NCDs without ferric ion catalysis, the present strategy induces two following effects: (1) an increase of pyrrolic N and a decrease of pyridinic N; (2) a more well-organized arrangement of graphitic core and more N moieties exposed on the surface of NCDs. Consequently, absolute fluorescence quantum yield is increased from 6.2% to 27.0% and fluorescence can be further enhanced in acidity-media. Such phenomena provide solid evidence that pyrrolic N enhances the fluorescence of NCDs while pyridinic N inhibits it. Besides, NCDs achieve selective response to ferric ions. The present work provides a deeper insight into the understanding of luminescence mechanism and causes broader interest in manipulating CDs chemical structure. © 2016 Elsevier Ltd

Sitiwaldi I.,Beijing Normal University | Xie B.-S.,Beijing Normal University | Xie B.-S.,Beijing Radiation Center
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2017

We investigate the electron–positron pair production process in an oscillating field with modulated amplitude in the quantum kinetic formalism. By comparing the number density in the oscillating field with and without modulation, we find that the pair production rate can be enhanced by several orders when the photon energy just reaches the threshold with the help of shifted frequency due to modulation. We also detect the same effect in a pulse train with subcycle structure. We demonstrate that the frequency threshold can be lowered by the frequency of the pulse train due to the modulation effect. We also find that the momentum distribution for a N-pulse train can reach N2 times the single pulse at the maximum value and the number density as a function of pulse number follows the power law with index 1.6 when the modulation effect is maximized. © 2017 The Authors

Gao H.Y.,Beijing Normal University | Shen Q.J.,Beijing Normal University | Zhao X.R.,Beijing Normal University | Yan X.Q.,Beijing Normal University | And 2 more authors.
Journal of Materials Chemistry | Year: 2012

1,4-diiodotetrafluorobenzene (1,4-DITFB) is an excellent halogen bonding donor and is used to assemble an organic phosphorescent co-crystal with carbazole in which 1,4-DITFB is expected to act as a functional synthon, the cement to link carbazole molecules by halogen bonding and heavy atom perturber to enhance phosphorescence of the emitter carbazole by spin-orbital coupling. The XRD reveals that the stoichiometry of (2:1) between 1,4-DITFB and carbazole occurs. An infinite chain is constructed by the C-I⋯π halogen bonding and the π⋯π stacking of edge to edge between two 1,4-DITFB molecules is significant in maintaining stability of the 1D infinite chain. The inter-chain bonding includes C-H⋯I hydrogen bonding, H⋯F or F⋯F contacts to extend the infinite chain to 3D structure. The calculated halogen bonding energy is ca. 23.0 kJ mol -1 based on the single crystal structure, indicating a strong halogen bonding. The co-crystal also is well characterized by powder XRD, FT-IR, Raman, and solid 19F NMR spectroscopy. Moreover, the co-crystal as suspension microparticles can be very easily assembled in water by dropping water into an ethanol solution of 1,4-DITFB and carbazole. The C-I⋯π halogen bonding of 1,4-DITFB with carbazole should be instructive to develop some phosphorescent nano- or micro-materials. © The Royal Society of Chemistry 2012.

Zi G.,Beijing Normal University
Science China Chemistry | Year: 2014

Organoactinide complexes containing terminal metal-ligand multiple bonds have received widespread attention over the past three decades. In the last few years, significant progress has been made in the synthesis and characterization of the imido, oxo, sulfido, and carbene-containing complexes of thorium. Such thorium complexes are of interest because of their unique structural properties, their potential application in novel group transfer reactions and catalysis, as well as their ability to engage the 5f orbitals in metal-ligand bonding. This short review summarizes the synthesis and reactivity of these thorium complexes. © 2014 Science China Press and Springer-Verlag Berlin Heidelberg.

Yang M.,CAS Research Center for Eco Environmental Sciences | Zheng S.,Beijing Normal University
Biomass and Bioenergy | Year: 2014

Microbial single-cell-protein (SCP) production from high-organic-strength industrial wastewaters is considered an attractive method for both wastewater purification and resource utilization. In the last two decades, pollutant removal-oriented yeast SCP production processes, i.e., yeast treatment processes, have attracted a great deal of attention from a variety of research groups worldwide. Different from conventional SCP production processes, yeast treatment processes are characterized by higher pollutant removal rates, lower production costs, highly adaptive yeast isolates from nature, no excess nutrient supplements, and are performed under non-sterile conditions. Furthermore, yeast treatment processes are similar to bacteria-dominated conventional activated sludge processes, which offer more choices for yeast SCP production and industrial wastewater treatment. This review discusses why highly adaptive yeast species isolated from nature are used in the yeast treatment process rather than commercial SCP producers. It also describes the application of yeast treatment processes for treating high-carboxyhydrate, oil-rich and high-salinity industrial wastewater, focusing primarily on high-strength biodegradable organic substances, which usually account for the major fraction of biochemical oxygen demand. Also discussed is the biodegradation of xenobiotics, such as color (including dye and pigment) and toxic substances (including phenols, chlorophenols, polycyclic aromatic hydrocarbons, etc.), present in industrial wastewater. Based on molecular information of yeast community structures and their regulation in yeast treatment systems, we also discuss how to maintain efficient yeast species in yeast biomass and how to control bacterial and mold proliferation in yeast treatment systems. © 2014 Elsevier Ltd.

Chen S.,Beijing Normal University | Chen B.,Beijing Normal University | Fath B.D.,Towson University | Fath B.D.,International Institute For Applied Systems Analysis
Environmental Pollution | Year: 2014

Urbanization is a strong and extensive driver that causes environmental pollution and climate change from local to global scale. Modeling cities as ecosystems has been initiated by a wide range of scientists as a key to addressing challenging problems concomitant with urbanization. In this paper, 'urban ecosystem modeling (UEM)' is defined in an inter-disciplinary context to acquire a broad perception of urban ecological properties and their interactions with global change. Furthermore, state-of-the-art models of urban ecosystems are reviewed, categorized as top-down models (including materials/energy-oriented models and structure-oriented models), bottom-up models (including land use-oriented models and infrastructure-oriented models), or hybrid models thereof. Based on the review of UEM studies, a future framework for explicit UEM is proposed based the integration of UEM approaches of different scales, guiding more rational urban management and efficient emissions mitigation. © 2014 Elsevier Ltd. All rights reserved.

Yang J.,Beijing Normal University | Chen B.,Beijing Normal University
Renewable and Sustainable Energy Reviews | Year: 2014

To respond to the call of greenhouse gas emissions mitigation, an efficient carbon accounting framework should be proposed. Traditional narrowly defined estimation protocols that consider the direct emissions from native energy consumption may generally lead to underestimates of the carbon emissions derived from providing products and services. To comprehensively evaluate the supply-chain carbon performance in all economic sectors of China, the Economic Input-Output Life Cycle Assessment (EIO-LCA) based carbon footprint accounting framework should be employed. Because carbon emissions also occur in non-energy production processes, carbon emissions from the non-energy industrial process should also be incorporated into the accounting framework. This paper assessed 3 scopes of carbon emissions of Chinese economic sectors, including (1) direct emissions from energy consumption, and the industrial process, (2) emissions from purchased energy, (3) supply chain emissions combining both fuel combustion and industrial processes. The results shown that there is a huge underestimation of the carbon emission from various sectors using traditional carbon protocols compared with the tier 3 supply-chain CO2 emission. The emissions from industrial processes also constitute a large proportion, which cannot be ignored. In addition, we find that embodied CO2 emissions in exports concentrated on primary energy intensive sectors, indicating the importance of restructuring of export goods and services. It is proved that the three tier model provides a tool for decision makers to identify the national high carbon emission sectors and make effective carbon mitigation strategies. © 2013 Elsevier Ltd.

Wan X.,RIKEN | Wan X.,Beijing Normal University | Cheng K.,RIKEN | Tanaka K.,RIKEN
Nature Neuroscience | Year: 2015

Humans, and animals, often encounter ambiguous situations that require a decision on whether to take an offense or a defense strategy. Behavioral studies suggest that a strategy decision is frequently made before concrete options are evaluated. It remains enigmatic, however, how a strategy is determined without exploration of options. Here we investigated neural correlates of quick offense-versus-defense strategy decision in a board game, shogi. We found that the rostral anterior cingulate cortex and the posterior cingulate cortex complementally encoded the defense and attack strategy values, respectively. The dorsolateral prefrontal cortex compared the two strategy values. Several brain regions were activated during decision of concrete moves under an instructed strategy, whereas none of them showed correlation with defense or attack strategy values in their activities during strategy decision. These findings suggest that values of alternative strategies represented in different parts of the cingulate cortex have essential roles in intuitive strategy decision-making. © 2015 Nature America, Inc. All rights reserved.

de Vries W.,Wageningen University | Du E.,Beijing Normal University | Butterbach-Bahl K.,Karlsruhe Institute of Technology
Current Opinion in Environmental Sustainability | Year: 2014

The carbon to nitrogen response of forest ecosystems depends on the possible occurrence of nitrogen limitation versus possible co-limitations by other drivers, such as low temperature or availability of phosphorus. A combination of nitrogen retention estimates and stoichiometric scaling is used to illustrate the most likely carbon-nitrogen responses for needle-leaved and broadleaved forests to atmospheric nitrogen deposition. Results are evaluated against field observations and nitrogen addition experiments. The likely change in carbon to nitrogen response with nitrogen deposition level is hypothesized, distinguishing three threshold values that mark the forest carbon responses. We estimated that at global scale nitrogen deposition currently increases the forest carbon sink by 276-448Tg Cyr-1, with approximately 60% retained in tree wood and 40% in soil. Furthermore, the long-term carbon response to nitrogen, accounting for nitrogen saturation over time is hypothesized. In this context, the role of global scale coupled carbon-nitrogen models is also evaluated in view of current knowledge affecting carbon-nitrogen responses, including interactions with other drivers. © 2014 Elsevier B.V.

Yi W.,Beijing Normal University | Tang H.,Beijing Normal University | Chen Y.,Beijing Normal University
IEEE Geoscience and Remote Sensing Letters | Year: 2011

In this letter, we present a novel object-oriented semantic clustering algorithm for high-spatial-resolution remote sensing images using the probabilistic latent semantic analysis (PLSA) model coupled with neighborhood spatial information. First of all, an image collection is generated by partitioning a large satellite image into densely overlapped subimages. Then, the PLSA model is employed to model the image collection. Specifically, the image collection is partitioned into two subsets. One is used to learn topic models, where the number of topics is determined using a minimum description length criterion. The other is folded in using the learned topic models. Therefore, every pixel in each subimage has been allocated a topic label. At last, the cluster label of every pixel in the large satellite image is derived from the topic labels of multiple subimages which cover the pixel in the image collection. Experimental results over a QUICKBIRD image show that the clusters of the proposed algorithm are better than K-means and Iterative Self-Organizing Data Analysis Technique Algorithm in terms of object-oriented property. © 2010 IEEE.

Chen J.,Beijing Normal University | Chen X.,Beijing Normal University | Cui X.,Beijing Normal University
IEEE Geoscience and Remote Sensing Letters | Year: 2011

Postclassification comparison (PCC) and change vector analysis (CVA) have been widely used for land use/cover change detection using remotely sensed data. However, PCC suffers from error cumulation stemmed from an individual image classification error, while a strict requirement of radiometric consistency in remotely sensed data is a bottleneck of CVA. This letter proposes a new method named CVA in posterior probability space (CVAPS), which analyzes the posterior probability by using CVA. The CVAPS approach was applied and validated by a case study of land cover change detection in Shunyi District, Beijing, China, based on multitemporal Landsat Thematic Mapper data. Accuracies of "change/no-change" detection and "from-to" types of change were assessed. The results show that error cumulation in PCC was reduced in CVAPS. Furthermore, the main drawbacks in CVA were also alleviated effectively by using CVAPS. Therefore, CVAPS is potentially useful in land use/cover change detection. © 2006 IEEE.

Zhao L.,Beijing Normal University | Yue W.,Beijing Normal University | Ren Y.,China National Institute of Clean and Low Carbon Energy
Electrochimica Acta | Year: 2014

Highly ordered and crystalline mesoporous In2O3 was synthesized using KIT-6 as the template and exhibited better electrochemical performance than its bulk counterpart. Moreover, it is interesting to note that the mesoporous In2O3 with small particle size showed enhanced performance compared to that with large particle size. However, the reversible capacity of mesoporous In2O3 still decreased remarkably, possibly owing to the collapse of mesopores during lithiation and delithiation processes. Therefore, these mesoporous In2O3 particles were further wrapped by graphene nanosheets through a stepwise heterocoagulation method. The graphene encapsulation may enhance the electrical conductivity of the overall electrode, avoid the aggregation of In 2O3 particles and even stabilize the mesostructure of In2O3 during cycles, which is beneficial to improving the electrochemical properties of mesoporous In2O3 particles. © 2013 Elsevier Ltd.

Mo J.-X.,Beijing Normal University | Mo J.-X.,Zhanjiang Normal University | Liu W.-B.,Beijing Normal University
European Physical Journal C | Year: 2014

To understand the effect of third order Lovelock gravity, P-V criticality of topological AdS black holes in Lovelock-Born-Infeld gravity is investigated. The thermodynamics is further explored with some more extensions and in some more detail than the previous literature. A detailed analysis of the limit case β → ∞ is performed for the seven-dimensional black holes. It is shown that, for the spherical topology, P-V criticality exists for both the uncharged and the charged cases. Our results demonstrate again that the charge is not the indispensable condition of P-V criticality. It may be attributed to the effect of higher derivative terms of the curvature because similar phenomenon was also found for Gauss-Bonnet black holes. For k=0, there would be no P-V criticality. Interesting findings occur in the case k=-1, in which positive solutions of critical points are found for both the uncharged and the charged cases. However, the P-v diagram is quite strange. To check whether these findings are physical, we give the analysis on the non-negative definiteness condition of the entropy. It is shown that, for any nontrivial value of α, the entropy is always positive for any specific volume v. Since no P-V criticality exists for k=-1 in Einstein gravity and Gauss-Bonnet gravity, we can relate our findings with the peculiar property of third order Lovelock gravity. The entropy in third order Lovelock gravity consists of extra terms which are absent in the Gauss-Bonnet black holes, which makes the critical points satisfy the constraint of non-negative definiteness condition of the entropy. We also check the Gibbs free energy graph and "swallow tail" behavior can be observed. Moreover, the effect of nonlinear electrodynamics is also included in our research. © 2014 The Author(s).

Zhang M.-J.,Beijing Normal University | Liu W.-B.,Beijing Normal University
European Physical Journal C | Year: 2014

Two types of interacting dark energy models are investigated using the type Ia supernova (SNIa), observational H(z) data (OHD), cosmic microwave background shift parameter, and the secular Sandage-Loeb (SL) test. In the investigation, we have used two sets of parameter priors including WMAP-9 and Planck 2013. They have shown some interesting differences. We find that the inclusion of SL test can obviously provide a more stringent constraint on the parameters in both models. For the constant coupling model, the interaction term has been improved to be only a half of the original scale on corresponding errors. Comparing with only SNIa and OHD, we find that the inclusion of the SL test almost reduces the best-fit interaction to zero, which indicates that the higher-redshift observation including the SL test is necessary to track the evolution of the interaction. For the varying coupling model, data with the inclusion of the SL test show that the parameter ξ at 1σ in Planck priors is ξ >3, where the constant ξ is characteristic for the severity of the coincidence problem. This indicates that the coincidence problem will be less severe. We then reconstruct the interaction δ(z), and we find that the best-fit interaction is also negative, similar to the constant coupling model. However, for a high redshift, the interaction generally vanishes at infinity. We also find that the phantom-like dark energy with wX<-1 is favored over the ΛCDM model. © 2014 The Author(s).

Shen Z.Y.,Beijing Normal University | Chen L.,Beijing Normal University | Chen T.,Beijing Normal University
Hydrology and Earth System Sciences | Year: 2012

The calibration of hydrologic models is a worldwide challenge due to the uncertainty involved in the large number of parameters. The difficulty even increases in a region with high seasonal variation of precipitation, where the results exhibit high heteroscedasticity and autocorrelation. In this study, the Generalized Likelihood Uncertainty Estimation (GLUE) method was combined with the Soil and Water Assessment Tool (SWAT) to quantify the parameter uncertainty of the stream flow and sediment simulation in the Daning River Watershed of the Three Gorges Reservoir Region (TGRA), China. Based on this study, only a few parameters affected the final simulation output significantly. The results showed that sediment simulation presented greater uncertainty than stream flow, and uncertainty was even greater in high precipitation conditions (from May to September) than during the dry season. The main uncertainty sources of stream flow came from the catchment process while a channel process impacts the sediment simulation greatly. It should be noted that identifiable parameters such as CANMX, ALPHA-BNK, SOL-K could be obtained with an optimal parameter range using calibration method. However, equifinality was also observed in hydrologic modeling in TGRA. This study demonstrated that care must be taken when calibrating the SWAT model with non-identifiable parameters because these may lead to equifinality of the parameter values. It was anticipated this study would provide useful information for hydrology modeling related to policy development in the Three Gorges Reservoir Region (TGRA) and other similar areas. © Author(s) 2012.

Jevrejeva S.,National Oceanography Center | Moore J.C.,Beijing Normal University | Moore J.C.,University of Lapland | Moore J.C.,Uppsala University | Grinsted A.,Copenhagen University
Global and Planetary Change | Year: 2012

Sea level rise over the coming centuries is perhaps the most damaging side of rising temperature (Anthoff et al., 2009). The economic costs and social consequences of coastal flooding and forced migration will probably be one of the dominant impacts of global warming (Sugiyama et al., 2008). To date, however, few studies (Nicholls et al., 2008; Anthoff et al., 2009) on infrastructure and socio-economic planning include provision for multi-century and multi-metre rises in mean sea level. Here we use a physically plausible sea level model constrained by observations, and forced with four new Representative Concentration Pathways (RCP) radiative forcing scenarios (Moss et al., 2010) to project median sea level rises of 0.57 for the lowest forcing and 1.10. m for the highest forcing by 2100 which rise to 1.84 and 5.49. m respectively by 2500. Sea level will continue to rise for several centuries even after stabilisation of radiative forcing with most of the rise after 2100 due to the long response time of sea level. The rate of sea level rise would be positive for centuries, requiring 200-400. years to drop to the 1.8. mm/yr 20th century average, except for the RCP3PD which would rely on geoengineering. © 2011.

Zhang W.-K.,Beijing Normal University
Chinese Journal of Chemical Physics | Year: 2016

Polarization dependent time-resolved infrared (TRIR) spectroscopy has proven to be a useful technique to study the structural dynamics in a photochemical process. The angular information of transient species is obtainable in this measurement, which makes it a valuable technique for the investigation of electron distribution, molecular structure, and conformational dynamics. In this review, we briefly introduce the principles and applications of polarization dependent TRIR spectroscopy. We mainly focused on the following topics: (i) an overview of TRIR spectroscopy, (ii) principles of TRIR spectroscopy and its advantages compared to the other ultrafast techniques, (iii) examples that use polarization dependent TRIR spectroscopy to probe a variety of chemical and dynamical phenomena including protein conformational dynamics, excited state electron localization, and photoisomerization, (iv) the limitations and prospects of TRIR spectroscopy. © 2016 Chinese Physical Society.

Sun Z.-X.,Beijing Normal University | Cheng Y.,Beijing Normal University
European Journal of Organic Chemistry | Year: 2012

NHC-catalyzed three-component reactions of α,β-unsaturated aldehydes (enals), nitrosoarenes, and α,β-unsaturated ketones (enones) were studied. The reactions proceeded through a cascade aza-benzoin condensation/oxo-Michael addition sequence to produce N,O-bisfunctionalized N-hydroxylacrylamides in moderate to good yields. This work not only provides an efficient method for the one-step formation both of the C-N and of the C-O bonds in N-alkoxyamides, but also advances the application of NHC organocatalysis in the field of multicomponent reactions. NHC-catalyzed three-component reactions of α,β-unsaturated aldehydes (enals), nitrosoarenes, and α,β-unsaturated ketones (enones) proceeded through a cascade aza-benzoin condensation/oxo-Michael addition sequence to produce N,O-bisfunctionalized N-hydroxylacrylamides in moderate to good yields. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Jevrejeva S.,Proudman Oceanographic Laboratory | Moore J.C.,Beijing Normal University | Grinsted A.,Copenhagen University
Geophysical Research Letters | Year: 2010

Using an inverse statistical model we examine potential response in sea level to the changes in natural and anthropogenic forcings by 2100. With six IPCC radiative forcing scenarios we estimate sea level rise of 0.6-1.6 m, with confidence limits of 0.59 m and 1.8 m. Projected impacts of solar and volcanic radiative forcings account only for, at maximum, 5% of total sea level rise, with anthropogenic greenhouse gasses being the dominant forcing. As alternatives to the IPCC projections, even the most intense century of volcanic forcing from the past 1000 years would result in 10-15 cm potential reduction of sea level rise. Stratospheric injections of SO2 equivalent to a Pinatubo eruption every 4 years would effectively just delay sea level rise by 12-20 years. A 21st century with the lowest level of solar irradiance over the last 9300 years results in negligible difference to sea level rise. Copyright © 2010 by the American Geophysical Union.

Su Y.,Beijing Normal University | Fang X.Q.,Beijing Normal University | Yin J.,Beijing Normal University
Science China Earth Sciences | Year: 2014

The occurrence of bumper or poor grain harvests in ancient China plays an important role in explaining how past climate changes affected the economy. Because of the lack of long-term continuous and high-resolution quantitative data for reconstructing the series of grain harvests in ancient China, understanding of the impacts and mechanisms involved in climate change is limited. This study presents a method designed for reconstructing grain harvest series by quantifying grain output levels based on the descriptions in historical documents. The method involves setting the grain output level for each year based on very specific meanings of different words, calculating a yield index based on the structure of each level and assessing grain yields (bumper or poor harvests) every 10 years. First, 1636 records related to grain yields (including crop yields, food security, agricultural disasters, grain prices, grain storage and people's livelihoods) for each year were retrieved from history books called the Twenty-Four Histories. Second, using this method, a 10-year resolution graded grain harvest series from the Western Han Dynasty to the Five Dynasties (206 BC-960 AD) is reconstructed. Finally, the relationship between the variations in temperature and precipitation and the fluctuation of grain yields is examined. The results show that from the Western Han Dynasty to the Five Dynasties, bumper, average and poor harvest decades accounted for 33.3%, 39.3% and 27.4% of the 1,166-year period, respectively. The grain yields during 206 BC-960 AD can be divided into three stages: a period of bumper harvests during 206-51 BC, poor harvests during 50 BC-590 AD and bumper harvests during 591-960 AD. Bumper harvest decades typically experienced a warm climate with normal or high levels of precipitation, while poor harvest decades had a cold and dry climate. A positive correlation was found between temperature and grain yield because a warm climate allows a full use of resources. The observed relationship between precipitation and grain yield indicated that both flooding and droughts cause poor harvests, which confirms that agricultural production in the monsoon climate of eastern China is greatly impacted by conditions of limited heat and extreme precipitation. © 2014 Science China Press and Springer-Verlag Berlin Heidelberg.

Fu Y.,Beijing Normal University | Liang F.,Beijing Normal University | Tian H.,Beijing Normal University | Hu J.,Beijing Normal University
Electrochimica Acta | Year: 2014

A novel nonenzymatic glucose sensor, based on gold nanoparticle-modified indium tin oxide electrode (Au/ITO) with ion implantation technique, is presented in this article. Ion implantation method is simple, low-cost and environmental friendly without using any of other chemicals. Through this method, the ITO substrate can be modified by gold nanoparticles (AuNPs) directly. The fabricated electrode was characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy analysis (XPS) and cyclic voltammetry (CV). Electrochemical oxidation of glucose with Au/ITO electrode was examined by CV in alkaline aqueous solution. The modified electrode exhibits good electrochemical behavior towards glucose, providing a wide linear range of 1∼170 μM and 0.2∼15 mM and a low detection limit with 0.4 μM. Moreover, this glucose sensor displays acceptable reproducibility and long-term stability. These results indicate that Au/ITO electrode makes it promising for the fabrication of nonenzymatic glucose sensors. © 2014 Elsevier Ltd.

Biogas plant construction has been boosted in rural China not only due to the immediate merit from biogas production but also the succeeding benefit from by-product utilization in agro-industry, both of which are significant strategies to address energy shortage and global warming issues. However, little work has been done to evaluate the coupling of biogas projects to traditional agrosystems from a life-cycle perspective, which is most important in process and system optimization in different senses. By taking persimmon cultivation and processing with supports from a household biogas plant as a case study, this study conducts a life cycle assessment of coupling biogas production to agro-industry in terms of energy, environmental and economic performance. The results suggest that each production stage following the biogas/digestate utilization chain (biogas operation-persimmon cultivation-product processing) is beneficial across all three aspects. However, a tradeoff only exists in utilizing digestate as top-dressing and employing biogas utilization as engine fuel, while biogas application in fresh-keeping and digestate reuse as base fertilizer fails to increase either energy production or greenhouse gas mitigation. The coupled system can be hopefully optimized through increasing fermentation efficiency and joint operation of biogas digesters. © 2013 Elsevier Ltd.

Sun Y.,Beijing Normal University | Jara A.J.,University of Applied Sciences and Arts Western Switzerland
Personal and Ubiquitous Computing | Year: 2014

Data management and information processing play the key roles in developing the Internet of Things (IoT). The requirements of a well-defined data model for IoT involve in six aspects: semantic supporting, active data extracting and explaining, flexibility and extensibility, enabling to manage massive and heterogeneous data, supporting formal organization, and solid mathematic-based theory. This paper aims to exploring an extensible and active semantic information organization model for IoT to meet the above requirements, and the primary idea is “Object-cored organizing data, event-based explaining data, and knowledge-based using data.” The proposed model involves two layers: the object layer and the event layer, and both of them are discussed in detail including conceptions, schema definitions, and the rule-based knowledge representation. Semantic reasoning can be supported by the knowledge base which involves in a set of reasoning rules on semantic relations among objects or among events correspondingly. © 2014, Springer-Verlag London.

Li Q.,Beijing Normal University | Cheng H.,Beijing Normal University | Zhou T.,Beijing Normal University | Lin C.,Beijing Normal University | Guo S.,South China Institute of Environmental Sciences
Atmospheric Environment | Year: 2012

Estimates of atmospheric emissions of lead from anthropogenic sources in China from 1990 to 2009 are presented with the information on emissions of both total lead and its spatial distribution in regions. The total emissions during the period 1990-2009 are nearly 200 000 tons. Motor vehicle gasoline combustion was the largest source of anthropogenic emissions. The estimated release of 117 800 t of lead represented 60% of the total emissions. Substantial decline occurred in 2001, when the total emissions were about 81% less than the 2000 value. The reduced lead content of motor vehicle gasoline is the primary reason for the decreased in lead emissions in 2001. After leaded gasoline was phased out, coal combustion became the principal source of emissions. Based on data on emissions from 2005 through 2009, the emissions are concentrated in eastern and central China due to the high level of coal consumption and non-ferrous metal smelting. The five provinces with the largest amounts of lead emissions are Shandong, Hebei, Shanxi, Henan and Jiangsu. These five regions produced nearly 40% of the total. © 2012 Elsevier Ltd.

Wang Y.,Beijing Normal University | Liang S.,Tsinghua University
Energy Policy | Year: 2013

China proposed a CO2 mitigation target in 2020 to deal with anthropogenic global climate change. Chinese policy makers mainly focus on three factors comprising consumption structure changes, energy technology development, and new energy increments. In addition, sectoral CO2 reduction is increasingly concerned in the world. Thus, it is significant to investigate integrated impacts of three factors to China's CO2 mitigation target as well as to identify key economic sectors for achieving this target. In this study, energy demand and CO2 emission in 2020 are predicted. Five scenarios are generated to illustrate the contributions of three factors. In addition, twelve key economic sectors for reducing energy demand and CO2 emission are identified from both production and final demand perspectives. Under integrated impacts of three factors, China's CO2 intensity per unit gross domestic product in 2020 will decrease by about 43.9% in 2020 than 2005 level. In the short term, China's CO2 mitigation will be highly dependent on energy technology development. In the long term, it will mainly rely on reshaped consumption structure changes and new energy development. In addition, China's future policies should focus on 12 identified key economic sectors. © 2013 Elsevier Ltd.

Li J.,Beijing Normal University | Li Q.,Tsinghua University | Xu K.,Hong Kong University of Science and Technology
Journal of Computational Physics | Year: 2011

The generalized Riemann problem (GRP) scheme for the Euler equations and gas-kinetic scheme (GKS) for the Boltzmann equation are two high resolution shock capturing schemes for fluid simulations. The difference is that one is based on the characteristics of the inviscid Euler equations and their wave interactions, and the other is based on the particle transport and collisions. The similarity between them is that both methods can use identical MUSCL-type initial reconstructions around a cell interface, and the spatial slopes on both sides of a cell interface involve in the gas evolution process and the construction of a time-dependent flux function. Although both methods have been applied successfully to the inviscid compressible flow computations, their performances have never been compared. Since both methods use the same initial reconstruction, any difference is solely coming from different underlying mechanism in their flux evaluation. Therefore, such a comparison is important to help us to understand the correspondence between physical modeling and numerical performances. Since GRP is so faithfully solving the inviscid Euler equations, the comparison can be also used to show the validity of solving the Euler equations itself. The numerical comparison shows that the GRP exhibits a slightly better computational efficiency, and has comparable accuracy with GKS for the Euler solutions in 1D case, but the GKS is more robust than GRP. For the 2D high Mach number flow simulations, the GKS is absent from the shock instability and converges to the steady state solutions faster than the GRP. The GRP has carbuncle phenomena, likes a cloud hanging over exact Riemann solvers. The GRP and GKS use different physical processes to describe the flow motion starting from a discontinuity. One is based on the assumption of equilibrium state with infinite number of particle collisions, and the other starts from the non-equilibrium free transport process to evolve into an equilibrium one through particle collisions. The different mechanism in the flux evaluation deviates their numerical performance. Through this study, we may conclude scientifically that it may NOT be valid to use the Euler equations as governing equations to construct numerical fluxes in a discretized space with limited cell resolution. To adapt the Navier-Stokes (NS) equations is NOT valid either because the NS equations describe the flow behavior on the hydrodynamic scale and have no any corresponding physics starting from a discontinuity. This fact alludes to the consistency of the Euler and Navier-Stokes equations with the continuum assumption and the necessity of a direct modeling of the physical process in the discretized space in the construction of numerical scheme when modeling very high Mach number flows. The development of numerical algorithm is similar to the modeling process in deriving the governing equations, but the control volume here cannot be shrunk to zero. © 2011 Elsevier Inc.

Miao C.,Peking University | Miao C.,Beijing Normal University | Ni J.,Peking University | Borthwick A.G.L.,University of Oxford | Yang L.,CAS Institute of Geographical Sciences and Natural Resources Research
Global and Planetary Change | Year: 2011

Water discharge and sediment load have changed continuously during the last half century in the Yellow River basin, China. In the present paper, data from 7 river gauging stations and 175 meteorological stations are analyzed in order to estimate quantitatively the contributions of human activities and climate change to hydrological response. Coefficients of water discharge (Cw) and sediment load (Cs) are calculated for the baseline period of 1950s-1960s according to the correlations between the respective hydrological series and regional precipitation. Consequently, the natural water discharge and natural sediment load time series are reconstructed from 1960s-2008. Inter-annual impacts are then separated from the impacts of human activities and climate change on the hydrological response of different regions of the Yellow River basin. It is found that human activities have the greatest influence on changes to the hydrological series of water discharge and sediment load, no matter whether the effect is negative or positive. Moreover, the impact of human activities is considerably greater on water discharge than sediment load. During 1970-2008, climate change and human activities respectively contribute 17% and 83% to the reduction in water discharge, and 14% and 86% to the reduction in sediment yield in the Upper reaches of Yellow River basin; The corresponding relative contributions in the Middle reaches are 71% and 29% to reductions in water discharge, and 48% and 52% to reductions in sediment load. Moreover, it is observed that the impacts of human activities on the whole basin are enhanced with time. In the 2000s, the impact of human activities exceeds that of climate change in the 2000s, with human activities directly responsible for 55% and 54% of the reductions in water discharge and sediment load in the whole basin. © 2011 Elsevier B.V.

Tao F.,CAS Institute of Geographical Sciences and Natural Resources Research | Zhang Z.,Beijing Normal University
Climatic Change | Year: 2011

Projections of future climate change are plagued with uncertainties from global climate models and emission scenarios, causing difficulties for impact assessments and for planners taking decisions on adaptation measure. Here, we developed an approach to deal with the uncertainties and to project the changes of maize productivity and water use in China using a process-based crop model, against a global mean temperature (GMT) increase scale relative to 1961-1990 values. From 20 climate scenarios output from the Intergovernmental Panel on Climate Change Data Distribution Centre, we adopted the median values of projected changes in monthly mean climate variables for representative stations and driven the CERES-Maize model to simulate maize production under baseline and future climate scenarios. Adaptation options such as automatic planting, automatic application of irrigation and fertilization were considered, although cultivars were assumed constant over the baseline and future. After assessing representative stations across China, we projected changes in maize yield, growing period, evapotranspiration, and irrigation-water use for GMT changes of 1°C, 2°C, and 3°C, respectively. Results indicated that median values of projected decreases in the yields of irrigated maize without (with) consideration of CO2-fertilization effects ranged from 1.4% to 10.9% (1.6% to 7.8%), 9.8% to 21.7% (10.2% to 16.4%), and 4.3% to 32.1% (3.9% to 26.6%) for GMT changes of 1°C, 2°C, and 3°C, respectively. Median values of projected changes in irrigation-water use without (with) consideration of CO2-fertilization effects ranged from -1.3% to 2.5% (-18.8% to 0.0%), -43.6% to 2.4% (-56.1% to -18.9%), and -19.6% to 2.2% (-50.6% to -34.3%), which were ascribed to rising CO2 concentration, increased precipitation, as well as reduced growing period with GMT increasing. For rainfed maize, median values of projected changes in yields without (with) consideration of CO2-fertilization effects ranged from -22.2% to -1.0% (-10.8% to 0.7%), -27.6% to -7.9% (-18.1% to -5.6%), and -33.7% to -4.6% (-25.9% to -1.6%). Approximate comparisons showed that projected maize yield losses were larger than previous estimates, particularly for rainfed maize. Our study presents an approach to project maize productivity and water use with GMT increases using process-based crop models and multiple climate scenarios. The resultant impact function is fundamental for identifying which climate change level is dangerous for food security. © 2010 Springer Science+Business Media B.V.

