Beijing, China
Beijing, China

Peking University , is a major Chinese research university located in Beijing and a member of the C9 League. It is the first established modern national university of China, founded as the "Imperial University of Peking" in 1898 as a replacement of the ancient Guozijian. By 1920, it had become a center for progressive thought. It has been consistently regarded by both domestic and international university rankings as, alongside Tsinghua University, the top higher learning institution in mainland China. In addition to academics, Peking University is especially renowned for its campus grounds, and the beauty of its traditional Chinese architecture.Throughout its history, the university has educated and hosted many prominent modern Chinese thinkers, including figures such as: Lu Xun, Mao Zedong, Gu Hongming, Hu Shih, Li Dazhao, and Chen Duxiu. Peking University was influential in the birth of China's New Culture Movement, May Fourth Movement, the Tiananmen Square protest of 1989 and many other significant events. Wikipedia.

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Peking University, Pkucare Pharmaceutical R&D Center and Pku Healthcare Industry Group Co. | Date: 2014-12-30

The present invention provides a polysubstituted pyridine compound of Formula I, a preparation method, a use and a pharmaceutical composition thereof. The polysubstituted pyridine compound of Formula I according to the present invention has an excellent anti-tumor effect, can inhibit various cell kinases simultaneously, has significantly excellent pharmacokinetic characteristics, and is very suitable for oral and intravenous administration. The pharmaceutical composition according to the present invention can be useful for treating tumors and cancers.

Peking University | Date: 2014-11-14

An ultraviolet light sensing circuit and sensing system. The ultraviolet light sensing circuit comprises a modulation unit and a phase delay unit, wherein the modulation unit comprises a first stage of inverter which is used for sensing ultraviolet light and is used as a voltage feedback modulation stage; and the phase delay unit comprises N stages of inverters which are connected in sequence, where N is an even number which is greater than or equal to 2. The modulation unit is connected to the phase delay unit in sequence, and the output voltage of the phase delay unit is fed to the modulation unit; and the modulation unit is modulated by a control signal which is a pulse signal. The ultraviolet light sensing circuit and sensing system can be used for ultraviolet light information communications. The ultraviolet light sensing circuit can sense ultraviolet light signals and output amplitude modulation wave signals.

Peking University, Pkucare Pharmaceutical R&D Center and Pku Healthcare Industry Group Co. | Date: 2017-02-15

The present invention provides a polysubstituted pyridine compound of Formula I, a preparation method, a use and a pharmaceutical composition thereof. The polysubstituted pyridine compound of Formula I according to the present invention has an excellent anti-tumor effect, can inhibit various cell kinases simultaneously, has significantly excellent pharmacokinetic characteristics, and is very suitable for oral and intravenous administration. The pharmaceutical composition according to the present invention can be useful for treating tumors and cancers.

ZTE Corporation and Peking University | Date: 2017-01-18

A method for compressing a local feature descriptor includes that: at least one local feature descriptor of a target image is selected; and multi-stage vector quantization is carried out on the selected at least one local feature descriptor according to a pre-set code book, and the local feature descriptor is quantized as a feature code stream, wherein the feature code stream includes serial numbers of code words obtained by means of the multi-stage vector quantization. A device for compressing a local feature descriptor and a storage medium are also provided.

The present invention relates to a rare earth-based nanoparticle magnetic resonance contrast agent and a preparation method thereof. The rare earth-based nanoparticle magnetic resonance contrast agent is rare earth-based inorganic nanoparticles having the surfaces coated with hydrophilic ligands. The rare earth-based nanoparticles are first obtained by a high-temperature oil phase reaction, and then the surfaces thereof are coated with hydrophilic molecules to obtain the rare earth-based nanoparticle magnetic resonance contrast agent. Compared with the existing clinical contrast agent, the magnetic resonance contrast agent of the present invention has a greatly improved relaxivity, a good imaging effect, a low required injection dose, and long in vivo residence time. In addition, the rigid structure of the inorganic nanoparticles can effectively reduce the leakage possibility of gadolinium ions.

Gao Y.,Peking University | Gao Y.,Beijing Technology and Business University | Wang L.,Peking University
IEEE Transactions on Automatic Control | Year: 2011

This technical note studies consensus problems of multiple agents with continuous-time second-order dynamics, where each agent can obtain its positions and velocities relative to its neighbors only at sampling instants. It is assumed that the sampling period of each agent is independent of the others' and the interaction topology among agents is time-varying, where the associated direct graphs may not have spanning trees. If the union graph of all direct graphs has a spanning tree, then there exist controller gains and sampling periods such that consensus is reached. Moreover, two approaches are presented to design such controller gains and sampling periods. Simulations are performed to validate the theoretical results. © 2011 IEEE.

Yu H.,Peking University
Journal of Materials Chemistry C | Year: 2014

Famous for their photoisomerization, azobenzene and its derivatives have been intensively studied as among the most fascinating advanced materials. In particular, azobenzene-containing liquid-crystalline polymer (LCP) materials show unique properties by combining the self-assembly of liquid crystals and photoresponsive performance of chromophores. Here, we highlight their intriguing properties and potential applications from photonics to photodriven motion as well as the novel nanotechnology. The photoresponsive features such as photochemical phase transition, photoinduced alignment and photo-triggered cooperative motion often result in a large modulation of the refractive index, which can be easily fixed in LCP films. This is very advantageous for their photonic applications. Upon forming connections by three-dimensional crosslinking, a large deformation can be photoinduced from the micro to the macro scale, enabling applications as photomechanical and photomobile materials to be found. Upon integrating with the microphase separation of well-defined block copolymers, they exhibit photocontrollable regular nanostructures on the macroscopic scale with excellent reproducibility and mass production, meaning they can be used as nanotemplates for nanoengineering and nanofabrication. This journal is © the Partner Organisations 2014.

Yan Q.,Peking University | Luo Z.,Peking University | Cai K.,Peking University | Ma Y.,Peking University | Zhao D.,Peking University
Chemical Society Reviews | Year: 2014

Molecular assemblies with well-defined structures capable of photo-induced electron transfer and charge transport or photochemical reactions are reviewed. Hierarchical supramolecular architectures, which assemble the modular units into specific spatial arrangements and facilitate them to work cooperatively, are vital for the achievement of photo-functions in these systems. The chemical design of molecular building blocks and noncovalent interactions exploited to realize supramolecular organizations are particularly discussed. Reviewing and recapitulating the chemical evolution traces of these accomplished systems will hopefully delineate certain fundamental design principles and guidelines useful for developing more advanced functions in the future. This journal is © the Partner Organisations 2014.

Li X.,Peking University
Journal of molecular neuroscience : MN | Year: 2012

Urea transporter B is one of urea transporters that selectively transport urea driven by urea gradient across membrane and expressed abundantly in brain. To determine the physiological role of UT-B in brain, UT-B localization, urea concentration, tissue morphology of brain, and behavioral phenotypes were studied in UT-B heterozygous mice via UT-B null mice. UT-B mRNA was expressed in olfactory bulb, cortex, caudate nucleus, hippocampus and hypothalamus of UT-B heterozygous mice. UT-B null mice exhibited depression-like behavior, with urea accumulation, nitric oxide reduction, and selective neuronal nitric oxide synthase level increase in hippocampus. After acute urea loading, the urea level increased, NO production decreased in hippocampus from both types of mice. Moreover, urea level was higher, and NO concentration was lower consistently in UT-B null hippocampus than that in heterozygous hippocampus. In vitro, 25 mM urea inhibited NO production too. Furthermore, UT-B knockout induced a long-lasting notable decrease in regional cerebral blood flow and altered morphology, such as loss of neurons in CA3 region, swelling, and membranous myelin-like structure formation within myelinated and unmyelinated fibers in hippocampus. These results suggest that urea accumulation in the hippocampus induced by UT-B deletion can cause depression-like behavior, which possibly attribute to disturbance in NOS/NO system.

Liu F.,Peking University | Hou Y.,Peking University | Gao S.,Peking University
Chemical Society Reviews | Year: 2014

Nanocomposites containing soft and hard magnetic phases have attracted immense attention for energy-related and biomedical applications. With exchange coupling between nanoscale grains in the composites, magnetization of the soft magnetic phase can rotate coherently with that of the hard magnetic phase. In particular, good control of the soft and hard phases at the nanoscale in the composites is of great importance for effective exchange coupling, allowing us to make the best of the strengths of soft and hard magnetic phases and to optimize the magnetic properties for targeted applications. In this review, we present the recent progress in the chemical synthesis and applications of exchange-coupled nanocomposites. Firstly, the principle of nanomagnetism and exchange coupling is introduced. Secondly, the characterization of exchange-coupled nanocomposites is summarized. Thirdly, the chemical methods for the production of different exchange-coupled nanocomposites are presented. Finally, applications of exchange-coupled nanocomposites in magnetic energy storage and biomedicine are addressed. This journal is © the Partner Organisations 2014.

Zhao P.,Peking University
International Journal of Sustainable Transportation | Year: 2013

The increasing emission of transport-related pollutants has become a key issue in relation to climate change mitigation and the improvement of air quality in China's cities. This article aims to examine the effects of changes in the built environment on transportation by examining the case of Beijing. Looking at household survey data, the analysis found that individual workers' commuting behavior (concerning travel destination, mode choice and travel time) is significantly related to some aspects of the built environment when socioeconomic and demographic characteristics are taken into account. There are obvious differences in the effects of the built environment on commuting across income groups, occupations and industries. © 2013 Copyright Taylor and Francis Group, LLC.

Mei H.,Peking University
Proceedings - International Computer Software and Applications Conference | Year: 2010

Internet is becoming an open, global, ubiquitous and smarter computer for our society and planet. Such "Internet as a Computer" requires substantial improvements in software characteristics such as collaborative, situational, autonomous, evolvable and trustworthy, which challenge existing software paradigms, including software model, software middleware and engineering approach. In this talk, a new software paradigm, called Internetware, is presented as a synergy of these future directions. © 2010 IEEE.

Liu H.,Peking University
The Chinese journal of dental research : the official journal of the Scientific Section of the Chinese Stomatological Association (CSA) | Year: 2011

To compare the effects of mineral trioxide aggregate (MTA) and calcium hydroxide (CH) for pulpotomy in primary molars. A randomised, bilateral self-controlled clinical trial was designed to compare the clinical effect of MTA and CH in pulpotomies in primary molars in 4- to 9-year-old children. Children with two similar-sized cavities on bilateral primary molar counterparts requiring pulpotomies were included. The two contralateral molars in each patient were randomly assigned to MTA or CH treatment. Clinical and radiographic examinations were performed to evaluate the treatment results at post-treatment recall. Seventeen pairs of self-controlled contralateral teeth were available for follow-up evaluations. The success rate of MTA was 94.1% (16/17), while the success rate of CH was 64.7% (11/17). Internal root resorption was the most frequent reason for failure in the CH group. Crown discolouration was common in the MTA-treated group. MTA was more successful than CH for pulpotomies in primary molar teeth, and may be a suitable replacement for CH in primary molar pulpotomies.