Liu C.,Beijing Normal University | Zhao K.,Beijing Normal University
Journal of Physical Chemistry B | Year: 2012

Dielectric properties of PAA-g-PEO-7% solutions with different counterions were measured as a function of concentration and temperature over a frequency range of 40 Hz to 110 MHz. After the contribution of electrode polarization effects was subtracted, the dielectric spectra of PAA-g-PEO-7% solutions showed three relaxation processes in the experimental frequency range, named low-, mid-, and high-frequency relaxation. The observed three relaxations were strictly analyzed by using the Cole-Cole relaxation function, and the dielectric parameters (dielectric increment Δε and the relaxation time τ) were obtained. The scaling relation of dielectric increment and relaxation time of high frequency with concentration Cp were obtained and compared with the predictions of scaling theories. The information on the dynamics and microstructure of PAA-g-PEO-7% was obtained. Using different counterion species, the mid-and high-frequency relaxation mechanisms were attributed to the fluctuation of condensed counterions and free counterions, respectively, and the low-frequency relaxation was considered to be caused by the interface polarization of a complex formed by the hydrogen bonding between carboxylic group of PAA and ether oxygen on the side-chain PEO. In addition, by means of Eyring equation, the thermodynamic parameters, enthalpy change ΔH and entropy change ΔS, of the three relaxations were calculated from the relaxation time and discussed from the microscopic thermodynamical view. © 2011 American Chemical Society.

Wang R.,Beijing Normal University | Cong L.-J.,Beijing Normal University | Yu C.,CAS Institute of Psychology
Journal of Vision | Year: 2013

The seminal study on perceptual learning of TDT (a texture discrimination task) has greatly shaped the field of perceptual learning up to the present time. However, here we demonstrate that this classic learning mostly involves temporal learning, rather than texture discrimination learning. Specifically, observers first practiced a letter identification task with backward masking to saturate the potential temporal learning of target-mask separation in TDT learning before they practiced the backward-masked TDT task directly. The temporal learning accounted for most of the overall TDT improvement, indicating TDT learning being mostly temporal learning. Meanwhile, the location specificity of TDT learning may be interpreted as temporal learning being confined to the trained location with conventional training because learning became mostly location invariant with double training. These results provide a new context to interpret the existing TDT brain imaging data aimed at understanding the neural mechanisms of perceptual learning. © 2013 ARVO.

Liu D.,Beijing Normal University | Liu H.,Beijing Normal University | Hu N.,Beijing Normal University
Journal of Physical Chemistry B | Year: 2012

Phenylboronic acid (PBA) moieties are grafted onto the backbone of poly(acrylic acid) (PAA), forming the PAA-PBA polyelectrolyte. The semi-interpenetrating polymer network (semi-IPN) films composed of PAA-PBA and poly(N,N-diethylacrylamide) (PDEA) were then synthesized on electrode surface with entrapped horseradish peroxidase (HRP), designated as PDEA-(PAA-PBA)-HRP. The films demonstrated reversible pH-, fructose-, and thermo-responsive on-off behavior toward electroactive probe K3Fe(CN)6 in its cyclic voltammetric (CV) response. This multiswitchable CV behavior of the system could be further employed to control and modulate the electrochemical reduction of H2O2 catalyzed by HRP immobilized in the films with K3Fe(CN)6 as the mediator in solution. The responsive mechanism of the system was also explored and discussed. The pH-sensitive property was attributed to the electrostatic interaction between the PAA component of the films and the probe at different pH; the thermo-responsive behavior originated from the structure change of PDEA hydrogel component of the films with temperature; the fructose-sensitive property was ascribed to the structure change of the films induced by the complexation between the PBA constituent and the sugar. This smart system could be used as a 3-input logic network composed of enabled OR (EnOR) gates in chemical or biomolecular computing by combining the multiresponsive property of the films and the amplification effect of bioelectrocatalysis and demonstrated the potential perspective for fabricating novel multiswitchable electrochemical biosensors and bioelectronic devices. © 2012 American Chemical Society.

Zhu L.,Capital Medical University | Zhu L.,Beijing Normal University | Zhu L.,University of Pennsylvania | Ploessl K.,University of Pennsylvania | Kung H.F.,University of Pennsylvania
Chemical Society Reviews | Year: 2014

Single photon emission computed tomography (SPECT) or positron emission computed tomography (PET) imaging agents for neurodegenerative diseases have a significant impact on clinical diagnosis and patient care. The examples of Parkinson's Disease (PD) and Alzheimer's Disease (AD) imaging agents described in this paper provide a general view on how imaging agents, i.e. radioactive drugs, are selected, chemically prepared and applied in humans. Imaging the living human brain can provide unique information on the pathology and progression of neurodegenerative diseases, such as AD and PD. The imaging method will also facilitate preclinical and clinical trials of new drugs offering specific information related to drug binding sites in the brain. In the future, chemists will continue to play important roles in identifying specific targets, synthesizing target-specific probes for screening and ultimately testing them by in vitro and in vivo assays. This journal is © the Partner Organisations 2014.

Cheng W.,Virginia Commonwealth University | Wang S.,Beijing Normal University | Cheng X.,George Washington University
IEEE Network | Year: 2014

The RFID System on Roads (RSR), which includes RFID tags deployed on roads and RFID readers installed on vehicles, is an essential platform for future transportation systems. It can provide unique features that are missing from the current systems, including lane level position, road traffic control information, vehicle distance estimation, real time driving behavior analysis, and so on. Based on these features, several novel vehicular applications can be implemented, which can significantly improve the transportation safety and efficiency. Specifically, the proposed applications on RSR include Assisted Navigation Systems, Electrical Traffic Control, Unmanned Patrol Systems, Vehicle Distance Estimation, Parking Assistant System, Route Tracing and Access Control, Unmanned Ground Vehicles. We also investigate the corresponding engineering/system and research challenges for implementing RSR and its applications in this article. © 2014 IEEE.

Ren W.,Beijing Normal University | Zi G.,Beijing Normal University | Fang D.-C.,Beijing Normal University | Walter M.D.,TU Braunschweig
Journal of the American Chemical Society | Year: 2011

The synthesis, structure, and reactivity of thorium oxo and sulfido metallocenes have been comprehensively studied. Heating of an equimolar mixture of the dimethyl metallocene [η 5-1,2,4-(Me 3C) 3C 5H 2] 2ThMe 2 (2) and the bis-amide metallocene [η 5-1,2,4-(Me 3C) 3C 5H 2] 2Th(NH-p-tolyl) 2 (3) in refluxing toluene results in the base-free imido thorium metallocene, [η 5-1,2,4-(Me 3C) 3C 5H 2] 2Th=N(p-tolyl) (4), which is a useful precursor for the preparation of oxo and sulfido thorium metallocenes [η 5-1,2,4- (Me 3C) 3C 5H 2] 2Th=E (E = O (5) and S (15)) by cycloaddition-elimination reaction with Ph 2C=E (E = O, S) or CS 2. The oxo metallocene 5 acts as a nucleophile toward alkylsilyl halides, while sulfido metallocene 15 does not. The oxo metallocene 5 and sulfido metallocene 15 undergo a [2 + 2] cycloaddition reaction with Ph 2CO, CS 2, or Ph 2CS, but they show no reactivity with alkynes. Density functional theory (DFT) studies provide insights into the subtle interplay between steric and electronic effects and rationalize the experimentally observed reactivity patterns. A comparison between Th, U, and group 4 elements shows that Th 4+ behaves more like an actinide than a transition metal. © 2011 American Chemical Society.

Li X.-Q.,Beijing Normal University
Frontiers of Physics | Year: 2016

In addition to the well-known Landauer–Büttiker scattering theory and the nonequilibrium Green’s function technique for mesoscopic transports, an alternative (and very useful) scheme is quantum master equation approach. In this article, we review the particle-number (n)-resolved master equation (n-ME) approach and its systematic applications in quantum measurement and quantum transport problems. The n-ME contains rich dynamical information, allowing efficient study of topics such as shot noise and full counting statistics analysis. Moreover, we also review a newly developed master equation approach (and its n-resolved version) under self-consistent Born approximation. The application potential of this new approach is critically examined via its ability to recover the exact results for noninteracting systems under arbitrary voltage and in presence of strong quantum interference, and the challenging non-equilibrium Kondo effect. © 2016, Higher Education Press and Springer-Verlag Berlin Heidelberg.

Zhu Z.,Hong Kong University of Science and Technology | Ma J.,University of Hong Kong | Wang Z.,Hong Kong University of Science and Technology | Mu C.,Hong Kong University of Science and Technology | And 7 more authors.
Journal of the American Chemical Society | Year: 2014

We report on a significant power conversion efficiency improvement of perovskite solar cells from 8.81% to 10.15% due to insertion of an ultrathin graphene quantum dots (GQDs) layer between perovskite and TiO2. A strong quenching of perovskite photoluminescence was observed at ∼760 nm upon the addition of the GQDs, which is pronouncedly correlated with the increase of the IPCE and the APCE of the respective cells. From the transient absorption measurements, the improved cell efficiency can be attributed to the much faster electron extraction with the presence of GQDs (90-106 ps) than without their presence (260-307 ps). This work highlights that GQDs can act as a superfast electron tunnel for optoelectronic devices. © 2014 American Chemical Society.

Cui M.,Kyoto University | Cui M.,Beijing Normal University | Ono M.,Kyoto University | Watanabe H.,Kyoto University | And 3 more authors.
Journal of the American Chemical Society | Year: 2014

The deposition of β-amyloid (Aβ) plaques in the parenchymal and cortical brain is accepted as the main pathological hallmark of Alzheimer's disease (AD); however, early detection of AD still presents a challenge. With the assistance of molecular imaging techniques, imaging agents specifically targeting Aβ plaques in the brain may lead to the early diagnosis of AD. Herein, we report the design, synthesis, and evaluation of a series of smart near-infrared fluorescence (NIRF) imaging probes with donor-acceptor architecture bridged by a conjugated π-electron chain for Aβ plaques. The chemical structure of these NIRF probes is completely different from Congo Red and Thioflavin-T. Probes with a longer conjugated π system (carbon-carbon double bond) displayed maximum emission in PBS (>650 nm), which falls in the best range for NIRF probes. These probes were proved to have affinity to Aβ plaques in fluorescent staining of brain sections from an AD patient and double transgenic mice, as well as in an in vitro binding assay using Aβ1-42 aggregates. One probe with high affinity (Ki = 37 nM, Kd = 27 nM) was selected for in vivo imaging. It can penetrate the blood-brain barrier of nude mice efficiently and is quickly washed out of the normal brain. Moreover, after intravenous injection of this probe, 22-month-old APPswe/PSEN1 mice exhibited a higher relative signal than control mice over the same period of time, and ex vivo fluorescent observations confirmed the existence of Aβ plaques. In summary, this probe meets most of the requirements for a NIRF contrast agent for the detection of Aβ plaques both in vitro and in vivo. © 2014 American Chemical Society.

Ma T.,Beijing Normal University | Ma T.,Beijing Computational Science Research Center | Lin H.-Q.,Beijing Computational Science Research Center | Hu J.,CAS Institute of Physics | Hu J.,Purdue University
Physical Review Letters | Year: 2013

We perform a systematic quantum Monte Carlo study of the pairing correlation in the S4 symmetric microscopic model for iron-based superconductors. It is found that the pairing with an extensive s-wave symmetry robustly dominates over other pairings at low temperature in a reasonable parameter region regardless of the change of Fermi surface topologies. The pairing susceptibility, the effective pairing interaction, and the (π, 0) antiferromagnetic correlation strongly increase as the on-site Coulomb interaction increases, indicating the importance of the effect of electron-electron correlation. Our nonbiased numerical results provide a unified understanding of the superconducting mechanism in iron pnictides and iron chalcogenides and demonstrate that the superconductivity is driven by strong electron-electron correlation effects. © 2013 American Physical Society.

Zhu X.-J.,University of Western Australia | Howell E.J.,University of Western Australia | Blair D.G.,University of Western Australia | Zhu Z.-H.,Beijing Normal University
Monthly Notices of the Royal Astronomical Society | Year: 2013

This paper reports a comprehensive study on the gravitational wave (GW) background from compact binary coalescences. We consider in our calculations newly available observationbased neutron star and black hole mass distributions and complete analytical waveforms that include post-Newtonian amplitude corrections. Our results show that: (i) post-Newtonian effects cause a small reduction in the GW background signal; (ii) below 100 Hz the background depends primarily on the local coalescence rate r0 and the average chirp mass and is independent of the chirp mass distribution; (iii) the effects of cosmic star formation rates and delay times between the formation and merger of binaries are linear below 100 Hz and can be represented by a single parameter within a factor of ~2; (iv) a simple power-law model of the energy density parameter ΩGW(f) ~ f 2/3 up to 50-100 Hz is sufficient to be used as a search template for ground-based interferometers. In terms of detection prospects of this background signal, we show that: (i) detection (a signal-to-noise ratio of 3) within one year of observation by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) detectors (H1-L1) requires a coalescence rate of r0 = 3 (0.2) Mpc-3 Myr-1 for binary neutron stars (binary black holes); (ii) this limit on r0 could be reduced threefold for two co-located and co-aligned detectors, whereas the currently proposed worldwide network of advanced instruments gives only ~30 per cent improvement in detectability; (iii) the improved sensitivity of the planned Einstein Telescope allows not only confident detection of the background but also the high-frequency components of the spectrum to be measured, possibly enabling rate evolutionary histories and mass distributions to be probed. Finally, we show that sub-threshold binary neutron star merger events produce a strong foreground, which could be an issue for future terrestrial stochastic searches of primordial GWs. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

Wang Y.,Beijing Normal University | Tu Z.-C.,Beijing Normal University
Communications in Theoretical Physics | Year: 2013

The Carnot-like heat engines are classified into three types (normal-, sub- and, super-dissipative) according to relations between the minimum irreversible entropy production in the "isothermal" processes and the time for completing those processes. The efficiencies at maximum power of normal-, sub- and super-dissipative Carnot-like heat engines are proved to be bounded between ηC/2 and ηC/(2 - ηC), ηC/2 and ηC, 0 and ηC/(2 - ηC), respectively. These bounds are also shared by linear, sub- and super-linear irreversible Carnot-like engines [Tu and Wang, Europhys. Lett. 98 (2012) 40001] although the dissipative engines and the irreversible ones are inequivalent to each other. © 2013 Chinese Physical Society and IOP Publishing Ltd.

Liu Z.-H.,China Institute of Atomic Energy | Bao J.-D.,Beijing Normal University | Bao J.-D.,Accelerator Centre
Physical Review C - Nuclear Physics | Year: 2013

Synthesis of element 120 in the 249Cf(50Ti,xn)299-x120 and 248Cm(54Cr,xn)302-x120 fusion evaporation reactions has been evaluated by means of a modified fusion by diffusion model. It is found that the fusion probability of the system 54Cr+248Cm is two times smaller than that of 50Ti+249Cf. On the other hand, the survival probability of the former is obviously greater than that of the latter. As a result, the loss in the fusion probability of the 54Cr+248Cm reaction is compensated by its gain in survival probability. The calculated maximum evaporation residue cross sections in the 249Cf(50Ti,3n)296120 and 248Cm(54Cr,4n)298120 reactions are quite close: 0.034 and 0.024 pb, respectively. Besides, as compared to the system 50Ti+249Cf, the 54Cr+248Cm combination has two advantages. First, 248Cm is much easier accumulate a sufficient amount for the target material than 249Cf. Second, the isotope 298120 has 178 neutrons, two neutrons more than the isotope 296120. Therefore, the 54Cr+248Cm combination should be one of most favorable candidates to produce superheavy element 120. © 2013 American Physical Society.

Li Z.-Y.,East China Normal University | Zhang Y.,East China Normal University | Zhang C.-W.,East China Normal University | Chen L.-J.,East China Normal University | And 5 more authors.
Journal of the American Chemical Society | Year: 2014

A new family of discrete hexakis-pillar[5]arene metallacycles with different sizes have been successfully prepared via coordination-driven self-assembly, which presented very few successful examples of preparation of discrete multiple pillar[n]arene derivatives. These newly designed hexakis-pillar[5]arene metallacycles were well characterized with one-dimensional (1-D) multinuclear NMR (1H and 31 P NMR), two-dimensional (2-D) 1H-1H COSY and NOESY, ESI-TOF-MS, elemental analysis, and PM6 semiempirical molecular orbital methods. Furthermore, the host-guest complexation of such hexakis-pillar[5]arene hosts with a series of different neutral ditopic guests G1-6 were well investigated. Through host-guest interactions of hexakis-pillar[5]arene metallacycles H2 or H3 with the neutral dinitrile guest G5, the cross-linked supramolecular polymers H2⊃(G5)3 or H3⊃(G5)3 were successfully constructed at the high-concentration region, respectively. Interestingly, these cross-linked supramolecular polymers transformed into the stable supramolecular gels upon increasing the concentrations to a relatively high level. More importantly, by taking advantage of the dynamic nature of metal-ligand bonds and host-guest interactions, the reversible multiple stimuli-responsive gel-sol phase transitions of such polymer gels were successfully realized under different stimuli, such as temperature, halide, and competitive guest, etc. The mechanism of such multiple stimuli-responsive processes was well illustrated by in situ multinuclear NMR investigation. This research not only provides a highly efficient approach to the preparation of discrete multiple pillar[n]arene derivatives but also presents a new family of multiple stimuli-responsive "smart" soft matters. © 2014 American Chemical Society.

Li Y.,Beijing Normal University | Niu J.,Beijing Normal University | Wang W.,Beijing Normal University
Chemosphere | Year: 2011

Photolysis of Enro in water was investigated under simulated sunlight irradiation using a Xenon lamp. The results showed that Enro photolysis followed apparent first-order kinetics. Increasing Enro concentration from 5.0 to 40.0mgL -1 led to the decrease of the photolysis rate constant from 1.6×10 -2 to 3.0×10 -3min -1. Compared with the acidic and basic conditions, the photolysis rate was faster at neutral condition. Both of nitrate and humic acid can markedly decrease the photolysis rate of Enro because they can competitively absorb photons with Enro. The electron spin resonance and reactive oxygen species scavenging experiments indicated that Enro underwent self-sensitized photooxidation via OH and 1O 2. After irradiation for 90min, only 13.1% reduction of TOC occurred in spite of fast photolysis of 58.9% of Enro, indicating that Enro was transformed into intermediates without complete mineralization. The photolysis of Enro involved three main pathways: decarboxylation, defluorination, and piperazinyl N 4-dealkylation. The bioluminescence inhibition rate using Vibrio fischeri increased to 67.2% at 60min and then decreased to 56.9% at 90min, indicative of the generation of some more toxic intermediates than Enro and then the degradation of the intermediates. The results will help us understand fundamental mechanisms of Enro photolysis and provide insight into the potential fate and transformation of Enro in surface waters. © 2011 Elsevier Ltd.

Ren B.-C.,Beijing Normal University | Wei H.-R.,Beijing Normal University | Deng F.-G.,Beijing Normal University
Laser Physics Letters | Year: 2013

To date, all work concerning the construction of quantum logic gates, an essential part of quantum computing, has focused on operating in one degree of freedom (DOF) for quantum systems. Here, we investigate the possibility of achieving scalable photonic quantum computing based on two DOFs for quantum systems. We construct a deterministic hyper-controlled-not (hyper-CNOT) gate operating in both the spatial mode and polarization DOFs for a photon pair simultaneously, using the giant optical Faraday rotation induced by a single-electron spin in a quantum dot inside a one-side optical microcavity as a result of cavity quantum electrodynamics. With this hyper-CNOT gate and linear optical elements, two-photon four-qubit cluster entangled states can be prepared and analyzed, which give an application to manipulate more information with less resources. We analyze the experimental feasibility of this hyper-CNOT gate and show that it can be implemented with current technology. © 2013 Astro Ltd.

Ren B.-C.,Beijing Normal University | Deng F.-G.,Beijing Normal University
Laser Physics Letters | Year: 2013

Hyperentanglement has attracted much attention due to its fascinating applications in quantum communication. However, it is impossible to purify a pair of photon systems in a mixed hyperentangled state with errors in two degrees of freedom using linear optical elements only, far different from all the existing entanglement purification protocols in a degree of freedom (DOF) for quantum systems. Here, we investigate the possibility of purifying a spatial-polarization mixed hyperentangled Bell state with the errors in both the spatial-mode and polarization DOFs, resorting to the nonlinear optics of a nitrogen-vacancy (NV) center in a diamond embedded in a photonic crystal cavity coupled to a waveguide. We present the first hyperentanglement purification protocol for purifying a pair of two-photon systems in a mixed hyperentangled Bell state with the errors in two DOFs. We also propose an efficient hyperentanglement concentration protocol for a partially hyperentangled Bell pure state, which has the maximal success probability in principle. These two protocols are useful in long-distance quantum communication with hyperentanglement. © 2013 Astro Ltd.

Yue L.,Beijing Normal University | Liu Y.-J.,Beijing Normal University | Fang W.-H.,Beijing Normal University
Journal of the American Chemical Society | Year: 2012

The peroxide decomposition that generates the excited-state carbonyl compound is the key step in most organic chemiluminescence, and chemically initiated electron exchange luminescence (CIEEL) has been widely accepted for decades as the general mechanism for this decomposition. The firefly dioxetanone, which is a peroxide, is the intermediate in firefly bioluminescence, and its decomposition is the most important step leading to the emission of visible light by a firefly. However, the firefly dioxetanone decomposition mechanism has never been explored at a reliable theoretical level, because the decomposition process includes biradical, charge-transfer (CT) and several nearly degenerate states. Herein, we have investigated the thermolysis of firefly dioxetanone in its neutral (FDOH) and anionic (FDO -) forms using second-order multiconfigurational perturbation theories in combination with the ground-state intrinsic reaction coordinate calculated via the combined hybrid functional with Coulomb attenuated exchange-correlation, and considered the solvent effect on the ground-state reaction path using the combined hybrid functional with Coulomb attenuated exchange-correlation. The calculated results indicate that the chemiluminescent decomposition of FDOH or FDO - does not take place via the CIEEL mechanism. An entropic trap was found to lead to an excited-state carbonyl compound for FDOH, and a gradually reversible CT initiated luminescence (GRCTIL) was proposed as a new mechanism for the decomposition of FDO -. © 2012 American Chemical Society.

He W.-Y.,Beijing Normal University | Chu Z.-D.,Beijing Normal University | He L.,Beijing Normal University
Physical Review Letters | Year: 2013

The perfect transmission in a graphene monolayer and the perfect reflection in a Bernal graphene bilayer for electrons incident in the normal direction of a potential barrier are viewed as two incarnations of the Klein paradox. Here we show a new and unique incarnation of the Klein paradox. Owing to the different chiralities of the quasiparticles involved, the chiral fermions in a twisted graphene bilayer show an adjustable probability of chiral tunneling for normal incidence: they can be changed from perfect tunneling to partial or perfect reflection, or vice versa, by controlling either the height of the barrier or the incident energy. As well as addressing basic physics about how the chiral fermions with different chiralities tunnel through a barrier, our results provide a facile route to tune the electronic properties of the twisted graphene bilayer. © 2013 American Physical Society.

Gong H.,Beijing Normal University | Li X.,Beijing Normal University
Analyst | Year: 2011

An electrochemical assay for the detection of silver ion was reported, which was based on the interaction of the Y-type, C-rich ds-DNA with Ag +. Upon addition of Ag+, Y-type, C-rich ds-DNA could form an intramolecular duplex, in which Ag+ can selectively bind to cytosine-cytosine (C-C) mismatches forming C-Ag+-C complex. The binding result was evaluated by electrochemical impedance spectroscopy (EIS) and analyzed with the help of Randles' equivalent circuits. The differences of charge transfer resistance, ΔRCT, after and before the addition of Ag+, allows the detection and quantitative analysis of Ag + with a detection limit of 10 fM. Moreover, cysteine (Cys) was applied to remove Ag+ from the C-Ag+-C complex, which allowed the Ag+ sensor to be reproduced. In the same way, ΔRCT for the C-Ag+-C system in the absence and presence of Cys allows the detection of Cys at a concentration as low as 100 fM. Finally, the potential application of the Ag+ sensor was also explored, such as in lake and drinking water. © 2011 The Royal Society of Chemistry.

Lin Z.,Beijing Normal University | Chen Y.,Beijing Normal University | Li X.,Beijing Normal University | Fang W.,Beijing Normal University
Analyst | Year: 2011

Conformational switch from hairpin DNA to G-quadruplex induced by Pb 2+ is studied by electrochemical impedance spectroscopy (EIS) in the presence of [Fe(CN)6]3-/4- as the redox probe. In the presence of Pb2+, the G-rich hairpin DNA opens the stem-loop and forms G-quadruplex structure, which gives rise to a sharp increase in the charge-transfer resistance (RCT) of the film reflected by the EIS. This structural change is also confirmed by circular dichroism (CD) measurements and UV-Vis spectroscopic analysis and calculated by density functional theory (DFT). On the basis of this, we develop a label-free electrochemical DNA biosensor for Pb2+ detection. With increasing concentrations of Pb2+, the differences in the charge-transfer resistance R CT before and after the Pb2+ incubation is linearly dependent on the logarithm of Pb2+ concentration within a range from 50 μM to 0.5 nM. The biosensor also exhibits good selectivity for Pb 2+ over other metal ions. This is a simple and label-free electrochemical method for Pb2+ detection making use of the G-quadruplex. © 2011 The Royal Society of Chemistry.

Yuan G.,Beijing Normal University | Yuan G.,China National Institute of Biological Sciences | Zhu B.,China National Institute of Biological Sciences
Biochimica et Biophysica Acta - Gene Regulatory Mechanisms | Year: 2012

Nucleosome particles, which are composed of core histones and DNA, are the basic unit of eukaryotic chromatin. Histone modifications and histone composition determine the structure and function of the chromatin; this genome packaging, often referred to as "epigenetic information", provides additional information beyond the underlying genomic sequence. The epigenetic information must be transmitted from mother cells to daughter cells during mitotic division to maintain the cell lineage identity and proper gene expression. However, the mechanisms responsible for mitotic epigenetic inheritance remain largely unknown. In this review, we focus on recent studies regarding histone variants and discuss the assembly pathways that may contribute to epigenetic inheritance. This article is part of a Special Issue entitled: Histone chaperones and Chromatin assembly. © 2011 Elsevier B.V.

He Y.,Beijing Normal University
Progress in Biochemistry and Biophysics | Year: 2012

Alzheimer's disease (AD) is a progressive, neurodegenerative disease characterized by impaired memory and other cognitive functions. Previous neuroimaging studies have demonstrated regional structural and functional changes. Recent progressions on multi-modal imaging techniques and human brain connectome methods have allowed us to explore alterations of structural and functional networks in AD. Using these approaches, many studies have discovered AD-related network disruption, including connectivity strength, network efficiency, modular structure and network hubs. These findings provide novel insights into the understanding of AD notion of network disintegration and might lead to uncover disease biomarker for early diagnosis in AD. Most importantly, these findings in AD have been also demonstrated in the individuals at risk for AD (e.g., mild cognitive impairment), suggesting that the neuroimaging studies of AD should be moved into the prodromal stage of AD from the dementia stage.

Chen B.,Beijing Normal University | Wang R.,CAS Research Center for Eco Environmental Sciences
Ecological Indicators | Year: 2014

The editorial section of the special issue of Ecological Indicators focuses on describing integrated ecological indicators for sustainable urban ecosystem evaluation and management. It probes we aim to probe into the regulation measures to optimize the configuration of water resources and realize the integration of the fundamental research innovation and the management practice, thus providing decision support for the integration of water security, ecological security and sustainable socio-economic development of cities and regions. A group of researchers introduces a new multi-layered indicator set for urban metabolism studies, which is designed to gather information on the definition, biophysical characteristics, and metabolic flows of megacities.

Liao R.-Z.,University of Stockholm | Liao R.-Z.,Beijing Normal University | Yu J.-G.,Beijing Normal University | Himo F.,University of Stockholm
Journal of Chemical Theory and Computation | Year: 2011

We present a systematic study of the decarboxylation step of the enzyme aspartate decarboxylase with the purpose of assessing the quantum chemical cluster approach for modeling this important class of decarboxylase enzymes. Active site models ranging in size from 27 to 220 atoms are designed, and the barrier and reaction energy of this step are evaluated. To model the enzyme surrounding, homogeneous polarizable medium techniques are used with several dielectric constants. The main conclusion is that when the active site model reaches a certain size, the solvation effects from the surroundings saturate. Similar results have previously been obtained from systematic studies of other classes of enzymes, suggesting that they are of a quite general nature. © 2011 American Chemical Society.

Fu H.,Beijing Normal University | Cui M.,Beijing Normal University | Tu P.,Beijing Normal University | Pan Z.,Beijing Normal University | Liu B.,Beijing Normal University
Chemical communications (Cambridge, England) | Year: 2014

A novel class of near-infrared molecules based on the donor-acceptor architecture were synthesized and evaluated as Aβ imaging probes. In vivo imaging studies suggested that MCAAD-3 could penetrate the blood-brain barrier and label Aβ plaques in the brains of transgenic mice. Computational studies could reproduce the experimental trends well.

Dai Z.,Beijing Normal University | He Y.,Beijing Normal University
Neuroscience Bulletin | Year: 2014

Alzheimer's disease (AD) is the most common type of dementia, comprising an estimated 60-80% of all dementia cases. It is clinically characterized by impairments of memory and other cognitive functions. Previous studies have demonstrated that these impairments are associated with abnormal structural and functional connections among brain regions, leading to a disconnection concept of AD. With the advent of a combination of non-invasive neuroimaging (structural magnetic resonance imaging (MRI), diffusion MRI, and functional MRI) and neurophysiological techniques (electroencephalography and magnetoencephalography) with graph theoretical analysis, recent studies have shown that patients with AD and mild cognitive impairment (MCI), the prodromal stage of AD, exhibit disrupted topological organization in large-scale brain networks (i.e., connectomics) and that this disruption is significantly correlated with the decline of cognitive functions. In this review, we summarize the recent progress of brain connectomics in AD and MCI, focusing on the changes in the topological organization of large-scale structural and functional brain networks using graph theoretical approaches. Based on the two different perspectives of information segregation and integration, the literature reviewed here suggests that AD and MCI are associated with disrupted segregation and integration in brain networks. Thus, these connectomics studies open up a new window for understanding the pathophysiological mechanisms of AD and demonstrate the potential to uncover imaging biomarkers for clinical diagnosis and treatment evaluation for this disease. © 2014 Shanghai Institutes for Biological Sciences, CAS and Springer-Verlag.

Liu Q.,Fudan University | Sun Y.,Fudan University | Li C.,Fudan University | Zhou J.,Fudan University | And 5 more authors.
ACS Nano | Year: 2011

A novel method of rare-earth cation-assisted ligand assembly has been developed to provide upconversion nanophosphors with T1-enhanced magnetic resonance (MR), radioactivity, and targeted recognition properties, making these nanoparticles potential candidates for multimodal bioimaging. The process of modifying the surface of the nanophosphors has been confirmed by transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, proton nuclear magnetic resonance, Fourier-transform infrared spectroscopy, energy-dispersive X-ray analysis, and so on. The versatility of this surface modification approach for incorporating functional molecules and fabricating fluorine-18-labeled magnetic-upconversion nanophosphors as multimodal bioprobes has been demonstrated by targeted cell imaging, in vivo upconversion luminescence, MR imaging, and positron emission tomography imaging of whole-body small animals. © 2011 American Chemical Society.

Sun G.-Y.,Beijing Normal University | Kou S.-P.,Beijing Normal University
Journal of Physics Condensed Matter | Year: 2011

In this paper, the Hubbard model on a honeycomb lattice is investigated by using an O(3) nonlinear σ model. A possible candidate for a quantum non-magnetic insulator in a narrow parameter region is found near the metal-insulator transition. After studying the magnetic properties of the quantum non-magnetic insulator, anomalous spin dynamics is shown. In addition, we find that this region could be widened by hole doping. © 2011 IOP Publishing Ltd.

Hao Z.,Beijing Normal University | Singh V.P.,Texas A&M University
Journal of Hydrology | Year: 2015

Drought is a recurring natural phenomenon that has plagued the civilization throughout its history. Due to the complex nature and widespread impacts of drought, there is a lack of universally accepted definition of drought, which also affects the development of drought indices to characterize drought conditions. Because an individual drought indicator is generally not sufficient for characterizing complex drought conditions and impacts, multiple drought-related variables and indices are required to capture different aspects of complicated drought conditions. To address this issue, a variety of multivariate drought indices have been developed recently to combine multiple drought-related variables and indices for integrated drought characterizations. This paper presents a comprehensive review of major multivariate drought indices developed recently. Different development methods of multivariate drought indices are introduced along with their strengths and limitations. This paper provides useful information for operational drought characterization with current multivariate drought indices and for the development of new multivariate drought indices. © 2015 Elsevier B.V.

Di Y.-M.,Jiangsu University | Wei H.-R.,Jiangsu University | Wei H.-R.,Beijing Normal University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We propose the generalized controlled X (gcx) gate as the two-qudit elementary gate, and based on Cartan decomposition, we also give the one-qudit elementary gates. Then we discuss the physical implementation of these elementary gates and show that it is feasible with current technology. With these elementary gates many important qudit quantum gates can be synthesized conveniently. We provide efficient methods for the synthesis of various kinds of controlled qudit gates and greatly simplify the synthesis of existing generic multi-valued quantum circuits. Moreover, we generalize the quantum Shannon decomposition (QSD), the most powerful technique for the synthesis of generic qubit circuits, to the qudit case. A comparison of ququart (d=4) circuits and qubit circuits reveals that using ququart circuits may have an advantage over the qubit circuits in the synthesis of quantum circuits. © 2013 American Physical Society.

Gao S.,Beijing Normal University | Zhang Y.,Beijing Normal University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

It has been shown that a nearly extremal black hole can be overcharged or overspun by a test particle if radiative and self-force effects are neglected, indicating that the cosmic censorship might fail. In contrast, the existing evidence in literature suggests that an extremal black hole cannot be overcharged or overspun in a similar process. In this paper, we show explicitly that even an exactly extremal black hole can be destroyed by a test particle, leading to a possible violation of the cosmic censorship. By considering higher-order terms, which were neglected in previous analysis, we show that the violation is generic for any extremal Kerr-Newman black hole with nonvanishing charge and angular momentum. We also find that the allowed parameter range for the particle is very narrow, indicating that radiative and self-force effects should be considered and may prevent violation of the cosmic censorship. © 2013 American Physical Society.

Zhang X.-M.,Beijing Normal University | Zhu J.-Y.,Beijing Normal University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

A general form of warm inflation with the dissipative coefficient Γ=Γ0(0)n(Tτ0)m in loop quantum cosmology is studied. In this case, we obtain conditions for the existence of a warm inflationary attractor in the context of loop quantum cosmology by using the method of stability analysis. The two cases when the dissipative coefficient is independent (m=0) and dependent (m≠0) on temperature are analyzed specifically. In the latter case, we use the new power spectrum which should be used when considering temperature dependence in the dissipative coefficient. We find that the thermal effect is enhanced in the case m>0. As in the standard inflation in loop quantum cosmology, we also reach the conclusion that quantum effect leaves a tiny imprint on the cosmic microwave background sky. © 2013 American Physical Society.

Wei H.-R.,Beijing Normal University | Deng F.-G.,Beijing Normal University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We present some deterministic schemes to construct universal quantum gates, that is, controlled- not, three-qubit Toffoli, and Fredkin gates, between flying photon qubits and stationary electron-spin qubits assisted by quantum dots inside double-sided optical microcavities. The control qubit of our gates is encoded on the polarization of the moving single photon and the target qubits are encoded on the confined electron spins in quantum dots inside optical microcavities. Our schemes for these universal quantum gates on a hybrid system have some advantages. First, all the gates are accomplished with a success probability of 100% in principle. Second, our schemes require no additional qubits. Third, the control qubits of the gates are easily manipulated and the target qubits are perfect for storage and processing. Fourth, the gates do not require that the transmission for the uncoupled cavity is balanceable with the reflectance for the coupled cavity, in order to get a high fidelity. Fifth, the devices for the three universal gates work in both the weak coupling and the strong coupling regimes, and they are feasible in experiment. © 2013 American Physical Society.

Yue X.-J.,Beijing Normal University | Zhu J.-Y.,Beijing Normal University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We investigate the scalar mode of perturbation of super inflation in the version of loop quantum cosmology in which the gauge invariant holonomy corrections are considered. Given a background solution, we calculate the power spectrum of the perturbation in the classical and loop quantum cosmology conditions. Then we compute the anisotropy originated from the perturbation. It is found that in the presence of the gauge invariant holonomy corrections the power spectrum is exponentially blue and the anisotropy also grows exponentially in the epoch of super inflation. © 2013 American Physical Society.

Liu Y.,Beijing Institute of Technology | Liu Y.,Beijing Normal University | Wang R.,Beijing Institute of Technology | Zhang X.,Beijing Institute of Technology
Optics Express | Year: 2014

Recently, there are great interest in studying the interaction between chiral molecules and plasmonic particles, because a weak circular dichroism (CD) signal in the ultraviolet (UV) region from chiral molecules can be both enhanced and transferred to the visible wavelength range by using plasmonic particles. Thus, ultrasensitive probe of tiny amounts of chiral substance by CD are worth waiting for. Here we present another way to strongly enhance CD of chiral molecules by using plasmonic particle cluster, which need not transfer to the visible wavelength. The method to calculate CD of chiral molecules in nanosphere clusters has been developed by means of multiple scattering of electromagnetic multipole fields. Our calculated results show that 2 orders of magnitude CD enhancement in the UV region for chiral molecules can be realized. Such a CD enhancement is very sensitive to the cluster structure. The cluster structure can cause chiroptical illusion in which a mirror symmetry in the CD spectra ofopposite enantiomeric molecules is broken. The correction of quantum size effect on the phenomenon has also been considered. Our findings open up an alternative avenue for the ultrasensitive detection and illusion of chiral information. © 2014 Optical Society of America.

Li Z.,Beijing Normal University
European Physical Journal C | Year: 2013

A generalized scenario, which is used to characterize the attenuated dilution of cold dark matter deviating from the standard case, is proposed for the interaction of cosmological dark sectors. This generalized framework cannot only fully recover the three frequently studied phenomenological parameterizations in the limit of the characteristic parameter α→-1,0 and +1, but also admits a much wider range of cosmological solutions for other values of α. Moreover, some cosmological consequences are examined by placing constraints on this generalized interacting model with current observational data. We find that, for α in the extended range of [-1.0, 1.0], the case in which the energy flow transfers from dark matter to dark energy is slightly favored by observations. © 2013 Springer-Verlag Berlin Heidelberg and Società Italiana di Fisica.

Talhelm T.,University of Virginia | Haidt J.,New York University | Oishi S.,University of Virginia | Zhang X.,Beijing Normal University | And 2 more authors.
Personality and Social Psychology Bulletin | Year: 2015

Henrich, Heine, and Norenzayan summarized cultural differences in psychology and argued that people from one particular culture are outliers: people from societies that are Western, educated, industrialized, rich, and democratic (WEIRD). This study shows that liberals think WEIRDer than conservatives. In five studies with more than 5,000 participants, we found that liberals think more analytically (an element of WEIRD thought) than moderates and conservatives. Study 3 replicates this finding in the very different political culture of China, although it held only for people in more modernized urban centers. These results suggest that liberals and conservatives in the same country think as if they were from different cultures. Studies 4 to 5 show that briefly training people to think analytically causes them to form more liberal opinions, whereas training them to think holistically causes shifts to more conservative opinions. © 2014 by the Society for Personality and Social Psychology, Inc.

Yang J.,Beijing Normal University | Chen B.,Beijing Normal University
Applied Energy | Year: 2014

Efforts have been made to establish a biogas-linked agricultural production mode to alleviate poverty and pressure on the environment in rural China. In this paper, we evaluate the performance of biogas engineering using emergy analysis in the context of a compound agricultural system. A set of emergy indices are incorporated in the analysis to describe the transformation of energy and materials in the system. We also performed a case study in Gongcheng Yao Autonomous County, China. The carbon mitigation performance, environmental and economic trade-offs, and sustainability level of the system encompassing biogas engineering, crop production and livestock subsystems was investigated in detail. The results showed that the biogas-linked agricultural production mode characterized by further metabolism within the system made a favorable contribution to carbon mitigation and material recycling, although its conversion efficiency was low. Finally, suggestions regarding local agricultural sustainability are provided to shed light on the policies of biogas promotion in rural China. © 2013 Elsevier Ltd.

Shen Z.,Beijing Normal University | Chen L.,Beijing Normal University | Xu L.,Beijing Normal University
PLoS ONE | Year: 2013

Best Management Practices (BMPs) are one of the most effective methods to control nonpoint source (NPS) pollution at a watershed scale. In this paper, the use of a topography analysis incorporated optimization method (TAIOM) was proposed, which integrates topography analysis with cost-effective optimization. The surface status, slope and the type of land use were evaluated as inputs for the optimization engine. A genetic algorithm program was coded to obtain the final optimization. The TAIOM was validated in conjunction with the Soil and Water Assessment Tool (SWAT) in the Yulin watershed in Southwestern China. The results showed that the TAIOM was more cost-effective than traditional optimization methods. The distribution of selected BMPs throughout landscapes comprising relatively flat plains and gentle slopes, suggests the need for a more operationally effective scheme, such as the TAIOM, to determine the practicability of BMPs before widespread adoption. The TAIOM developed in this study can easily be extended to other watersheds to help decision makers control NPS pollution. © 2013 Shen et al.

Wang N.,Guangxi Normal University | Liu M.,Guangxi Normal University | Liu M.,Beijing Normal University
Physical Review C - Nuclear Physics | Year: 2010

The mass and isospin dependence of symmetry energy coefficients asym of finite nuclei are investigated with the measured nuclear masses incorporating the liquid drop mass formula. The enhanced asym for nearly symmetric nuclei are observed. To describe the mass and isospin dependence of asym, a modified formula based on the conventional surface-symmetry term is proposed and the corresponding rms deviation of nuclear masses is checked. © 2010 The American Physical Society.

Wang N.,Guangxi Normal University | Liu M.,Guangxi Normal University | Liu M.,Beijing Normal University | Wu X.,China Institute of Atomic Energy
Physical Review C - Nuclear Physics | Year: 2010

We propose a semiempirical nuclear mass formula based on the macroscopic-microscopic method in which the isospin and mass dependence of model parameters are investigated with the Skyrme energy density functional. The number of model parameters is considerably reduced compared with the finite range droplet model. The rms deviation with respect to 2149 measured nuclear masses is reduced by 21%, falling to 0.516MeV. The new magic number N=16 in light neutron-rich nuclei and the shape coexistence phenomena for some nuclei have been examined with the model. The shell corrections of superheavy nuclei are also predicted. © 2010 The American Physical Society.

Liu Z.-H.,China Institute of Atomic Energy | Bao J.-D.,Beijing Normal University | Bao J.-D.,Accelerator Centre
Physical Review C - Nuclear Physics | Year: 2010

We have reevaluated the 136Xe(136Xe,xn)272-xHs reaction with a modified fusion-by-diffusion model. In this model, the early dynamics of neck growth is taken into account in terms of the two-dimensional Langevin equation. By numerically solving the dynamic equations, the probability distribution of the separation between the surfaces of two approaching nuclei at the injection point in an asymmetric fission valley is obtained. Before reaching the asymmetric fission valley, the strong electrostatic repulsion may force the system to redisintegrate in a quasifissionlike process. We find that more than 80% of quasifission events occur during the transition from dinuclear to mononuclear regimes for the Xe136+Xe136 reaction. This observation gives credence to the conjecture that the quasifission reaction channel most likely occurs in an early stage of collective motion. By incorporating this essential physical ingredient into the calculations, the modified fusion-by-diffusion model nicely accounts for the experiment of the Xe136+Xe136 reaction performed in Dubna. © 2010 The American Physical Society.

Ma M.,Beijing Normal University | Liu J.,Beijing Normal University | Wang X.,Beijing Normal University
Ecotoxicology | Year: 2011

The structural and functional attributes of biofilms from Lake Baiyangdian, China, were tested to evaluate the utility of biofilms as indicators of macrophyte-dominated lake health. Biofilms on artificial substrata were sampled at 8 sites in the lake during different seasons. The responses of biofilms to land use and water quality changes were analyzed. The biofilm structural and functional attributes fluctuated seasonally. All attributes we tested differed significantly with different land use. Generally, biomass and enzyme activities increased, whereas chl c/a decreased with human disturbance. Attributes were strongly correlated to environmental variables, especially the trophic status of the lake. Overall, biofilms were good indicators of macrophyte-dominated lake health. The proportions of Bacillariophyta and Cyanophyta, Chlorophyll-a, b, chlorophyll-b/a, chlorophyll-c/a, algal density, β-glucosidase, aminopeptidase and ash-free dry weight of biofilms are recommended as tools for assessing responses to land use changes, and for monitoring the effectiveness of ecosystem rehabilitation. © 2011 Springer Science+Business Media, LLC.

Yue W.,Beijing Normal University | Tao S.,Beijing Normal University | Fu J.,Beijing Normal University | Gao Z.,Beijing Normal University | Ren Y.,China National Institute of Clean and Low Carbon Energy
Carbon | Year: 2013

Graphene-based Cr2O3 composites are prepared and exhibit better electrochemical properties than free Cr2O3 particles without the graphene. The synthesis procedure consists of the direct growth of CrOOH on the surface of graphene and the subsequent thermal decomposition of CrOOH to Cr2O3. Moreover, the electrochemical properties of graphene-based Cr2O3 are further improved through carbon coating, and two strategies are developed. Interestingly, the carbon layers pyrolyzed from glucose on CrOOH can separate the particles on the graphene and limit their growth, while those on Cr 2O3 merely cover the particles and cannot prevent particle aggregation. Consequently, compared to the latter carbon-coated composite, the former shows further improved electrochemical behavior.

Wei H.-R.,Beijing Normal University | Ren B.-C.,Beijing Normal University | Deng F.-G.,Beijing Normal University
Quantum Information Processing | Year: 2013

Quantum discord, as a measure of all quantum correlations, has been proposed as the key resource in certain quantum communication tasks and quantum computational models without containing much entanglement. Dakić et al. (Phys Rev Lett 105:190502, 2010) introduced a geometric measure of quantum discord (GMQD) and derived an explicit formula for any two-qubit state. Luo and Fu (Phys Rev A 82:034302, 2010) introduced another form of GMQD and derived an explicit formula for arbitrary state in a bipartite quantum system. However, the explicit analytical expression for any bipartite system was not given. In this work, we give out the explicit analytical expressions of the GMQD for a two-parameter class of states in a qubit-qutrit system and study its dynamics for the states under various dissipative channels in the first time. Our results show that all these dynamic evolutions do not lead to a sudden vanishing of GMQD. Quantum correlations vanish at an asymptotic time for local or multi-local dephasing, phase-flip, and depolarizing noise channels. However, it does not disappear even though t → ∞ for local trit-flip and local trit-phase-flip channels. Our results maybe provide some important information for the application of GMQD in hybrid qubit-qutrit systems in quantum information. © 2012 Springer Science+Business Media, LLC.

Lu H.,Beijing Normal University | Pang Y.,Texas A&M University | Pope C.N.,Texas A&M University | Pope C.N.,University of Cambridge
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We study conformally invariant theories of gravity in six dimensions. In four dimensions, there is a unique such theory that is polynomial in the curvature and its derivatives, namely, Weyl-squared, and furthermore all solutions of Einstein gravity are also solutions of the conformal theory. By contrast, in six dimensions there are three independent conformally invariant polynomial terms one could consider. There is a unique linear combination (up to overall scale) for which Einstein metrics are also solutions, and this specific theory forms the focus of our attention in this paper. We reduce the equations of motion for the most general spherically symmetric black hole to a single fifth-order differential equation. We obtain the general solution in the form of an infinite series, characterized by five independent parameters, and we show how a finite three-parameter truncation reduces to the already known Schwarzschild-AdS metric and its conformal scaling. We derive general results for the thermodynamics and the first law for the full five-parameter solutions. We also investigate solutions in extended theories coupled to conformally invariant matter, and in addition we derive some general results for conserved charges in cubic-curvature theories in arbitrary dimensions. © 2013 American Physical Society.

Jin Y.,Beijing Normal University
Proceedings - 2012 International Conference on Computer Science and Electronics Engineering, ICCSEE 2012 | Year: 2012

A topic detection and tracking method combining semantic analysis with Suffix Tree Clustering (STC) algorithm is presented. A feature selection using NLP algorithm was introduced to select the noun, verb and name entity as the input of STC. Focusing on the topic drifting, we formed the VSM of cluster by the key words extracted from the nodes of suffix tree by mutual information algorithm. After the similarity computing of clusters and topic detection and tracking, a semantic analysis was introduced to filter the words with same meaning and analyze the semantic structure of words in label of cluster. Finally a content-relevant description was generated for each topic. The experiments showed that this method can detect and track the topics from the news articles effectively. © 2012 IEEE.

Zhang Q.-G.,Beijing Normal University | Buckling A.,University of Exeter
Ecology | Year: 2016

The classical, ecological, paradox of enrichment describes a phenomenon that resource enrichment destabilizes predator-prey systems by exacerbating population oscillations. Here we suggest a new, evolutionary, paradox of enrichment. Resource enrichment can lead to more asymmetrical predator-prey coevolution (i.e., extremely high levels of prey defenses against predators) that decreases predator abundances and increases predator extinction risk. A major reason for this is that high resource availability can reduce fitness costs associated with prey defenses. In our experiments with a bacterium and its lytic phage, nutrient-balanced resource enrichment led to patterns in population demography and coevolutionary dynamics consistent with this coevolution-based paradox of enrichment; in particular, phage population extinction events were observed under nutrient-rich, not nutrient-poor, conditions. Consistent with ecological studies, carbon-biased resource enrichment (with carbon availability disproportionately increased relative to other nutrients) did not destabilize dynamics, and the asymmetry of coevolution was not altered in this context. Our work highlights the importance of integrating ecological and evolutionary thinking for studies of the consequences of nutrient pollution and other types of environmental changes. © 2016 by the Ecological Society of America.

Zhang J.,Beijing Normal University | Wu L.,City University of Hong Kong
PLoS ONE | Year: 2013

Background:An ecological flow network is a weighted directed graph in which the nodes are species, the edges are "who eats whom" relationships and the weights are rates of energy or nutrient transferred between species. Allometric scaling is a ubiquitous feature for flow systems such as river basins, vascular networks and food webs.Methodology:The "ecological network analysis" can serve to reveal hidden allometries, the power law relationship between the throughflux and the indirect impact of node i, directly from the original flow networks without any need to cut edges in the network. The dissipation law, which is another significant scaling relationship between the energy dissipation (respiration) and the throughflow of any species, is also obtained from an analysis of the empirical flow networks. Interestingly, the exponents of the allometric law (η) and the dissipation law (γ) show a strong relationship for both empirical and simulated flow networks. The dissipation law exponent γ, rather than the topology of the network, is the most important factors that affect the allometric exponent η. Conclusions:The exponent η can be interpreted as the degree of centralization of the network, i.e., the concentration of impacts (direct and indirect influences on the entire network along all energy flow pathways) on hubs (the nodes with large throughflows). As a result, we find that as γ increases, the relative energy loss of large nodes increases, η decreases, i.e., the relative importance of large species decreases. Moreover, the entire flow network is more decentralized. Therefore, network flow structure (allometry) and thermodynamic constraints (dissipation) are linked. © 2013 Zhang, Wu.

Zhang Z.-H.,Central China Normal University | Guo X.-H.,Beijing Normal University | Yang Y.-D.,Central China Normal University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Recently, the large CP asymmetries in B±→π ±π+π- decays were found by the LHCb Collaboration to localize in the region mπ+π -2<0.4 GeV2. We find such large localized CP asymmetries may be due to the interference between a light scalar and ρ0(770) intermediate resonances. Consequently, we argue that the distribution of CP asymmetries in the Dalitz plots of three-body B decays could be very helpful for identifying the presence of the scalar resonance. © 2013 American Physical Society.

Liu Z.,Beijing Normal University | Reddy G.,University of Maryland University College | Thirumalai D.,University of Maryland University College
Journal of Physical Chemistry B | Year: 2012

A theoretical basis for the molecular transfer model (MTM), which takes into account the effects of denaturants by combining experimental data and molecular models for proteins, is provided. We show that the MTM is a mean field-like model that implicitly takes into account denaturant-induced many body interactions. The MTM in conjunction with the coarse-grained self organized polymer model with side chains (SOP-SC) for polypeptide chains is used to simulate the folding of the src-SH3 domain as a function of temperature (T) and guanidine hydrochloride (GdmCl) concentration [C]. Besides reproducing the thermodynamic aspects of SH3 folding, the SOP-SC also captures the cooperativity of the folding transitions. A number of experimentally testable predictions are also made. First, we predict that the melting temperature Tm([C]) decreases linearly as [C] increases. Second, we show that the midpoints C m,i and melting temperatures Tm,i at which individual residues acquire 50% of their native contacts differ from the global midpoint (Cm ≈ 2.5 M) and melting temperature (Tm = 355 K) at which the folded and unfolded states coexist. Dispersion in Cm,i is greater than that found for Tm,i. Third, folding kinetics at [C] = 0 M shows that the acquisition of contacts between all the secondary structural elements and global folding occur nearly simultaneously. Finally, from the free energy profiles as a function of the structural overlap function and the radius of gyration of the protein, we find that at a fixed T the transition state moves toward the folded state as [C] increases in accord with the Hammond postulate. In contrast, we predict that along the locus of points Tm([C]) the location of the transition state does not change. The theory and the models used here are sufficiently general for studying the folding of other single domain proteins. © 2012 American Chemical Society.

Deng F.-G.,Beijing Normal University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

We propose an optimal nonlocal entanglement concentration protocol (ECP) for multiphoton systems in a partially entangled pure state, resorting to the projection measurement on an additional photon. One party in quantum communication first performs a parity-check measurement on her photon in an N-photon system and an additional photon, and then she projects the additional photon into an orthogonal Hilbert space for dividing the original N-photon systems into two groups. In the first group, the N parties will obtain a subset of N-photon systems in a maximally entangled state. In the second group, they will obtain some less-entangled N-photon systems which are the resource for the entanglement concentration in the next round. By iterating the entanglement concentration process several times, the present ECP has the maximal success probability, which is just equivalent to the entanglement of the partially entangled state. That is, this ECP is an optimal one. © 2012 American Physical Society.

Possessing power contributes to high self-esteem, but how power enhances self-esteem is still unknown. As power is associated with both self-oriented goals and social-responsibility goals, we proposed that power predicts self-esteem through two positive personal and interpersonal results: authenticity and relationship satisfaction. Three studies were carried out with a total of 505 Chinese participants, including college students and adults, who completed surveys that assessed personal power, self-esteem, authenticity, relationship satisfaction, communal orientation, and social desirability. Hierarchical multiple regression analyses demonstrated that power, authenticity, and relationship satisfaction each uniquely contributed to self-esteem. More importantly, multiple mediation analysis showed that authenticity and relationship satisfaction both mediated the effects of power on self-esteem, even when controlling for participants' communal orientation and social desirability. Our findings demonstrate that authenticity and relationship satisfaction represent two key mechanisms by which power is associated with self-esteem. © 2015 Yi Nan Wang. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Pang X.,Beijing Normal University | Jin W.J.,Beijing Normal University
New Journal of Chemistry | Year: 2015

The halogen bond specific solvent effect in halogenated solvents was investigated by ESR, Raman spectroscopy, X-ray diffraction and unrestricted MP2 calculations using the ESR probe TEMPO. From ESR spectroscopy, 14N isotropic hyperfine splitting (HFS) constant aN values are higher in halogenated than non-halogenated solvents as solvent polarity is near to each other, and plotting aN values vs. solvent acceptor number (AN) provides a linear correlation. These results could be attributed to the formation of halogen bonding (XB) and indicate that as specific solvent effect halogen bonding does exist in halogenated solvents, particularly in halo-perfluoro-solvents, in which the halogen bonding between the nucleophilic solutes and halogenated solvent molecules is so strong that it must not be ignored. In both halogen- and hydrogen-containing solvents, halogen bonding and hydrogen bonding may co-exist. Calculations show that the strength of hydrogen bond may be slightly stronger than the corresponding halogen bond. However, the halogen bond becomes more competitive going from chlorine(Cl)-substituted to bromine(Br)-substituted to iodine(I)-substituted solvents, and it is possible that XB solvent effects become preponderant in I-substituted solvents. The analysis of Mulliken atomic spin densities on N and O atoms also proved that when the XB is formed, the spin densities on O would transfer to N, further indicating that the increase of aN should be ascribed to XB specific solvent effects. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2015.

Zhu Y.,Jiangnan University | Liu X.,Jiangnan University | Gao J.,Jiangnan University | Zhang Y.,Jiangnan University | Zhao F.,Beijing Normal University
Optics Express | Year: 2014

We develop a novel model of the probability density of the orbital angular momentum (OAM) modes for Hankel-Bessel beams in paraxial turbulence channel based on the Rytov approximation. The results show that there are multi-peaks of the mode probability density along the radial direction. The peak position of the mode probability density moves to beam center with the increasing of non-Kolmogorov turbulence-parameters and the generalized refractive-index structure parameters and with the decreasing of OAM quantum number, propagation distance and wavelength of the beams. Additionally, larger OAM quantum number and smaller non-Kolmogorov turbulence-parameter can be selected in order to obtain larger mode probability density. The probability density of the OAM mode crosstalk is increasing with the decreasing of the quantum number deviation and the wavelength. Because of the focusing properties of Hankel-Bessel beams in turbulence channel, compared with the Laguerre-Gaussian beams, Hankel-Bessel beams are a good light source for weakening turbulence spreading of the beams and mitigating the effects of turbulence on the probability density of the OAM mode. © 2014 Optical Society of America.

Ke Y.,McGill University | Xia K.,Beijing Normal University | Guo H.,McGill University
Physical Review Letters | Year: 2010

By first principles analysis, we systematically investigate effects of oxygen vacancies (OV) in the MgO barrier of Fe/MgO/Fe magnetic tunnel junctions. The interchannel diffusive scattering by disordered OVs located at or near the Fe/MgO interface drastically reduces the tunnel magnetoresistance ratio (TMR) from the ideal theoretical limit to the presently observed much smaller experimental range. Interior OVs are far less important in influencing TMR, but they significantly increase the junction resistance. Filling OV with nitrogen atoms restores TMR to near the ideal theoretical limit. © 2010 The American Physical Society.

Li T.,Beijing Normal University | Yang G.-J.,Beijing Normal University | Deng F.-G.,Beijing Normal University | Deng F.-G.,Beijing University of Posts and Telecommunications
Optics Express | Year: 2014

Atomic ensembles are effective memory nodes for quantum communication network due to the long coherence time and the collective enhancement effect for the nonlinear interaction between an ensemble and a photon. Here we investigate the possibility of achieving the entanglement distillation for nonlocal atomic ensembles by the input-output process of a single photon as a result of cavity quantum electrodynamics. We give an optimal entanglement concentration protocol (ECP) for two-atomic-ensemble systems in a partially entangled pure state with known parameters and an efficient ECP for the systems in an unknown partially entangled pure state with a nondestructive parity-check detector (PCD). For the systems in a mixed entangled state, we introduce an entanglement purification protocol with PCDs. These entanglement distillation protocols have high fidelity and efficiency with current experimental techniques, and they are useful for quantum communication network with atomic-ensemble memories. © 2014 Optical Society of America.

Ren B.-C.,Beijing Normal University | Du F.-F.,Beijing Normal University | Deng F.-G.,Beijing Normal University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

Hyperentanglement, defined as the entanglement in several degrees of freedom (DOFs) of a quantum system, has attracted much attention recently. Here we investigate the possibility of concentrating the two-photon four-qubit systems in partially hyperentangled states in both the spatial mode and the polarization DOFs with linear optics. We first introduce our parameter-splitting method to concentrate the systems in the partially hyperentangled states with known parameters, including partially hyperentangled Bell states and cluster states. Subsequently, we present another two nonlocal hyperentanglement concentration protocols (hyper-ECPs) for the systems in partially hyperentangled unknown states, resorting to the Schmidt projection method. It will be shown that our parameter-splitting method is very efficient for the concentration of the quantum systems in partially entangled states with known parameters, resorting to linear-optical elements only. All these four hyper-ECPs are feasible with current technology and they may be useful in long-distance quantum communication based on hyperentanglement as they require only linear optical elements. © 2013 American Physical Society.

Liu Y.-K.,Beijing Normal University | Yang S.-J.,Beijing Normal University | Yang S.-J.,CAS Institute of Theoretical Physics
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We present an exact solution to the stationary coupled nonlinear Gross-Pitaevskii equations, which govern the motion of the spinor Bose-Einstein condensates. The solitonic solution is a twisted half-skyrmion in 3D space. By making a map from the Cartesian coordinates to the toroidal coordinates, we demonstrate it is a linked half-unknot with a fractional topological charge. © 2013 American Physical Society.

Han Z.,Beijing Normal University | Cui B.,Beijing Normal University
Ecological Engineering | Year: 2016

Ponds significantly contribute to local and regional biodiversity by supporting wide-ranging communities of aquatic organisms. However, ponds are often disturbed by intensive anthropogenic activities because of their accessibility. Hence, methods to assess the effects of anthropogenic activities on ponds are of great importance. In this study, we developed an integrated stress index (ISI) to characterize the integrated stress from different types of anthropogenic activities on ponds and then tested the robustness of this index through sensitivity analysis. We also examined the relationships between ISI and the species richness and biomass of different macrophytes through regression analyses. Results showed that ISI significantly negatively correlates with total species richness but significantly positively correlates with total biomass. Emergent, floating-leaved, and submerged species exhibited different responses to ISI. Moreover, ISI produced more significant effects on species richness and biomass of different macrophytes than eutrophication. Therefore, eutrophication is not the only stress to be treated in the area of study. These findings provide pond restoration-useful insights into the relationships among inhibiting anthropogenic activities, water level management, harvesting, and species composition. © 2016 Elsevier B.V.

Gu R.,Beijing Normal University | Huang Y.-X.,Beijing Normal University | Luo Y.-J.,Beijing Normal University
Psychophysiology | Year: 2010

It has been suggested that anxious individuals are more prone to feel that negative outcomes are particularly extreme and to interpret ambiguous outcomes as negative compared to nonanxious individuals. Previous studies have demonstrated that the feedback negativity (FN) component of event-related brain potential (ERP) is sensitive to outcome evaluation and outcome expectancy. Hence, we predicted that the FN should be different between high trait-anxiety (HTA) and low trait-anxiety (LTA) individuals. To test our hypothesis, the ERPs were recorded during a simple monetary gambling task. The FN was measured as a difference wave created across conditions. We found that the amplitude of the FN indicating negative versus positive outcomes was significantly larger for LTA individuals compared to HTA individuals. However, there was no significant difference in the FN between groups in response to ambiguous versus positive outcomes. The results indicate that there is a relationship between the FN and individual differences in anxiety. We suggest that these results reflect the impact of anxiety on outcome expectation. Our results challenge the reinforcement learning theory of error-related negativity, which proposes that ERN and FN reflect the same cognitive process. Copyright © 2010 Society for Psychophysiological Research.

Cai B.,Chinese Research Academy of Environmental Sciences | Zhang L.,Beijing Normal University
Energy Policy | Year: 2014

Different names/concepts and therefore different spatial boundaries for cities in China are responsible for the conflicting and confusing results associated with urban CO2 emissions accounting. In this study, four types of urban boundaries, i.e., city administrative boundary (UB1), city district boundary (UB2), city built-up area (UB3) and urban proper (UB4), were identified and defined. Tianjin was subsequently selected as the case city to illustrate the different performances of CO2 emissions with respect to these four boundaries using a 1-km grid dataset built bottom-up by point-emission sources. Different urban boundaries can induce a difference in CO2 emissions as large as 654%. UB1 and UB2 are not the appropriate proxies for urban boundaries in the analysis of urban CO2 emissions, although UB1 is a widely adopted boundary. UB3 is a good representative of city clusters and urban sprawl in a certain region, whereas UB4 is the appropriate system boundary for such issues as urban CO2 emissions in light of landscape characteristics and pertinent human activities, as well as the comparability to counterparts in developed countries. These results provide sound policy implications for the improvement of urban energy management and carbon emission abatement in China. © 2013 Elsevier Ltd.

Qu L.-J.,Beijing Normal University
Communications in Theoretical Physics | Year: 2012

Scaling theory of charged cylindrical polyelectrolyte brushes is developed. The dependence of brush thickness on the grafting density, charge fraction, and chain length is analyzed. A full phase diagram is established. Characteristics and boundaries between different regimes of cylindrical polyelectrolyte brushes are summarized. Special attentions are paid to electrostatic interaction induced stiffening and counterion condensation effects. If the Bjerrum length of the solution is larger than the Kuhn length of the polyelectrolyte chains, counterion condensation occurs in the strongly charged polyelectrolyte brushes. On the contrary, the electrostatic interaction stretches the strongly charged grafted polyelectrolyte chains to their contour length. © 2012 Chinese Physical Society and IOP Publishing Ltd.

Yan X.Q.,Beijing Normal University | Zhao X.R.,Beijing Normal University | Wang H.,Beijing Normal University | Jin W.J.,Beijing Normal University
Journal of Physical Chemistry B | Year: 2014

On the basis of the varying amplitude and patterns of the 19F NMR chemical shift of C6F5X (X = F, Cl, Br, I) in the presence of chloride anions, bonding models of C6F 5X·Cl- complexes were tentatively established, and the relevant binding constants were obtained. Interaction models were also simulated using computational chemistry. The theoretical computations were found to be highly consistent with the results of the experiments. The results show that C6F5Br/C6F5I and Cl- were prone to forming C-I/Br···Cl- σ-hole bonding complexes with the 19F NMR signal shifting to higher fields, and the interaction strength of the C6F5I·· ·Cl- σ-hole bond was larger than that of C 6F5Br···Cl-; C 6F6/C6F5Cl and Cl- formed π-hole···Cl- bonding complexes with the signal shifting to lower fields, and the interaction strength of C 6F6 was larger than that of C6F5Cl. The binding constant of the C6F5I··· Cl- σ-hole bonding complex is 38.0 M-1, which is nearly 165- to 345-fold larger than that of the other C6F 5X·Cl- complexes. On the basis of the above results, solid phase extraction experiments were designed, and the results demonstrated the potential applicability of the C- I···Cl- σ-hole bond in separation science. © 2014 American Chemical Society.

Dong H.,CAS Beijing National Laboratory for Molecular | Bo Z.,Beijing Normal University | Hu W.,CAS Beijing National Laboratory for Molecular
Macromolecular Rapid Communications | Year: 2011

A planar conjugated copolymer named HXS-1 was applied in thin film phototransistors. Similar to organic field-effect transistors using V G to control the source-drain current, in phototransistors, the light is used to substitute V G as an independent variable to control the output of the transistors to realize light detection and signal magnification in a single organic device. All devices exhibited high performance with an on/off ratio up to 4.6×10 4 (the highest on/off ratio of organic or polymer phototransistors), which could be assigned to i) the wide absorption features of HXS-1 in the whole UV-vis range, ii) the ideal HOMO energy level of HXS-1 (5.21 eV) to align with Au electrodes (5.2 eV) and iii) the high mobility of the polymer thin films (∼0.06 cm 2/Vs). Moreover, the devices, both under continuous operation conditions and long term measurement conditions, exhibited excellent stability, indicating potential applications of the devices in polymer-based optoelectronics. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yao H.,Beijing Normal University | Yao H.,Ningxia Medical University | Hu N.,Beijing Normal University
Journal of Physical Chemistry B | Year: 2011

In this work, triply responsive films with a specific binary architecture combining layer-by-layer assembly (LbL) and hydrogel polymerization were successfully prepared. First, concanavalin A (Con A) and dextran (Dex) were assembled into {Con A/Dex}5 LbL layers on electrode surface by the lectin-sugar biospecific interaction between them. The poly (N,N- diethylacrylamide) (PDEA) hydrogels with entrapped horseradish peroxidase (HRP) were then synthesized by polymerization on the surface of LbL inner layers, forming {Con A/Dex}5-(PDEA-HRP) films. The films demonstrated reversible pH-, thermo-, and salt-responsive on-off behavior toward electroactive probe Fe(CN)63- in its cyclic voltammetric responses. This multiple stimuli-responsive films could be further used to realize triply switchable electrochemical reduction of H2O2 catalyzed by HRP immobilized in the films and mediated by Fe(CN) 63- in solution. The responsive mechanism of the films was explored and discussed. The pH-sensitive property of the system was attributed to the electrostatic interaction between the {Con A/Dex}5 inner layers and the probe at different pH, and the thermoand salt-responsive behaviors should be ascribed to the structure change of PDEA hydrogels for the PDEA-HRP outermost layers under different conditions. The concept of binary architecture was also used to fabricate {Con A/Dex}5-(PDEA-GOD) films on electrodes, where GOD = glucose oxidase, which was applied to realize the triply switchable bioelectrocatalysis of glucose by GODin the films with ferrocenedicarboxylic acid as the mediator in solution. This film system with the unique binary architecture may establish a foundation for fabricating a novel type of multicontrollable biosensors based on bioelectrocatalysis with immobilized enzymes. © 2011 American Chemical Society.