Zhou W.,Nagaoka University of Technology | Yu H.,Peking University
ACS Applied Materials and Interfaces | Year: 2012

Upon supramolecular self-assembly, novel conductive hybrid nanofibers were successfully fabricated using three amphiphilic salts, azopyridinium, aniline hydrochloride, and alkylbenzenesulfate-based anionic surfactants. The interactions like π-π stacking and ionic bonding among the different compounds played important roles in preparation of these multicomponent hybrid nanofibers. These were demonstrated by measurements of XRD, UV-vis absorption, and FTIR spectra. Interesting conductivity in an order of magnitude of 1 × 10 -7 to 1 × 10 -5 S/cm was observed in films of the fabricated hybrid nanofibers, which was attributed to the existence of freely movable ions, showing their possible applications as bionanomaterials and nanoelectronic devices. The fabrication processes of the conductive nanofibers might provide references for simulation of nerve fibers in nature. © 2012 American Chemical Society.

Chen X.,Peking University | Xu L.,Peking University
Agricultural and Forest Meteorology | Year: 2012

We used Ulmus pumila leaf unfolding and leaf fall data collected at 46 stations during the 1986-2005 period to construct and validate daily temperature-based spatial phenology models. These models allowed simulation of the 20-year mean and yearly spatial patterns of U. pumila growing season beginning and end dates. This work was undertaken to explore the ecological mechanisms driving tree phenology spatial patterns and examine tree phenology spatial responses to temperature across China's temperate zone. The results show that spatial patterns of daily temperatures within the optimum spring and autumn length periods control spatial patterns of growing season beginning and end dates, respectively. Regarding 20-year mean growing season modeling, mean growing season beginning date correlates negatively with mean daily temperature within the optimum spring length period at the 46 stations. The mean spring spatial phenology model explained 90% of beginning date variance (P<0.001) with a Root Mean Square Error (RMSE) of 4.6 days. In contrast, mean growing season end date correlates positively with mean daily temperature within the optimum autumn length period at the 46 stations. The mean autumn spatial phenology model explained 82% of end date variance (P<0.001) with a RMSE of 5.6 days. On average, a spatial shift in mean spring and autumn daily temperatures by 1°C may induce a spatial shift in mean beginning and end dates by -3.1 days and 2.6 days, respectively. Similarly, a significant negative and positive correlation was detectable between beginning date and spring daily temperature and between end date and autumn daily temperature at the 46 stations for each year, respectively. In general, the explained variances for yearly spatial phenology models are less than those of mean spatial phenology models, whereas the RMSEs of yearly models are greater than those of mean models. On average, a spatial shift in spring and autumn daily temperatures by 1°C in a year may induce a spatial shift in beginning and end dates between -4.28 days and -2.75 days and between 2.17 days and 3.16 days in the year, respectively. Moreover, both mean and yearly spatial phenology models perform satisfactorily in predicting beginning and end dates of the U. pumila growing season at external stations. Further analysis showed that the negative spatial response of yearly beginning date to spring daily temperature was stronger in warmer years than in colder years. This finding suggests that climate warming in late winter and spring may enhance sensitivity of the growing season's spatial response due to the relationship of beginning date to temperature. © 2011 Elsevier B.V.

Jin J.,Peking University | Zhang H.,Peking University | Zhang H.,University of Michigan | Kong L.,Peking University | And 2 more authors.
Nucleic Acids Research | Year: 2014

With the aim to provide a resource for functional and evolutionary study of plant transcription factors (TFs), we updated the plant TF database PlantTFDB to version 3.0 ( After refining the TF classification pipeline, we systematically identified 129 288 TFs from 83 species, of which 67 species have genome sequences, covering main lineages of green plants. Besides the abundant annotation provided in the previous version, we generated more annotations for identified TFs, including expression, regulation, interaction, conserved elements, phenotype information, expert-curated descriptions derived from UniProt, TAIR and NCBI GeneRIF, as well as references to provide clues for functional studies of TFs. To help identify evolutionary relationship among identified TFs, we assigned 69 450 TFs into 3924 orthologous groups, and constructed 9217 phylogenetic trees for TFs within the same families or same orthologous groups, respectively. In addition, we set up a TF prediction server in this version for users to identify TFs from their own sequences. © 2013 The Author(s). Published by Oxford University Press.

Wang S.,Peking University | Ladizhansky V.,University of Guelph
Progress in Nuclear Magnetic Resonance Spectroscopy | Year: 2014

Membrane proteins mediate many critical functions in cells. Determining their three-dimensional structures in the native lipid environment has been one of the main objectives in structural biology. There are two major NMR methodologies that allow this objective to be accomplished. Oriented sample NMR, which can be applied to membrane proteins that are uniformly aligned in the magnetic field, has been successful in determining the backbone structures of a handful of membrane proteins. Owing to methodological and technological developments, Magic Angle Spinning (MAS) solid-state NMR (ssNMR) spectroscopy has emerged as another major technique for the complete characterization of the structure and dynamics of membrane proteins. First developed on peptides and small microcrystalline proteins, MAS ssNMR has recently been successfully applied to large membrane proteins. In this review we describe recent progress in MAS ssNMR methodologies, which are now available for studies of membrane protein structure determination, and outline a few examples, which highlight the broad capability of ssNMR spectroscopy. © 2014 Elsevier B.V. All rights reserved.

Wang T.,Peking University | Jiao N.,Peking University | Jiao N.,Chinese Academy of Sciences
Journal of the American Chemical Society | Year: 2013

A novel TEMPO-catalyzed aerobic oxygenation and nitrogenation of hydrocarbons via C=C double-bond cleavage has been disclosed. The reaction employs molecular oxygen as the terminal oxidant and oxygen-atom source by metal-free catalysis under mild conditions. This method can be used for the preparation of industrially and pharmaceutically important N- and O-containing motifs, directly from simple and readily available hydrocarbons. © 2013 American Chemical Society.

Wang X.,Tsinghua University | Tang S.,Peking University
International Journal for Numerical Methods in Engineering | Year: 2013

We design a class of accurate and efficient absorbing boundary conditions for molecular dynamics simulations of crystalline solids. In one space dimension, the proposed matching boundary conditions take the form of a linear constraint of displacement and velocity at atoms near the boundary, where the coefficients are determined by matching the dispersion relation with a minimal number of atoms involved. Bearing the nice features of compactness, locality, and high efficiency, the matching boundary conditions are then extended to treat the out-of-plane wave problems in the square lattice. We construct multidirectional absorbing boundary conditions via operator multiplications. Reflection coefficient analysis and numerical studies verify their effectiveness for spurious reflection suppression in all directions. Compact and local in both space and time, they are directly applicable to nonlinear lattices and multiscale simulations. © 2012 John Wiley & Sons, Ltd.

Xiao Y.-F.,Peking University
Nature Photonics | Year: 2016

Non-reciprocal devices, such as circulators and isolators, are indispensable components in classical and quantum information processing in integrated photonic circuits. Aside from these applications, the non-reciprocal phase shift is of fundamental interest for exploring exotic topological photonics, such as the realization of chiral edge states and topological protection. However, incorporating low-optical-loss magnetic materials into a photonic chip is technically challenging. In this study we experimentally demonstrate non-magnetic non-reciprocity using optomechanical interactions in a whispering gallery microresonator, as proposed in a previous work. Optomechanically induced non-reciprocal transparency and amplification are observed and a non-reciprocal phase shift of up to 40° is also demonstrated. The underlying mechanism of optomechanically induced non-reciprocity has great potential for all-optical controllable isolators and circulators, as well as non-reciprocal phase shifters in integrated photonic chips. © 2016 Nature Publishing Group

Han W.,Peking University | Han W.,IBM | Kawakami R.K.,Ohio State University | Kawakami R.K.,University of California at Riverside | And 2 more authors.
Nature Nanotechnology | Year: 2014

The isolation of graphene has triggered an avalanche of studies into the spin-dependent physical properties of this material and of graphene-based spintronic devices. Here, we review the experimental and theoretical state-of-art concerning spin injection and transport, defect-induced magnetic moments, spin-orbit coupling and spin relaxation in graphene. Future research in graphene spintronics will need to address the development of applications such as spin transistors and spin logic devices, as well as exotic physical properties including topological states and proximity-induced phenomena in graphene and other two-dimensional materials. © 2014 Macmillan Publishers Limited.

Mechanical stress plays a key role in the development of cartilage degradation in osteoarthritis (OA). Nevertheless, the role of long noncoding RNAs in mechanical stress-induced regulation of chondrocytes remains unclear. The aim of this study was to explore the function of mechanical stress-related long noncoding RNAs in cartilage. Tissue samples were collected from 50 patients and chondrocytes were exposed to cyclic tensile strain (CTS). A total of 107 lncRNAs were differentially expressed in damaged cartilage versus intact cartilage. Of these lncRNAs, 51 were upregulated and 56 were downregulated in the damaged tissue. The TMSB4 pseudogene, lncRNA-MSR, was upregulated in the damaged cartilage and was activated in chondrocytes in response to mechanical stress. Furthermore, lncRNA-MSR regulated the expression of TMSB4 by competing with miRNA-152 in chondrocytes. Our results demonstrated that upregulation of lncRNA-MSR initiates pathological changes that lead to cartilage degradation, and the inhibition of lncRNA-MSR could represent a potential therapeutic target for OA.Molecular Therapy (2016); doi:10.1038/mt.2016.151. © 2016 Official journal of the American Society of Gene & Cell Therapy

Li K.,Peking University
Science of the Total Environment | Year: 2011

In the present study, indoor and outdoor air samples were collected using four types of air samplers often used for airborne bacterial sampling. These air samplers included two solid impactors (BioStage and RCS), one liquid impinger (BioSampler), and one filter sampler with two kinds of filters (a gelatin and a cellulose acetate filter). The collected air samples were further processed to analyze the diversity and abundance of culturable bacteria and total bacteria through standard culture techniques, denaturing gradient gel electrophoresis (DGGE) fingerprinting and quantitative polymerase chain reaction (qPCR) analysis.The DGGE analysis indicated that the air samples collected using the BioStage and RCS samplers have higher culturable bacterial diversity, whereas the samples collected using the BioSampler and the cellulose acetate filter sampler have higher total bacterial diversity. To obtain more information on the sampled bacteria, some gel bands were excised and sequenced. In terms of sampling efficiency, results from the qPCR tests indicated that the collected total bacterial concentration was higher in samples collected using the BioSampler and the cellulose acetate filter sampler.In conclusion, the sampling bias and efficiency of four kinds of air sampling systems were compared in the present study and the two solid impactors were concluded to be comparatively efficient for culturable bacterial sampling, whereas the liquid impactor and the cellulose acetate filter sampler were efficient for total bacterial sampling. © 2011 Elsevier B.V.

Sun Q.,Peking University
Chemical Physics Letters | Year: 2013

In this Letter, Raman spectroscopy is employed to study supercooled water down to a temperature of 248 K at ambient pressure. Based on our interpretation of the Raman OH stretching band, decreasing temperature mainly leads to a structural transition from the single donor-single acceptor (DA) to the double donor-double acceptor (DDAA) hydrogen bonding motif. Additionally, a local statistical interpretation of the water structure is proposed, which reveals that a water molecule interacts with molecules in the first shell through various local hydrogen-bonded networks. From this, a local structure order parameter is proposed to explain the short-range order and long-range disorder. © 2013 Elsevier B.V. All rights reserved.

Bmi1 has been identified as an important regulator in breast cancer, but its relationship with other signaling molecules such as ERα and HER2 is undetermined. The expression of Bmi1 and its correlation with ERα, PR, Ki-67, HER2, p16INK4a, cyclin D1 and pRB was evaluated by immunohistochemistry in a collection of 92 cases of breast cancer and statistically analyzed. Stimulation of Bmi1 expression by ERα or 17β-estradiol (E2) was analyzed in cell lines including MCF-7, MDA-MB-231, ERα-restored MDA-MB-231 and ERα-knockdown MCF-7 cells. Luciferase reporter and chromatin immunoprecipitation assays were also performed. Immunostaining revealed strong correlation of Bmi1 and ERα expression status in breast cancer. Expression of Bmi1 was stimulated by 17β-estradiol in ERα-positive MCF-7 cells but not in ERα-negative MDA-MB-231 cells, while the expression of Bmi1 did not alter expression of ERα. As expected, stimulation of Bmi1 expression could also be achieved in ERα-restored MDA-MB-231 cells, and at the same time depletion of ERα decreased expression of Bmi1. The proximal promoter region of Bmi1 was transcriptionally activated with co-transfection of ERα in luciferase assays, and the interaction of the Bmi1 promoter with ERα was confirmed by chromatin immunoprecipitation. Moreover, in breast cancer tissues activation of the ERα-coupled Bmi1 pathway generally correlated with high levels of cyclin D1, while loss of its activity resulted in aberrant expression of p16INK4a and a high Ki-67 index, which implied a more aggressive phenotype of breast cancer. Expression of Bmi1 is influenced by ERα, and the activity of the ERα-coupled Bmi1 signature impacts p16INK4a and cyclin D1 status and thus correlates with the tumor molecular subtype and biologic behavior. This demonstrates the important role which is played by ERα-coupled Bmi1 in human breast cancer.

Wang A.,Peking University
IEEE Photonics Technology Letters | Year: 2011

A Faraday rotator mirror incorporating a Gaussian bandpass filter was used as the reflected end of an Er-doped superfluorescent fiber source to improve its mean wavelength thermal stability. Several different filters were modeled in this fiber source system, and the optimal central wavelength was chosen to be 1558 nm with the bandwidth of 15 nm. With a Faraday rotator mirror incorporating such a filter in an Er-doped fiber source, the mean wavelength variation was measured to be 8 ppm from -40°C to 60°C. The bandwidth reached 16 nm. The pump power was 70 mW at 974.2 nm and the output power reached 18 mW with 6-m Er-doped fiber. © 2006 IEEE.

Li L.,Peking University
IEEE Antennas and Wireless Propagation Letters | Year: 2014

In this letter, we study the subwavelength imaging of sparse broadband sources inside a disordered medium by processing the data acquired by a single antenna. A mathematical model has been developed for solving such a problem based on the idea of sparse reconstruction. We show that the strongly disordered medium can serve as an efficient apparatus for compressive measurement, which shifts the complexity of devising compressive sensing (CS) hardware from the design, fabrication, and electronic control to a simple and single-calibration procedure. The proposed method and associated results can find applications in several imaging disciplines, such as optics, terahertz (THz), RF or ultrasound imaging. © 2002-2011 IEEE.

Mahmood N.,Peking University | Zhang C.,Peking University | Yin H.,Peking University | Hou Y.,Peking University
Journal of Materials Chemistry A | Year: 2014

Due to their unique properties, together with their ease of synthesis and functionalization, graphene-based materials have been showing great potential in energy storage and conversion. These hybrid structures display excellent material characteristics, including high carrier mobility, faster recombination rate and long-time stability. In this review, after a short introduction to graphene and its derivatives, we summarize the recent advances in the synthesis and applications of graphene and its derivatives in the fields of energy storage (lithium ion, lithium-air, lithium-sulphur batteries and supercapacitors) and conversion (oxygen reduction reaction for fuel cells). This article further highlights the working principles and problems hindering the practical applications of graphene-based materials in lithium batteries, supercapacitors and fuel cells. Future research trends towards new methodologies to the design and the synthesis of graphene-based nanocomposite with unique architectures for electrochemical energy storage and conversion are also proposed. © The Royal Society of Chemistry.

Meiron Y.,Peking University | Laor A.,Technion - Israel Institute of Technology
Monthly Notices of the Royal Astronomical Society | Year: 2013

Supermassive black holes are expected to pair as a result of galaxy mergers, and form a bound binary at parsec or sub-parsec scales. These scales are unresolved even in nearby galaxies, and thus detection of non-active black hole binaries must rely on stellar dynamics. Here we show that these systems could be indirectly detected through the trail that the black holes leave as they spiral inwards. We analyse two numerical simulations of inspiralling black holes (equal masses and 10:1 mass ratio) in the stellar environment of a galactic centre. We studied the effect of the binary on the structure of the stellar population, with particular emphasis on projected kinematics and directly measurable moments of the velocity distribution. We present those moments as high-resolution 2D maps. As shown in past scattering experiments, a torus of stars counter-rotating with respect to the black holes exists in scales ∼5-10 times larger than the binary separation. While this is seen in the average velocity map in the unequal mass case, it is obscured by a more strongly corotating outer region in the equal mass case; however, the inner counter-rotation could still be detected by studying the higher moments of the velocity distribution. Additionally, the maps reveal a dip in velocity dispersion in the inner region, as well as more pronounced signatures in the higher distribution moments. These maps could serve as templates for integral held spectroscopy observations of nearby galactic centres. The discovery of such signatures may help census the population of supermassive black hole binaries and refine signal rate predictions for future space-based low-frequency gravitational wave detectors. © 2013 The Authors.

Li X.,University of Texas at Austin | Zhang F.,University of Pennsylvania | Niu Q.,University of Texas at Austin | Niu Q.,Peking University
Physical Review Letters | Year: 2013

We analyze the Landau level (LL) structure in a MoS2 trilayer and find a field-dependent unconventional Hall plateau sequence ν=⋯,-2M-6,-2M-4,-2M-2,-2M-1,⋯,-5,-3,-1,0,2,4,⋯. Because of orbital asymmetry, the low-energy Dirac fermions become heavily massive and the LL energies grow linearly with B, rather than with √B. Spin-orbital couplings break spin and valley degenerate LL's into two groups, with LL crossing effects present in the valence bands. In a p-n junction, spin-resolved fractionally quantized conductance appears in two-terminal measurements with a controllable spin-polarized current that can be probed at the interface. We also show the tunability of zero-field spin Hall conductivity. © 2013 American Physical Society.

Yuan H.B.,Peking University | Liu X.W.,Peking University | Xiang M.S.,Peking University
Monthly Notices of the Royal Astronomical Society | Year: 2013

By using the 'standard pair' technique of pairing stars of almost nil and high extinction but otherwise with almost identical stellar parameters from the Sloan Digital Sky Survey (SDSS), and combining this information with photometry from the SDSS, Galaxy Evolution Explorer (GALEX), Two Micron All Sky Survey (2MASS) and Wide-field Infrared Survey Explorer (WISE) photometry ranging from the far ultraviolet (UV) to the mid-infrared (mid-IR), we measure dust reddening in the FUV - NUV, NUV - u, u - g, g - r, r - i, i - z, z - J, J - H, H - Ks, Ks - W1 and W1 - W2 colours for thousands of Galactic stars. The measurements, together with the E(B - V) values given by Schlegel et al., allow us to derive the observed, model-free reddening coefficients for these colours. The results are compared with previous measurements and with the predictions of various Galactic reddening laws. We find that (i) the dust reddening map of Schlegel et al. overestimates E(B - V) by about 14 per cent, consistent with the recent work of Schlafly et al. and Schlafly & Finkbeiner; (ii) after accounting for the d fferences in reddening normalization, the newly deduced reddening coefficients for colours FUV - NUV, NUV - u, u - g, g - r, r - i, i - z, z - J, J - H and H - Ks differ by respectively -1640, 15.5, 12.6, -0.8, 3.4, -0.7, 3.5, 2.5 and 1.4 per cent from the predictions of the Fitzpatrick reddening law for an assumed total-to-selective extinction ratio R(V) = 3.1, and by respectively -1730, 13.0, 8.1, 10.0, 8.0, -13.5, -1.7, -6.7 and -17.1 per cent from the predictions of the CCM reddening law; and (iii) all the new reddening coefficients, except those for NUV - u and u - g, favour the R(V) = 3.1 Fitzpatrick reddening law over the R(V) = 3.1 CCM and O'Donnell reddening laws. Using the Ks-band extinction coefficient predicted by the R(V)=3.1 Fitzpatrick lawand the observed reddening coefficients, we deduce new extinction coefficients for the FUV, NUV, u, g, r, i, z, J, H, W1 and W2 passbands. We recommend that the new reddening and extinction coefficients should be used in the future and that the Fitzpatrick reddening law in the UV should probably be updated. We stress, however, that the FUV- and NUV-band coefficients should be used with caution, given their relatively largemeasurement uncertainties. Finally, potential applications of the 'standard pair' technique with the upcoming LAMOST Galactic surveys are discussed. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Zhang Y.,Peking University | Yang Y.,Peking University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

This Letter investigates the finite-time consensus problems of second-order multi-agent systems in the presence of one and multiple leaders under a directed graph. Specifically, we propose two bounded control laws, which are independent of velocity information, to deal with the finite-time consensus tracking problem with one leader and the finite-time containment control problem with multiple leaders, respectively. With the aid of homogeneous theory, some sufficient conditions are established for the achievement of the finite-time tracking control problem of second-order multi-agent systems. Numerical examples are finally provided to illustrate the theoretical results. © 2012 Published by Elsevier B.V.

Gao J.,Southern Methodist University | Li C.S.,Beijing University of Technology | Li C.S.,Peking University | Zhu H.X.,SLAC
Physical Review Letters | Year: 2013

We present the complete calculation of the top-quark decay width at next-to-next-to-leading order in QCD, including next-to-leading electroweak corrections as well as finite bottom quark mass and W boson width effects. In particular, we also show the first results of the fully differential decay rates for the top-quark semileptonic decay t→W+(l+ν)b at next-to-next-to-leading order in QCD. Our method is based on the understanding of the invariant mass distribution of the final-state jet in the singular limit from effective field theory. Our result can be used to study arbitrary infrared-safe observables of top-quark decay with the highest perturbative accuracy. © 2013 American Physical Society.