He Y.,Beijing Normal University | Evans A.,Montreal Neurological Institute
Current Opinion in Neurology | Year: 2010

Purpose of review: In recent years, there has been an explosion of studies on network modeling of brain connectivity. This review will focus mainly on recent findings concerning graph theoretical analysis of human brain networks with a variety of imaging modalities, including structural MRI, diffusion MRI, functional MRI, and EEG/MEG. Recent findings: Recent studies have utilized graph theoretical approaches to investigate the organizational principles of brain networks. These studies have consistently shown many important statistical properties underlying the topological organization of the human brain, including modularity, small-worldness, and the existence of highly connected network hubs. Importantly, these quantifiable network properties were found to change during normal development, aging, and various neurological and neuropsychiatric diseases such as Alzheimer's disease and schizophrenia. Moreover, several studies have also suggested that these network properties correlate with behavioral and genetic factors. Summary: The exciting research regarding graph theoretical analysis of brain connectivity yields truly integrative and comprehensive descriptions of the structural and functional organization of the human brain, which provides important implications for health and disease. Future research will most likely involve integrative models of brain structural and functional connectivity with multimodal neuroimaging data, exploring whether graph-based brain network analysis could yield reliable biomarkers for disease diagnosis and treatment. © 2010 Wolters Kluwer Health | Lippincott Williams and Wilkins.

Zhang X.,Beijing Normal University | Lu H.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

We consider four-dimensional Einstein gravity minimally coupled to a dilaton scalar field with a supergravity-inspired scalar potential. We obtain an exact time-dependent spherically symmetric solution describing gravitational collapse to a static scalar-hairy black hole. The solution can be asymptotically AdS, flat or dS depending on the value of the cosmological constant parameter Λ in the potential. As the advanced time u increases, the metric approaches the static limit in an exponential fashion, i.e., e-u/u0 with u0~1/(α4M0)1/3, where M0 is the mass of the final black hole and α is the second parameter in the potential. Similarly to the Vaidya solution, at u=0, the spacetime can be matched to an (A)dS or flat vacuum except that at the origin a naked singularity may occur. Moreover, a limiting case of our solution with α=0 gives rise to an (A)dS generalization of the Roberts solution. Our results provide a new model for investigating formation of real life black holes with Λ≥0. For Λ<0, it can be instead used to study non-equilibrium thermalization of certain strongly-coupled field theory. © 2014 .

Xie W.-J.,Beijing Normal University | Xie W.-J.,Yuncheng University | Zhang F.-S.,Beijing Normal University | Zhang F.-S.,Beijing Radiation Center | Zhang F.-S.,Accelerator Centre
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

The isospin-dependent quantum molecular dynamics model is used to investigate the nuclear collective flow observables in semicentral 197Au+197Au collisions at 400A MeV. It is found that the calculated results can reproduce both the experimental data and the other theoretical calculations. We find that the cluster production influences the rapidity dependence of directed flow of protons but less influences the results of tritons. Neutron-proton differential collective flows have larger values when taking the neutron effective mass less than the one of protons as compared with the case of neutron effective mass greater than the one of protons at larger rapidities and transverse momenta. Thus neutron-proton differential collective flows are proposed to be a useful probe to the neutron-proton effective mass splitting and the momentum-dependent symmetry potential. © 2014 Elsevier B.V.

Wu W.,Beijing Normal University
Immunology and Cell Biology | Year: 2015

The calcineurin B subunit (CnB) is the regulatory subunit of Cn, a Ca2+/calmodulin-dependent serine/threonine protein phosphatase. In this study, we demonstrate that extracellular CnB was effectively internalized through a CD14-independent Toll-like receptor 4 (TLR4) pathway, which led to the phosphorylation of nuclear factor (NF)-kappa-B inhibitor alpha (IκB-α) and upregulation of pro-inflammatory cytokines in human monocytes. CnB-induced IκB-α phosphorylation is completely dependent on TNF receptor-associated factor 3 (TRAF3) but not TRAF6, which is indispensable for IκB-α phosphorylation in response to lipopolysaccharide. The loss-of-function CnB mutants were able to induce IκB-α phosphorylation, further indicating that this novel role of CnB is completely independent of the phosphatase function of Cn. Taken together, these findings demonstrate that CnB is a novel host-derived immunostimulatory factor, having a role as an agonist in monocytes, and specificity in TLR4 signaling through TRAF3 and TRAF6, in response to various agonists.Immunology and Cell Biology advance online publication, 17 November 2015; doi:10.1038/icb.2015.91. © 2015 Australasian Society for Immunology Inc.

Wang H.,Beijing Normal University
Mini reviews in medicinal chemistry | Year: 2010

Species of the genus Iris (Iridaceae) have a long history of traditional medicinal use in many places of the world, and they have been previously recognized as rich sources of secondary metabolites, in which flavonoids are found predominantly. During the last decade (1999-2008) over 90 flavonoid constituents have been discovered and characterized, including 38 new compounds, from 15 species of Iris. This review elucidates the structural features of these flavonoid constituents, and gives the details of their source, identification, biological activity and chemotaxonomy significance. At last, a checklist of the flavonoid compounds in Iris by species is given.

Xiao K.,Hunan Institute of Technology | He X.-K.,Hunan First Normal University | Zhu J.-Y.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

Phenomenological effect of the super-inflation in loop quantum cosmology (LQC) is discussed. We investigate the case that the Universe is filled with the interacting field between massive scalar field and radiation. Considering the damping coefficient Γ as a constant, the changes of the scale factor during super-inflation with four different initial conditions are discussed, and we find that the changes of the scale factor depends on the initial values of energy density of the scalar field and radiation at the bounce point. But no matter which initial condition is chosen, the radiation always dominated at the late time. Moreover, we investigate whether the super-inflation can provide enough e-folding number. For the super-inflation starts from the quantum bounce point, the initial value of Hubble parameter H(ti)~0, then it is possible to solve the flatness problem and horizon problem. As an example, following the method of [18] to calculate particle horizon on the condition that the radiation dominated at bounce point, and we find that the Universe has had enough time to be homogeneous and isotopic. © 2013 Elsevier B.V.

Lu H.,Beijing Normal University | Yang W.,Beijing Normal University
Classical and Quantum Gravity | Year: 2013

We consider D-dimensional Einstein gravity coupled to (n - 1) U(1) vector fields and (n - 2) dilatonic scalars. We find that for some appropriate exponential dilaton couplings of the field strengths, the equations of motion for the static charged ansatz can be reduced to a set of one-dimensional Toda equations. This allows us to obtain a general class of explicit black holes with mass and (n - 1) independent charges. The near-horizon geometry in the extremal limit is AdS2 × SD - 2. The n = 2 case gives the Reissner-Nordstrøm solution, and the n = 3 example includes the Kaluza-Klein dyon. We study the global structure and the black hole thermodynamics and obtain the universal entropy product formula. We also discuss the characteristics of extremal multi-charge black holes that have positive, zero or negative binding energies. © 2013 IOP Publishing Ltd.

Chen D.,China West Normal University | Zeng X.,Beijing Normal University | Zeng X.,Sichuan University of Arts and Science
General Relativity and Gravitation | Year: 2013

A d-dimensional Schwarzschild black hole is quantized by the action variable and the Bohr-Sommerfeld quantization rule in this paper. We find that the spectra of the horizon area and the entropy are evenly spaced. The black hole mass is also quantized and it's spectrum spacing is proportional inversely to the mass. The ground state appears and has a constant entropy πkB. The ground state mass is shown to be the black hole remnant predicted by the generalized uncertainty principle and may be a candidate of dark matter. © 2012 Springer Science+Business Media New York.

Li W.-J.,Beijing Normal University | Wu J.-P.,Beijing Normal University
Nuclear Physics B | Year: 2013

By imposing the relativistic boundary term and Lorentz violating that in the dilatonic black brane with a Lifshitz like IR geometry and AdS4 boundary, we study the properties of the spectral functions of the fermions. We find that in the two fixed points, there are emergent Fermi-surface structures and many properties seem to be in agreement with that of Fermi liquid. Especially, the low energy behavior exhibits a linear dispersion relation. In addition, we also find that a holographic flat band also emerges in this background of the dilatonic black brane. © 2012 Elsevier B.V.

Li X.,Capital Normal University | Sun H.-L.,Beijing Normal University | Wu X.-S.,Capital Normal University | Qiu X.,Capital Normal University | Du M.,Tianjin Normal University
Inorganic Chemistry | Year: 2010

Three porous lanthanide-organic frameworks, [Ln4(OH)4(3-SBA)4(H2O)4] 3 nH2O [Ln = EuIII (1), n = 10; GdIII (2), n = 10; Tb III (3), n = 8; 3-SBA = 3-sulfobenzoate], have been prepared by a hydrothermal synthesis method. They are isomorphous and crystallize in a tetragonal system with space group P 421c. The structure can be considered to be built up by cubanelike [Ln4(OH)4]8+ secondary building units, which are further connected by 3-SBA to form a 3D coordination framework with 1D pores along the c direction for accommodation of novel T8(3) water tapes or zigzag water chains. Furthermore, in these compounds, the [Ln4(OH)4]8+ units and 3-SBA ligands serve as 12-connected and 3-connected nodes, respectively, resulting in a unique (3, 12)-connected framework with the Schläfli symbol of (43)4(4 20.628.818). The luminescent properties of the EuIII (1) and TbIII (3) complexes have been studied, showing characteristic emissions at room temperature. Variable-temperature magnetic susceptibility studies indicate that the GdIII complex 2 displays weak antiferromagnetic coupling through μ 3-OH-pathways. © 2010 American Chemical Society.

Lu H.,Beijing Normal University | Wang Z.-L.,Korea Institute for Advanced Study
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We study the Dirac equation of a charged massless spinor on the general charged AdS black hole of conformal gravity. The equation can be solved exactly in terms of Heun's functions. We obtain the exact Green's function in the phase space (ω, k). This allows us to obtain Fermi surfaces for both Fermi and non-Fermi liquids. Our analytic results provide a more elegant approach of studying some strongly interacting fermionic systems not only at zero temperature, but also at any finite temperature. At zero temperature, we analyse the motion of the poles in the complex ω plane and obtain the leading order terms of the dispersion relation, expressed as the Laurent expansion of ω in terms of k. We illustrate new distinguishing features arising at the finite temperature. The Green's function with vanishing ω at finite temperature has a fascinating rich structure of spiked maxima in the plane of k and the fermion charge q. © 2012 Elsevier B.V.

Liao K.,Beijing Normal University | Li Z.,Beijing Normal University | Ming J.,Beijing Normal University | Zhu Z.-H.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We use the newly published 28 observational Hubble parameter data (H(z)) and current largest SNe Ia samples (Union2.1) to test whether the universe is transparent. Three cosmological-model-independent methods (nearby SNe Ia method, interpolation method and smoothing method) are proposed through comparing opacity-free distance modulus from Hubble parameter data and opacity-dependent distance modulus from SNe Ia. Two parameterizations, τ(z)=2εz and τ(z)=(1+z)2ε-1 are adopted for the optical depth associated to the cosmic absorption. We find that the results are not sensitive to the methods and parameterizations. Our results support a transparent universe. © 2012 Elsevier B.V.

Liao K.,Beijing Normal University | Zhu Z.-H.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

In this Letter, we propose a new generalized Ricci dark energy (NGR) model to unify Ricci dark energy (RDE) and XCDM. Our model can distinguish between RDE and XCDM by introducing a parameter β called weight factor. When β = 1, NGR model becomes the usual RDE model. The XCDM model is corresponding to β = 0. Moreover, NGR model permits the situation where neither β = 1 nor β = 0 We then perform a statefinder analysis on NGR model to see how β effects the trajectory on the r-s plane. In order to know the value of β, we constrain NGR model with latest observations including type Ia supernovae (SNe Ia) from Union2 set (557 data), baryonic acoustic oscillation (BAO) observation from the spectroscopic Sloan Digital Sky Survey (SDSS) data release 7 (DR7) galaxy sample and cosmic microwave background (CMB) observation from the 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) results. With Markov Chain Monte Carlo (MCMC) method, the constraint result is β=0.08-0.21 +0.30(1σ)-0.28 +0.43(2σ), which manifests the observations prefer a XCDM universe rather than RDE model. It seems RDE model is ruled out in NGR scenario within 2. σ regions. Furthermore, we compare it with some of successful cosmological models using AIC information criterion. NGR model seems to be a good choice for describing the universe. © 2012 Elsevier B.V.

Yuan Z.-Q.,Beijing Normal University | Zheng Z.-G.,Beijing Normal University
Frontiers of Physics | Year: 2013

The spatiotemporal propagation of a momentum excitation on the finite Fermi-Pasta-Ulam lattices is investigated. The competition between the solitary wave and phonons gives rise to interesting propagation behaviors. For a moderate nonlinearity, the initially excited pulse may propagate coherently along the lattice for a long time in a solitary wave manner accompanied by phonon tails. The lifetime of the long-transient propagation state exhibits a sensitivity to the nonlinear parameter. The solitary wave decays exponentially during the final loss of stability, and the decay rate varying with the nonlinear parameter exhibits two different scaling laws. This decay is found to be related to the largest Lyapunov exponent of the corresponding Hamiltonian system, which manifests a transition from weak to strong chaos. The mean-free-path of the solitary waves is estimated in the strong chaos regime, which may be helpful to understand the origin of anomalous conductivity in the Fermi-Pasta-Ulam lattice. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.

He Q.,Beijing Normal University | Cui B.,Beijing Normal University | An Y.,Shanghai JiaoTong University
PLoS ONE | Year: 2012

Background: Biological invasions have become the focus of considerable concern and ecological research, yet the relative importance of abiotic and biotic factors in controlling the invasibility of habitats to exotic species is not well understood. Spartina species are highly invasive plants in coastal wetlands; however, studies on the factors that control the success or failure of Spartina invasions across multiple habitat types are rare and inconclusive. Methodology and Principal Findings: We examined the roles of physical stress and plant interactions in mediating the establishment of the smooth cordgrass, Spartina alterniflora, in a variety of coastal habitats in northern China. Field transplant experiments showed that cordgrass can invade mudflats and low estuarine marshes with low salinity and frequent flooding, but cannot survive in salt marshes and high estuarine marshes with hypersaline soils and infrequent flooding. The dominant native plant Suaeda salsa had neither competitive nor facilitative effects on cordgrass. A common garden experiment revealed that cordgrass performed significantly better when flooded every other day than when flooded weekly. These results suggest that physical stress rather than plant interactions limits cordgrass invasions in northern China. Conclusions and Significance: We conclude that Spartina invasions are likely to be constrained to tidal flats and low estuarine marshes in the Yellow River Delta. Due to harsh physical conditions, salt marshes and high estuarine marshes are unlikely to be invaded. These findings have implications for understanding Spartina invasions in northern China and on other coasts with similar biotic and abiotic environments. © 2012 He et al.

Peng S.,Beijing Normal University | Wu W.,Beijing Normal University | Chen J.,Beijing Normal University
Chemosphere | Year: 2011

PAH removal with surfactant enhanced washing was investigated through a series of laboratory tests to examine the effect of stirring speed, washing time, surfactant concentration, liquid/solid ratio, temperature, and on-and-off mode. The first four factors show significant influence on the PAH removal while the latter two do not. Total removal ratio and a new proposed parameter, solubilization percentage, are used to evaluate the effectiveness quantitatively. © 2010 Elsevier Ltd.

Wang L.,Beijing Normal University | Yang Z.,Beijing Normal University | Niu J.,Beijing Normal University
Chemosphere | Year: 2011

In aqueous environment temperature is considered to play a significant role in the sorption process of polycyclic aromatic hydrocarbons (PAHs) and its influence on the sorption equilibrium is indicative of sorption energies and mechanisms. In this study, sorptions of five PAHs on three heterogeneous sorbents including one river sediment (YHR), one estuary sediment (YRD) and one treated sediment with organic matter removed (IM) were carried out at a range of temperature from 5°C to 35°C. Stronger sorptions were observed at lower temperatures, with the equilibrium sorption coefficient Kd increasing 2-5 times as the temperature decreases 30°C. The increase of Kd value was attributed primarily to the change of PAH water solubility, which predicted 40-75% of the increase of Kd in the sorption process. To provide insight into the sorption mechanism, enthalpy change (ΔHS) for the sorption process was calculated and the values were observed to be negative for all of the interactions, suggesting that the exothermal sorption of PAHs inversely dependents on temperature. Based on the values of ΔHS, van der Waals forces were inferred as the main sorption mechanism for the PAHs, especially on the YHR sediment which contained more organic matter. For sorption of larger size PAHs on the sorbents with low organic matter, specific interactions were deduced to contribute to the overall sorption. © 2010 Elsevier Ltd.

Zeng X.-X.,Chongqing Jiaotong University | Liu W.-B.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

In the spirit of AdS/CFT correspondence, we study the thermalization of a dual conformal field theory to Gauss-Bonnet gravity by modeling a thin-shell of dust that interpolates between a pure AdS and a Gauss-Bonnet AdS black brane. The renormalized geodesic length and minimal area surface, which in the dual conformal field theory correspond to two-point correlation function and expectation value of Wilson loop, are investigated respectively as thermalization probes. The result shows that as the Gauss-Bonnet coefficient increases, the thermalization time decreases for both the thermalization probes, which can also be confirmed by studying the motion profile of the geodesic and minimal area surface. In addition, for both the renormalized geodesic length and minimal area surface, there is an overlapped region for a fixed boundary separation, which implies that the Gauss-Bonnet coupling constant has little effect on the thermalization probes there. © 2013 Elsevier B.V.

Mo J.-X.,Beijing Normal University | Mo J.-X.,Zhanjiang Normal University | Liu W.-B.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

In this Letter, the nature of phase transition at the critical point of P-V criticality in the extended phase space of RN-AdS black holes has been investigated. By treating the cosmological constant and its conjugate quantity as thermodynamic pressure and volume respectively, we introduce the original expressions of Ehrenfest equations directly into the black hole research instead of utilizing the analogy of Ehrenfest equations. We carry out an analytical check of Ehrenfest equations and prove that both Ehrenfest equations are satisfied. So the black hole undergoes a second order phase transition at the critical point. This result is consistent with the nature of liquid-gas phase transition at the critical point, hence deepening the understanding of the analogy of charged AdS black holes and liquid-gas systems. © 2013 Elsevier B.V.

Wu X.-Y.,Beijing Normal University | Zheng Z.-G.,Beijing Normal University
Frontiers of Physics | Year: 2013

A hierarchical cluster-tendency (HCT) method in analyzing the group structure of networks of the global foreign exchange (FX) market is proposed by combining the advantages of both the minimal spanning tree (MST) and the hierarchical tree (HT). Fifty currencies of the top 50 World GDP in 2010 according to World Bank's database are chosen as the underlying system. By using the HCT method, all nodes in the FX market network can be "colored" and distinguished. We reveal that the FX networks can be divided into two groups, i.e., the Asia-Pacific group and the Pan-European group. The results given by the hierarchical cluster-tendency method agree well with the formerly observed geographical aggregation behavior in the FX market. Moreover, an oil-resource aggregation phenomenon is discovered by using our method. We find that gold could be a better numeraire for the weekly-frequency FX data. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg.

Abdukerim N.,Beijing Normal University | Li Z.-L.,Beijing Normal University | Xie B.-S.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

For different fields of supercycle and subcycle laser pulses, the effects of laser pulse shape and carrier envelope phase on pair production are investigated by solving quantum Vlasov equation. By changing the pulse width and shape, the nonlinear behaviors of momentum distribution function and number density of created electron-positron pairs are obtained. It is found that there exist the multiphoton processes and stabilization phenomenon in pair production for supercycle situation. Our study may shed a light on optimizing the form of applied laser field to enhance the created pairs number, for example, when other conditions are fixed, the flat-top super-Gaussian laser pulse has advantage on pairs production. © 2013 Elsevier B.V.

Liu S.,Beijing Normal University | Zhang T.-J.,Beijing Normal University | Zhang T.-J.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

Cosmological observables could be used to construct cosmological models; however, a fixed number of observables limited to the light cone are not enough to uniquely determine a certain model. In this paper, we employ a reconstructed spherically symmetric, inhomogeneous model that shares the same angular-diameter-distance-redshift relationship d A(z) and Hubble parameter H(z) besides ΛCDM model (which we call LTB-ΛCDM model in this paper), that may provide another solution. Cosmic age, which is off the light cone, could be used to distinguish between these two models. We derive the formulae for age calculation with origin conditions. From the data given by 9-year WMAP measurement, we compute the likelihood of the parameters in these two models respectively by using the Distance Prior method and perform likelihood analysis by generating Monte Carlo Markov Chain for the purpose of bringing tighter constraints on the parameters Ωm and H0 (the parameters that we use for calculation). The results yield: tΛCDM = 13.76 ± 0.09 Gyr, tLTB-ΛCDM = 11.38 ± 0.15 Gyr, both in 1σ agreement with the constraint of cosmic age given by metal-deficient stars. © 2014 The Authors.

Yang H.-X.,Fuzhou University | Rong Z.,University of Electronic Science and Technology of China | Wang W.-X.,Beijing Normal University
New Journal of Physics | Year: 2014

The paradox of cooperation among selfish individuals still puzzles scientific communities. Although a large amount of evidence has demonstrated that the cooperator clusters in spatial games are effective in protecting the cooperators against the invasion of defectors, we continue to lack the condition for the formation of a giant cooperator cluster that ensures the prevalence of cooperation in a system. Here, we study the dynamical organization of the cooperator clusters in spatial prisoner's dilemma game to offer the condition for the dominance of cooperation, finding that a phase transition characterized by the emergence of a large spanning cooperator cluster occurs when the initial fraction of the cooperators exceeds a certain threshold. Interestingly, the phase transition belongs to different universality classes of percolation determined by the temptation to defect b. Specifically, on square lattices, 1 < b < 4/3 leads to a phase transition pertaining to the class of regular site percolation, whereas 3/2 < b < 2 gives rise to a phase transition subject to invasion percolation with trapping. Our findings offer a deeper understanding of cooperative behavior in nature and society. © 2014 IOP Publishing and Deutsche Physikalische Gesellschaft.

Yang Y.-F.,Beijing Normal University | Zhu T.,Beijing Normal University | Niu D.-K.,Beijing Normal University
Genome Biology and Evolution | Year: 2013

Despite the prevalence of intron losses during eukaryotic evolution, the selective forces acting on them have not been extensively explored. Arabidopsis thaliana lost half of its genome and experienced an elevated rate of intron loss after diverging from A. lyrata. The selective force for genome reduction was suggested to have driven the intron loss. However, the evolutionary mechanism of genome reduction is still a matter of debate. In this study, we found that intron-lost genes have high synonymous substitution rates. Assuming that differences in mutability among different introns are conserved among closely related species, we used the nucleotide substitution rate between orthologous introns in other species as the proxy of themutation rate of Arabidopsis introns, either lost or extant. The lost introns were found to have higher mutation rates than extant introns. At the genome-wide level, A. thaliana has a higher mutation rate than A. lyrata, which correlates with the higher rate of intron loss and rapid genome reduction of A. thaliana. Our results indicate that selection to minimize mutational hazards might be the selective force for intron loss, and possibly also for genome reduction, in the evolution of A. thaliana. Small genome size and lower genome-wide intron density were widely reported to be correlated with phenotypic features, such as high metabolic rates and rapid growth. We argue that the mutational-hazard hypothesis is compatible with these correlations, by suggesting that selection for rapid growth might indirectly increase mutational hazards. © 2013 The Author(s).

Wang P.,Beijing Normal University | Qin L.,Beijing Normal University | Li X.-Q.,Beijing Normal University
New Journal of Physics | Year: 2014

Compared with the quantum trajectory equation (QTE), the quantum Bayesian approach has the advantage of being more efficient to infer a quantum state under monitoring, based on the integrated output of measurements. For weak measurement of qubits in circuit quantum electrodynamics (cQED), properly accounting for the measurement backaction effects within the Bayesian framework is an important problem of current interest. Elegant work towards this task was carried out by Korotkov in 'bad-cavity' and weak-response limits (Korotkov 2011 Quantum Bayesian approach to circuit QED measurement (arXiv:1111.4016)). In the present work, based on insights from the cavity-field states (dynamics) and the help of an effective QTE, we generalize the results of Korotkov to more general system parameters. The obtained Bayesian rule is in full agreement with Korotkovs result in limiting cases and as well holds satisfactory accuracy in non-limiting cases in comparison with the QTE simulations. We expect the proposed Bayesian rule to be useful for future cQED measurement and control experiments. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Li W.,Beijing Normal University | Hu M.,Beijing Normal University
Frontiers of Environmental Science and Engineering | Year: 2014

Considering the significant roles of the policies in developing environmental finance, an overview is conducted on the environmental finance policies (EFPs) in China. This paper analyzed the definition, scope, evolution and main instruments of EFPs. The implementation progress of financial activities on each instrument are investigated respectively. Then the experiences learned from and failures discovered in the development of the EFPs are discussed well recommendations for further improvement of the EFPs and their implementation are provided. Our study found that the EFPs have been established in China after a four-phase evolution since the early 1980s. The policies have played a critical role in leading to a rapid development in environmental finance by involving more financial instruments to accomplish the objective-led environmental plans. Driven by the policies, the new green credit (GC), green security (GS), and green insurance (GI) instruments have been phased in as supplements to the conventional command and control approaches to improve the environmental governance of financial activities and pollution sources. However, the market mechanism of financial institution is limited due to their defensive and incapable performance on implementation some of EFP instruments. To further strengthen the effectiveness of EFPs in facilitating environmental management, recommendations are made mainly on the aspects including developing more specific policy guidelines, enhancing information sharing and disclosure, providing sufficient economic incentives, establishing environmental liabilities with financial activities, and involving issues related to climate change, and biodiversity and ecosystem service. © 2014 Higher Education Press and Springer-Verlag Berlin Heidelberg.

Cui M.,Beijing Normal University
Current Medicinal Chemistry | Year: 2014

The deposition of β-amyloid (Aβ) plaques in the parenchymal and cortical brain is accepted as the main pathological hallmark of Alzheimer's disease (AD). According to the amyloid cascade hypothesis, the Aβ deposition in the brain appears to be a good diagnostic biomarker for AD and may also be a good predictive biomarker of this disease. Molecular imaging of Aβ plaques in the brain with positron emission tomography (PET), single photon emission computed tomography (SPECT) or molecular optical imaging represents a promising approach to the early diagnosis of AD and monitoring the effectiveness of novel therapies for this devastating disease. Our review focuses on the past and recent knowledge in this field with respect to small organic molecules that have been utilized for the development of Aβ imaging probes. © 2014 Bentham Science Publishers.

Mo J.-X.,Zhanjiang Normal University | Mo J.-X.,Beijing Normal University | Li G.-Q.,Zhanjiang Normal University | Liu W.-B.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

In this Letter, we explore another novel Ehrenfest scheme which can also be utilized in the P-V criticality research of RN-AdS black holes. The novel form of Ehrenfest scheme is neither the one in classical thermodynamics nor the analogy one proposed for grand-canonical ensemble in literatures. After a detailed derivation of the novel Ehrenfest equations, an analytical check is carried out at the critical point of P-V criticality of RN-AdS black holes. It is shown once again that the phase transition at the critical point is a second order one. Both the novel Ehrenfest scheme developed in this Letter and the classical Ehrenfest equations utilized in our former research can be applied to investigate the nature of phase transition at the critical point of P-V criticality of AdS black holes. © 2014 The Authors.

Liu H.-S.,Zhejiang University of Technology | Lu H.,Beijing Normal University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

We show that for n-dimensional Einstein gravity coupled to a scalar field with mass-squared m02=-n(n-2)/(4ℓ2), the first law of thermodynamics of (charged) AdS black holes will be modified by the boundary conditions of the scalar field at asymptotic infinity. Such scalars can arise in gauged supergravities in four and six dimensions, but not in five or seven. The result provides a guiding principle for constructing designer black holes and solitons in general dimensions, where the properties of the dual field theories depend on the boundary conditions. © 2014 The Authors.

Zhang Q.,Beijing Normal University | Wang Y.P.,CSIRO | Matear R.J.,CSIRO | Pitman A.J.,University of New South Wales | Dai Y.J.,Beijing Normal University
Geophysical Research Letters | Year: 2014

Allowable CO2 emissions are the emissions of CO2 allowed in order to follow a prescribed atmospheric CO2 concentration pathway. Allowable emissions depend on the uptake rates by the land and ocean and carbon-climate interaction. Few Earth System Models used for estimating allowable emissions include nitrogen limitation on land, and none include phosphorus. We provide the first estimate of how nitrogen and phosphorus limitations alter the allowable emissions between 2006 and 2100 for two representative concentration pathways (RCPs). We show that nutrient limitations on land have little influence on ocean carbon uptake but reduce the land carbon uptake and allowable emissions by 69 Pg C (21%) for RCP2.6 and by 250 Pg C (13%) for RCP8.5 by 2100, as compared with the emissions estimated using integrated assessment models. We therefore demonstrate the importance of nutrient limitations in estimating future CO2 emissions to achieve the climate change limits implied by RCPs. ©2013. The Authors.

Lu H.,Beijing Normal University | Pope C.N.,Texas A&M University | Pope C.N.,University of Cambridge
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We propose homogeneous metrics of Petrov type III that describe gyrating Schrödinger geometries as duals to some nonrelativistic field theories, in which the Schrödinger symmetry is broken further so that the phase space has a linear dependence of the momentum in a selected direction. We show that such solutions can arise in four-dimensional Einstein-Weyl supergravity as well as higher-dimensional extended gravities with quadratic curvature terms coupled to a massive vector. In Einstein-Weyl supergravity, the gyrating Schrödinger solutions can be supersymmetric, preserving 14 of the supersymmetry. We obtain the exact Green function in the phase space associated with a bulk free massive scalar. © 2012 American Physical Society.

Qin L.,Beijing Normal University | Ma Y.,Beijing Normal University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

Coherent state functional integrals for the minisuperspace models of quantum cosmology are studied. By the well-established canonical theories, the transition amplitudes in the path-integral representations of Wheeler-DeWitt quantum cosmology and loop quantum cosmology can be formulated through group averaging. The effective action and Hamiltonian with higher-order quantum corrections are thus obtained in both models within the scheme of Gaussian coherent states. It turns out that for a nonsymmetric Hamiltonian constraint operator, the Moyal *-product emerges naturally in the effective Hamiltonian. This reveals the intrinsic relation among coherent state functional integral, effective theory, and Moyal *-product. Moreover, both the resulted effective theories imply a possible quantum cosmological effect in large scale limit under certain condition. © 2012 American Physical Society.

Ren B.-C.,Beijing Normal University | Wei H.-R.,Beijing Normal University | Hua M.,Beijing Normal University | Li T.,Beijing Normal University | Deng F.-G.,Beijing Normal University
Optics Express | Year: 2012

Bell-state analysis (BSA) is essential in quantum communication, but it is impossible to distinguish unambiguously the four Bell states in the polarization degree of freedom (DOF) of two-photon systems with only linear optical elements, except for the case in which the BSA is assisted with hyperentangled states, the simultaneous entanglement in more than one DOF. Here, we propose a scheme to distinguish completely the 16 hyperentangled Bell states in both the polarization and the spatialmode DOFs of two-photon systems, by using the giant nonlinear optics in quantum dot-cavity systems. This scheme can be applied to increase the channel capacity of long-distance quantum communication based on hyperentanglement, such as entanglement swapping, teleportation, and superdense coding. We use hyperentanglement swapping as an example to show the application of this HBSA. © 2012 Optical Society of America.

Wu J.-P.,Beijing Normal University | Ma Y.,Beijing Normal University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We study the perturbation of the effective Hamiltonian constraint with holonomy correction from Euclidean loop quantum gravity. The Poisson bracket between the corrected Hamiltonian constraint and the diffeomorphism constraint is derived for vector modes. Some specific form of the holonomy correction function fcdi is found, which satisfies that the constraint algebra is anomaly free. This result confirms the possibility of nontrivial holonomy corrections from full theory while preserving anomaly-free constraint algebra in the perturbation framework. It also gives valuable hints on the possible form of holonomy corrections in the effective loop quantum gravity. © 2012 American Physical Society.

Chen Y.,Beijing Normal University | Zhu B.,Beijing Normal University | Han Y.,Beijing Normal University | Bo Z.,Beijing Normal University
Journal of Materials Chemistry | Year: 2012

The controlled preparation of organic nanotubes via self-assembly of polycyclic aromatics is a contemporary challenge for supramolecular science. Here, we show that the self-assembly of pyrene-containing cationic amphiphiles, 3-(4-(pyren-6-yl)phenoxy)propan-1-ammonium salts (PyPA-Cl, PyPA-Br, and PyPA-SO 4), can form high aspect ratio nanotubes with a uniform diameter distribution. We have also demonstrated that the counter anions also play an important role in the self-assembling results. The self-assembly of pyrene-containing cationic amphiphilic molecules with monovalent anions (Cl - and Br -) forms exclusively uniform nanotubes; whereas the self-assembly of amphiphiles with bivalent counter anions (SO 4 2-) forms exclusively high aspect ratio nanoribbons. Furthermore, we have found that the diameter of the PyPA-Br nanotubes is larger than that of the PyPA-Cl nanotubes. The research results reported herein represent an important step towards the preparation of functional nanostructures with controlled 1D architectures. © 2012 The Royal Society of Chemistry.