Zhang B.,Peking University | Zhang B.,University of Nevada, Las Vegas | Kumar P.,University of Texas at Austin
Physical Review Letters | Year: 2013

The IceCube Collaboration recently reported a stringent upper limit on the high energy neutrino flux from gamma-ray bursts (GRBs), which provides a meaningful constraint on the standard internal shock model. Recent broadband electromagnetic observations of GRBs also challenge the internal shock paradigm for GRBs, and some competing models for γ-ray prompt emission have been proposed. We describe a general scheme for calculating the GRB neutrino flux, and compare the predicted neutrino flux levels for different models. We point out that the current neutrino flux upper limit starts to constrain the standard internal shock model. The dissipative photosphere models are also challenged if the cosmic ray luminosity from GRBs is at least 10 times larger than the γ-ray luminosity. If the neutrino flux upper limit continues to go down in the next few years, then it would suggest the following possibilities: (i) the photon-to-proton luminosity ratio in GRBs is anomalously high for shocks, which may be achieved in some dissipative photosphere models and magnetic dissipation models; or (ii) the GRB emission site is at a larger radius than the internal shock radius, as expected in some magnetic dissipation models such as the internal collision-induced magnetic reconnection and turbulence model. © 2013 American Physical Society.

Jiang F.,Peking University | Wu Y.-D.,Peking University
Journal of the American Chemical Society | Year: 2014

Ab initio protein folding via physical-based all-atom simulation is still quite challenging. Using a recently developed residue-specific force field (RSFF1) in explicit solvent, we are able to fold a diverse set of 14 model proteins. The obtained structural features of unfolded state are in good agreement with previous observations. The replica-exchange molecular dynamics simulation is found to be efficient, resulting in multiple folding events for each protein. Transition path time is found to be significantly reduced under elevated temperature. © 2014 American Chemical Society.

Wang Z.,Peking University | Li L.,Peking University | Huang Y.,Peking University
Journal of the American Chemical Society | Year: 2014

We describe a direct synthesis of various ynones from readily available aldehydes and hypervalent alkynyl iodides. In this method, a gold catalyst and a secondary amine work synergistically to produce the trisubstituted allenyl aldehyde, which can be converted to the desired ynone through an in situ C-C bond oxidative cleavage using molecular oxygen. © 2014 American Chemical Society.

He Q.Y.,Swinburne University of Technology | He Q.Y.,Peking University | Reid M.D.,Swinburne University of Technology
Physical Review Letters | Year: 2013

We develop the concept of genuine N-partite Einstein-Podolsky-Rosen (EPR) steering. This nonlocality is the natural multipartite extension of the original EPR paradox. Useful properties emerge that are not guaranteed for genuine multipartite entangled states. In particular, there is a close link with the task of one-sided, device-independent quantum secret sharing. We derive inequalities to demonstrate multipartite EPR steering for Greenberger-Horne- Zeilinger and Gaussian continuous variable states in loophole-free scenarios. © 2013 American Physical Society.

Fan P.,Peking University | Guo D.,Peking University
Oecologia | Year: 2010

Among tree fine roots, the distal small-diameter lateral branches comprising first- and second-order roots lack secondary (wood) development. Therefore, these roots are expected to decompose more rapidly than higher order woody roots. But this prediction has not been tested and may not be correct. Current evidence suggests that lower order roots may decompose more slowly than higher order roots in tree species associated with ectomycorrhizal (EM) fungi because they are preferentially colonized by fungi and encased by a fungal sheath rich in chitin (a recalcitrant compound). In trees associated with arbuscular mycorrhizal (AM) fungi, lower order roots do not form fungal sheaths, but they may have poorer C quality, e.g. lower concentrations of soluble carbohydrates and higher concentrations of acid-insolubles than higher order roots, thus may decompose more slowly. In addition, litter with high concentrations of acid insolubles decomposes more slowly under higher N concentrations (such as lower order roots). Therefore, we propose that in both AM and EM trees, lower order roots decompose more slowly than higher order roots due to the combination of poor C quality and high N concentrations. To test this hypothesis, we examined decomposition of the first six root orders in Fraxinus mandshurica (an AM species) and Larix gmelinii (an EM species) using litterbag method in northeastern China. We found that lower order roots of both species decomposed more slowly than higher order roots, and this pattern appears to be associated mainly with initial C quality and N concentrations. Because these lower order roots have short life spans and thus dominate root mortality, their slow decomposition implies that a substantial fraction of the stable soil organic matter pool is derived from these lower order roots, at least in the two species we studied. © 2010 Springer-Verlag.

Zhou X.-J.,Peking University | Zhang H.,Peking University
Autophagy | Year: 2012

Autophagy is now emerging as a spotlight in trafficking events that activate innate and adaptive immunity. It facilitates innate pathogen detection and antigen presentation, as well as pathogen clearance and lymphocyte homeostasis. In this review, we first summarize new insights into its functions in immunity, which underlie its associations with autoimmunity. As some lines of evidence are emerging to support its role in autoimmune and autoinflammatory diseases, we further discuss whether and how it affects autoimmune diseases including systemic lupus erythematosus, rheumatoid arthritis, diabetes mellitus and multiple sclerosis, as well as autoinflammatory diseases, such as Crohn disease and vitiligo. © 2012 Landes Bioscience.

Wang X.-Q.,Peking University | Zhang Q.,Peking University
European Journal of Pharmaceutics and Biopharmaceutics | Year: 2012

pH-sensitive polymeric nanoparticles are promising for oral drug delivery, especially for peptide/protein drugs and poorly water-soluble medicines. This review describes current status of pH-sensitive polymeric nanoparticles for oral drug delivery and introduces the mechanisms of drug release from them as well as possible reasons for absorption improvement, with emphasis on our contribution to this field. pH-sensitive polymeric nanoparticles are prepared mainly with polyanions, polycations, their mixtures or cross-linked polymers. The mechanisms of drug release are the result of carriers' dissolution, swelling or both of them at specific pH. The possible reasons for improvement of oral bioavailability include the following: improve drug stability, enhance mucoadhesion, prolong resident time in GI tract, ameliorate intestinal permeability and increase saturation solubility and dissolution rate for poorly water-soluble drugs. As for the advantages of pH-sensitive nanoparticles over conventional nanoparticles, we conclude that (1) most carriers used are enteric-coating materials and their safety has been approved. (2) The rapid dissolution or swelling of carriers at specific pH results in quick drug release and high drug concentration gradient, which is helpful for absorption. (3) At the specific pH carriers dissolve or swell, and the bioadhesion of carriers to mucosa becomes high because nanoparticles turn from solid to gel, which can facilitate drug absorption. © 2012 Elsevier B.V. All rights reserved.

Wei C.,Peking University | Wang X.,Peking University | Zheng M.,Peking University | Cheng H.,Peking University
Current Opinion in Cell Biology | Year: 2012

The calcium ion is the simplest and most versatile second messenger in biology. Harboring a myriad of calcium effector proteins, migrating cells display an exquisite multiscaled and multilayered architecture of intracellular calcium dynamics. In motile fibroblasts, for instance, there are transient calcium microdomains ('calcium flickers') of ∼5 μm in diameter and 10-2000. ms in duration, a rising flicker activity gradient along the rear-to-front axis, and a shallow background calcium concentration gradient in the opposite direction. When subjected to external gradients of guidance cues, local flicker gradients are created de novo in the leading edge, which steer cells to turn in new directions as defined by the asymmetry of the flicker activity, apparently by a stochastic decision-making mechanism. These recent findings provide a glimpse into how spatiotemporally coordinated calcium gradients orchestrate cellular behavior as complex as directional movement. © 2011 Elsevier Ltd.

Anti-inflammatory cytokine and its genetic variations may play an important role in the process of atherosclerosis. We assessed whether serum interleukin-10 (IL-10) and its genetic variations are associated with ischemic stroke in a Chinese general population. An epidemiological survey on cardiovascular diseases and their risk factors was carried in a general population in Beijing in 2005. Serum IL-10, IL-6, p-selectin, soluble intercellular adhesion molecule-1 and C-reactive protein were analyzed using ELISA kits, while three IL-10 Single Nucleotide Polymorphisms (SNP) (rs1800872, rs1554286 and rs3021094) were genotyped in 1475 participants. A high serum IL-10 (top tertile) was significantly associated with ischemic stroke (multivariable adjusted odds ratio (OR) =0.50; 95%CI 0.31-0.81). Rs1800872 (AA vs. AC+CC genotype, OR=1.60; 1.06-2.39), rs1554286(TT vs. CT+CC genotype, OR=1.59; 1.06-2.39), and rs3021094 (CC/CA vs. AA genotype, OR=1.64; 1.04-2.60) were all significantly associated with ischemic stroke even after controlling for age, sex, smoking, systolic blood pressure, total cholesterol, glucose, body mass index and serum IL-10. The SNP score (a summary index of these SNPs) and IL-10 (top tertile) together significantly improved the discriminative power in predicting ischemic stroke by 3.3% (95%CI: 0.2-6.4, p=0.0398) compared to predictions based on conventional risk factors alone. The lower serum IL-10 concentration and its selected genetic variations were significantly associated with an increased likelihood of ischemic stroke in this cross-sectional study. Our results suggest that more prospective studies should be conducted to provide stronger evidence justifying the use of IL-10 and its SNPs as new biomarkers to identify a predisposition towards ischemic stroke.

Bian K.,Peking University | Park J.-M.J.,Virginia Polytechnic Institute and State University
IEEE Transactions on Mobile Computing | Year: 2013

In decentralized cognitive radio (CR) networks, establishing a link between a pair of communicating nodes requires that the radios 'rendezvous in a common channel such a channel is called a rendezvous channel-to exchange control information. When unlicensed (secondary) users opportunistically share spectrum with licensed (primary or incumbent) users, a given rendezvous channel may become unavailable due to the appearance of licensed user signals. Ideally, every node pair should be able to rendezvous in every available channel (i.e., maximize the rendezvous diversity) so that the possibility of rendezvous failures is minimized. Channel hopping (CH) protocols have been proposed previously for establishing pairwise rendezvous. Some of them enable pairwise rendezvous over all channels but require global clock synchronization, which may be very difficult to achieve in decentralized networks. Maximizing the pairwise rendezvous diversity in decentralized CR networks is a very challenging problem. In this paper, we present a systematic approach for designing CH protocols that maximize the rendezvous diversity of any node pair in decentralized CR networks. The resulting protocols are resistant to rendezvous failures caused by the appearance of primary user (PU) signals and do not require clock synchronization. The proposed approach, called asynchronous channel hopping (ACH), has two noteworthy features: 1) any pair of CH nodes are able to rendezvous on every channel so that the rendezvous process is robust to disruptions caused by the appearance of PU signals; and 2) an upper bounded time-to-rendezvous (TTR) is guaranteed between the two nodes even if their clocks are asynchronous. We propose two optimal ACH designs that maximize the rendezvous diversity between any pair of nodes and show their rendezvous performance via analytical and simulation results. © 2002-2012 IEEE.

Wan X.,Peking University
Computational Linguistics | Year: 2011

The lack of reliable Chinese sentiment resources limits research progress on Chinese sentiment classification. However, there are many freely available English sentiment resources on the Web. This article focuses on the problem of cross-lingual sentiment classification, which leverages only available English resources for Chinese sentiment classification.We first investigate several basic methods (including lexicon-based methods and corpus-based methods) for cross-lingual sentiment classification by simply leveraging machine translation services to eliminate the language gap, and then propose a bilingual co-training approach to make use of both the English view and the Chinese view based on additional unlabeled Chinese data. Experimental results on two test sets show the effectiveness of the proposed approach, which can outperform basic methods and transductive methods. © 2011 Association for Computational Linguistics.

Chen L.,Peking University | Zhang X.-R.,Peking University
Energy Conversion and Management | Year: 2014

Solar collector has become a hot topic both in scientific research and engineering applications. Among the various applications, the hot water supply demand accounts for a large part of social energy consumption and has become one promising field. The present study deals with a novel solar thermal conversion and water heater system achieved by supercritical CO2 natural circulation. Experimental systems are established and tested in Zhejiang Province (around N 30.0, E 120.6) of southeast China. The current system is designed to operate in the supercritical region, thus the system can be compactly made and achieve smooth high rate natural convective flow. During the tests, supercritical CO2 pipe flow with Reynolds number higher than 6700 is found. The CO2 fluid temperature in the heat exchanger can be as high as 80 C and a stable supply of hot water above 45 C is achieved. In the seasonal tests, relative high collector efficiency generally above 60.0% is obtained. Thermal and performance analysis is carried out with the experiment data. Comparisons between the present system and previous solar water heaters are also made in this paper. © 2013 Elsevier B.V. All rights reserved.

Kang J.,Peking University | Rivest S.,Laval University
Endocrine Reviews | Year: 2012

Liver X receptors (LXR) are nuclear receptors that have emerged as key regulators of lipid metabolism. In addition to their functions as cholesterol sensors, LXR have also been found to regulate inflammatory responses in macrophages. Alzheimer's disease (AD) is a neurodegenerative disease characterized by a progressive cognitive decline associated with inflammation. Evidence indicates that the initiation and progression of AD is linked to aberrant cholesterol metabolism and inflammation. Activation of LXR can regulate neuroinflammation and decrease amyloid-β peptide accumulation. Here, we highlight the role of LXR in orchestrating lipid homeostasis and neuroinflammation in the brain. In addition, diabetes mellitus is also briefly discussed as a significant risk factor for AD because of the appearing beneficial effects of LXR on glucose homeostasis. The ability of LXR to attenuate AD pathology makes them potential therapeutic targets for this neurodegenerative disease. © 2012 by The Endocrine Society.

Background:Only about half of patients with type 2 diabetes treated with antihyperglycemic drugs achieve glycemic control (HbA1c <7%), most commonly due to poor treatment adherence. Glucagon-like peptide-1 (GLP-1) receptor agonists act on multiple targets involved in glucose homeostasis and have a low risk of causing hypoglycemia. While GLP-1 receptor (GLP-1R) agonists share the same mechanism of action, clinical profiles of individual agents differ, particularly between short- and long-acting agents. In this article, recent findings regarding the pharmacology of GLP-1 agonists are reviewed, and the clinical effects of short- versus long-acting agents are compared.Data sources:Relevant articles were identified through a search of PubMed using the keywords glucagon-like peptide-1, GLP-1, glucagon-like peptide-1 receptor agonist, GLP-1R agonist, and exenatide for publications up to 22 May 2015. Supporting data were obtained from additional searches for albiglutide, dulaglutide, liraglutide and lixisenatide as well as from the bibliographies of key articles.Findings:Short-acting GLP-1R agonists produce greater reductions in postprandial glucose levels by slowing gastric emptying, whereas long-acting GLP-1R agonists produce greater reductions in fasting blood glucose by stimulating insulin secretion from the pancreas. These characteristics can be exploited to provide individualized treatment to patients. A large body of evidence supports the benefits of short- and long-acting exenatide as add-on therapy in patients with inadequate glycemic control despite maximum tolerated doses of metformin and/or sulfonylurea. Exenatide is generally well tolerated and no new safety concerns were identified during long-term follow-up of up to 5 years. A limitation of this review of short-and long-acting GLP-1 receptor agonists is that it focuses on exenatide rather than all the drugs in this class. However, the focus on a single molecule helps to avoid any confusion that may be introduced as a result of differences in molecular structure and size.Conclusions:Short-acting GLP-1R agonists including exenatide are well suited to patients with type 2 diabetes with exaggerated postprandial glucose excursions and for co-administration with basal insulin therapy. Long-acting GLP-1R agonists including once weekly exenatide offer greater convenience and are well suited to patients who require specific control of fasting hyperglycemia. © 2015 Taylor & Francis.

Liu X.,Lanzhou University | Luo Z.-G.,Peking University | Sun Z.-F.,Lanzhou University
Physical Review Letters | Year: 2010

The analysis of the mass spectrum and the calculation of the strong decay of P-wave charmonium states strongly purport to explain the newly observed X(3915) and X(4350) as new members in the P-wave charmonium family, i.e., χc0′ for X(3915) and χc2′′ for X(4350). Under the P-wave charmonium assignment to X(3915) and X(4350), the JPC quantum numbers of X(3915) and X(4350) must be 0++ and 2++ respectively, which provide important criteria to test the P-wave charmonium explanation for X(3915) and X(4350) proposed by this Letter. The decay behavior of the remaining two P-wave charmonium states with the second radial excitation is predicted, and an experimental search for them is suggested. © 2010 The American Physical Society.

Chen H.,Peking University | Chen G.Q.,Peking University
Renewable Energy | Year: 2011

As a substitute for diesel and considered a renewable energy, rapeseed-based biodiesel has attracted increasing attention in China. The present work to estimate energy cost of rapeseed-based biodiesel in China is based on embodied energy intensities for various inputs out of a recent extended input-output analysis for Chinese economy, and the accounted life-cycle process of biodiesel production includes four main stages as agricultural crop production, transportation, industrial conversion characterized by alkali-catalyzed transesterification and wastewater treatment. Due to the low rapeseed yield and intensive chemical fertilizer use in China, the overall energy cost of rapeseed-based biodiesel is estimated at 1.1 times of its biodiesel energy output, corresponding to a negative energy return, with essential policy-making implications, in contrast to the positive ones usually reported in previous researches. © 2010.

Chen Z.M.,Peking University | Chen G.Q.,Peking University
Energy Policy | Year: 2011

Presented in this study is an empirical analysis of embodied carbon dioxide emissions induced by fossil fuel combustion for the world divided into three supra-national coalitions, i.e., G7, BRIC, and the rest of the world (ROW), via the application of a multi-region input-output modeling for 2004. Embodied emission intensities for the three coalitions are calculated and compared, with market exchange rate and purchase power parity separately used to investigate the difference between nominal and real production efficiencies. Emissions embodied in different economic activities such as production, consumption, import, and export are calculated and analyzed accordingly, and remarkable carbon trade imbalances associated with G7 (surplus of 1.53 billion tons, or 36% its traded emissions) and BRIC (deficit of 1.37 billion tons, or 51% its traded emissions) and approximate balance with ROW (deficit of 0.16 billion tons, or 3% its traded emissions) are concretely revealed. Carbon leakages associated with industry transfer and international trades are illustrated in terms of impacts on global climate policies. The last but not least, per capita consumption based emissions for G7, BRIC, and ROW are determined as 12.95, 1.53, and 2.22 tons, respectively, and flexible abatement policies as well as equity on per capita entitlement are discussed. © 2011 Elsevier Ltd.

Liu Z.,University of Wisconsin - Madison | Liu Z.,Peking University
Journal of Climate | Year: 2012

The emerging interest in decadal climate prediction highlights the importance of understanding the mechanisms of decadal to interdecadal climate variability. The purpose of this paper is to provide a review of our understanding of interdecadal climate variability in the Pacific and Atlantic Oceans. In particular, the dynamics of interdecadal variability in both oceans will be discussed in a unified framework and in light of historical development. General mechanisms responsible for interdecadal variability, including the role of ocean dynamics, are reviewed first. A hierarchy of increasingly complex paradigms is used to explain variability. This hierarchy ranges from a simple red noise model to a complex stochastically driven coupled ocean-atmosphere mode. The review suggests that stochastic forcing is the major driving mechanism for almost all interdecadal variability, while ocean-atmosphere feedback plays a relatively minor role. Interdecadal variability can be generated independently in the tropics or extratropics, and in the Pacific or Atlantic. In the Pacific, decadal-interdecadal variability is associated with changes in the wind-driven upper-ocean circulation. In the North Atlantic, some of the multidecadal variability is associated with changes in the Atlantic meridional overturning circulation (AMOC). In both the Pacific and Atlantic, the time scale of interdecadal variability seems to be determined mainly by Rossby wave propagation in the extratropics; in the Atlantic, the time scale could also be determined by the advection of the returning branch of AMOC in the Atlantic. One significant advancement of the last two decades is the recognition of the stochastic forcing as the dominant generation mechanism for almost all interdecadal variability. Finally, outstanding issues regarding the cause of interdecadal climate variability are discussed. The mechanism that determines the time scale of each interdecadal mode remains one of the key issues not understood. It is suggested that much further understanding can be gained in the future by performing specifically designed sensitivity experiments in coupled ocean-atmosphere general circulation models, by further analysis of observations and cross-model comparisons, and by combining mechanistic studies with decadal prediction studies. © 2012 American Meteorological Society.

Zhang Y.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

As a consequence of the LSND anomaly and other hints of an eV scale sterile neutrino from particle physics and cosmology, the neutrino sector of the standard model of particle physics has to be extended and the smallest extension is the (3+1) model, i.e., three active neutrinos plus one sterile one. In this work we study the neutrino mass matrix Mν with three texture zeros in the (3+1) model, assuming all the neutrino states are of Majorana type. With the mass hierarchy between the active and sterile neutrinos as well as the smallness of the reactor neutrino mixing and active-sterile mixing, the analytical expressions can be greatly simplified. We systematically examine all the 120 texture zeros, via both analytical and numerical analysis, and find that the 100 textures with zeros in the fourth column and row of Mν can hardly be compatible with experiments; whereas, 19 of the other 20 are feasible. We can foresee that the active neutrino masses are required to be around 0.01 eV and the next generation neutrinoless double beta decay experiments are promising to test these textures. Many other phenomenologically meaningful predictions are also obtained. All the CP conserving (3+1) textures with three zeros are excluded by experiments. © 2013 American Physical Society.