Yue W.,Beijing Normal University | Lin Z.,Beijing Normal University | Jiang S.,Beijing Normal University | Yang X.,Beijing Normal University
Journal of Materials Chemistry | Year: 2012

Graphene-encapsulated mesoporous metal oxides (e.g. Co 3O 4, Cr 2O 3 and NiO) as novel anode materials for lithium-ion batteries were simply synthesized by adjusting the pH of mesoporous metal oxides and graphene oxide suspensions to set values (e.g. 5-6 for metal oxides, 7-8 for graphene oxide) and mixing the two suspensions in the presence of reducing agents. These composites synthesized by this facile method exhibited superior electrochemical performance, including remarkably high capacity, high rate capability and excellent cycle performance. The improved performance may be attributed to the high dispersion of mesoporous particles separated by graphene nanosheets and the high electrical conductivity of graphene. © The Royal Society of Chemistry 2012.

Li Y.,Beijing Normal University | Zhang H.,CAS Beijing National Laboratory for Molecular | Qi C.,Beijing Normal University | Guo X.,CAS Beijing National Laboratory for Molecular | Guo X.,Peking University
Journal of Materials Chemistry | Year: 2012

We demonstrate the use of P3HT-spiropyran blends as an active layer to achieve reversible photoswitching effects in solution-processed organic field-effect transistors (OFETs). Conformational changes of spiropyrans triggered by light with different wavelengths produce two distinct interaction strengths at organic/organic interfaces that can reversibly modulate the channel conductance of OFETs in a noninvasive manner. This concept of organic-organic interfacial modification offers attractive new prospects for the development of organic electronic devices with desired properties. © 2012 The Royal Society of Chemistry.

Zhang P.,Beijing Normal University | Ding L.,Ohio State University
Physical Review Special Topics - Physics Education Research | Year: 2013

This paper reports a cross-grade comparative study of Chinese precollege students' epistemological beliefs about physics by using the Colorado Learning Attitudes Survey about Sciences (CLASS). Our students of interest are middle and high schoolers taking traditional lecture-based physics as a mandatory science course each year from the 8th grade to the 12th grade in China. The original CLASS was translated into Mandarin through a rigorous transadaption process, and then it was administered as a pencil-and-paper in-class survey to a total of 1318 students across all the five grade levels (8-12). Our results showed that although in general student epistemological beliefs became less expertlike after receiving more years of traditional instruction (a trend consistent with what was reported in the previous literature), the cross-grade change was not a monotonous decrease. Instead, students at grades 9 and 12 showed a slight positive shift in their beliefs measured by CLASS. Particularly, when compared to the 8th graders, students at the 9th grade demonstrated a significant increase in their views about the conceptual nature of physics and problem-solving sophistication. We hypothesize that both pedagogical and nonpedagogical factors may have contributed to these positive changes. Our results cast light on the complex nature of the relationship between formal instruction and student epistemological beliefs.© http://creativecommons. org/licenses/by/3.0/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 Y.-S.,Beijing Normal University | Qiu X.-B.,Beijing Normal University
Journal of Genetics and Genomics | Year: 2012

Histone modifications are proposed to constitute a " histone code" for epigenetic regulation of gene expression. However, recent studies demonstrate that histones have to be disassembled from chromatin during transcription. Recent evidence, though not conclusive, suggests that histones might be degradable after being removed from chromatin during transcription. Degradation of overexpressed excessive histones, instead of native histones, has been shown to be dependent on proteasomes and ubiquitination. Since the 26S proteasome usually recognizes polyubiquitinated substrates, it is critical to demonstrate whether degradation of histones is mediated by polyubiquitination. Unexpectedly, there is almost no evidence that any ubiquitin ligase can promote polyubiquitination-dependent degradation of constitutive histones. Meanwhile, acetylation and phosphorylation are also associated with histone degradation. This review attempts to summarize the current knowledge on the transcription-coupled degradation of histones and its regulation by posttranslational protein modifications. © 2012.

Quan X.,Beijing Normal University | Tang H.,Beijing Normal University | Ma J.,Beijing Normal University
Journal of Hazardous Materials | Year: 2011

With a conjugative plasmid pJP4 carrying strain as the donor, two bioaugmentation experiments were conducted in a microcosm biofilm reactor with 2,4-D as the sole carbon source operated in fed-batch mode, and an enlarged lab-scale sequence batch biofilm reactor with mixed carbon sources of 2,4-D and other easily biodegradable compounds, respectively. In the microcosm study under sole carbon source condition, bioaugmentation led to a persistently increased 2,4-D degradation rate in the five operation cycles with enhancement of 13-64%. For the enlarged lab-scale bioaugmentation experiment under mixed carbon source conditions, no enhancement in 2,4-D removal could be observed during start-up period. After a period of operation, biofilm samples from the bioaugmented reactor demonstrated a stronger degradation capacity than the control and showed the presence of a large number of transconjugants. This study indicates that bioaugmentation based on plasmid horizontal transfer is a feasible strategy to establish functional microbial community in a biofilm reactor, and the strong selective pressure of 2,4-D existing alone and persistently was more favorable for the success of gene augmentation. © 2010 Elsevier B.V.

Gong B.,State University of New York at Buffalo | Gong B.,Beijing Normal University
Accounts of Chemical Research | Year: 2012

Through specific molecular shapes and repeating polymeric sequences, biomacromolecules encode information about both structure and function. Inspired by DNA molecules, we have conceived a strategy to encode linear molecular strands with sequences that specify intermolecular association, and we and our collaborators have supported this idea through our experimental work. This Account summarizes the design and development of a class of molecular duplexes with programmable hydrogen-bonding sequences and adjustable stabilities.The specific system involves oligoamide strands synthesized from readily available monomeric modules based on standard amide (peptide) chemistry. By covalently linking three types of basic building blocks in different orders, we create oligoamide strands with various arrangements of amide O and H atoms that provide arrays of hydrogen bonding sequences. Because one of the two edges of these molecules presents the sequences of hydrogen-bond donors and acceptors, these oligoamide strands associate via their hydrogen-bonding edges into double-stranded pairs or duplexes. Systematic studies have demonstrated the strict sequence specificity and tunable stability of this system. These structurally simple duplexes exhibit many features associated with DNA sequences such as programmable sequence specificity, shape and hydrogen-bonding complementarity, and cooperativity of multipoint interactions.Capable of specifying intermolecular associations, these duplexes have formed supramolecular structures such as β-sheets and non-covalent block copolymers and have templated chemical reactions. The incorporation of dynamic covalent interactions into these H-bonded duplexes has created association units that undergo sequence-specific association and covalent ligation in both nonpolar solvents and polar media including water. These new association units may facilitate the development of new dynamic covalent structures, and new properties are emerging from these structures. For example, we discovered hydrogen-bonded duplexes that could gelate different organic solvents, and we could tune the gelatinization by adjusting the multiple side chains attached to the duplexes. In addition, we have recently designed duplexes whose formation and dissociation are controlled by changes in external stimuli such as acidity.With their programmable specificity and tunable stability, these molecular duplexes have provided a systematic approach for the association of different structural units. Further development of this system could facilitate the creation of many supramolecular and dynamic covalent structures. Because these duplexes are easily modifiable and information is easily encoded and retrieved, this system may address some of the remaining challenges facing information-storing molecules including self-replication. © 2012 American Chemical Society.

Liang F.,Beijing Normal University | Jia M.,Beijing Normal University | Hu J.,Beijing Normal University
Electrochimica Acta | Year: 2012

A facile ion implantation method was developed to prepare a novel Pt nanoparticles loaded ITO (PtNPs/ITO) electrode. The resulting nanoparticles were characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and electrochemical methods. From the result of electrochemical oxidation of nitrite, we observed that the PtNPs/ITO electrode exhibited excellent electrocatalytic activity, which might be useful in nitrite sensor. The oxidation current of nitrite was linear to its concentration in the range of 5-800 μM and the detection limit (S/N = 3) was down to 0.4 μM. Upon immobilization of the surface of PtNPs/ITO with cytochrome c, Cyt c/PtNPs/ITO for H 2O 2 biosensor was developed. The characteristics of the biosensor were studied by UV-vis absorption spectra and electrochemical methods. The results revealed that the modified electrode could enhance electron transfer of Cyt c and retain electrochemical activity, good stability and reproducibility. The immobilized Cyt c exhibited a rapid response to H 2O 2, low detection limit of 0.1 μM and high sensitivity of 37.20 μA mM -1. © 2012 Elsevier Ltd. All rights reserved.

Grainger S.,Center for Australian Weather and Climate Research | Frederiksen C.S.,Center for Australian Weather and Climate Research | Zheng X.,Beijing Normal University
Climate Dynamics | Year: 2013

An assessment is made of the modes of interannual variability in the seasonal mean summer and winter Southern Hemisphere 500 hPa geopotential height in the twentieth century in models from the Coupled Model Intercomparison Project phase 3 (CMIP3) dataset. The analysis is done for both the intraseasonal and slow components of the geopotential height. When the CMIP3 models are assessed against reanalysis data, the spatial structure and variance of the leading modes in the intraseasonal component are generally well reproduced. There are systematic differences between the models in their reproduction of the leading modes in the slow component. An overall score using the leading modes in the slow component allows a categorisation of CMIP3 model performance. Using an ensemble from four models that suitably reproduce the twentieth century modes, modes of variability in the slow-internal and slow-external components are estimated. The leading mode of the slow-external component is shown to be related to observed changes in greenhouse gas concentrations. In this ensemble, there is little change in the leading modes in the intraseasonal component in the twenty-first century. Larger changes in variance, and subtle changes in regional-scale structure, are found for the leading modes in the slow-internal component. These are related to changes in the slowly varying dynamics of the Southern Annular Mode and the El Niño-Southern Oscillation. By far the biggest change is in the leading mode of the slow-external component. The spatial structure becomes uniform in the twenty-first century, and the variance increases with increasing greenhouse gas concentrations. © 2013 Springer-Verlag Berlin Heidelberg.

Garrett T.J.,University of Utah | Zhao C.,Lawrence Livermore National Laboratory | Zhao C.,Beijing Normal University
Atmospheric Measurement Techniques | Year: 2013

This paper describes a method for using interferometer measurements of downwelling thermal radiation to retrieve the properties of single-layer clouds. Cloud phase is determined from ratios of thermal emission in three "microwindows" at 862.5 cm-1, 935.8 cm-1, and 988.4cm-1 where absorption by water vapour is particularly small. Cloud microphysical and optical properties are retrieved from thermal emission in the first two of these micro-windows, constrained by the transmission through clouds of primarily stratospheric ozone emission at 1040 cm-1. Assuming a cloud does not approximate a blackbody, the estimated 95% confidence retrieval errors in effective radius re, visible optical depth τ, number concentration N, and water path WP are, respectively, 10%, 20%, 38% (55% for ice crystals), and 16%. Applied to data from the Atmospheric Radiation Measurement programme (ARM) North Slope of Alaska - Adjacent Arctic Ocean (NSA-AAO) site near Barrow, Alaska, retrievals show general agreement with both ground-based microwave radiometer measurements of liquid water path and a method that uses combined shortwave and microwave measurements to retrieve r e, τ and N. Compared to other retrieval methods, advantages of this technique include its ability to characterise thin clouds year round, that water vapour is not a primary source of retrieval error, and that the retrievals of microphysical properties are only weakly sensitive to retrieved cloud phase. The primary limitation is the inapplicability to thicker clouds that radiate as blackbodies and that it relies on a fairly comprehensive suite of ground based measurements. © Author(s) 2013.

Shi Q.,University of Maryland University College | Liang S.,University of Maryland University College | Liang S.,Beijing Normal University
Journal of Geophysical Research: Atmospheres | Year: 2013

Recent progress in observation and modeling studies indicates that the Tibetan Plateau (TP) has been experiencing solar dimming coincident with changes of surface and atmospheric conditions since the early 1980s. However, changes and variability of the surface radiation budget over the entire Tibetan Plateau have rarely been analyzed in association with meteorological observations. Taking into consideration the limitations in ground measurements, reanalysis products, and remote sensing products, this paper applies the fused data (described in Part 1 of this two-paper series) to analyze the seasonal and annual spatial pattern and temporal variation in the surface radiation budget (SRB) over the TP from 1984 to 2007. The climatology and interannual variability of five SRB components - downward shortwave irradiance, albedo, downward longwave flux, upward longwave flux, and net all-wave radiation - are presented and analyzed in conjunction with atmospheric (cloud cover, water vapor) and surface (temperature, snow cover, normalized difference vegetation index) conditions over the Tibetan Plateau. Over the entire Tibetan Plateau, regardless of the increase of downward longwave radiation that counteracts the increase of upward longwave radiation, the interaction of solar dimming with changes of surface albedo has dominated the marked decrease of all-wave net radiation since the mid-1980s. This result indicates that the weakening and strengthening of the relationship between the components of SRB and the correlated variables of atmospheric or surface conditions exhibit a seasonal dependency over the TP. Moreover, most peaks and drops in the SRB anomalies are consistent to variations in two dominant variables. © 2013. Her Majesty the Queen in Right of Canada. American Geophysical Union.

Jiang B.,Beijing Normal University | Liang S.,Beijing Normal University | Liang S.,University of Maryland University College
Journal of Geophysical Research: Atmospheres | Year: 2013

Northern China is an environmentally vulnerable region with a severe water shortage. Several ecological restoration projects since the 1980s have greatly increased vegetation greenness. This study aims to assess the impacts of the changes in vegetation greenness from 1982 to 2008 on the atmospheric precipitable water (PW) over northern China during the summer seasons (June, July, and August) using reanalysis PW and satellite vegetation index data. Several statistical methods, such as linear regression (piecewise, stepwise), the Empirical Orthogonal Function, Pearson's correlation, have been used to explore the variations in and the coupling between vegetation greenness and PW. The influences of three major atmospheric circulations (the East Asian summer monsoon, the South Asian summer monsoon, and the Westerly circulation) have also been considered and excluded. The results show that summer vegetation greenness within the semi-arid western part of northern China, including the Tibetan Plateau, is closely linked to summer PW after excluding the influences of atmospheric circulations and that vegetation accounts for as much as 30% of the total PW variance. Vegetation greenness in the central and western water-limited regions of northern China has significant (>90% confidence level) positive impacts on summer PW. After investigating the relationships among evapotranspiration (ET), PW, and precipitation, it was concluded that strengthened ET driven by increased vegetation greenness makes a major contribution to increased PW. Different from the earlier hypothesis in the literature "only intact contiguous cover of natural forest having extensive borders with larger water bodies is able to keep land moisten up to an optimal for life level everywhere on land," this study found that interior forest covered regions with adequate water supply can also provide an ET benefit of PW for other regions. This study demonstrates the implications of large-scale ecological restoration projects on the hydrological cycle in arid/semi-arid regions. Key Points Vegetation is very important to the moisture cycle in water-limited region ET controlled by terrestrial vegetation is a main reason ©2013. American Geophysical Union. All Rights Reserved.

Wang K.,Beijing Normal University | Dickinson R.E.,University of Texas at Austin
Reviews of Geophysics | Year: 2013

Atmospheric downward longwave radiation at the surface (Ld) varies with increasing CO2 and other greenhouse gases. This study quantifies the uncertainties of current estimates of global Ld at monthly to decadal timescales and its global climatology and trends during the past decades by a synthesis of the existing observations, reanalyses, and satellite products. We find that current Ld observations have a standard deviation error of ~3.5 W m-2 on a monthly scale. Observations of Ld by different pyrgeometers may differ substantially for lack of a standard reference. The calibration of a pyrgeometer significantly affects its quantification of annual variability. Compared with observations collected at 169 global land sites from 1992 to 2010, the L d derived from state-of-the-art satellite cloud observations and reanalysis temperature and humidity profiles at a grid scale of ~1° has a bias of ±9 W m-2 and a standard deviation of 7 W m -2, with a nearly zero overall bias. The standard deviations are reduced to 4 W m-2 over tropical oceans when compared to L d observations collected by 24 buoy sites from 2002 to 2011. The -4 W m-2 bias of satellite Ld retrievals over tropical oceans is likely because of the overestimation of Ld observations resulting from solar heating of the pyrgeometer. Our best estimate of global means L d from 2003 to 2010 are 342 ± 3 W m-2 (global), 307 ± 3 W m-2 (land), and 356 ± 3 W m-2 (ocean). Estimates of Ld trends are seriously compromised by the changes in satellite sensors giving changes of water vapor profiles. Key Points Ld observations have a standard deviation error of ~3.5 W m-2 at a monthly scale Satellite and reanalysis Ld has a standard deviation of 7 W m-2 Global mean Ld is 342 W m-2 (global), 307 W m-2 (land), and 356 W m-2 (ocean) ©2013. American Geophysical Union. All Rights Reserved.

Gao J.,Beijing Normal University | Li A.,University of Missouri | Jiang B.W.,Beijing Normal University
Earth, Planets and Space | Year: 2013

We model the ̃ 1-19 μm infrared (IR) extinction curve toward the Galactic Center (GC) in terms of the standard silicate-graphite interstellar dust model. The grains are taken to have a power law size distribution with an exponential decay above some size. The best-fit model for the GC IR extinction constrains the visual extinction to be Ay ̃ 38-42 mag. The limitation of the model, i.e., its difficulty in simultaneously reproducing both the steep ̃ 1-3 pm near-IR extinction and the flat ̃ 3-8 μm mid-IR extinction is discussed. We argue that this difficulty could be alleviated by attributing the extinction toward the GC to a combination of dust in different environments: dust in diffuse regions (characterized by small Rv and steep near-IR extinction), and dust in dense regions (characterized by large Ry and flat UV extinction). © The Society of Geomagnetism and Earth Planetary and Space Sciences (SGEPSS).

Wang K.,Beijing Normal University | Dickinson R.E.,University of Texas at Austin | Ma Q.,Beijing Normal University | Augustine J.A.,National Oceanic and Atmospheric Administration | Wild M.,ETH Zurich
Journal of Climate | Year: 2013

Surface incident solar radiation G determines our climate and environment, and has been widely observed with a single pyranometer since the late 1950s. Such observations have suggested a widespread decrease between the 1950s and 1980s (global dimming), that is, at a rate of -3.5 W m-2 decade21 (or -2% decade-1) from 1960 to 1990. Since the early 1990s, the diffuse and direct components of G have been measured independently, and a more accurate G has been calculated by summing these two measurements. Data from this summation method suggest that G increased at a rate of 6.6 W m-2decade-1 (3.6% decade-1) from 1992 to 2002 (brightening) at selected sites. The brightening rates from these studies were also higher than those from a single pyranometer. In this paper, the authors used 17 years (1995-2011) of parallel measurements by the two methods from nearly 50 stations to test whether these two measurement methods of G provide similar long-term trends. The results show that although measurements of G by the two methods agree very well on a monthly time scale, the long-term trend from 1995 to 2011 determined by the single pyranometer is 2-4 W m-2 decade-1 less than that from the summation method. This difference of trends in the observed G is statistically significant. The dependence of trends of G on measurement methods uncovered here has an important implication for the widely reported global dimming and brightening based on datasets collected by different measurement methods; that is, the dimming might have been less if measured with current summation methods. © 2013 American Meteorological Society.

Zhang Y.,Beijing Normal University | Liang S.,Beijing Normal University | Liang S.,University of Maryland University College
Global Change Biology | Year: 2014

The forests of northeastern China store nearly half of the country's total biomass carbon stocks. In this study, we investigated the changes in forest biomass by using satellite observations and found that a significant increase in forest biomass took place between 2001 and 2010. To determine the possible reasons for this change, several statistical methods were used to analyze the correlations between forest biomass dynamics and forest disturbances (i.e. fires, insect damage, logging, and afforestation and reforestation), climatic factors, and forest development. Results showed that forest development was the most important contributor to the increasing trend of forest biomass from 2001 to 2010, and climate controls were the secondary important factor. Among the four types of forest disturbance considered in this study, forest recovery from fires, and afforestation and reforestation during the past few decades played an important role in short-term biomass dynamics. This study provided observational evidence and valuable information for the relationships between forest biomass and climate as well as forest disturbances. © 2014 John Wiley & Sons Ltd.

Li P.,University of Sichuan | Kou S.-P.,Beijing Normal University
Journal of Physics Condensed Matter | Year: 2012

The spin 1 bilinear-biquadratic model H= ij[cosS i S j+sin(S i S j) 2] on a square lattice in the region 0<<π/4 is studied in a fermion representation with a p-wave pairing Bardeen-Cooper-Schrieffer type of mean-field theory. Our results show there may exist a non-trivial gapped spin liquid with time-reversal symmetry spontaneously breaking. This exotic state manifests its topological nature by forming chiral states at the edges. To show this more clearly, we set up and solved a ribbon system. We got a gapless dispersion representing the edge modes beneath the bulk modes. The edge modes with nonzero longitudinal momentum (k x0) convect in opposite directions at the two edges, which leads to a twofold degeneracy, while the modes with zero longitudinal momentum (k x=0) turn out to be Majorana fermion states. The edge spin correlation functions are found to decay following a power law with increasing distance. We also calculated the contribution of the edge modes to the specific heat and obtained a linear law at low temperatures. © 2012 IOP Publishing Ltd.

Zhang J.,Beijing Normal University | Feng Y.,Beijing Normal University
Physica A: Statistical Mechanics and its Applications | Year: 2014

Weights of edges and nodes on food webs which are available from the empirical data hide much information about energy flows and biomass distributions in ecosystem. We define a set of variables related to weights for each species i, including the throughflow Ti, the total biomass Xi, and the dissipated flow Di (output to the environment) to uncover the following common patterns in 19 empirical weighted food webs: (1) DGBD distributions (Discrete version of a Generalized Beta Distribution), a kind of deformed Zipf's law, of energy flow and storage biomass; (2) The allometric scaling law Ti∝Xiα, which can be viewed as the counterpart of the Kleiber's 3/4 law at the population level; (3) The dissipation law Di∝Tiβ; and (4) The gravity law, including univariate version fij∝(TiTj) γ and bivariate approvement fij∝T i γ1Tj γ2. These patterns are very common and significant in all collected webs, as a result, some remarkable regularities are hidden in weights. © 2014 Elsevier B.V. All rights reserved.

Zhang J.,Renmin University of China | Zhou R.,Beijing Normal University | Zhou R.,Center for Collaboration and Innovation in Brain and Learning science
PLoS ONE | Year: 2014

The main goal of this study was to investigate how automatic emotion regulation altered the hemispheric asymmetry of ERPs elicited by emotion processing. We examined the effect of individual differences in automatic emotion regulation on the late positive potential (LPP) when participants were viewing blocks of positive high arousal, positive low arousal, negative high arousal and negative low arousal pictures from International affect picture system (IAPS). Two participant groups were categorized by the Emotion Regulation-Implicit Association Test which has been used in previous research to identify two groups of participants with automatic emotion control and with automatic emotion express. The main finding was that automatic emotion express group showed a right dominance of the LPP component at posterior electrodes, especially in high arousal conditions. But no right dominance of the LPP component was observed for automatic emotion control group. We also found the group with automatic emotion control showed no differences in the right posterior LPP amplitude between high- and low-arousal emotion conditions, while the participants with automatic emotion express showed larger LPP amplitude in the right posterior in high-arousal conditions compared to low-arousal conditions. This result suggested that AER (Automatic emotion regulation) modulated the hemispheric asymmetry of LPP on posterior electrodes and supported the right hemisphere hypothesis. © 2014 Zhang, Zhou.

Li D.,Yanshan University | Li X.,Beijing Normal University | Hagihira S.,Osaka University | Sleigh J.W.,Waikato Hospital
British Journal of Anaesthesia | Year: 2013

BackgroundFourier bicoherence has previously been applied to investigate phase coupling in the EEG in anaesthesia. However, there are significant theoretical limitations regarding its sensitivity in detecting transient episodes of inter-frequency coupling. Therefore, we used a recently developed wavelet bicoherence method to investigate the cross-frequency coupling in the EEG of patients under isoflurane anaesthesia; examining the relationship between the patterns of wavelet bicoherence and the isoflurane concentrations.MethodsWe analysed a set of previously published EEG data, obtained from 29 patients who underwent elective abdominal surgery under isoflurane anaesthesia. Artifact-free, 1 min EEG segments at different isoflurane concentrations were extracted from each subject and the wavelet bicoherence calculated for all pairs of frequencies from 0.5 to 20 Hz.ResultsIsoflurane caused two peaks in the α (6-13 Hz) and slow δ (<1 Hz) regions of the bicoherence matrix diagonal. Higher concentrations of isoflurane shifted the α peak to lower frequencies [11.3 (0.9) Hz at 0.3% to 7.1 (1.2) Hz at 1.5%], as has been previously observed in the power spectra. Outside the diagonal, we also found a significant α peak that was phase-coupled to the slow δ waves; higher concentrations of isoflurane shifted this peak to lower frequencies [10.8 (1.2) to 7.7 (0.7) Hz].ConclusionsIsoflurane caused cross-frequency coupling between α and slow δ waves. Increasing isoflurane concentration slowed the α frequencies where the coupling had occurred. This phenomenon of α-δ coupling suggests that slow cortical oscillations organize the higher α band activity, which is consistent with other studies in natural sleep. © The Author [2012].

Cao S.,Beijing Normal University | Zhu Z.-H.,Beijing Normal University
Astronomy and Astrophysics | Year: 2012

Context. Strong-lensing has developed into an important astrophysical tool for probing cosmology and galaxies (their structures, formations, and evolutions). Now several hundreds of strong-lens systems produced by massive galaxies have been discovered, which may form well-defined samples useful for statistical analyses. Aims. We aim to collect relatively complete lens-redshift data from various large systematic surveys of gravitationally lensed quasars and check the possibility of using these as a future supplement to other cosmological probes. Methods. We use the distribution of gravitationally-lensed image separations observed in the Cosmic Lens All-Sky Survey (CLASS), the PMN-NVSS Extragalactic Lens Survey (PANELS), the Sloan Digital Sky Survey (SDSS) and other surveys, considering a singular isothermal ellipsoid (SIE) model for galactic potentials as well as improved new measurements of the velocity dispersion function of galaxies based on the SDSS DR5 data and recent semi-analytical modeling of galaxy formation to constrain two dark-energy models (ΛCDM and constant w) under a flat universe assumption. Results. We find that the current lens-redshift data yield a relatively weak constraint on the model parameter Ω Λ = 0.85 -0.18 +0.11 for the simplest cosmological constant model. However, by combing the redshift data with the cosmic macrowave background data, we obtain Ω Λ = 0.78 -0.03 +0.02; by combing the redshift data with the baryonic acoustic oscillation peak and the comic macrowave background data, we obtain a more stringent result: Ω Λ = 0.75 -0.02 +0.02. We obtain w <-0.52 at 68.3% CL with the lens-redshift data for the constant w of a dynamical dark-energy model, therefore, the current quintessence dark-energy model is still included at 1σ and a super-negative equation of state is not necessarily favored by this strong lensing data. We notice that the joint data can also provide a good fit with Ω x = 0.80 -0.17 +0.17, w =-1.12 -1.88 +0.57 and Ω x = 0.71 -0.07 +0.07, w =-0.78 -0.34 +0.22, respectively, which agree with the flat Λ CDM model at 1σ. © 2012 ESO.

Wang Y.,Beijing Normal University | Ma N.,Beijing Normal University | Chen G.,Beijing Normal University
PLoS ONE | Year: 2012

Background: It has been extensively developed in recent years that cell-permeable small molecules, such as polyamide, can be programmed to disrupt transcription factor-DNA interfaces and can silence aberrant gene expression. For example, cyclic pyrrole-imidazole polyamide that competes with glucocorticoid receptor (GR) for binding to glucocorticoid response elements could be expected to affect the DNA dependent binding by interfering with the protein-DNA interface. However, how such small molecules affect the transcription factor-DNA interfaces and gene regulatory pathways through DNA structure distortion is not fully understood so far. Methodology/Principal Findings: In the present work, we have constructed some models, especially the ternary model of polyamides+DNA+GR DNA-binding domain (GRDBD) dimer, and carried out molecular dynamics simulations and free energy calculations for them to address how polyamide molecules disrupt the GRDBD and DNA interface when polyamide and protein bind at the same sites on opposite grooves of DNA. Conclusions/Significance: We found that the cyclic polyamide binding in minor groove of DNA can induce a large structural perturbation of DNA, i.e. a >4 Å widening of the DNA minor groove and a compression of the major groove by more than 4 Å as compared with the DNA molecule in the GRDBD dimer+DNA complex. Further investigations for the ternary system of polyamides+DNA+GRDBD dimer and the binary system of allosteric DNA+GRDBD dimer revealed that the compression of DNA major groove surface causes GRDBD to move away from the DNA major groove with the initial average distance of ~4 Å to the final average distance of ~10 Å during 40 ns simulation course. Therefore, this study straightforward explores how small molecule targeting specific sites in the DNA minor groove disrupts the transcription factor-DNA interface in DNA major groove, and consequently modulates gene expression. © 2012 Wang et al.

Wei W.,Beijing Normal University | Chen C.,University of California at Irvine | Yang T.,Beijing Normal University | Zhang H.,Beijing Normal University | Zhou X.,Beijing Normal University
Human Brain Mapping | Year: 2014

Quantities can be represented using either mathematical language (i.e., numbers) or natural language (i.e., quantifiers). Previous studies have shown that numerical processing elicits greater activation in the brain regions around the intraparietal sulcus (IPS) relative to other semantic processes. However, little research has been conducted to investigate whether the IPS is also critical for the semantic processing of quantifiers in natural language. In this study, 20 adults were scanned with functional magnetic resonance imaging while they performed semantic distance judgment involving six types of materials (i.e., frequency adverbs, quantity pronouns and nouns, animal names, Arabic digits, number words, and dot arrays). Conjunction analyses of brain activation showed that numbers and dot arrays elicited greater activation in the right IPS than did words (i.e., animal names) or quantifiers (i.e., frequency adverbs and quantity pronouns and nouns). Quantifiers elicited more activation in left middle temporal gyrus and inferior frontal gyrus than did numbers and dot arrays. No differences were found between quantifiers and animal names. These findings suggest that, although quantity processing for numbers and dot arrays typically relies on the right IPS region, quantity processing for quantifiers typically relies on brain regions for general semantic processing. Thus, the IPS does not appear to be the only brain region for quantity processing. Hum Brain Mapp 35:444-454, 2014. © 2012 Wiley Periodicals, Inc.

Lu H.,Beijing Normal University | Perkins A.,Imperial College London | Pope C.N.,Texas A&M University | Pope C.N.,University of Cambridge | Stelle K.S.,Imperial College London
Physical Review Letters | Year: 2015

Extensions of Einstein gravity with higher-order derivative terms arise in string theory and other effective theories, as well as being of interest in their own right. In this Letter we study static black-hole solutions in the example of Einstein gravity with additional quadratic curvature terms. A Lichnerowicz-type theorem simplifies the analysis by establishing that they must have vanishing Ricci scalar curvature. By numerical methods we then demonstrate the existence of further black-hole solutions over and above the Schwarzschild solution. We discuss some of their thermodynamic properties, and show that they obey the first law of thermodynamics. © 2015 American Physical Society.

Mishra A.,University of Missouri | Li A.,University of Missouri | Jiang B.W.,Beijing Normal University
Astrophysical Journal | Year: 2015

The mysterious "21 μm" emission feature seen almost exclusively in the short-lived protoplanetary nebula (PPN) phase of stellar evolution remains unidentified since its discovery two decades ago. This feature is always accompanied by the equally mysterious, unidentified "30 μm" feature and the so-called "unidentified infrared" (UIR) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm which are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. The 30 μm feature is commonly observed in all stages of stellar evolution from the asymptotic giant branch through PPN to the planetary nebula phase. We explore the interrelations among the mysterious 21, 30 μm, and UIR features of the 21 μm sources. We derive the fluxes emitted in the observed UIR, 21, and 30 μm features from published Infrared Space Observatory or Spitzer/IRS spectra. We find that none of these spectral features correlate with each other. This argues against a common carrier (e.g., thiourea) for both the 21 μm feature and the 30 μm feature. This also does not support large PAH clusters as a possible carrier for the 21 μm feature. © 2015. The American Astronomical Society. All rights reserved.

Miao C.,Beijing Normal University | Duan Q.,Beijing Normal University | Yang L.,CAS Institute of Geographical Sciences and Natural Resources Research | Borthwick A.G.L.,University College Cork
PLoS ONE | Year: 2012

Global Circulation Models (GCMs) contributed to the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) and are widely used in global change research. This paper assesses the performance of the AR4 GCMs in simulating precipitation and temperature in China from 1960 to 1999 by comparison with observed data, using system bias (B), root-mean-square error (RMSE), Pearson correlation coefficient (R) and Nash-Sutcliffe model efficiency (E) metrics. Probability density functions (PDFs) are also fitted to the outputs of each model. It is shown that the performance of each GCM varies to different degrees across China. Based on the skill score derived from the four metrics, it is suggested that GCM 15 (ipsl_cm4) and GCM 3 (cccma_cgcm_t63) provide the best representations of temperature and precipitation, respectively, in terms of spatial distribution and trend over 10 years. The results also indicate that users should apply carefully the results of annual precipitation and annual temperature generated by AR4 GCMs in China due to poor performance. At a finer scale, the four metrics are also used to obtain best fit scores for ten river basins covering mainland China. Further research is proposed to improve the simulation accuracy of the AR4 GCMs regarding China. © 2012 Miao et al.

Fan Z.-Y.,Beijing Normal University | Lu H.,Beijing Normal University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Einstein gravities in general dimensions coupled to a cosmological constant and extended with quadratic curvature invariants admit a variety of black holes that may asymptote to Minkowski, anti-de Sitter or Lifshitz spacetimes. We adopt the Wald formalism to derive an explicit formula for calculating the thermodynamical first law for the static black holes with spherical, toric, or hyperbolic isometries in these theories. This allows us to derive or rederive the first laws for a wide range of black holes in the literature. Furthermore, we construct many new exact solutions and obtain their first laws. © 2015 American Physical Society.

Lu H.,Beijing Normal University | Vazquez-Poritz J.F.,New York City College of Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We construct an exact time-dependent charged dilaton C metric in four-dimensional N=4 gauged supergravity. The scalar field drives the time evolution by transferring energy to the black holes, thereby causing their masses to increase and their acceleration to decrease. The values of the electric/magnetic and scalar charges determine three regions of potential time evolution. This solution holographically describes a strongly coupled three-dimensional conformal field theory on the background of an evolving black hole. We also find new static charged dilaton C metrics, which arise in four-dimensional Einstein-Maxwell-dilaton theories whose scalar potential can be expressed in terms of a superpotential. © 2015 American Physical Society.

Zhang Q.-G.,Beijing Normal University | Buckling A.,University of Exeter
Evolutionary Applications | Year: 2012

The evolution of multi-antibiotic resistance in bacterial pathogens, often resulting from de novo mutations, is creating a public health crisis. Phages show promise for combating antibiotic-resistant bacteria, the efficacy of which, however, may also be limited by resistance evolution. Here, we suggest that phages may be used as supplements to antibiotics in treating initially sensitive bacteria to prevent resistance evolution, as phages are unaffected by most antibiotics and there should be little cross-resistance to antibiotics and phages. In vitro experiments using the bacterium Pseudomonas fluorescens, a lytic phage, and the antibiotic kanamycin supported this prediction: an antibiotic-phage combination dramatically decreased the chance of bacterial population survival that indicates resistance evolution, compared with antibiotic treatment alone, whereas the phage alone did not affect bacterial survival. This effect of the combined treatment in preventing resistance evolution was robust to immigration of bacteria from an untreated environment, but not to immigration from environment where the bacteria had coevolved with the phage. By contrast, an isogenic hypermutable strain constructed from the wild-type P. fluorescens evolved resistance to all treatments regardless of immigration, but typically suffered very large fitness costs. These results suggest that an antibiotic-phage combination may show promise as an antimicrobial strategy. © 2012 Blackwell Publishing Ltd.

Cao S.,Beijing Normal University | Biesiada M.,Beijing Normal University | Biesiada M.,University of Silesia | Gavazzi R.,University Pierre and Marie Curie | And 2 more authors.
Astrophysical Journal | Year: 2015

In this paper, we assemble a catalog of 118 strong gravitational lensing systems from the Sloan Lens ACS Survey, BOSS emission-line lens survey, Lens Structure and Dynamics, and Strong Lensing Legacy Survey and use them to constrain the cosmic equation of state. In particular, we consider two cases of dark energy phenomenology: the XCDM model, where dark energy is modeled by a fluid with constant w equation-of-state parameter, and in the Chevalier-Polarski-Linder (CPL) parameterization, where w is allowed to evolve with redshift, w(z) = w0 + w1 z/1 + z. We assume spherically symmetric mass distribution in lensing galaxies, but we relax the rigid assumption of the SIS model in favor of a more general power-law index γ, also allowing it to evolve with redshifts γ(z). Our results for the XCDM cosmology show agreement with values (concerning both w and γ parameters) obtained by other authors. We go further and constrain the CPL parameters jointly with γ(z). The resulting confidence regions for the parameters are much better than those obtained with a similar method in the past. They are also showing a trend of being complementary to the Type Ia supernova data. Our analysis demonstrates that strong gravitational lensing systems can be used to probe cosmological parameters like the cosmic equation of state for dark energy. Moreover, they have a potential to judge whether the cosmic equation of state evolved with time or not. © 2015. The American Astronomical Society. All rights reserved.

Zhang J.,Beijing Normal University | Yu T.,Beijing Normal University
Physica A: Statistical Mechanics and its Applications | Year: 2010

As huge complex systems consisting of geographic regions, natural resources, people and economic entities, countries follow the allometric scaling law which is ubiquitous in ecological, and urban systems. We systematically investigated the allometric scaling relationships between a large number of macroscopic properties and geographic (area), demographic (population) and economic (GDP, gross domestic production) sizes of countries respectively. We found that most of the economic, trade, energy consumption, communication related properties have significant super-linear (the exponent is larger than 1) or nearly linear allometric scaling relations with the GDP. Meanwhile, the geographic (arable area, natural resources, etc.), demographic (labor force, military age population, etc.) and transportation-related properties (road length, airports) have significant and sub-linear (the exponent is smaller than 1) allometric scaling relations with area. Several differences of power law relations with respect to the population between countries and cities were pointed out. First, population increases sub-linearly with area in countries. Second, the GDP increases linearly in countries but not super-linearly as in cities. Finally, electricity or oil consumption per capita increases with population faster than cities. © 2010 Elsevier B.V. All rights reserved.

Wang F.,Beijing Normal University | Wen J.,Beijing Normal University | Huang L.,Beijing Normal University | Huang J.,Beijing Normal University | Jin O.,Beijing Normal University
Chemical Communications | Year: 2012

A highly sensitive and water-soluble "switch-on" fluorescent probe with aggregation-induced emission characteristics was developed for protein quantification and visualization. It offers a rapid, economic and effective way for the assay of complete serum proteins and disease-marker proteins. © 2012 The Royal Society of Chemistry.

Cao W.,Beijing Normal University | Zheng X.-J.,Beijing Normal University | Fang D.-C.,Beijing Normal University | Jin L.-P.,Beijing Normal University
Dalton Transactions | Year: 2014

Two new Schiff base complexes, [ZnL(Ac)]2 (1) and [CuLCl]·H2O (2) (HL = 2-(2′-hydroxynaphthylmethylene) aminophenylbenzimidazole, Ac = acetate) were synthesized by a one-pot reaction and characterized by elemental analyses, IR and single-crystal X-ray diffraction. Fluorescence of complex 1 showed "on-off-on" switching when Cu2+ and cyanide were sequentially detected. This phenomenon was investigated by UV-Vis absorption, fluorescence and ESI-MS spectra, and theoretical calculations to explain the response. Complex 1 can selectively respond to Cu2+ with the fluorescence "turn-off" owing to the formation of complex 2 in the solution. Interestingly, the quenched fluorescence of complex 1 by Cu2+ ions could be turned on after the addition of cyanide owing to the displacement of L- by CN- to form [Cu(CN)x]n-, making complex 1 a selective CN - probe. In addition, the results of the MTT assay experiment indicate that complex 1 has a low toxicity to cells and can be used to detect intracellular Cu2+ ion by live cell imaging. © 2014 the Partner Organisations.

Ding B.-W.,Beijing Normal University | Naumov P.,Abu Dhabi University | Liu Y.-J.,Beijing Normal University
Journal of Chemical Theory and Computation | Year: 2015

Cypridina hilgendorfii (sea firefly) is a bioluminescent crustacean whose bioluminescence (BL) reaction is archetypal for a number of marine organisms, notably other bioluminescent crustaceans and coelenterates. Unraveling the mechanism of its BL is paramount for future applications of its strongly emissive lumophore. Cypridina produces light in a three-step reaction: First, the cypridinid luciferin is activated by an enzyme to produce a peroxide intermediate, cypridinid dioxetanone (CDO), which then decomposes to generate excited oxyluciferin (OxyCLnH∗). Finally, OxyCLnH∗ deexcites to its ground state along with emission of bright blue light. Unfortunately, the detailed mechanism of the critical step, the thermolysis of CDO, remains unknown, and it is unclear whether the light emitter is generated from a neutral form (CDOH) or anionic form (CDO-) of the CDO precursor. In this work, we investigated the key step in the process by modeling the thermal decompositions of both CDOH and CDO-. The calculated results indicate that the decomposition of CDO- occurs via the gradually reversible charge transfer (CT)-initiated luminescence (GRCTIL) mechanism, whereas CDOH decomposes through an entropic trapping mechanism without an obvious CT process. The thermolysis of CDO- is sensitive to solvent effects and is energetically favorable in polar environments compared with the thermolysis of CDOH. The thermolysis of CDO- produces the excited oxyluciferin anion (OxyCLn-∗), which combines with a proton from the environment to form OxyCLnH∗, the actual light emitter for the natural system. © 2015 American Chemical Society.

Chen Y.,Beijing Normal University | Chen Y.,Kansas State University | Ratra B.,Beijing Normal University
Astronomy and Astrophysics | Year: 2012

We use angular size versus redshift data for galaxy clusters provided by Bonamente and collaborators to place constraints on model parameters of constant and time-evolving dark energy cosmological models. These constraints are compatible with those from other recent data, but are not very restrictive. A joint analysis of the galaxy cluster angular-size data with the more restrictive baryon acoustic oscillation peak length scale and supernova Type Ia apparent-magnitude data, favors a spatially flat cosmological model currently dominated by a time-independent cosmological constant, but does not exclude time-varying dark energy. © 2012 ESO.

Shi Q.,University of Maryland University College | Liang S.,University of Maryland University College | Liang S.,Beijing Normal University
Journal of Geophysical Research: Atmospheres | Year: 2013

The surface radiation budget (SRB) over the Tibetan Plateau (TP) greatly influences local climate, climate extremes (e.g., drought, flood) in China, and the East Asian monsoon. However, current estimates of SRB from models and satellite data are subject to large errors, and ground-measured data sets within this region are rather limited over the TP. Our objective is to determine the SRB over the TP by integrating information from three sources: (1) four ground-measured data sets from AsiaFlux, ChinaFLUX, GAME/Tibet, and CAMP/Tibet; (2) four reanalysis data sets from Climate Forecast System Reanalysis, Modern-Era Retrospective Analysis for Research and Applications, ERA-Interim, and Japanese 25-year Reanalysis; and (3) two remote sensing data sets, Global Energy and Water Cycle Experiment Surface Radiation Budget and International Satellite Cloud Climatology Project FD. This study, the first of a two-paper series, presents the methodology. Individual radiation components of reanalysis and remote sensing data set were first validated using ground-measured data from 1997 to 2007; then, a linear regression method was applied to generate the fused data from July 1983 to December 2007. The cross-validation results indicate that the monthly mean root-mean-square errors (RMSEs) of fused downward shortwave irradiance and albedo are 15.1 W m-2 and 0.05, respectively; the RMSEs of the downward and upward longwave fluxes are 13.3 and 8.4 W m-2, respectively; and the RMSE of all-wave net radiation is as low as 18.9 W m-2. Compared to nine sites with long-term observation of downward shortwave irradiance, the fused data represent the decadal variations with higher correlation than using individual products, suggesting the potential for application of the fused data sets in climatic and environmental research. Key Points The surface radiation budget over the Tibetan Plateau is validatedA multiple linear regression method is applied to integrate multiple datasetsThe fused data insolation agreed well with that of other stations ©2013. American Geophysical Union. All Rights Reserved.

Cheng Y.,Beijing Normal University | Peng J.-H.,Beijing Normal University | Li J.-Q.,Beijing Normal University
Journal of Organic Chemistry | Year: 2010

(Figure Presented) 1-Thiocarbamoyl imidazo[l,5-a]pyridinium inner salts, which were obtained readily from the addition of C,N-substituted heterocyclic carbenes imidazo[1,5-a]pyridine-l-ylidenes to isothiocyanates, are powerful ambident nucleophilic zwitterions. They acted as nitrogen nucleophiles toward ethyl propiolate to produce polyfunctionalized pyrrole derivatives in high yields. When treated with dimethyl acetylenedicarboxylate, they behaved exclusively as sulfur nucleophiles to afford fully substituted thiophenes in excellent yields. This work provides highly efficient orthogonal synthesis of polyfunctionalized pyrroles and thiophenes that were not easily obtained by other chemical means. © 2010 American Chemical Society.

Liu H.-S.,Zhejiang University of Technology | Liu H.-S.,Texas A&M University | Lu H.,Beijing Normal University | Pope C.N.,Texas A&M University | Pope C.N.,University of Cambridge
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We study the shear viscosity to entropy ratio η/S in the boundary field theories dual to black-hole backgrounds in theories of gravity coupled to a scalar field, and generalizations including a Maxwell field and nonminimal scalar couplings. Motivated by the observation in simple examples that the saturation of the η/S≥1/(4π) bound is correlated with the existence of a generalized Smarr relation for the planar black-hole solutions, we investigate this in detail for the general black-hole solutions in these theories, focusing especially on the cases where the scalar field plays a nontrivial role and gives rise to an additional parameter in the space of solutions. We find that a generalized Smarr relation holds in all cases, and in fact it can be viewed as the bulk gravity dual of the statement of the saturation of the viscosity to entropy bound. We obtain the generalized Smarr relation, whose existence depends upon a scaling symmetry of the planar black-hole solutions, by two different but related methods, one based on integrating the first law of thermodynamics, and the other based on the construction of a conserved Noether charge. © 2015 American Physical Society.

Wang S.,Beijing Normal University | Wang S.,University of Missouri | Li A.,University of Missouri | Jiang B.W.,Beijing Normal University
Astrophysical Journal | Year: 2015

The sizes of interstellar grains are widely distributed, ranging from a few angstroms to a few micrometers. The ultraviolet (UV) and optical extinction constrains the dust in the size range of a couple hundredths of micrometers to several submicrometers. The near and mid infrared (IR) emission constrains the nanometer-sized grains and angstrom-sized very large molecules. However, the quantity and size distribution of micrometer-sized grains remain unknown because they are gray in the UV/optical extinction and they are too cold and emit too little in the IR to be detected by IRAS, Spitzer, or Herschel. In this work, we employ the ∼3-8 μm mid-IR extinction, which is flat in both diffuse and dense regions to constrain the quantity, size, and composition of the μm-sized grain component. We find that, together with nano- and submicron-sized silicate and graphite (as well as polycyclic aromatic hydrocarbons), μm-sized graphite grains with C/H ≈ 137 ppm and a mean size of ∼1.2 μm closely fit the observed interstellar extinction of the Galactic diffuse interstellar medium from the far-UV to the mid-IR, as well as the near-IR to millimeter thermal emission obtained by COBE/DIRBE, COBE/FIRAS, and Planck up to λ ≲ 1000 μm. The μm-sized graphite component accounts for ∼14.6% of the total dust mass and ∼2.5% of the total IR emission. © 2015. The American Astronomical Society. All rights reserved..

Fan Z.-Y.,Beijing Normal University | Lu H.,Beijing Normal University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We consider Einstein gravity in general dimensions, coupled to a scalar field either minimally or nonminimally, together with a generic scalar potential. By making appropriate choices of the scalar potential, we obtain large classes of new scalar hairy black holes that are asymptotic to planar anti-de Sitter spacetimes. For some classes of solutions, we can promote the scalar charge to be dependent on the advanced or retarded times in the Eddington-Finkelstein coordinates and obtain exact dynamic solutions. In particular, one class of the collapse solutions describes the evolution from the AdS vacua to some stable black hole states, driven by a conformally massless scalar. It is an explicit demonstration of nonlinear instability of the AdS vacuum that is stable at the linear level. © 2015 American Physical Society.

Xue G.,Beijing Normal University | Xue G.,University of Southern California | Dong Q.,Beijing Normal University | Chen C.,University of California at Irvine | And 3 more authors.
Science | Year: 2010

Repeated study improves memory, but the underlying neural mechanisms of this improvement are not well understood. Using functional magnetic resonance imaging and representational similarity analysis of brain activity, we found that, compared with forgotten items, subsequently remembered faces and words showed greater similarity in neural activation across multiple study in many brain regions, including (but not limited to) the regions whose mean activities were correlated with subsequent memory. This result addresses a longstanding debate in the study of memory by showing that successful episodic memory encoding occurs when the same neural representations are more precisely reactivated across study episodes, rather than when patterns of activation are more variable across time.

Lexical Pragmatics has focused to date on implicature by inference in lexicon and the pragmatic presupposition on statements related to sentences (utterances) and text (discourse). This paper aims to address an issue to be termed Lexical Presupposition (LP). The study elaborates on an extended notion of presupposition in the categorization construed in lexis in a historical context on a cognitive basis. In particular, it discusses LP in terms of ostensive inferences in ancient Chinese categorization: the functions of the radicals in their derivatives in Shuowen Jiezi. In fact, these radicals work to constitute a ground-figure opposition with the most salient and characteristic features resembling statement assertions in sentences, which may be called lexical assertions, or LAs, i.e., 'there is LP' and 'LP have/be/do LA' or LA (LP). This propositional analogy aims to recover or reconstruct the possible historical mechanisms of categorization and to analyze three general groups of LPs that contain a number of sub-types: constitutional (meronymic, taxonomic, material), manner (means [agent, instrument, and medium] and comparison-and-contrast), and other minor ones. In these processes, metaphors play an important role. The findings of this paper should be applicable to word formation in other languages, such as Indo-European languages. © 2015 Elsevier B.V.

Liu W.,Beijing Normal University | Liu W.,Bielefeld University
Infinite Dimensional Analysis, Quantum Probability and Related Topics | Year: 2010

In this paper we investigate some regularity property for the solution to SPDE. Under certain assumptions we prove that the solution of an SPDE takes values in some subspace of the original state space if the initial condition does so. As examples, the main result is applied to different types of SPDE such as stochastic reaction-diffusion equations, the stochastic p-Laplace equation, stochastic porous media and fast diffusion equations in Hilbert space. © 2010 World Scientific Publishing Company.

Zhang X.,Beijing Normal University | Lu H.,Beijing Normal University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We examine a one-parameter family of analytical solutions representing spherically symmetric collapse of a nonlinear massless scalar field with self-interaction in an asymptotically flat spacetime. The time evolution exhibits a type of critical behavior. Depending on the scalar charge parameter q as compared to a critical value q∗, the incoming scalar wave collapses either to a globally naked central singularity if qq∗ (strong field), both having finite asymptotic masses. Near the critical evolution, the black hole mass follows a product-logarithmic scaling law: -M2lnM∼q-q∗ with 0q∗. The solution admits no self-similarity and satisfies the null and the strong energy conditions. © 2015 American Physical Society.

Liu Y.,Beijing Normal University | Guo X.-H.,Beijing Normal University | Wang C.,Beijing Normal University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

In this work, we study weak transitions of Λb to light baryons Λ and p in the Bethe-Salpeter equation approach. In the heavy quark limit, based on the picture that Λb is composed of a heavy b-quark and a light diquark, the Bethe-Salpeter equation for Λb was established in previous works. Although the light baryon Λ(p) is composed of various quark-diquark configurations based on the SU(6) spin-flavor wave functions, only the configuration s(ud)0,0 [u(ud)0,0] [(ud)0,0 is a scalar diquark composed of u and d quarks] contributes to Λb→Λ (Λb→p) transition. We establish the Bethe-Salpeter equations for the systems s(ud)0,0 and u(ud)0,0 and calculate their Bethe-Salpeter wave functions in the covariant instantaneous approximation with the kernel containing both scalar confinement and one-gluon-exchange terms. Then, the form factors for Λb→Λ and Λb→p weak transitions are obtained with Bethe-Salpeter wave functions for Λb, Λ, and p. Consequently, we calculate the branching ratios of Λb→ΛP, Λb→ΛV, Λ→pP, and Λb→pV (P and V denote pseudoscalar and vector mesons, respectively) in the factorization approach. © 2015 American Physical Society.

Han X.,Beijing Normal University | Shen Z.,Beijing Normal University | Wang W.-X.,Beijing Normal University | Di Z.,Beijing Normal University
Physical Review Letters | Year: 2015

Reconstructing complex networks from measurable data is a fundamental problem for understanding and controlling collective dynamics of complex networked systems. However, a significant challenge arises when we attempt to decode structural information hidden in limited amounts of data accompanied by noise and in the presence of inaccessible nodes. Here, we develop a general framework for robust reconstruction of complex networks from sparse and noisy data. Specifically, we decompose the task of reconstructing the whole network into recovering local structures centered at each node. Thus, the natural sparsity of complex networks ensures a conversion from the local structure reconstruction into a sparse signal reconstruction problem that can be addressed by using the lasso, a convex optimization method. We apply our method to evolutionary games, transportation, and communication processes taking place in a variety of model and real complex networks, finding that universal high reconstruction accuracy can be achieved from sparse data in spite of noise in time series and missing data of partial nodes. Our approach opens new routes to the network reconstruction problem and has potential applications in a wide range of fields. © 2015 American Physical Society.

A chemical kinetic submechanism proposed here is an essential prerequisite to model autoignition of methyl esters at low temperature region (less than ~900K), where reactions of methyl-ester peroxy radicals (ROO) and hydroperoxy methyl-ester radicals (QOOH) are crucial and relatively unexplored. The potential energy surfaces of the methyl butanoate peroxy radicals+O2 systems are computed by the G3MP2B3 composite approach. 114 pathways are identified leading to the formation of key radicals in the ignition kernel such as OH and HO2.Particular attention is focused on: (1) intramolecular H-migration of ROO, (2) unimolecular dissociations of ROO and QOOH and (3) reactions of ROO+HO2. Using the canonical transition state theory, the high-pressure limit rate constants for reactions in the kinetic submechanism are calculated. Standard enthalpy of formation, entropy and heat capacities are evaluated for intermediates and products formed during combustion by means of the standard statistical mechanics formulae. The agreement and disagreement between our calculated kinetic parameters and previous estimates offer further insight into the uncertainty associated with theoretical estimation. We perform the branching ratio analysis for the competing channels between the reverse dissociation of ROO (ROO→R+O2) and explored unimolecular reactions decomposing ROO. Additionally, we also quantify the similarity and dissimilarity between the rate constants determined here and those previously calculated for normal alkanes. Finally, the effect of transition state size on the rate constants for the isomerizations of methyl-ester peroxy radicals is systematically analyzed. © 2014 The Combustion Institute.

Zhang L.,Beijing Normal University | Liu L.,Beijing Normal University | Li X.,Beijing Normal University | Song Y.,Beijing Normal University | Liu J.,Beijing Normal University
Human Brain Mapping | Year: 2015

A functional polymorphism (5-hydroxytryptamine transporter linked polymorphic region [5-HTTLPR]) in the promoter region of human serotonin transporter gene has been found to be associated with several dimensions of neuroticism and psychopathology, especially anxiety. However, the neural basis underlying the association between 5-HTTLPR and anxiety is less clear. Here, we explored how 5-HTTLPR influenced anxiety by modulating the spontaneous brain activities in Han Chinese. First, we found an association between 5-HTTLPR and anxiety only in the male and not in the female population, where male S/S homozygotes had a significantly higher level of anxiety than male L allele carriers. Then, we examined how 5-HTTLPR influenced anxiety at both regional and network levels in the brain at rest. At the regional level, we found a significantly higher fractional amplitude of low-frequency fluctuations in the amygdala in male S/S homozygotes relative to male L allele carriers. At the network level, male S/S homozygotes showed a weaker resting-state functional connectivity (RSFC) between the amygdala and various regions, including the insula, Heschl's gyrus, lateral occipital cortex, superior temporal gyrus, and hippocampus, and a stronger RSFC between the amygdala and various regions, including the supramariginal gyrus and middle frontal gyrus. However, at both levels, only was the amygdala-insula RSFC correlated with anxiety. Mediation analyses further revealed that the amygdala-insula RSFC mediated the association between 5-HTTLPR and anxiety. In short, our study provided the first empirical evidence that the amygdala-insula RSFC served as the neural basis underlying the association between 5-HTTLPR and anxiety, suggesting a potential neurogenetic susceptibility mechanism for anxiety. © 2015 Wiley Periodicals, Inc.

Yao W.,Munich University of Applied Sciences | Wei Y.,Beijing Normal University
IEEE Geoscience and Remote Sensing Letters | Year: 2013

An automated approach to extracting 3-D individual trees in urban areas is developed based on jointly analyzing airborne LiDAR data and imagery. First, the spectral, geometric, and spatial context attributes are defined and integrated at the LiDAR point level. Then, a binary AdaBoost classifier is used to separate points belonging to trees from other urban objects. Once the classification is completed, a spectral clustering method by applying the normalized cuts to a graph structure of point clouds of the vegetation class is performed to segment single trees. The geometric and spectral attributes play an important role in establishing the weight matrix, which measures the similarity between every two graph nodes and determines the cut function. The performance of the approach is validated by real urban data sets, which were acquired over two European cities. The results show that 3-D individual trees can be detected with mean accuracy of up to 0.65 and 0.12 m for tree position and height. Based on the results of this work, geometric and biophysical properties of individual trees can be further retrieved. © 2013 IEEE.

Hong W.,Beijing Normal University | Zhang L.,Beijing Normal University
Infinite Dimensional Analysis, Quantum Probability and Related Topics | Year: 2010

An intrinsic multi-type branching structure within the transient (1, R)-RWRE is revealed. The branching structure enables us to specify the density of the absolutely continuous invariant measure for the Markov chain of environments seen from the particle and reprove the LLN with a drift explicitly in terms of the environment. © 2010 World Scientific Publishing Company.

Zhao Y.,Beijing Normal University | Deng W.,The Hong Kong Institute of Education
Resources, Conservation and Recycling | Year: 2014

The environmental impacts of food waste management strategies and the effects of energy mix wereevaluated using a life cycle assessment model, EASEWASTE. Three different strategies involving land-fill, composting and combined digestion and composting as core technologies were investigated. Theresults indicate that the landfilling of food waste has an obvious impact on global warming, althoughthe power recovery from landfill gas counteracts some of this. Food waste composting causes seri-ous acidification (68.0 PE) and nutrient enrichment (76.9 PE) because of NH3and SO2emissions duringdecomposition. Using compost on farmland, which can marginally reduce global warming (-1.7 PE),acidification (-0.8 PE), and ecotoxicity and human toxicity through fertilizer substitution, also leads tonutrient enrichment as neutralization of emissions from N loss (27.6 PE) and substitution (-12.8 PE). Acombined digestion and composting technology lessens the effects of acidification (-12.2 PE), nutrientenrichment (-5.7 PE), and global warming (-7.9 PE) mainly because energy is recovered efficiently, whichdecreases emissions including SO2, Hg, NOx, and fossil CO2during normal energy production. The changeof energy mix by introducing more clean energy, which has marginal effects on the performance of com-posting strategy, results in apparently more loading to acidification and nutrient enrichment in the othertwo strategies. These are mainly because the recovered energy can avoid fewer emissions than beforedue to the lower background values in power generation. These results provide quantitative evidence fortechnical selection and pollution control in food waste management. © 2014 Elsevier Ltd. All rights reserved.

He L.,Beijing Normal University
Solid State Communications | Year: 2010

In the literature [A. Kumar, S.M. Yusuf, L. Keller, J.V. Yakhmi, Phys. Rev. Lett. 101 (2008) 207206], the ferromagnetic ordering temperature between the Cu and Fe moments in Cu0.73Mn0.77[Fe(CN)6]{dot operator}zH2O was assumed to be 17.9 K, and the antiferromagnetic ordering temperature of the Mn moments with respect to the Cu and Fe moments in Cu0.73Mn0.77[Fe(CN)6]{dot operator}zH2O was assumed to be 13.5 K. In this paper, I give a distinct explanation about the experimental results of Cu0.73Mn0.77[Fe(CN)6]{dot operator}zH2O based on the mean field theory and propose a reasonable microscopic magnetic structure in CMF near the Curie temperature. According to my analysis, the Cu, Mn, and Fe moments become ordered at the same temperature, 17.9 K. © 2009 Elsevier Ltd. All rights reserved.

Tian G.,Beijing Normal University | Qiao Z.,Beijing Normal University | Xu X.,CAS Institute of Geographical Sciences and Natural Resources Research
Environmental Pollution | Year: 2014

Atmospheric pollution has become a significant challenge in Beijing metropolitan region, China. In this study, wavelet analysis and gray analysis were proposed to explore the temporal characteristics of particulate matter (PM10) and its relationships with meteorological factors during 2001-2012. The analysis indicated that air quality had got better significantly over the last decade. It was clearly interannual, seasonal, and monthly variation of atmospheric pollution, which represented that the air quality was the worst in spring, and got better in summer, subsequently tended to be more serious in autumn and winter. Generally atmospheric pressure was the most important meteorological feature influencing on PM10, followed by relative humidity and wind speed. However, the dominant meteorological factors influencing the atmospheric pollution were different in the four seasons. The results suggest that urban design and effective measures based on the relationship between meteorological factors and PM10 would be effective for improving atmospheric pollution. © 2014 Elsevier Ltd. All rights reserved.

Qin R.,Henan Normal University | Bo Z.,Beijing Normal University
Macromolecular Rapid Communications | Year: 2012

A set of monodisperse 2,7-linked carbazole oligomers (3-mer, 5-mer, 7-mer, and 9-mer) was synthesized, and their photophysical, electrochemical, and thermal properties were investigated. In solutions, these oligomers exhibited bright blue emission with almost quantitative fluorescence quantum yield. The emission spectra of these oligomers in films are quite different. 3-Mer and 5-mer exhibited featureless emission spectra, whereas 7-mer and 9-mer showed well-resolved emission spectra. Four monodisperse 2,7-linked carbazole oligomers are synthesized by modular chemistry, and their photophysical, electrochemical, and thermal properties are investigated. These oligomers in solutions exhibit blue emissions with high quantum efficiency. The onset oxidation potential slightly hoists and the HOMO level becomes lower when the conjugation length increases. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wu Z.,Beijing Normal University | Hu T.,Beijing Normal University | He L.,National Institutes for Food and Drug Control of China | Gong B.,State University of New York at Buffalo
Organic Letters | Year: 2012

Treating derivatives of m-phenylenediamine having different electron-richness and reactivities with triphosgene in the presence of triethylamine led to aromatic tetraurea macrocycles in high yields. Factors important for efficiently forming these macrocycles include the molar ratio (2:1) between the diamine and triphosgene, reaction temperature (-75 °C), and solvent (CH2Cl2). By controlling the order and rate for adding diamines, tetraurea macrocycles consisting of two different types of monomeric residues have also been obtained in high yields. © 2012 American Chemical Society.

Zhang L.,Beijing Normal University | Wang P.,Beijing Normal University
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2012

The traditional detection methods for these regions of interest in high resolution remote sensing image generally search the whole image on the basis of prior knowledge, which leads to high computational complexity. A new fast detection algorithm based on human visual characteristic for these regions of interest in high resolution remote sensing image is proposed. The new algorithm based on visual attention model applies spatial dimension reduction strategy to confirm these focuses of visual attention. According to the positions of focuses of visual attention, the new algorithm describes these relevant regions of interest in the original remote sensing image. The experimental results show that the new algorithm could not only have the lower computational complexity, but also avoid image segmentation and feature detection for the whole image and improve the detection efficiency of regions of interest in high resolution remote sensing image.

Zhang L.,Beijing Normal University
Zhongguo Jiguang/Chinese Journal of Lasers | Year: 2012

The traditional visual attention model for the detection of visual saliency regions in the remote sensing image can lead to high computational complexity and low precision of detection. A new fast detection algorithm of visual saliency regions is proposed. The new algorithm firstly decreases the spatial resolution by integer wavelet transform, which can reduce the computational complexity of detection of the visual focus of attention. Then, the new algorithm proposes the two-dimensional discrete moment transform for visual feature fusion, which can generate the saliency map of the remote sensing image which has more abundant information of edge and texture. Finally, the region growing strategy based on the visual focus of attention is proposed in the saliency map analysis to acquire the precise contours of the visual saliency regions. The experimental results show that the new algorithm can not only effectively reduce the computational complexity of the detection of visual saliency regions in the remote sensing image, but also be able to accurately describe the contour information of visual saliency regions. In addition, it can avoid image segmentation and feature extraction for the whole image. The new algorithm provides a certain reference for the target detection of the remote sensing image in the future.

Tian G.,Beijing Normal University | Qiao Z.,Beijing Normal University
Environmental Pollution | Year: 2014

Urban development affects the material circulation and energy flow of ecosystems, thereby affecting the Net Primary Productivity (NPP). The loss of NPP due to urban expansion was calculated integrating GLO-PEM with remote sensing and GIS techniques in China during the period of 1989-2000. Using urban expansion and the mean NPP for the different land use types in the fourteen regions, the total loss of NPP was calculated as 0.95 Tg C, which accounted for 0.03% of the national NPP of 1989. The total loss of NPP due to the transformation from cropland to urban land accounted for 91.93%, followed by forest (7.17%) and grassland (0.69%). However, the conversion from unused land, industrial and construction land, and water bodies to urban land resulted in an increase in the NPP. The regions locating in eastern China and middle China had large reductions in the total NPP due to urban expansion. © 2013 Elsevier Ltd. All rights reserved.

Wang Z.,Beijing Normal University | Wang C.,Beijing Normal University | Pei Y.,Beijing Normal University
Bioresource Technology | Year: 2013

In this study, the effect of drinking water treatment residuals (WTRs), non-hazardous byproducts from drinking water treatment plants, on anaerobic ammonium oxidation (anammox) in lake sediments were investigated, qualitatively and quantitatively based on enrichment tests. The results suggested that after the enrichment, anammox were strengthened significantly in enriched sediments with no WTRs (ESNW) and with WTRs (ESW). Comparatively, anammox bacteria in ESW were more aggregated than ESNW. The activity (9.2nmolg-1h-1) and abundance (9.8×107copiesg-1) of anammox bacteria in ESW were also higher than ESNW (6.1nmolg-1h-1and 8.9×107copiesg-1). Further analysis suggested that after enrichment, anammox bacteria in sediments were phylogenetically more distant from Candidatus Kuenenia; anammox bacteria in ESW were closely related to Candidatus Brocadia. Overall, WTRs promoted aggregation, strengthened activity and increased abundance of anammox bacteria in lake sediments. Therefore, WTRs can enhance anammox in lake sediments. © 2013 Elsevier Ltd.

Quan X.-C.,Beijing Normal University | Quan Y.-P.,Beijing Normal University | Tao K.,Beijing Normal University | Jiang X.-M.,Beijing Normal University
Bioresource Technology | Year: 2013

This study compared the difference in microbial community and power generation capacity of air-cathode MFCs enriched under anode aerobic and anaerobic conditions. Results showed that MFCs successfully started with continuous air inputting to anode chamber. The aerobic enriched MFC produced comparable and even more electricity with the fuels of acetate, glucose and ethanol compared to the anaerobic MFC when returning to anaerobic condition. The two MFCs showed a slightly different microbial community for anode biofilms (a similarity of 77%), but a highly similar microbial community (a similarity of 97%) for anolyte microbes. The anode biofilm of aerobic enriched MFC showed the presence of some specific bacteria closely related to Clostridium sticklandii, Leucobacter komagatae and Microbacterium laevaniformans. The anaerobic enriched MFC found the presence of a large number of yeast Trichosporon sp. This research demonstrates that it is possible to enrich oxygen-tolerant anode respiring bacteria through purposely aeration in anode chamber. © 2012 Elsevier Ltd.