Anttu N.,Lund University | Xu H.Q.,Lund University | Xu H.Q.,Peking University
Optics Express | Year: 2013

Vertical arrays of direct band gap III-V semiconductor nanowires (NWs) hold the prospect of cheap and efficient next-generation photovoltaics, and guidelines for successful light-management are needed. Here, we use InP NWs as a model system and find, through electrodynamic modeling, general design principles for efficient absorption of sun light in nanowire arrays by systematically varying the nanowire diameter, the nanowire length, and the array period. Most importantly, we discover the existence of specific band-gap dependent diameters, 170 nm and 410 nm for InP, for which the absorption of sun light in the array is optimal, irrespective of the nanowire length. At these diameters, the individual InP NWs of the array absorb light strongly for photon energies just above the band gap energy due to a diameter-tunable nanophotonic resonance, which shows up also for other semiconductor materials of the NWs. Furthermore, we find that for maximized absorption of sun light, the optimal period of the array increases with nanowire length, since this decreases the insertion reflection losses. © 2013 Optical Society of America.

Li N.,Peking University | Liu C.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Lüscher's formula relates the elastic scattering phase shifts to the two-particle energy levels in a finite cubic box. The original formula was obtained for elastic scattering of two massive spinless particles in the center-of-mass frame. In this paper, we consider the case for the scattering of a spin 1/2 particle with a spinless particle in a multichannel scattering. A generalized relation between the energy of the two-particle system and the scattering matrix elements is established. We first obtain this relation using quantum mechanics in both the center-of-mass frame and in a general moving frame. The result is then generalized to quantum field theory, using methods outlined by Hansen and Sharpe. We verify that the results obtained using both methods are equivalent up to terms that are exponentially suppressed in the box size. © 2013 American Physical Society.

Zhang J.L.,Peking University
Computational Statistics and Data Analysis | Year: 2014

Bayesian p values are a popular and important class of approaches for Bayesian model checking. They are used to quantify the degree of surprise from the observed data given the specified data model and prior distribution. A systematic investigation is conducted to compare three Bayesian p values - the posterior predictive p value, the sampled posterior p value and the calibrated posterior predictive p value. Their general computation costs are compared, and several examples that incorporate both simple and complex Bayesian models are used to compare their frequency properties. It is recommended to use the sampled posterior p value because it is computationally least expensive and safest. © 2014 Elsevier B.V. All rights reserved.

Guo Y.,Peking University
Environmental health : a global access science source | Year: 2014

Little evidence is available about the association between temperature and cerebrovascular mortality in China. This study aims to examine the effects of ambient temperature on cerebrovascular mortality in different climatic zones in China. We obtained daily data on weather conditions, air pollution and cerebrovascular deaths from five cities (Beijing, Tianjin, Shanghai, Wuhan, and Guangzhou) in China during 2004-2008. We examined city-specific associations between ambient temperature and the cerebrovascular mortality, while adjusting for season, long-term trends, day of the week, relative humidity and air pollution. We examined cold effects using a 1°C decrease in temperature below a city-specific threshold, and hot effects using a 1°C increase in temperature above a city-specific threshold. We used a meta-analysis to summarize the cold and hot effects across the five cities. Beijing and Tianjin (with low mean temperature) had lower thresholds than Shanghai, Wuhan and Guangzhou (with high mean temperature). In Beijing, Tianjin, Wuhan and Guangzhou cold effects were delayed, while in Shanghai there was no or short induction. Hot effects were acute in all five cities. The cold effects lasted longer than hot effects. The hot effects were followed by mortality displacement. The pooled relative risk associated with a 1°C decrease in temperature below thresholds (cold effect) was 1.037 (95% confidence interval (CI): 1.020, 1.053). The pooled relative risk associated with a 1°C increase in temperature above thresholds (hot effect) was 1.014 (95% CI: 0.979, 1.050). Cold temperatures are significantly associated with cerebrovascular mortality in China, while hot effect is not significant. People in colder climate cities were sensitive to hot temperatures, while people in warmer climate cities were vulnerable to cold temperature.

Ge Q.,Peking University
Developmental and comparative immunology | Year: 2013

The thymus is the primary organ for functional T lymphocyte development in jawed vertebrates. A new study in the jawless fish, lampreys, indicates the existence of a primitive thymus in these surviving representatives of the most ancient vertebrates, providing strong evidence of co-evolution of T cells and thymus. This review summarizes the wealth of data that have been generated towards understanding the evolution of the thymus in the vertebrates. Progress in identifying genetic networks and cellular mechanisms that control thymus organogenesis in mammals and their evolution in lower species may inspire the development of new strategies for medical interventions targeting faulty thymus functions. Copyright © 2012 Elsevier Ltd. All rights reserved.

Ling X.,Peking University | Zhang J.,Peking University
Journal of Physical Chemistry C | Year: 2011

Graphene-enhanced Raman scattering (GERS) has been discovered, and the chemical enhancement mechanism based on charge transfer was thought as the main reason for the enhancement. We reported herein the effect of an interference phenomenon, a well-known reason for influencing the Raman scattering intensity, on the GERS using SiO2/Si substrates with different SiO2 thicknesses. First, it was found that the variation of Raman intensity of graphene on different thicknesses of SiO2/Si substrates followed the interference law. When the GERS system was moved on these substrates, where copper phthalocyanine (CuPc) and protoporphyrin IX (PPP) were constructed on graphene, the variation of the Raman intensity of the molecules on graphene and on SiO2/Si substrate also followed the interference law well. However, for the GERS system, the Raman intensity of the molecules is obviously enhanced compared to the molecules on SiO2/Si substrates. The results show that when we compare the Raman scattering intensity of the molecule in the GERS system and non-GERS system on a SiO2/Si substrate with the same SiO2 thickness, an interference phenomenon will not influence the comparison of the intensity. Meanwhile, charge transfer between graphene and the molecule is proven existent regardless of the thick SiO2/Si substrate on which GERS occurs, by comparing the G-band shift of graphene before and after the deposition of the molecule, which further indicates the interaction between the molecule and graphene plays an important role in GERS. This work will be beneficial for the further understanding of the origin of GERS. © 2011 American Chemical Society.

Large discrepancies among the laminar flame speeds and Markstein lengths of methane/air mixtures measured by different researchers using the same constant-pressure spherical flame method are observed. As an effort to reduce these discrepancies, one linear model (LM, the stretched flame speed changes linearly with the stretch rate) and two non-linear models (NM I and NM II, the stretched flame speed changes non-linearly with the stretch rate) for extracting the laminar flame speed and Markstein length from propagating spherical flames are investigated. The accuracy and performance of the LM, NM I, and NM II are found to strongly depend on the Lewis number. It is demonstrated that NM I is the most accurate for mixtures with large Lewis number (positive Markstein length) while NM II is the most accurate for mixtures with small Lewis number (negative Markstein length). Therefore, in order to get accurate laminar flame speed and Markstein length from spherical flame experiments, different non-linear models should be used for different mixtures. The validity of the theoretical results is further demonstrated by numerical and experimental studies. The results of this study can be used directly in spherical flame experiments measuring the laminar flame speed and Markstein length. © 2010 The Combustion Institute.

Zhang H.,Peking University | Chen Z.,Peking University
Combustion and Flame | Year: 2011

Spherical flame initiation and propagation with thermally sensitive intermediate kinetics are studied analytically within the framework of large activation energy and quasi-steady assumptions. A correlation describing different flame regimes and transitions among the ignition kernels, flame balls, propagating spherical flames, and planar flames is derived. Based on this correlation, spherical flame propagation and initiation are then investigated. The flame propagation speed, Markstein length, and critical ignition power and radius are found to strongly depend on the Lewis numbers of fuel and radical and the heat of reaction. For spherical flame propagation, the trajectory is shown to change significantly with the fuel Lewis number and a C-shaped solution curve of flame propagation speed as a function of flame radius is observed for large fuel Lewis numbers. The Markstein length is shown to increase/decrease monotonically with the fuel/radical Lewis number. The influence of stretch on flame propagation (i.e. the absolute value of Markstein length) is found to decrease with the heat of reaction. For spherical flame initiation, the critical ignition power and radius are shown to increase with the fuel Lewis number and to decrease with the radical Lewis number and heat of reaction. Three different flame initiation regimes are observed and discussed. Furthermore, the validity of theoretical prediction is confirmed by transient numerical simulations including thermal expansion and detailed chemistry. © 2010 The Combustion Institute.

Xing Z.-Z.,CAS Institute of High Energy Physics | Xing Z.-Z.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

In addition to three active neutrinos ν e, ν μ, and ν τ, one or more light sterile neutrinos have been conjectured to account for the LSND, MiniBooNE, and reactor antineutrino anomalies (at the sub-eV mass scale) or for warm dark matter in the Universe (at the keV mass scale). Heavy Majorana neutrinos at or above the TeV scale have also been assumed in some seesaw models. Such hypothetical particles can weakly mix with active neutrinos, and thus their existence can be detected at low energies. In the (3+3) scenario with three sterile neutrinos we present a full parametrization of the 6×6 flavor mixing matrix in terms of 15 rotation angles and 15 phase angles. We show that this standard parametrization allows us to clearly describe the salient features of some problems in neutrino phenomenology, such as (a) possible contributions of light sterile neutrinos to the tritium beta decay and neutrinoless double-beta decay, (b) leptonic CP violation and deformed unitarity triangles of the 3×3 flavor mixing matrix of three active neutrinos, (c) a reconstruction of the 6×6 neutrino mass matrix in the type-(I+II) seesaw mechanism, and (d) flavored and unflavored leptogenesis scenarios in the type-I seesaw mechanism with three heavy Majorana neutrinos. © 2012 American Physical Society.

Li Z.,Peking University | Li Z.,Chinese Academy of Sciences
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We note that the theoretical prediction of neutrinos from gamma-ray bursts (GRBs) by IceCube overestimates the GRB neutrino flux, because they ignore both the energy dependence of the fraction of proton energy transferred to charged pions and the radiative energy loss of secondary pions and muons when calculating the normalization of the neutrino flux. After correction, GRB neutrino flux is reduced by a factor ∼5 for typical GRB spectral parameters and may be consistent with the present zero event detected by IceCube. More observations are important to push the sensitivity below the prediction and test whether GRBs are the sources of ultrahigh energy cosmic rays. © 2012 American Physical Society.

Yin H.,Peking University | Zhang C.,Peking University | Liu F.,Peking University | Hou Y.,Peking University
Advanced Functional Materials | Year: 2014

It is extremely desirable but challenging to create highly active, stable, and low-cost catalysts towards oxygen reduction reaction to replace Pt-based catalysts in order to perform the commercialization of fuel cells. Here, a novel iron nitride/nitrogen doped-graphene aerogel hybrid, synthesized by a facile two-step hydrothermal process, in which iron phthalocyanine is uniformly dispersed and anchored on graphene surface with the assist of π-π stacking and oxygen-containing functional groups, is reported. As a result, there exist strong interactions between FexN nanoparticles and graphene substrates, leading to a synergistic effect towards oxygen reduction reaction. It is worth noting that the onset potential and current density of the hybrid are significantly better and the charge transfer resistance is much lower than that of pure nitrogen-doped graphene aerogel, free FexN and their physical mixtures. The hybrid also exhibits comparable catalytic activity as commercial Pt/C at the same catalyst loading, while its stability and resistance to methanol crossover are superior. Interestingly, it is found that, apart from the active nature of the hybrid, the large surface area and porosity are responsible for its excellent onset potential and the high density of Fe-N-C sties and small size of FexN particles boost charge transfer rate. A novel macroporous iron nitride/nitrogen doped-graphene aerogel hybrid is reported as a highly active, stable, and low-cost catalyst for oxygen reduction reaction. The strong interactions between FexN nanoparticles and graphene substrates boost its performance. It is also found that surface area, porosity, density of Fe-N-C sties, and particle sizes affect electrocatalytic activity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Jiang F.,Peking University | Wang L.,Peking University
Systems and Control Letters | Year: 2011

The consensus state is an important and fundamental quantity for consensus problems of multi-agent systems, which indicates where all the dynamical agents reach. In this paper, weighted average consensus with respect to a monotonic function, which means that the trajectories of the monotonic function along the state of each agent reach the weighted average of their initial values, is studied for a group of kinematic agents with time-varying topology. By constructing a continuous nonlinear distributed protocol, such a consensus problem can be solved in finite time even though the time-varying topology involves unconnected graphs. Then the distributed protocol is employed to compute the maximum-likelihood estimation of unknown parameters over sensor networks. Compared with the existing results, the estimate scheme proposed here may reduce the costs of data communication, storage memory, book-keeping and computational overheads. © 2011 Elsevier B.V. All rights reserved.

Han F.,Peking University
Respirology | Year: 2012

Narcolepsy-cataplexy syndrome is characterized by excessive daytime sleepiness, cataplexy, sleep paralysis, hypnagogic hallucinations and disturbed nocturnal sleep. It is strongly associated with the genetic marker, human leucocyte antigen (HLA) DQB1*06:02. A deficit in the endogenous hypocretin/orexin system due to neuronal degeneration in the lateral hypothalamus, induced by an autoimmune-mediated process, is the primary pathophysiology associated with the human disease. The important finding of an association with hypocretin genes in animal models of narcolepsy has led to the establishment of cerebrospinal fluid hypocretin measurements as a new diagnostic test for human narcolepsy. This is a fascinating story of translation of basic science research into clinical practice in sleep medicine during the past decade. Recent advances have shed light on the associations between respiratory medicine and narcolepsy-cataplexy research. The first is that upper airway infections, including H1N1 and/or streptococcal infections, may initiate or reactivate an immune response that leads to loss of hypocretin-secreting cells and narcolepsy in genetically susceptible individuals. The second is that an increased incidence of sleep disordered breathing among narcoleptic subjects may relate to the impairment of central control of breathing, linked to hypocretin deficiency or carriage of HLADQB1*06:02, in animals and human subjects with narcolepsy, respectively, indicating neural dysfunction in an area where respiratory and sleep-wake systems are closely interrelated. © 2012 Asian Pacific Society of Respirology.

Ye Y.,Peking University | Dai L.,Peking University
Journal of Materials Chemistry | Year: 2012

The Schottky junction, with merits of material universality, low cost and easy fabrication, is an alternative structure for solar cells. Compared to traditional indium-tin-oxide (ITO) based Schottky junction solar cells, graphene-based ones have merits of low cost, performance stability, and are applicable to flexible devices. In this highlight, we survey the recent research on graphene-based Schottky junction solar cells, including graphene-on-silicon Schottky junction solar cells and graphene/single NW (NB) Schottky junction solar cells. The working principle of them is discussed. These works demonstrate that graphene-based Schottky junction structures are promising candidates for developing diverse novel high-efficient and low-cost photovoltaic devices. The perspective and challenge of them are also discussed and anticipated. © The Royal Society of Chemistry 2012.

Chen M.,Peking University | Kallenberg C.G.M.,University of Groningen
Nature Reviews Rheumatology | Year: 2010

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) include Wegener granulomatosis, microscopic polyangiitis, Churgĝ€ "Strauss syndrome and renal-limited vasculitis. This Review highlights the progress that has been made in our understanding of AAV pathogenesis and discusses new developments in the treatment of these diseases. Evidence from clinical studies, and both in vitro and in vivo experiments, supports a pathogenic role for ANCAs in the development of AAV; evidence is stronger for myeloperoxidase-ANCAs than for proteinase-3-ANCAs. Neutrophils, complement and effector T cells are also involved in AAV pathogenesis. With respect to treatment of AAV, glucocorticoids, cyclophosphamide and other conventional therapies are commonly used to induce remission in generalized disease. Pulse intravenous cyclophosphamide is equivalent in efficacy to oral cyclophosphamide but seems to be associated with less adverse effects. Nevertheless, alternatives to cyclophosphamide therapy have been investigated, such as the use of methotrexate as a less-toxic alternative to cyclophosphamide to induce remission in non-organ-threatening or non-life-threatening AAV. Furthermore, rituximab is equally as effective as cyclophosphamide for induction of remission in AAV and might become the standard of therapy in the near future. Controlled trials in which specific immune effector cells and molecules are being therapeutically targeted have been initiated or are currently being planned. © 2010 AJA, SIMM & SJTU All rights reserved.

Song H.,Peking University | Song H.,Ohio State University
Nuclear Physics A | Year: 2013

In this article, we briefly review recent progress related to extracting the quark-gluon plasma (QGP) specific shear viscosity from the flow data measured at Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC). © 2013 Elsevier B.V.

Zhang Z.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

We study the multi-Sommerfeld enhancement in the case where V(r) is composed of different kinds of potentials. We show that there are special properties of the multi-Sommerfeld enhancement. The physical content of the multi-Sommerfeld mechanism is carefully demonstrated. The multi-Sommerfeld enhancement might play a role in dark matter annihilation. © 2014 The Author.

Li Z.,Peking University | Ren W.,University of California at Riverside | Liu X.,Beijing Institute of Technology | Xie L.,Nanyang Technological University
Automatica | Year: 2013

This paper considers the distributed consensus problem of multi-agent systems with general continuous-time linear dynamics for both the cases without and with a leader whose control input might be nonzero and time varying. For the case without a leader, based on the relative output information of neighboring agents, two types of distributed adaptive dynamic consensus protocols are proposed, namely, the edge-based adaptive protocol which assigns a time-varying coupling weight to each edge in the communication graph and the node-based adaptive protocol which uses a time-varying coupling weight for each node. These two adaptive protocols are designed to ensure that consensus is reached in a fully distributed fashion for all undirected connected communication graphs. It is shown that the edge-based adaptive consensus protocol is applicable to arbitrary switching connected graphs. For the case where there exists a leader whose control input is possibly nonzero and bounded, a distributed continuous adaptive protocol is designed to guarantee the ultimate boundedness of the consensus error with respect to any communication graph which contains a directed spanning tree with the leader as the root and whose subgraph associated with the followers is undirected, requiring neither global information of the communication graph nor the upper bound of the leader's control input. A distributed discontinuous protocol is also discussed as a special case. Simulation examples are finally given to illustrate the theoretical results. © 2013 Published by Elsevier Ltd.

Li N.,Beijing University of Technology | Zhu S.-L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We reinvestigate the possibility of X(3872) as a DD ̄* molecule with JPC=1 ++ within the framework of both the one-pion-exchange model and the one-boson-exchange model. After careful treatment of the S-D wave mixing, the mass difference between the neutral and charged D(D*) mesons and the coupling of the DD ̄* pair to D*D ̄*, a loosely bound molecular state X(3872) emerges quite naturally with large isospin violation in its flavor wave function. For example, the isovector component is 26.24% if the binding energy is 0.30 MeV, where the isospin breaking effect is amplified by the tiny binding energy. After taking into account the phase space difference and assuming the 3π and 2π come from a virtual omega and rho meson respectively, we obtain the ratio of these two hidden-charm decay modes: B(X(3872) →π +π -π0J/ψ)/B(X(3872) →π +π -J/ψ)=0.42 for the binding energy being 0.3 MeV, which is consistent with the experimental value. © 2012 American Physical Society.

Cai H.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

Supersymmetric models with extended electroweak gauge groups have the potential to enhance the Higgs quartic interaction through nondecoupling D-terms. We consider the D-term enhancement effect in a vector top partner model, where the quadratic divergence to the Higgs mass from the virtual top quark is canceled by its corresponding spin-1 superpartners. We are going to show that the model can predict a Higgs mass beyond the LEP bound and is consistent with the precision electroweak constraints. © 2012 American Physical Society.

Du W.,Peking University
Investigative ophthalmology & visual science | Year: 2012

Retinal neovascularization (NV) is a major cause of blindness. Recent research suggests that factors other than VEGF participate in this process. This study aimed to determine the role of ephrin-A4 in retinal NV. The expression and effect of ephrin-A4 was investigated in a mouse model of oxygen-induced retinopathy (OIR) and the RF/6A retina endothelial cell line. Ephrin-A4 expression and VEGF signaling pathway phosphorylation were determined by PCR, immunohistochemistry, and western blot analyses. ShRNA was used to silence ephrin-A4 in vitro and in vivo. Retinal flat mounts and tube formation assays were performed to evaluate ephrin-A4 function in the NV process in vivo and in vitro. Ephrin-A4 was overexpressed in the retina of OIR mice and in RF/6A and RPE cells after CoCl 2 stimulation. In vitro, Ephrin-A4/Fc treatment significantly increased the tube number of RF/6A cells on a membrane preparation and the phosphorylation levels of VEGR2, Akt1, and ERK1/2 in RF/6A cells. Moreover, ephrin-A4 knockout markedly suppressed pathologic neovascularization in vivo and inhibited the proliferation and tube formation capacity of RF/6A cells in vitro. Furthermore, in the absence of ephrin-A4, the phosphorylation of VEGFR2, Akt1, and ERK1/2 was defective under VEGF 165 stimulation, and the proangiogenic function of VEGF 165 was also compromised. This study suggests that ephrin-A4 plays an important role in retinal NV and is a potential target against retinal NV. The proangiogenic function of ephrin-A4 may be linked to its crucial role in the VEGF signaling pathway.

Zhang Y.,Peking University | Lee D.H.S.,Glaxosmithkline
Neuroscientist | Year: 2011

Amyloid β (Aβ) plaque, comprised mainly by Aβ peptides, is an important pathology of Alzheimer's brains. Major efforts have been devoted to targeting this neurotoxic Aβ peptide for discovering disease-modifying treatments for Alzheimer's disease. Inasmuch as Aβ is found in both the brain and the periphery, it is hypothesized that there is some form of equilibrium for the Aβ in the brain and the periphery such that Aβ can be transported across the blood-brain barrier. By modulating the periphery Aβ levels, it is predicted that the brain Aβ levels will undergo concomitant changes, forming the basis of the "sink hypothesis" for Aβ lowering strategies. In this review, the significance and implication of this sink hypothesis as well as how the sink hypothesis may contribute to the recent Aβ-based drug discovery in AD are discussed. Ultimately, the validity of the sink hypothesis will be resolved when the appropriate Aβ agents are being tested in the clinic. © 2011 The Author(s).