Reich P.B.,University of Minnesota | Reich P.B.,University of Western Sydney | Rich R.L.,University of Minnesota | Lu X.,Beijing Normal University | And 3 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2014

Leaf life span is an important plant trait associated with interspecific variation in leaf, organismal, and ecosystem processes. We hypothesized that intraspecific variation in gymnosperm needle traits with latitude reflects both selection and acclimation for traits adaptive to the associated temperature and moisture gradient. This hypothesis was supported, because across 127 sites along a 2,160-km gradient in North America individuals of Picea glauca, Picea mariana, Pinus banksiana, and Abies balsamea had longer needle life span and lower tissue nitrogen concentration with decreasing mean annual temperature. Similar patterns were noted for Pinus sylvestris across a north-south gradient in Europe. These differences highlight needle longevity as an adaptive feature important to ecological success of boreal conifers across broad climatic ranges. Additionally, differences in leaf life span directly affect annual foliage turnover rate, which along with needle physiology partially regulates carbon cycling through effects on gross primary production and net canopy carbon export. However, most, if not all, global land surface models parameterize needle longevity of boreal evergreen forests as if it were a constant. We incorporated temperature-dependent needle longevity and %nitrogen, and biomass allocation, into a land surface model, Community Atmosphere Biosphere Land Exchange, to assess their impacts on carbon cycling processes. Incorporating realistic parameterization of these variables improved predictions of canopy leaf area index and gross primary production compared with observations from flux sites. Finally, increasingly low foliage turnover and biomass fraction toward the cold far north indicate that a surprisingly small fraction of new biomass is allocated to foliage under such conditions. © 2014 PNAS.

Zhang J.-Z.,Beijing Normal University
Journal of Applied Physics | Year: 2014

Energy relaxation of the hot electrons in Si-doped bulk GaN is studied theoretically, taking into account non-equilibrium polar optical phonons, electron degeneracy, and screening from the mobile electrons. The electron power dissipation and energy relaxation time are calculated as functions of the electron temperature Te, the hot-phonon effect (HPE) is examined by varying the optical phonon lifetime values, and the results are compared with previous calculations for typical GaN-based heterostructures. Particular attention is paid to the distinct temperature Te dependences of the power loss and the energy relaxation time τE at the low and high electron temperatures. At low electron temperatures (Te<500 K), the exponential rise of phonon generation number, fast weakened screening and HPE result in a rapid increase of power loss and sharp drop of relaxation time with Te. At high electron temperatures (Te>1500 K), the power loss increases slowly with Te due to the decrease in phonon generation rate, and the temperature-dependence of the energy relaxation time depends on the polar optical phonon lifetime - saturation in energy relaxation occurs when the phonon lifetime increases or varies little with Te. Our calculated temperature dependences of the energy relaxation time are in good agreement with experimental findings [Liberis et al., Appl. Phys. Lett. 89, 202117 (2006); Matulionis et al., Phys. Status Solidi C 2, 2585 (2005)]. With no HPE, the electron energy relaxation is much faster in bulk GaN (τE∼several tens femtoseconds) than in the GaN-based heterostructures. However, stronger hot-phonon re-absorption occurs in bulk GaN due to rapid polar-optical phonon emission compared to phonon decay. Therefore, including HPE yields very close power loss and energy relaxation times in bulk and heterostructures with similar densities of electrons (τE∼ several tenths of a picosecond). Transparent expressions for energy relaxation are obtained in the Boltzmann approximation, which are very useful for resolving the temperature dependences of the energy relaxation in the low- and high-Te regions. © 2014 AIP Publishing LLC.

Wang S.,Beijing Normal University | Jiang B.W.,Beijing Normal University
Astrophysical Journal Letters | Year: 2014

Whether the near-infrared (NIR) extinction law is universal has long been a debated topic. Based on the APOGEE H-band spectroscopic survey, a key project of SDSS-III, the intrinsic colors of a large number of giant stars are accurately determined from the stellar effective temperature. Taking advantage of this and using a sample of 5942 K-type giants, the NIR extinction law is carefully revisited. The color excess ratio E(J-H)/E(J-K S), representative of the NIR extinction law, shows no dependence on the color excess when E(J-K S) changes from 0.3 to 4.0, which implies a universal NIR extinction law from diffuse to dense regions. The constant value of E(J-H)/E(J-K S), 0.64, corresponds to a power law index of 1.95. The other two ratios, E(H-K S)/E(J-K S) and E(J-H)/E(H-K S), are 0.36 and 1.78, respectively. The results are consistent with the MRN dust size distribution. © 2014. The American Astronomical Society. All rights reserved..

Yoo H.,University of Maryland University College | Li Z.,University of Maryland University College | Li Z.,Beijing Normal University
Climate Dynamics | Year: 2012

Knowledge of cloud properties and their vertical structure is important for meteorological studies due to their impact on both the Earth's radiation budget and adiabatic heating within the atmosphere. The objective of this study is to evaluate bulk cloud properties and vertical distribution simulated by the US National Oceanic and Atmospheric Administration National Centers for Environmental Prediction Global Forecast System (GFS) using three global satellite products. Cloud variables evaluated include the occurrence and fraction of clouds in up to three layers, cloud optical depth, liquid water path, and ice water path. Cloud vertical structure data are retrieved from both active (CloudSat/CALIPSO) and passive sensors and are subsequently compared with GFS model results. In general, the GFS model captures the spatial patterns of hydrometeors reasonably well and follows the general features seen in satellite measurements, but large discrepancies exist in low-level cloud properties. More boundary layer clouds over the interior continents were generated by the GFS model whereas satellite retrievals showed more low-level clouds over oceans. Although the frequencies of global multi-layer clouds from observations are similar to those from the model, latitudinal variations show discrepancies in terms of structure and pattern. The modeled cloud optical depth over storm track region and subtropical region is less than that from the passive sensor and is overestimated for deep convective clouds. The distributions of ice water path (IWP) agree better with satellite observations than do liquid water path (LWP) distributions. Discrepancies in LWP/IWP distributions between observations and the model are attributed to differences in cloud water mixing ratio and mean relative humidity fields, which are major control variables determining the formation of clouds. © 2012 Springer-Verlag.

Wang K.C.,Beijing Normal University | Dickinson R.E.,University of Texas at Austin | Wild M.,ETH Zurich | Liang S.,University of Maryland University College
Atmospheric Chemistry and Physics | Year: 2012

The Earth's climate is driven by surface incident solar radiation (R s). Direct measurements have shown that R s has undergone significant decadal variations. However, a large fraction of the global land surface is not covered by these observations. Satellite-derived R s has a good global coverage but is of low accuracy in its depiction of decadal variability. This paper shows that daily to decadal variations of R s, from both aerosols and cloud properties, can be accurately estimated using globally available measurements of Sunshine Duration (SunDu). In particular, SunDu shows that since the late 1980's R s has brightened over Europe due to decreases in aerosols but dimmed over China due to their increases. We found that variation of cloud cover determines R s at a monthly scale but that aerosols determine the variability of R s at a decadal time scale, in particular, over Europe and China. Because of its global availability and long-term history, SunDu can provide an accurate and continuous proxy record of R s, filling in values for the blank areas that are not covered by direct measurements. Compared to its direct measurement, R s from SunDu appears to be less sensitive to instrument replacement and calibration, and shows that the widely reported sharp increase in R s during the early 1990s in China was a result of instrument replacement. By merging direct measurements collected by Global Energy Budget Archive with those derived from SunDu, we obtained a good coverage of R s over the Northern Hemisphere. From this data, the average increase of R s from 1982 to 2008 is estimated to be 0.87 W mg-2 per decade. © 2012 Author(s).

Wang K.C.,Beijing Normal University | Dickinson R.E.,University of Texas at Austin | Su L.,Beijing City University | Trenberth K.E.,U.S. National Center for Atmospheric Research
Atmospheric Chemistry and Physics | Year: 2012

Atmospheric aerosols affect both human health and climate. PMX is the mass concentration of aerosol particles that have aerodynamic diameters less than X 1/4m, PM10 was initially selected to measure the environmental impact of aerosols. Recently, it was realized that fine particles are more hazardous than larger ones and should be measured. Consequently, observational data for PM2.5 have been obtained but only for a much shorter period than that of PM10. Optical extinction of aerosols, the inverse of meteorological visibility, is sensitive to particles less than 1.0 1/4m. These fine particles only account for a small part of total mass of aerosols although they are very efficient in light extinction. Comparisons are made between PM10 and PM2.5 over the period when the latter is available and with visibility data for a longer period. PM10 has decreased by 44% in Europe from 1992 to 2009, 33% in the US from 1993 to 2010, 10% in Canada from 1994 to 2009, and 26% in China from 2000 to 2011. However, in contrast, aerosol optical extinction has increased 7% in the US, 10% in Canada, and 18% in China during the above study periods. The reduction of optical extinction over Europe of 5% is also much less than the 44% reduction in PM10. Over its short period of record PM2.5 descreased less than PM10. Hence, PM10 is neither a good measure of changes in smaller particles nor of their long-term trends, a result that has important implications for both climate impact and human health effects. The increased fraction of anthropogenic aerosol emission, such as from vehicle exhaust, to total atmospheric aerosols partly explains this contrasting trend of optical and mass properties of aerosols.

Niu F.,Beijing Normal University | Niu F.,The Interdisciplinary Center | Li Z.,Beijing Normal University | Li Z.,The Interdisciplinary Center
Atmospheric Chemistry and Physics | Year: 2012

Aerosols may modify cloud properties and precipitation via a variety of mechanisms with varying and contradicting consequences. Using a large ensemble of satellite data acquired by the Moderate Resolution Imaging Spectroradiometer onboard the Earth Observing System's Aqua platform, the CloudSat cloud profiling radar and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite over the tropical oceans, we identified two distinct correlations of clouds and precipitation with aerosol loading. Cloud-top temperatures are significantly negatively correlated with increasing aerosol index (AI) over oceans and aerosol optical depth (AOT) over land for deep mixed-phase clouds with liquid droplets near the warm bases and ice crystals near the cold tops; no significant changes were found for uniformly liquid clouds. Precipitation rates are positively correlated with the AI for mixed-phase clouds, but negatively correlated for liquid clouds. These distinct correlations might be a manifestation of two potential mechanisms: the invigoration effect (which enhances convection and precipitation) and the microphysical effect (which suppresses precipitation). We note that the highly limited information garnered from satellite products cannot unequivocally support the causal relationships between cloud-top temperature/precipitation rate and aerosol loading. But if aerosols are indeed the causes for the observed relationships, they may change the overall distribution of precipitation, leading to a more extreme and unfavorable rainfall pattern of suppressing light rains and fostering heavy rains. © 2012 Author(s).

Wang K.,Beijing Normal University | Dickinson R.E.,University of Texas at Austin | Liang S.,University of Maryland University College
Journal of Climate | Year: 2012

Pan evaporation (EP), an index of atmospheric evaporative demand, has been widely reported to have weakened in the past decades. However, its interpretation remains controversial because EP observations are not globally available and observations of one of its key controls, surface incident solar radiation Rs, are even less available. Using global-distributed Rs from both direct measurements (available through the Global Energy Balance Archive) and derived from sunshine duration, the authors calculated the potential evaporation from 1982 to 2008 from approximately 1300 stations. The findings herein show that the contribution of water vapor pressure deficit (VPD) to monthly variability of EP is much larger than that of other controlling factors, of Rs, wind speed (WS), and air temperature Ta. The trend of the aerodynamic component of EP, which includes contributions of VPD, WS, and Taa, accounted for 86% of the long-term trend of EP. The aerodynamic component was then calculated from 4250 globally distributed stations and showed a negligible averaged trend from 1973 to 2008 because the reduction in WS canceled out the impact of the elevated VPD. The long-term trend of WS dominates the long-term trend of the aerodynamic component of EP at the 4250 stations. Atmospheric evaporative demand increased in most arid and semiarid areas, indicating a decrease in water availability in those areas. © 2012 American Meteorological Society.

Wang K.,Beijing Normal University | Augustine J.,National Oceanic and Atmospheric Administration | Dickinson R.E.,University of Texas at Austin
Journal of Geophysical Research: Atmospheres | Year: 2012

Surface incident solar radiation (Rs) drives weather and climate changes. Observations of Rs have been widely used as reference data to evaluate climate model simulations and satellite retrievals. However, few have studied uncertainties of Rs observations, especially long term. This paper compares Rs from 1995 to 2011 at collocated sites collected by the Surface Radiation Budget Network (SURFRAD), the U.S. Climate Reference Network (USCRN) and the AmeriFlux network. SURFRAD stations have measured separately the diffuse and direct components of Rs as well as Rs by a pyranometer, while Rs was measured by a pyranometer or a net radiometer at the USCRN and AmeriFlux sites. Rs can be calculated by summing the diffuse and direction radiation measurements. Rs measured by the summation technique was compared those measured by a pyranometer or a net radiometer at collocated sites. Agreement among these four independent Rs measurements is good with correlation coefficients higher than 0.98 and an average error (one standard deviation) of about 4% at both hourly and monthly time scales. Rs has a large spatial variability at the hourly time scale, even exceeding 100Wm-2 in ∼6km. This spatial variability is substantially reduced at the monthly time scale. The two independent measurement systems at the SURFRAD sites agree rather well in annual variability of Rs with an average relative standard deviation error of 34%. The errors are 71% and 85% for the USCRN and AmeriFlux sites. Evidently, caution should be taken when using the Rs data collected at the USCRN and AmeriFlux sites to study annual variability of Rs. © 2012. American Geophysical Union. All Rights Reserved.

Ma C.,Beijing Normal University | Zhang T.-J.,Beijing Normal University | Zhang T.-J.,Peking University
Astrophysical Journal | Year: 2011

We use simulated Hubble parameter data in the redshift range 0 ≤ z ≤ 2 to explore the role and power of observational H(z) data in constraining cosmological parameters of the ΛCDM model. The error model of the simulated data is empirically constructed from available measurements and scales linearly as z increases. By comparing the median figures of merit calculated from simulated data sets with that of current Type Ia supernova (SNIa) data, we find that as many as 64 further independent measurements of H(z) are needed to match the parameter constraining power of SNIa. If the error of H(z) could be lowered to 3%, the same number of future measurements would be needed, but then the redshift coverage would only be required to reach z = 1. We also show that accurate measurements of the Hubble constant H 0 can be used as priors to increase the H(z) data's figure of merit. © 2011. The American Astronomical Society. All rights reserved.

Gai N.,Beijing Normal University | Gai N.,Yale University | Basu S.,Yale University | Chaplin W.J.,University of Birmingham | Elsworth Y.,University of Birmingham
Astrophysical Journal | Year: 2011

NASA's Kepler mission is providing basic asteroseismic data for hundreds of stars. One of the more common ways of determining stellar characteristics from these data is by the so-called grid-based modeling. We have made a detailed study of grid-based analysis techniques to study the errors (and error correlations) involved. As had been reported earlier, we find that it is relatively easy to get very precise values of stellar radii using grid-based techniques. However, we find that there are small, but significant, biases that can result because of the grid of models used. The biases can be minimized if metallicity is known. Masses cannot be determined as precisely as the radii and suffer from larger systematic effects. We also find that the errors in mass and radius are correlated. A positive consequence of this correlation is that log g can be determined both precisely and accurately with almost no systematic biases. Radii and log g can be determined with almost no model dependence to within 5% for realistic estimates of errors in asteroseismic and conventional observations. Errors in mass can be somewhat higher unless accurate metallicity estimates are available. Age estimates of individual stars are the most model dependent. The errors are larger, too. However, we find that for star clusters, it is possible to get a relatively precise age if one assumes that all stars in a given cluster have the same age. © 2011. The American Astronomical Society. All rights reserved.

Singh R.B.,University of Delhi | Shi C.,Beijing Normal University
Advances in Meteorology | Year: 2014

Global land use and land cover pattern has greatly changed in the past 50 years, which exerts direct or indirect influence on the climate change remarkably at both regional and global scales. Therefore, observing and estimating the land use impacts on surface climate is essential and has been continuously promoted by researchers. This paper explores the advancement in the models, data, and application for observing and estimating the land use impacts on surface climate and points out further research needs and priorities, which hopefully will provide some references for related studies. © 2014 R. B. Singh and Chenchen Shi.

He L.,Beijing Normal University
Solid State Communications | Year: 2010

Analysis of available experimental data reveals that monodisperse Mn3O4 nanoparticles show anomalous size dependent blocking temperature. This work presents a simple analysis which provides insight into the nature of this anomaly. My analysis pointed out that the magnetic anisotropy Kmag follows the power law Kmag ∼ D- 3 in all Mn3O4 nanoparticles (D is the average diameter of particles). The influences of the size dependent magnetic anisotropy of Mn3O4 nanoparticles on the size dependent blocking temperature, the coercivity of Mn3O4 nanoparticles, and also the magnetic properties of core-shell MnO/Mn3O4 nanoparticles were analyzed. © 2010 Elsevier Ltd. All rights reserved.

Yuan Z.,CAS Institute of Physics | Wang S.,CAS Institute of Physics | Xia K.,Beijing Normal University
Solid State Communications | Year: 2010

We studied the spin-transfer torques acting on magnetic domain walls in the presence of a nonequilibrium thermal distribution using a generalized Landauer-Büttiker formalism, where the energy flow is described on the same footing as the electric current. First-principles transport calculations have been performed in Ni and Co domain walls as typical examples. The temperature difference between two sides of the domain wall can induce remarkable spin- transfer torques, which are comparable with the current-induced torques required for the domain wall motion. © 2009 Elsevier Ltd. All rights reserved.

Zhang F.,Beijing Normal University | Zhang S.,Beijing Normal University | Duan X.-F.,Beijing Normal University
Organic Letters | Year: 2012

The unprecedented substitution of a nitro group with aryl or alkenyl groups of Grignard reagents affords 2-aryl or alkenylpyridine N-oxides in modest to high yields with high chemoselectivity. This protocol allows a simple and clean synthesis of various 2-substituted pyridine N-oxides and the corresponding pyridine derivatives. Furthermore, straightforward one-pot iterative functionality of pyridine N-oxides could also be achieved simply by successive applications of two Grignard reagents. © 2012 American Chemical Society.

Zhang D.,Fudan University | Zi G.,Beijing Normal University
Chemical Society Reviews | Year: 2015

Since the discovery of a stable N-heterocyclic carbene (NHC), the use of NHCs in chemistry has developed rapidly over the past two decades. These interesting compounds are predominantly employed in organometallic chemistry as ligands for various metal centers, and as organocatalysts for a variety of transformations. In particular, the NHC transition metal complexes have received widespread attention, and significant progress has been made in the development of group 4 NHC-complexes in the last few years. These group 4 NHC-complexes are of interest because of their unique structural properties, and their potential application in organic transformations and catalysis. This review covers the superior design strategies for NHC ligands to stabilize early transition metals and well-defined group 4 metal complexes with mono- and multi-dentate NHC ligands. In this context, four types of NHC-complexes, i.e., carbon-functionalized NHCs, nitrogen-functionalized NHCs, oxygen-functionalized NHCs and nitrogen/oxygen-functionalized unsymmetric NHCs, are described. In addition, the use of group 4 NHC-complexes as catalysts in olefin (co)polymerization, ring-opening polymerization of rac-lactide, copolymerization of epoxides and CO2, as well as hydroamination/cyclization of aminoalkenes, is presented. Furthermore, limitations and challenges are discussed. This journal is © The Royal Society of Chemistry.

Zi G.,Beijing Normal University | Zhang F.,Beijing Normal University | Song H.,Nankai University
Chemical Communications | Year: 2010

A highly enantioselective group 5 metal amide catalyst system is reported for the hydroaminoalkylation of secondary amines to give chiral amines in good yields with excellent ee values (up to 93%) by loading of 5% precatalyst. © 2010 The Royal Society of Chemistry.

Yan D.,Beijing Normal University | Yan D.,Beijing University of Chemical Technology
Chemistry - A European Journal | Year: 2015

Molecule-based micro-/nanomaterials have attracted considerable attention because their properties can vary greatly from the corresponding macro-sized bulk systems. Recently, the construction of multicomponent molecular solids based on crystal engineering principles has emerged as a promising alternative way to develop micro-/nanomaterials. Unlike single-component materials, the resulting multicomponent systems offer the advantages of tunable composition, and adjustable molecular arrangement, and intermolecular interactions within their solid states. The study of these materials also supplies insight into how the crystal structure, molecular components, and micro-/nanoscale effects can influence the performance of molecular materials. In this review, we describe recent advances and current directions in the assembly and applications of crystalline multicomponent micro-/nanostructures. Firstly, the design strategies for multicomponent systems based on molecular recognition and crystal engineering principles are introduced. Attention is then focused on the methods of fabrication of low-dimensional multicomponent micro-/nanostructures. Their new applications are also outlined. Finally, we briefly discuss perspectives for the further development of these molecular crystalline micro-/nanomaterials. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

Wang N.,University of Florida | Wang N.,Beijing Normal University | Braun E.L.,University of Florida | Kimball R.T.,University of Florida
Molecular Biology and Evolution | Year: 2012

Although many phylogenetic studies have focused on developing hypotheses about relationships, advances in data collection and computation have increased the feasibility of collecting large independent data sets to rigorously test controversial hypotheses or carefully assess artifacts that may be misleading. One such relationship in need of independent evaluation is the position of Passeriformes (perching birds) in avian phylogeny. This order comprises more than half of all extant birds, and it includes one of the most important avian model systems (the zebra finch). Recent large-scale studies using morphology, mitochondrial, and nuclear sequence data have generated very different hypotheses about the sister group of Passeriformes, and all conflict with an older hypothesis generated using DNA-DNA hybridization. We used novel data from 30 nuclear loci, primarily introns, for 28 taxa to evaluate five major a priori hypotheses regarding the phylogenetic position of Passeriformes. Although previous studies have suggested that nuclear introns are ideal for the resolution of ancient avian relationships, introns have also been criticized because of the potential for alignment ambiguities and the loss of signal due to saturation. To examine these issues, we generated multiple alignments using several alignment programs, varying alignment parameters, and using guide trees that reflected the different a priori hypotheses. Although different alignments and analyses yielded slightly different results, our analyses excluded all but one of the five a priori hypotheses. In many cases, the passerines were sister to the Psittaciformes (parrots), and taxa were members of a larger clade that includes Falconidae (falcons) and Cariamidae (seriemas). However, the position of Coliiformes (mousebirds) was highly unstable in our analyses of 30 loci, and this represented the primary source of incongruence among analyses. Mousebirds were united with passerines or parrots in some analyses, suggesting an additional hypothesis that needs to be considered in future studies. There was no clear evidence that base-compositional convergence, saturation, or long-branch attraction affected our conclusions. These results provide independent evidence excluding four major hypotheses about the position of passerines, allowing the extensive studies on this group to be placed in a more rigorous evolutionary framework. © The Author 2011. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved.

Yue L.,Beijing Normal University | Liu Y.-J.,Beijing Normal University
Journal of Chemical Theory and Computation | Year: 2013

The chemiluminescence phenomenon of 3-(2′-spiroadamantyl)-4-methoxy- 4-(3″-phosphoryloxy)-phenyl-1,2-dioxetane (AMPPD or m-AMPPD) has been routinely applied in clinical diagnostics. Although the AMPDD chemiluminescence immunoassay is one of the most successful immunoassays, the mechanism of AMPPD chemiluminescence remains largely unknown. The AMPPD chemiluminescence process is composed of three steps: AMPPD is enzymatically triggered to produce 3-(2′-spiroadamantyl)-4-methoxy-4-(3″-hydroxyphenyl)-1,2-dioxetane (m-AMPD); m-AMPD decomposes into the excited-state methyl m-oxybenzoate anion (m-MOB-); the excited-state m-MOB- relaxes to its ground state and emits light. Obviously, the middle step is critical for the chemiluminescence and has not been well understood because of both experimental and theoretical difficulties. We performed the first theoretical study on the chemiluminescent decomposition mechanism of m-AMPD and its para isomer, p-AMPD, using the complete active space self-consistent field and the second-order multiconfigurational perturbation methods in addition to the density functional method. This investigation revealed that (1) neither the intramolecular chemical initiated electron exchange luminescence (CIEEL) nor the concerted charge transfer (CT) mechanism can describe the decomposition of m- and p-AMPD well. Instead, their decomposition occurs according to our previously proposed mechanism of gradually reversible CT-initiated luminescence. (2) The different stabilities of the m- and p-AMPD chemiexcited states might be the basis for the large difference in their chemiluminescence efficiencies. (3) The relationship between the chemiluminescence efficiency and the position of the electron donor on the aromatic ring, the so-called "odd/even selection rule," does not fully explain the chemiluminescence efficiency of dioxetanes. The odd/even selection rule is only correct for partial dioxetanes, because it does not capture the origin of the relationship between the chemiluminescence and the donor. We revealed that the origin consists of a combination of conjugation, induction, and steric effects. On the basis of this combination of effects, we theoretically designed some 1,2-dioxetanes to guide experimentalists in the synthesis of these excellent chemiluminescent molecules. © 2013 American Chemical Society.

Liu H.-C.,Beijing Normal University | Liu H.-C.,Hong Kong University of Science and Technology | Xiong J.,Beijing Normal University
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2013

We discuss theoretically the visibility and contrast-to-noise ratio (CNR) of high-order thermal ghost imaging with natural light. Five cases of an object beam and a reference beam with different polarized light are analyzed. Theoretical calculations show that a higher-order N can optimize the ghost imaging in both visibility and CNR in all five cases. © 2013 Optical Society of America.

Wen M.,University of Utah | Lin D.,Beijing Normal University
Child Development | Year: 2012

Using recent cross-sectional data of rural children aged from 8 to 18 in Hunan Province of China, this article examines psychological, behavioral, and educational outcomes and the psychosocial contexts of these outcomes among children left behind by one or both of their rural-to-urban migrant parents compared to those living in nonmigrant families. The results showed that left-behind children were disadvantaged in health behavior and school engagement but not in perceived satisfaction. The child's psychosocial environment, captured by family socioeconomic status, socializing processes, peer and school support, and psychological traits, were associated with, to varying extent, child developmental outcomes in rural China. These influences largely remain constant for the sampled children regardless of their parents' migrant status. © 2011 The Authors. Child Development © 2011 Society for Research in Child Development, Inc.

Yu M.,Tsinghua University | Wang A.,Beijing Normal University | Wang Y.,Beijing Normal University | Li C.,Tsinghua University | Shi G.,Tsinghua University
Nanoscale | Year: 2014

Atomic layer deposition (ALD) was applied to deposit ZnO on graphene aerogel, and this composite was used as an anode material for lithium ion batteries. This electrode material was further modified by an ultrathin Al2O3layer via ALD to stabilize its electrochemical stability. These two metal oxides were uniformly immobilized on graphene frameworks, and the Al2O3coating strongly improved the electrochemical performances of ZnO-graphene aerogel composite anodes. Particularly, the composite with 10 ALD cycles of Al2O3coating (denoted as ZnO-G-10) exhibited a high initial discharge capacity of 1513 mA h g-1and maintained a reversible capacity of 490 mA h g-1after 100 cycles at a current density of 100 mA g-1. Furthermore, the capacity retention rate increased from 70% to 90% in comparison with its uncoated counterpart after 100 cycles. The ZnO-G-10 anode also showed good rate-capability, delivering a discharge capacity of 415 mA h g-1at 1000 mA g-1. The improved electrochemical performance is attributed to the formation of an artificial solid electrolyte interphase layer, stabilizing ZnO and the electrolyte by preventing the aggregation of Zn/ZnO nanograins and the side reaction that would cause the degradation of anodes. This journal is © the Partner Organisations 2014.

Chen S.,Beijing Normal University | Chen B.,Beijing Normal University
Bioresource Technology | Year: 2013

Wastewater treatment systems are increasingly designed for the recovery of valuable chemicals and energy in addition to waste stream disposal. Herein, the life-cycle energy production and emissions mitigation of a typical domestic wastewater treatment system were assessed, in which different combinations of biogas use and sludge processing lines for industrial or household applications were considered. The results suggested that the reuse of biogas and sludge was so important in the system's overall energy balance and environmental performance that it may offset the cost in the plant's installation and operation. Combined heat and power and household utilization were two prior options for net energy production, provided an ideal power conversion efficiency and biogas production. The joint application of household biogas use and sludge nutrient processing achieved both high net energy production and significant environmental remediation across all impact categories, representing the optimal tradeoff for domestic wastewater treatment. © 2013 Elsevier Ltd.

Wu L.-X.,Beijing Normal University | Wu L.-X.,China University of Mining and Technology | Qin K.,China University of Mining and Technology | Liu S.-J.,Northeastern University China
Proceedings of the IEEE | Year: 2012

Although earthquakes are difficult to be predicted because of the complexity of the Earth system and the uncertainty of seismogenic processes, GEOSS provides multiple sources of observation data and brings a possibility to extract a thermal anomaly that would have a significant effect on earthquake prediction. Referring to the analysis on the lithosphere-coversphere-atmosphere (LCA) coupling due to stress enhancement in seismogenic zone, six thermal parameters, including surface latent heat flux (SLHF), thermal infrared radiation (TIR), outgoing longwave radiation (OLR), diurnal temperature range (DTR), atmospheric temperature, and skin temperature, are selected for GEOSS-based earthquake anomaly recognition (EAR). The inherent relations between the six thermal parameters are preliminarily introduced in consideration of possible LCA coupling. With overquantity, quasi-synchronism, and geo-consistency being defined as three rules for data mining, a deviation-time-space-thermal (DTS-T) EAR method as well as its procedures are developed in this paper. With 2008 M7.3 Yutian earthquake, China, 2008 M8.0 Wenchuan earthquake, China, and 2010 M7.1 Christchurch earthquake, New Zealand, being examples of tectonic earthquakes, the technical procedures of DTS-T method are demonstrated, which show that the obtained compositive thermal anomaly has a significant effect on earthquake prediction. © 2012 IEEE.

Yang W.,Beijing Normal University | Yang Z.,Beijing Normal University
Ecological Engineering | Year: 2014

Environmental flows play an important role in sustaining or enhancing the ecosystem services provided by wetlands. In this study, we quantified ecosystem services values and used the results to design an environmental flows regime for Baiyangdian Lake, the largest shallow freshwater lake in northern China. To do so, we proposed explicit tradeoffs among ecosystem services. We used emergy analysis to value the lake's ecosystem services from 1980 to 2011. We found that the regulating services contributed most to the total ecosystem services value from 1980 to 1989, followed by provisioning and cultural services; after 1990, the contribution of provisioning services became far greater than those of the other two services, followed by regulating services until 1998 and cultural services thereafter. We examined the relationships among the ecosystem services and environmental flow regimes, and found that regulating was strongly related and provisioning was moderately strongly related to all of the environmental flow components except for inflows; in contrast, cultural services were only weakly related to these components except for drought duration. Furthermore, we divided the study period's environmental flow regimes into four scenarios (high, intermediate, low, and extremely low flow regimes), which correspond to different environmental flow management strategies. Under the four scenarios, tradeoffs existed between all pairs of services. However, the intermediate flow regime provided the best overall tradeoff among the three services, and is therefore the recommended environmental flows regime. This form of analysis can therefore guide local environmental flows decisions that involve tradeoffs between different management objectives. © 2014 Elsevier B.V.

Fang D.,Beijing Normal University | Chen B.,Beijing Normal University
Applied Energy | Year: 2016

Rapid urbanization and the expansion of metropolitan areas have resulted in severe demands on water and energy resources, which threaten the sustainability of the urban economy and environment. In this paper, an input-output model and linkage analysis are used to detect the synergetic effects of water and energy consumption and interactions among economic sectors. Beijing is chosen as a case study to investigate the water-energy nexus and the water and energy importing and exporting functions of major economic sectors. The results reveal that the agriculture and food processing sectors are major virtual water suppliers, while petroleum and natural gas processing, and electricity production sectors are major embodied energy suppliers. These energy suppliers mainly import intermediate products to satisfy the final demand of Beijing, thus transferring resources pressure to other regions. With rapid urbanization, the real estate industry sector chain has become an important water-energy nexus node and resources transfer node. The real estate sector needs large amounts of virtual water and embodied energy resource inputs to continue its production and thereby promote the growth of logistical industries. The transportation sector was also found to be important energy consumer and energy transfer node. In addition, the services sector, contributing one fourth of Beijing's total GDP, is a key water-energy nexus node because it consumes considerable amounts of both virtual water and embodied energy resources to support its production pattern. © 2016.

Tian Y.,Beijing Normal University | Jim C.Y.,University of Hong Kong | Wang H.,Beijing Normal University
Landscape and Urban Planning | Year: 2014

The interrelated nature of landscape metrics calls for their joint application in analyzing complicated landscape patterns and associated ecological processes. Using geographic information system, remote-sensing and factor-analysis techniques, the landscape patterns of urban green spaces (UGS) in the compact city of Hong Kong were analyzed for their landscape-ecological quality in different land uses and districts. Using the Fragstat software, some key indices were selected to characterize the landscape mosaic with reference to patch size, patch shape, proximity relationship and edge configuration. Some old districts have smaller and more heterogeneous UGS than newer ones due to relatively low-quality landscape attributes. The landscape patterns of UGS have not improved with old-town renewal and new-town developments. In land uses with less human disturbance, UGS tend to be larger, and more homogeneous to enhance ecosystem services, and are closer to each other with more green cover to enhance connectivity and facilitate movements of organisms and people between proximal patches. Furthermore, vegetation-dominated land uses often have more complicated and hence longer UGS edges than other land uses to augment interfacial benefits. Of the 11 land uses, Government, institution and community and open space have more complicated UGS edges than more human-dominated types. The findings could inform the landscape-pattern design of UGS in compact cities to optimize their ecological qualities and benefits to both nature and residents, and to reinforce urban nature conservation. © 2013 Elsevier B.V.

Wei H.-R.,Beijing Normal University | Deng F.-G.,Beijing Normal University | Deng F.-G.,Beijing University of Posts and Telecommunications
Optics Express | Year: 2014

We present some compact quantum circuits for a deterministic quantum computing on electron-spin qubits assisted by quantum dots inside single-side optical microcavities, including the CNOT, Toffoli, and Fredkin gates. They are constructed by exploiting the giant optical Faraday rotation induced by a single-electron spin in a quantum dot inside a single-side optical microcavity as a result of cavity quantum electrodynamics. Our universal quantum gates have some advantages. First, all the gates are accomplished with a success probability of 100% in principle. Second, our schemes require no additional electron-spin qubits and they are achieved by some input-output processes of a single photon. Third, our circuits for these gates are simple and economic. Moreover, our devices for these gates work in both the weak coupling and the strong coupling regimes, and they are feasible in experiment. © 2013 Optical Society of America.

Shi W.,Beijing Normal University | Zeng W.,Beijing Normal University
Frontiers of Environmental Science and Engineering | Year: 2014

The homogeneous risk characteristics within a sub-area and the heterogeneous from one sub-area to another are unclear using existing environmental risk zoning methods. This study presents a new zoning method by determining and categorizing the risk characteristics using the k-means clustering data mining technology. The study constructs indices and develops index quantification models for environmental risk zoning by analyzing the mechanism of environmental risk occurrence. We calculate the source risk index, air risk field index, water risk field index, and target vulnerability of the study area with Nanjing Chemical Industrial Park using a 100 m × 100 m mesh grid as the basic zoning unit, and then use k-means clustering to analyze the environmental risk in the area. We obtain the optimal clustering number with the largest average silhouette coefficient by calculating the average silhouette coefficients of clustering at different k-values. The clustering result with the optimal clustering number is then used for the environmental risk zoning, and the zoning result is mapped using the geographic information system. The study area is divided into five sub-areas. The common environmental risk characteristics within the same sub-area, as well as the differences between subareas, are presented. The zoning is helpful in risk management and is convenient for decision makers to distribute limited resources to different sub-areas in the design of risk reducing intervention. © 2013, Higher Education Press and Springer-Verlag Berlin Heidelberg.

Qiao J.,Beijing Normal University
Anti-cancer agents in medicinal chemistry | Year: 2014

Tea catechins exhibit a broad range of pharmacological activities that impart beneficial effects on human health. Epigallocatechin-3-gallate (EGCG), one of the major tea catechins, has been widely associated with cancer prevention and treatment. In addition, tea catechins in combination with anticancer drugs are being evaluated as a new cancer treatment strategy. However, the interactions of anticancer drugs with tea catechins are largely unknown. Accumulated data indicate significant interactions between anticancer drugs and tea catechins, such as synergistic tumor inhibition or antagonist activity. Therefore, it is critical to understand comprehensively the effects of tea catechins on anticancer drugs. Focusing on evidence from preclinical studies, this paper will review the interactions between anticancer drugs and tea catechins, including pharmacodynamics and pharmacokinetics effects. We hope that by detailing the interactions between anticancer drugs and tea catechins, more attention will be directed to this important therapeutic combination in the future.

Wu J.,Arizona State University | Wu J.,Beijing Normal University
Landscape and Urban Planning | Year: 2014

Ecosystems and landscapes around the world have become increasingly domesticated through urbanization. Cities have been the engines of socioeconomic development but also the centers of major environmental problems since the industrial revolution. Numerous studies have shown that our urban ecosystems and landscapes are on an unsustainable trajectory. Global sustainability depends critically on cities, and urban ecology can - and needs to - play a key role in the transition toward sustainability. In this paper, I review different definitions and perspectives of urban ecology, discuss major advances and key issues, and propose a framework to help move the field forward. After almost 90 years of development, urban ecology has evolved into a truly transdisciplinary enterprise that integrates ecological, geographical, planning, and social sciences. The most salient thrust of current research activities in the field is the emerging urban sustainability paradigm which focuses on urban ecosystem services and their relations to human well-being. While urbanization is complex in many ways, we do know a lot about its patterns, processes, and effects. More specifically, we know a great deal about urban growth patterns in space and time, the underlying drivers and mechanisms, and myriad effects of urbanization on biodiversity, ecological processes, and ecosystem services. Compared to their ancient counterparts, contemporary cities tend to be bigger in physical size and ecological footprint, faster in growth rate in terms of both population and urbanized land, and more irregular in landscape composition and configuration. As coevolving human-environment systems, cities are spatially heterogeneous, complex adaptive systems. As such, the dynamic trajectory of cities can never be fully predicted or controlled, but can and should be influenced or guided in more desirable directions through planning and design activities that are based on urban ecological knowledge and sustainability principles. © 2014 Elsevier B.V.

Liu G.,Beijing Normal University | Yang Z.,Beijing Normal University | Chen B.,Beijing Normal University | Ulgiati S.,Parthenope University of Naples
Ecological Modelling | Year: 2014

As the center of human activities and social civilization, cities have developed at the cost of serious environmental degradation and huge eco-environmental pressure, which further lower human living standards and impede the sustainable development of urban ecosystems. Current urban dynamic methods have broader views and focus more on ecological aspects, e.g., the impact of emissions and resource consumption, but they lack a rigorous thermodynamic framework. Consequently, there is a need to modify existing processes and develop new technologies that minimize environmental impact while stimulating ecological flow. This paper describes the development of a forecasting model, named the emergy-based urban dynamic model, capable of accurately simulating the observed resource consumption, economic growth, and environmental impact of Beijing from 1999 to 2039. This model differs from previous urban emergy models by monitoring the negative effects to human well-being and ecosystem integrity in the developing urban system. A fresh perspective focuses on urban comprehensive performance, linking such impacts to a supply-side environmental cost evaluation (including ecological service supply, ecological and economic losses, and investment for treatment). In this introductory paper, we present the conceptual considerations of the most important components of the emergy-based urban dynamic model: the urban assets, lands, capitals, population, water resources, and economic and environmental loss. Each subsystem in this model will enrich the feedback dynamics, policy levers, and post-scenario analyses. Statistical information and calibration were also considered in this dynamic emergy accounting. The simulation revealed that water resources will be the most important limiting factor for the sustainable development of Beijing. A better approach would not be more engineering projects to deliver new supplies but to curb demand through efficiency improvements in water supply and consumption using the rule of law and economic incentives. The results of the simulation revealed that after the year 2015, many emergy indicators will collapse. The results of our study will enable urban policy planners to understand these inter-linkages by addressing specific damages to human health and the ecosystem's integrity, as well as by linking such impacts to a supply-side environmental cost evaluation. © 2013 Elsevier B.V.

Hu L.,Beijing Normal University | Jiao J.J.,University of Hong Kong
Hydrological Processes | Year: 2014

Land reclamation may have a significant influence on groundwater regimes. Analytical solutions have been developed in the past to study the impact of land reclamation on a steady-state groundwater flow and transient flow in fill materials, assuming that the reclamation site consists of a single zone of uniform hydraulic parameters. In this paper, we derive analytical solutions to describe the transient water table change in response to multi-stage land reclamation where the fill material is uniform in each stage but the hydraulic conductivity of the fill material varies from stage to stage. By introducing the method of separation of variables, we develop a transient analytical solution to study the impact of land reclamation consisting of fill material with different hydraulic properties on groundwater dynamics. The results show that the water table first increases significantly into the reclaimed zone following the fill material deposition, and then the increase gradually propagates into the original aquifer. The change of water table in the original aquifer mainly depends on the value of hydraulic conductivity of the fill materials. Examples in this paper illustrate how the aquifer system experiences a long time unsteady-state flow as a result of the reclamation, and it takes at least tens of years for the system to approach a new equilibrium. It is suggested that for a large-scale reclamation project, the response of the groundwater regime to reclamation should be carefully studied. © 2013 John Wiley & Sons, Ltd.

Guo T.,Beijing Normal University | Misra M.,Pennsylvania State University | Tam J.W.,Pennsylvania State University | Tam J.W.,Washington State University | Kroll J.F.,Pennsylvania State University
Journal of Experimental Psychology: Learning Memory and Cognition | Year: 2012

In 2 experiments, relatively proficient Chinese-English bilinguals decided whether Chinese words were the correct translations of English words. Critical trials were those on which incorrect translations were related in lexical form or meaning to the correct translation. In Experiment 1, behavioral interference was revealed for both distractor types, but event-related potentials (ERPs) revealed a different time course for the 2 conditions. Semantic distractors elicited effects primarily on the N400 and late positive component (LPC), with a smaller N400 and a smaller LPC over the posterior scalp but a larger LPC over the anterior scalp relative to unrelated controls. In contrast, translation form distractors elicited a larger P200 and a larger LPC than did unrelated controls. To determine whether the translation form effects were enabled by the relatively long, 750-ms stimulus onset asynchrony (SOA) between words, a 2nd ERP experiment was conducted using a shorter, 300-ms, SOA. The behavioral results revealed interference for both types of distractors, but the ERPs again revealed different loci for the 2 effects. Taken together, the data suggest that proficient bilinguals activate 1st-language translations of words in the 2nd language after they have accessed the meaning of those words. The implications of this pattern for claims about the nature of cross-language activation when bilinguals read in 1 or both languages are discussed. © 2012 American Psychological Association.

Li W.-J.,Beijing Normal University | Meyer R.,University of Crete | Zhang H.,University of Crete
Journal of High Energy Physics | Year: 2012

Driven by the landscape of garden-variety condensed matter systems, we have investigated how the dual spectral function behaves at the non-relativistic as well as relativistic fermionic fixed point by considering the probe Dirac fermion in an extremal charged dilatonic black hole with zero entropy. Although the pattern for both of the appearance of flat band and emergence of Fermi surface is qualitatively similar to that given by the probe fermion in the extremal Reissner-Nordstrom AdS black hole, we find a distinctly different low energy behavior around the Fermi surface, which can be traced back to the different near horizon geometry. In particular, with the peculiar near horizon geometry of our extremal charged dilatonic black hole, the low energy behavior exhibits the universal linear dispersion relation and scaling property, where the former indicates that the dual liquid is a Fermi one while the latter implies that the dual liquid is not exactly of Landau Fermi type. © SISSA 2012.

Tu Z.-C.,Beijing Normal University
Chinese Physics B | Year: 2012

This review reports several key advances on the theoretical investigations of efficiency at maximum power of heat engines in the past five years. The analytical results of efficiency at maximum power for the Curzon - Ahlborn heat engine, the stochastic heat engine constructed from a Brownian particle, and Feynman's ratchet as a heat engine are presented. It is found that: the efficiency at maximum power exhibits universal behavior at small relative temperature differences; the lower and the upper bounds might exist under quite general conditions; and the problem of efficiency at maximum power comes down to seeking for the minimum irreversible entropy production in each finite-time isothermal process for a given time. © 2012 Chinese Physical Society and IOP Publishing Ltd.

Wang H.,Beijing Normal University | Wang W.,Luoyang Normal University | Jin W.J.,Beijing Normal University
Chemical Reviews | Year: 2016

The σ-hole and π-hole are the regions with positive surface electrostatic potential on the molecule entity; the former specifically refers to the positive region of a molecular entity along extension of the Y-Ge/P/Se/X covalent σ-bond (Y = electron-rich group; Ge/P/Se/X = Groups IV-VII), while the latter refers to the positive region in the direction perpendicular to the σ-framework of the molecular entity. The directional noncovalent interactions between the σ-hole or π-hole and the negative or electron-rich sites are named σ-hole bond or π-hole bond, respectively. The contributions from electrostatic, charge transfer, and other terms or Coulombic interaction to the σ-hole bond and π-hole bond were reviewed first followed by a brief discussion on the interplay between the σ-hole bond and the π-hole bond as well as application of the two types of noncovalent interactions in the field of anion recognition. It is expected that this review could stimulate further development of the σ-hole bond and π-hole bond in theoretical exploration and practical application in the future. © 2016 American Chemical Society.

Wang C.,Beijing Normal University | Yuan N.,Beijing Normal University | Pei Y.,Beijing Normal University
Journal of Environmental Quality | Year: 2014

Drinking water treatment residuals (WTRs), by-products generated during treatment of drinking water, can be reused as environmental amendments to remediate contamination. However, this beneficial reuse may be hampered by the potential release of toxic contaminants (e.g., metals) in the WTRs. In present study, batch tests and then fractionation, in vitro digestion, and the toxicity characteristic leaching procedure were used to investigate the release and extractability of metals in the Fe/Al hydroxides comprised WTRs under differing pH. The results demonstrated that significant release from WTRs for Ba, Be, Ca, Cd, Co, Cr, Fe, Mg, Mn, Pb, Sr, and Zn occurred under low pH (acid condition); for As, Mo, and V under high pH (alkaline condition); and for Al, Cu, and Ni under both conditions. In comparison, most metals in the WTRs were more easily released under low pH, but the release was stable at a relatively low level between pH 6 and 9, especially under alkaline conditions. Further analysis indicated that the chemical extractability and bioaccessibility of many metals was found to increase in the WTRs after being leached, even though the leached WTRs could still be considered nonhazardous. These results demonstrated that pH had a substantial effect on the lability of metals in WTRs. Overall, caution should be used when considering pH conditions during WTRs reuse to avoid potential metal pollution. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Xie T.,Beijing Normal University | He Y.,Beijing Normal University
Frontiers in Psychiatry | Year: 2012

Alzheimer's disease (AD) is the most common form of dementia. As an incurable, progressive, and neurodegenerative disease, it causes cognitive and memory deficits. However, the biological mechanisms underlying the disease are not thoroughly understood. In recent years, non-invasive neuroimaging and neurophysiological techniques [e.g., structural magnetic resonance imaging (MRI), diffusion MRI, functional MRI, and EEG/MEG] and graph theory based network analysis have provided a new perspective on structural and functional connectivity patterns of the human brain (i.e., the human connectome) in health and disease. Using these powerful approaches, several recent studies of patients with AD exhibited abnormal topological organization in both global and regional properties of neuronal networks, indicating that AD not only affects specific brain regions, but also alters the structural and functional associations between distinct brain regions. Specifically, disruptive organization in the whole-brain networks in AD is involved in the loss of small-world characters and the re-organization of hub distributions. These aberrant neu-ronal connectivity patterns were associated with cognitive deficits in patients with AD, even with genetic factors in healthy aging. These studies provide empirical evidence to support the existence of an aberrant connectome of AD. In this review we will summarize recent advances discovered in large-scale brain network studies of AD, mainly focusing on graph theoretical analysis of brain connectivity abnormalities. These studies provide novel insights into the pathophysiological mechanisms of AD and could be helpful in developing imaging biomarkers for disease diagnosis and monitoring. © 2012 Xie and He.

Sun P.C.,Beijing Normal University | Wu Y.L.,Beijing Normal University | Gao J.W.,South China Normal University | Cheng G.A.,Beijing Normal University | And 2 more authors.
Advanced Materials | Year: 2013

A large contrast in the electrical and thermal conductivities via a first order phase transition in surface-functionalized carbon nanotube(CNT)/hexadecane composites is reported. Surface modification of the CNTs improves the electrical conductivity contrast and the stability of the composites. We demonstrate that, with these composites, the electrical conductivity changes above 105 times and the thermal conductivity varies up to 3 times at 18 °C. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yang W.,Beijing Normal University | Chen X.,Beijing Normal University
Physical Chemistry Chemical Physics | Year: 2014

A combined approach of the multiconfigurational perturbation theory with the Rice-Ramsperger-Kassel-Marcus methodology has been employed to calculate the minimum potential energy profiles and the rates of excited state intra-molecular proton transfer (ESIPT) for the WOLED material molecule of HBFO and its four meta- or para-substituted compounds in gas phase, acetonitrile and cyclohexane solvents. The kinetic control for these reactions is quantitatively determined and extensively studied on the basis of the accurate potential energy surfaces when the thermodynamic factor associated with the free energy change becomes negligible in the case of the existence of a significant barrier in the ESIPT process. These computational efforts contribute to a deep understanding of the ESIPT mechanism, dual emission characteristics, kinetic controlling factor, substituent and solvent effects for these material molecules. The white light emission is generated by the establishment of dynamic equilibrium between enol and keto forms in the charge transfer excited SCT( 1ππ*) state. The performance of white light emission is quantitatively demonstrated to be mainly sensitive to the molecular tailoring approach of the electronic properties of meta- or para- substituents by the modulation of the forward/backward ESIPT rate ratio. The quality of white light emission is slightly tunable through its surrounding solvent environment. These computational results will provide a useful strategy for the molecular design of OLED and WOLED materials. This journal is © 2014 the Owner Societies.

Li Y.,Beijing Normal University | Fang D.-C.,Beijing Normal University
Physical Chemistry Chemical Physics | Year: 2014

The reaction mechanisms of [4+2] cycloaddition reactions between dienes and dienophiles have been investigated with several density functional theory (DFT) methods, such as CAM-B3LYP, BMK, M062x wB97x and wB97xd, and the obtained results show that most of the reactions are synchronous or asynchronous. The stability of the transition state is moderated by the interaction of frontier molecular orbitals (FMOs), in which a diene acts as an electron-donating partner and a dienophile acts as an electron-acceptor from the charge transfer direction in the transition state. The activation free energy barriers have been calculated with both gas-phase translational entropy and solution translational entropy, in which those from gas-phase translational entropy (output of the Gaussian job) are far away from the experimental estimations. It has been found that free-energy barriers generated from solution translational entropies with CAM-B3LYP+IDSCRF/6-31G(d), BMK+IDSCRF/6-31G(d) and wB97x+IDSCRF/6-31G(d) are very close to the experimental measurements, but both M062x and wB97xd methods predict too low free-energy barriers for most of the studied reactions. The substituent and solvent effects on reaction dynamic data have also been addressed. This journal is © the Partner Organisations 2014.

Chen Y.-M.,Beijing Normal University | Chass G.A.,Queen Mary, University of London | Fang D.-C.,Beijing Normal University
Physical Chemistry Chemical Physics | Year: 2014

A novel reaction mechanism is presented for an ortho-magnesium carboxylate driven aromatic nucleophilic substitution in naphthoic acids, supported by high-level density functional theory. Results show that the rate-determining aspects involve an R-group transfer from a Grignard reagent Mg-atom to the C1-atom on a naphthalene ring. This transfer is moderated by a molecular corral comprised of two solvent THF molecules and the naphthoic acid, which collectively marshal the R-group into position. The CAM-B3LYP method was employed together with the all-electron DZVP basis set. Solvent was treated using an implicit dielectric continuum (PCM method) and IDSCRF atomic-radii. Further evolved solvent models were also investigated, consisting of explicit solvating particles forming a primary solvation layer framing the reaction center. Reaction barriers obtained are in close agreement with experimental trends, with R-group substituent-identity tempering repulsion with the molecular corral, in-turn modulating the free-energy barriers. Partitioning of the dynamic bases of entropy contribution to free-energy was central to the successful experimental-theoretical synergy. © 2014 the Owner Societies.

Ye Q.,Beijing Normal University
European Physical Journal: Special Topics | Year: 2014

In the past three decades, the electric energy industry made great contribution to support rapid social and economic development in China, and meanwhile has been grown at the highest rate in the human history owing to the economic reform. In its new national development plan, more investment has been put into installation of both electricity generating capacity and transmitting capacity in order to meet fast growing demand of electric energy. However, energy resources, both fossil fuel and renewable types, and energy consumption and load centers in China are not evenly distributed in both spatial and temporal dimensions. Moreover, dominated by coal as its primary energy source, the whole eastern China is now entering an environmental crisis in which pollutants emitted by coal power plants contribute a large part. To balance the regional differences in energy sources and energy consumption while meeting the steadily increasing demands for electric energy for the whole country, in addition to increase electric generating capacity, building large-scale, long-distance ultra high voltage power grids is the top priority for next five years.China is a country prone to almost all kinds of natural disasters due to its vast, complex geographical and climatic conditions. In recent years, frequent natural disasters, especially extreme weather and climate events, have threatened the safety, reliability and stability of electric energy system in China. Unfortunately, with fast growth rate but lacking of risk assessing and prevention mechanism, many infrastructure constructions, including national power grids, are facing integrated and complex economic, social, institutional and ecological risks.In this paper, based on a case analysis of the Great Ice Storm in southern China in January 2008, risks of building a resilient power grid to deal with increasing threats from extreme weathers are discussed. The paper recommends that a systematic approach based on the social-ecological system framework should be applied to assess the risk factors associated with the power grid, and the tools to deal with complex dynamic systems need to be applied to deal with constant changes in the whole social-ecological system. © 2014, EDP Sciences and Springer.

Dong W.,Beijing Normal University | Jiang Y.,National Climate Center | Yang S.,National Oceanic and Atmospheric Administration
Climatic Change | Year: 2010

The climatic seasons in China, defined by station-specific daily temperature measures, have changed substantially during the past decades. In the majority of the country, the length of summer has extended and the length of winter has shortened since the 1950s. These changes in the lengths of seasons are linked to the changes in the starting dates of seasons. Namely, the starting date of summer has advanced and the starting date of winter has shifted back. Averaged across the whole country, the starting date of summer has been brought forward by 5. 8 days and the season has extended 9 days. On the other hand, the starting date of winter has been delayed by 5. 6 days and the season has shortened by 11 days. The changes for spring and fall are relatively smaller. Particularly, spring has started earlier by 5. 7 days but shortened by 0. 3 day, and fall has started later by 3. 2 days but lengthened by 2. 3 days. The changes in seasons exhibit apparent regional differences. They are more significant in the north than in the south where the trend of some local changes in seasons is opposite to that of the rest of the country. © 2009 Springer Science+Business Media B.V.

Lin Y.,Beijing Normal University | Zhan X.,Peking University
Advanced Energy Materials | Year: 2015

In the past two years, non-fullerene acceptors including polymers and small molecules have become the focus of many research efforts. Fullerene-free organic solar cells (OSCs) have shown efficiencies of up to 6.8% for solution-processed devices, and even up to 8.4% for vacuum-deposited devices, which have been significantly improved relative to those disclosed 2 years ago (generally <4%). Non-fullerene acceptor materials are a new focus in the OSC field. Tailoring extended fused-rings with electron-deficient groups is an effective strategy for design of acceptors. Here, very recent developments in several systems of fused ring-based electron acceptors, such as halogenated (sub or subna)phthalocyanine, imide-functionalized rylene, and linear fused-rings end capped with electron deficient blocks, are reviewed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ye Z.,Beijing Normal University
Computers and Mathematics with Applications | Year: 2015

In this paper we establish the regularity criteria of solutions to the three space dimensions generalized viscous Hall-magnetohydrodynamics. Moreover, we also prove that there exist classical solutions globally in time to the generalized viscous Hall-MHD if the initial data is small enough or the fractional Laplacian dissipation powers α and β are suitably large. These results are some improvements of very recent work (Chae and Lee, 2014) established by Chae and Lee. © 2015 Elsevier Ltd.

Zhu X.,Beijing Normal University | Chen J.,Beijing Normal University | Gao F.,NASA | Chen X.,Beijing Normal University | Masek J.G.,NASA
Remote Sensing of Environment | Year: 2010

Due to technical and budget limitations, remote sensing instruments trade spatial resolution and swath width. As a result not one sensor provides both high spatial resolution and high temporal resolution. However, the ability to monitor seasonal landscape changes at fine resolution is urgently needed for global change science. One approach is to "blend" the radiometry from daily, global data (e.g. MODIS, MERIS, SPOT-Vegetation) with data from high-resolution sensors with less frequent coverage (e.g. Landsat, CBERS, ResourceSat). Unfortunately, existing algorithms for blending multi-source data have some shortcomings, particularly in accurately predicting the surface reflectance of heterogeneous landscapes. This study has developed an enhanced spatial and temporal adaptive reflectance fusion model (ESTARFM) based on the existing STARFM algorithm, and has tested it with both simulated and actual satellite data. Results show that ESTARFM improves the accuracy of predicted fine-resolution reflectance, especially for heterogeneous landscapes, and preserves spatial details. Taking the NIR band as an example, for homogeneous regions the prediction of the ESTARFM is slightly better than the STARFM (average absolute difference [AAD] 0.0106 vs. 0.0129 reflectance units). But for a complex, heterogeneous landscape, the prediction accuracy of ESTARFM is improved even more compared with STARFM (AAD 0.0135 vs. 0.0194). This improved fusion algorithm will support new investigations into how global landscapes are changing across both seasonal and interannual timescales. © 2010 Elsevier Inc.

Liu J.,Beijing Normal University | Tai X.-C.,University of Bergen | Huang H.,Beijing Normal University | Huan Z.,Beijing Normal University
IEEE Transactions on Image Processing | Year: 2013

This paper proposes a general weighted $l^{2}-l0 norms energy minimization model to remove mixed noise such as Gaussian-Gaussian mixture, impulse noise, and Gaussian-impulse noise from the images. The approach is built upon maximum likelihood estimation framework and sparse representations over a trained dictionary. Rather than optimizing the likelihood functional derived from a mixture distribution, we present a new weighting data fidelity function, which has the same minimizer as the original likelihood functional but is much easier to optimize. The weighting function in the model can be determined by the algorithm itself, and it plays a role of noise detection in terms of the different estimated noise parameters. By incorporating the sparse regularization of small image patches, the proposed method can efficiently remove a variety of mixed or single noise while preserving the image textures well. In addition, a modified K-SVD algorithm is designed to address the weighted rank-one approximation. The experimental results demonstrate its better performance compared with some existing methods. © 2012 IEEE.

Fan M.,China Electric Power Research Institute | Zhang Z.,China Electric Power Research Institute | Su A.,Beijing Normal University | Su J.,China Electric Power Research Institute
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2013

The planning methods and operation modes of traditional distribution network are difficult to accommodate the high penetration of distributed energy resources (DER). Active distribution network (ADN), based on the application of information and communication technology (ICT) and advanced metering infrastructure (AMI), is one of the alternative solutions. In this paper, the impact of DER on the traditional distribution network was analyzed and thus the necessity of developing ADN was clarified; The basic concept of ADN, its research tendency, the differences between traditional distribution networks and ADN and the corresponding research results were introduced; Some enabling technologies which are cost-effective for the transitions from the existing distribution network to the active distribution network were discussed. With the progress of the available techniques, ADN can balance the power at distribution levels, and between transmission and distribution levels, that is, ADN will be an infrastructure as a regional exchange of all kinds of energy. © 2013 Chin. Soc. for Elec. Eng.

Xu D.,Beijing Normal University | Yin Y.,Beijing Normal University | Li H.,Beijing Normal University
Journal of Scheduling | Year: 2010

Although scheduling problems with machine availability have attracted many researchers' attention, most of the past studies are mainly focused on one or several prefixed machine maintenance activities. In this research, we assume that the time needed to perform one maintenance activity is an increasing linear function of the total processing time of the jobs that are processed after the machine's last maintenance activity. We consider two scheduling problems with such maintenance requirement in this paper. The first problem is a parallel machine scheduling problem where the length of the time interval between any two consecutive maintenance activities is between two given positive numbers. The objective is to minimize the maintenance makespan, i.e., the completion time of the last finished maintenance. The second problem is a single machine scheduling problem where the length of the time interval between any two consecutive maintenance activities is fixed and the objective is to minimize the makespan, i.e., the completion time of the last finished job. We propose two approximation algorithms for the considered problems and analyze their performances. © 2010 Springer Science+Business Media, LLC.

Zhang Q.-G.,Beijing Normal University | Buckling A.,University of Oxford | Buckling A.,University of Exeter
Ecology Letters | Year: 2011

Understanding the conditions under which rapid evolutionary adaptation can prevent population extinction in deteriorating environments (i.e. evolutionary rescue) is a crucial aim in the face of global climate change. Despite a rapidly growing body of work in this area, little attention has been paid to the importance of interspecific coevolutionary interactions. Antagonistic coevolution commonly observed between hosts and parasites is likely to retard evolutionary rescue because it often reduces population sizes, and results in the evolution of costly host defence and parasite counter-defence. We used experimental populations of a bacterium Pseudomonas fluorescens SBW25 and a bacteriophage virus (SBW25Φ2), to study how host-parasite coevolution impacts viral population persistence in the face of gradually increasing temperature, an environmental stress for the virus but not the bacterium. The virus persisted much longer when it evolved in the presence of an evolutionarily constant host genotype (i.e. in the absence of coevolution) than when the bacterium and virus coevolved. Further experiments suggest that both a reduction in population size and costly infectivity strategies contributed to viral extinction as a result of coevolution. The results highlight the importance of interspecific evolutionary interactions for the evolutionary responses of populations to global climate change. © 2011 Blackwell Publishing Ltd/CNRS.

Yang X.,Beijing Normal University | Yan D.,Beijing Normal University | Yan D.,Beijing University of Chemical Technology
Chemical Science | Year: 2016

Luminescent metal-organic frameworks (MOFs) have received much attention due to their wide structural tunability and potential application in light-emitting diodes, biological imaging and chemical sensors. However, successful examples of long-persistent afterglow MOFs are still quite limited to date. In this work, we report that two types of Zn-terephthalate (TPA) MOFs (namely [Zn(TPA)(DMF)] (1-DMF) and MOF-5) could exhibit an obvious room-temperature afterglow emission with a time-resolved luminescence lifetime as high as 0.47 seconds. The phosphorescence-based afterglow was also highly sensitive to the temperature, and the reversible emission intensity could be recycled under high/low temperatures. Moreover, both 1-DMF and MOF-5 showed highly tunable afterglow phosphorescence colors (from cyan to yellow and from green to red, respectively) upon treatment with pyridine solution. The fluorescence/phosphorescence emission color of MOF-5 can be reversibly switched due to the addition and removal of a pyridine guest to and from the host nanochannel, as shown in both experimental and computational studies. Therefore, this work not only shows a facile method to develop MOF-based long-afterglow materials at room temperature, but also presents a strategy to tune their phosphorescence in a wide range based on host-guest interactions. © 2016 The Royal Society of Chemistry.

Liu P.S.,Beijing Normal University
Materials Science and Engineering A | Year: 2010

Porous metal foams with isotropic three-dimensional reticulated structure are excellent engineering materials with dual attributes of structural and functional characteristics, and they may bear shearing or torsional or bending loads when they are used as engineering components in various cases. With the octahedral model, the mechanical behavior is investigated for the component of these materials under shearing loads, the loading state of struts within the porous body is analyzed for these materials under torsion, and the mechanical performance is further discussed for these materials under bending moment based on their properties of uniaxial tension and compression. Using the simple manner of segregating analysis, the relevant mechanical relationships are respectively derived from the corresponding mathematical deduction for these materials under those loads. The results show that, when the porous body endures the fracture resulting from shearing loads or from torsion, the maximum nominal shearing stress or the nominal torque for the porous component can be described with the porosity and the inherent characteristic parameters of the metal foam itself. Also, the applicable maximum nominal bending moment can be expressed as a function of the porosity for the metal foams under bending moment. This mathematical relationship may be regarded as the extension of the expression about the relationship between the maximum nominal stress and the porosity for these materials under uniaxial tensile and compressive loads. From these mathematical relations, the loading criterions may be directly and conveniently achieved for these materials under the corresponding loads, respectively. © 2010.

Yu J.,Beijing Normal University | Xu N.,Beijing Normal University | Wei Q.,Beijing Normal University | Wang L.,Beijing Normal University
Journal of Materials Chemistry C | Year: 2013

Polyaddition reactions of N-hydroxy maleopimarimide with divinyl ether compounds were carried out to give novel polymers with ester acetal linkages in the main chain. The polymers have good solubility in common organic solvents and relatively high Tg temperatures. The number-average molecular weights of the polymers range from 4000 to 5500, with Mw/M n of 1.7-2.3. The thermal decomposition temperatures of the polymers are above 220 °C. The film of the obtained polymers showed excellent transparency to UV light above 230 nm. The ester acetal linkage of the polymer chain can be cleaved in the presence of strong acid under mild heating. Making use of the high acidolytic activity of the polymers, positive-tone chemically amplified i-line photoresists can be formed from them and 2,1- diazonaphthoquinone-4-sulfonate, in which the well known photoactive compound can also function as a photoacid generator. The photolithographic performance of the photoresists was evaluated using an i-line exposure system with high photosensitivity and resolution. This journal is © 2013 The Royal Society of Chemistry.

Dai J.,Beijing Normal University | Dai J.,International Institute For Applied Systems Analysis | Fath B.,International Institute For Applied Systems Analysis | Fath B.,Towson University | Chen B.,Beijing Normal University
Renewable and Sustainable Energy Reviews | Year: 2012

The prominent conflict between consumption and environmental resources is acknowledged as a significant force in affecting the social-ecological community balance. The whole process of resource allocation, utilization, efficiency and outcome are crucial clues in uncovering the structural and functional characteristics in complex consuming systems. Herein, network relationship provides a system-oriented modeling technique for examining the structure as well as flow of materials or energy from an input-output perspective. Meanwhile, extended exergy, the only currently available thermodynamic based metric for social-economic environmental impacts associated with energy consumption, manpower and monetary operation as well as environmental emission, is an extension of the labor theory of value and a possible sustainability metric. The core purpose of this research is to construct a network of the social-economic consumption system of China using extended exergy analysis to explain the interrelationship among different sectors within a thermodynamic metric. Therefore, we firstly make a database of extended exergy accounting in the Chinese consumption system. Data are available for 2007, which can be divided into seven sectors based on the reclassification of the regularly published 42-sector Input-Output Table, namely, (1) Agriculture, (2) Extraction, (3) Conversion, (4) Industry, (5) Transportation, (6) Tertiary, and (7) Domestic sectors. Then we will construct an extended exergy network to gain insight into the thermodynamic distribution within sectoral criterion. Lastly, the network results and indicator analysis are explained for Chinas social metabolism maintained by a large quantity of energy, resources, and labor, as well as the environmental costs, within an exergy foundation. © 2012 Elsevier Ltd. All rights reserved.

Wang K.,Beijing Normal University | Dickinson R.E.,University of Texas at Austin
Reviews of Geophysics | Year: 2012

This review surveys the basic theories, observational methods, satellite algorithms, and land surface models for terrestrial evapotranspiration, E (or E, i.e., latent heat flux), including a long-term variability and trends perspective. The basic theories used to estimate E are the Monin-Obukhov similarity theory (MOST), the Bowen ratio method, and the Penman-Monteith equation. The latter two theoretical expressions combine MOST with surface energy balance. Estimates of E can differ substantially between these three approaches because of their use of different input data. Surface and satellite-based measurement systems can provide accurate estimates of diurnal, daily, and annual variability of E. But their estimation of longer time variability is largely not established. A reasonable estimate of E as a global mean can be obtained from a surface water budget method, but its regional distribution is still rather uncertain. Current land surface models provide widely different ratios of the transpiration by vegetation to total E. This source of uncertainty therefore limits the capability of models to provide the sensitivities of E to precipitation deficits and land cover change. © 2012 by the American Geophysical Union.

Chen S.,Beijing Normal University | Chen B.,Beijing Normal University
Renewable and Sustainable Energy Reviews | Year: 2012