Fang X.,Peking University | Liu X.-W.,Peking University
Monthly Notices of the Royal Astronomical Society | Year: 2013

In Paper I, we presented a deep, long-slit spectrum of the bright Saturn nebula NGC 7009. Numerous permitted lines emitted by the C+, N+, O+ and Ne+ ions were detected. Gaussian profile fitting to the spectrum yielded more than 1000 lines, the majority of which are optical recombination lines (ORLs) of heavy-element ions. In the current paper, we present a critical analysis of the rich optical recombination spectrum of NGC 7009, in the context of the biabundance nebular model proposed by Liu et al. Transitions from individual multiplets are checked carefully for potential blended lines. The observed relative intensities are compared with the theoretical predictions based on high-quality effective recombination coefficients, now available for the recombination line spectrum of a number of heavy-element ions. The possibility of plasma diagnostics using the ORLs of various heavy-element ions is discussed in detail. The line ratios that can be used to determine electron temperature are presented for each ion, although there is still a lack of adequate atomic data and some of the lines are still not detected in the spectrum of NGC 7009 due to weakness and/or line blending. Plasma diagnostics based on the NII and OII recombination spectra both yield electron temperatures close to 1000 K, which is lower than those derived from the collisionally excited line (CEL) ratios (e.g. the [OIII] and [N II] nebular-to-auroral line ratios; see Paper I for details) by nearly one order of magnitude. The very low temperatures yielded by the OII and NII ORLs indicate that they originate from very cold regions. The C2+/H+, N2+/H+, O2+/H+ and Ne2+/H+ ionic abundance ratios derived from ORLs are consistently higher, by about a factor of 5, than the corresponding values derived from CELs. In calculating the ORL ionic abundance ratios, we have used the newly available high-quality effective recombination coefficients, and adopted an electron temperature of ~1000 K, as given by the ORL diagnostics and as a consequence presumably representing the physical conditions prevailing in the regions where the heavy-element ORLs arise. Measurements of the ultraviolet (UV) and infrared (IR) CELs from the literature are used to calculate CEL ionic abundance ratios when optical data are not available for the ionic species. A comparison of results of plasma diagnostics and abundance determinations for NGC 7009 points to the existence of 'cold', metal-rich (i.e. H-deficient) inclusions embedded in the hot, diffuse ionized gas, first postulated by Liu et al. At electron temperatures yielded by the N II and O II ORLs, the predicted relative intensities of ORLs agree well with the observed values, indicating that the current quantum calculations of the recombination spectra of those two ionic species well represent the recombination processes under nebular conditions. Deviations from the LS coupling, noticed in an earlier quantitative spectroscopy byLiu et al. for the same object, are again confirmed, especially for recombination lines of the 4f-3d transition array. For N II, aswell as for O II, the ionic abundances derived from different J-resolved transitions within amultiplet, or from the transitions belonging to different multiplets, agree with each other. This is another evidence that the new effective recombination coefficients are reliable. New calculations of the effective recombination coefficients for the Ne II lines at nebular temperatures and densities are needed. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.

CML treatment with tyrosine kinase inhibitors (TKIs) has improved many patients' prognosis, but during the disease's terminal phase, the blast crisis (CML-BC), has been disappointing. Allo-HSCT is another treatment, but survival rates are still disappointing. Currently, a combination of these two is suggested but with little evidence. This retrospective comparison reports on this combination and TKI alone for treatment of CML-BC. Of the 83 CML-BC patients, 45 received TKIs (imatinib; nilotinb or dasatinib after imatinib resistance; TKIs group) and 38 were treated with allo-HSCT after TKI (TKIs+allo-HSCT group). Treatment success was measured in terms of the hematologic, cytogenic and molecular responses, and subject outcome. Follow-up was 30-126 months or until death. Univariate and multivariate analyses determined EFS and OS predictors. Allo-HSCT significantly improved the 4-year OS (46.7 vs 9.7%, P<0.001) and EFS (47.1 vs 6.7%, P<0.001) compared to TKI treatment alone. Hemoglobin <100 g/L, non-return to chronic phase after TKI therapy and TKI treatment alone are independent adverse predictors of OS and EFS. Allo-HSCT with individualized intervention after TKI therapy is superior to TKI alone for CML-BC.Bone Marrow Transplantation advance online publication, 21 July 2014; doi:10.1038/bmt.2014.146.

Zhao S.,Peking University | Liu S.,U.S. Geological Survey
Global Change Biology | Year: 2014

Scaling is central to ecology and Earth system sciences. However, the importance of scale (i.e. resolution and extent) for understanding carbon dynamics across scales is poorly understood and quantified. We simulated carbon dynamics under a wide range of combinations of resolution (nine spatial resolutions of 250 m, 500 m, 1 km, 2 km, 5 km, 10 km, 20 km, 50 km, and 100 km) and extent (57 geospatial extents ranging from 108 to 1 247 034 km2) in the southeastern United States to explore the existence of scale dependence of the simulated regional carbon balance. Results clearly show the existence of a critical threshold resolution for estimating carbon sequestration within a given extent and an error limit. Furthermore, an invariant power law scaling relationship was found between the critical resolution and the spatial extent as the critical resolution is proportional to An (n is a constant, and A is the extent). Scale criticality and the power law relationship might be driven by the power law probability distributions of land surface and ecological quantities including disturbances at landscape to regional scales. The current overwhelming practices without considering scale criticality might have largely contributed to difficulties in balancing carbon budgets at regional and global scales. © 2013 John Wiley & Sons Ltd.

Li Y.,Peking University | Wang J.,Peking University
European Journal of Cardio-thoracic Surgery | Year: 2013

OBJECTIVES: We summarize our experiences of video-assisted thoracoscopic surgery (VATS) sleeve lobectomy with bronchoplasty for non-small-cell lung cancer and discuss the indications and technical details of the operation. METHODS: From September 2011 to December 2012, 15 patients underwent VATS sleeve lobectomy with bronchoplasty at our institution (right upper lobe 10, right middle and lower lobes 1, left lower lobe 2 and left upper lobe 2), with mediastinal lymphadenectomy. Three incisions were utilized. The utility incision was made at the fourth intercostal space, anterior axillary line. Simple continuous and simple interrupted suturing of the membranous and cartilaginous portions of the bronchus were performed for the anastomosis. RESULTS: All procedures were uneventful, with a median operative time of 165 min, a median bronchial anastomosis time of 44 min and a median blood loss of 150 ml. There were no conversions to thoracotomy. There were 14 squamous carcinomas and 1 adenocarcinoma. All patients recovered well, and 1 experienced a minor complication. The median duration of chest tube drainage was 5.4 days, and the median length of hospital stay was 7 days. All patients were followed postoperatively for a range of 1-16 months without tumour recurrence. CONCLUSIONS: VATS sleeve lobectomy with bronchoplasty is safe and effective. The utility incision placed at the fourth intercostal space, anterior axillary line, is convenient for the anastomosis, and the suturing technique is expeditious and secure. Preserving the azygos vein does not compromise exposure for the anastomosis. This technique is very suitable for centrally located lung cancers <3 cm in diameter, particularly when the cancers are located within the brachial lumen. © The Author 2013. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.

Rein H.,Institute for Advanced Study | Liu S.-F.,Peking University
Astronomy and Astrophysics | Year: 2012

REBOUND is a new multi-purpose N-body code which is freely available under an open-source license. It was designed for collisional dynamics such as planetary rings but can also solve the classical N-body problem. It is highly modular and can be customized easily to work on a wide variety of different problems in astrophysics and beyond. REBOUND comes with three symplectic integrators: leap-frog, the symplectic epicycle integrator (SEI) and a Wisdom-Holman mapping (WH). It supports open, periodic and shearing-sheet boundary conditions. REBOUND can use a Barnes-Hut tree to calculate both self-gravity and collisions. These modules are fully parallelized with MPI as well as OpenMP. The former makes use of a static domain decomposition and a distributed essential tree. Two new collision detection modules based on a plane-sweep algorithm are also implemented. The performance of the plane-sweep algorithm is superior to a tree code for simulations in which one dimension is much longer than the other two and in simulations which are quasi-two dimensional with less than one million particles. In this work, we discuss the different algorithms implemented in REBOUND, the philosophy behind the code's structure as well as implementation specific details of the different modules. We present results of accuracy and scaling tests which show that the code can run efficiently on both desktop machines and large computing clusters. © 2012 ESO.

Herczeg G.J.,Peking University | Hillenbrand L.A.,California Institute of Technology
Astrophysical Journal | Year: 2015

Absolute ages of young stars are important for many issues in pre-main-sequence stellar and circumstellar evolution but long have been recognized as difficult to derive and calibrate. In this paper, we use literature spectral types and photometry to construct empirical isochrones in Hertzsprung-Russell diagrams for low mass stars and brown dwarfs in the η Cha, Cha, and TW Hya Associations and the β Pic and Tuc-Hor Moving Groups. A successful theory of pre-main-sequence evolution should match the shapes of the stellar loci for these groups of young stars. However, when comparing the combined empirical isochrones to isochrones predicted from evolutionary models, discrepancies lead to a spectral type (mass) dependence in stellar age estimates. Improved prescriptions for convection and boundary conditions in the latest models of pre-main-sequence evolution lead to a significantly improved correspondence between empirical and model isochrones, with small offsets at low temperatures that may be explained by observational uncertainties or by model limitations. Independent of model predictions, linear fits to combined stellar loci of these regions provide a simple empirical method to order clusters by luminosity with a reduced dependence on spectral type. Age estimates calculated from various sets of modern models that reproduce Li depletion boundary ages of the β Pic Moving Group also imply a ∼4 Myr age for the low mass members of the Upper Sco OB Association, which is younger than the 11 Myr age that has been recently estimated for intermediate and high mass members. © 2015. The American Astronomical Society. All rights reserved..

Zeng T.-S.,Peking University | Wang C.,Tsinghua University | Zhai H.,Tsinghua University
Physical Review Letters | Year: 2015

Recently it has been theoretically proposed and experimentally demonstrated that a spin-orbit coupled multicomponent gas in a 1D lattice can be viewed as a spinless gas in a synthetic 2D lattice with a magnetic flux. In this Letter we consider interaction effects in such a Fermi gas, and propose these effects can be easily detected in a charge pumping experiment. Using 1/3 filling of the lowest 2D band as an example, in the strongly interacting regime, we show that the charge pumping value gradually approaches a universal fractional value for large spin components and low filling of the 1D lattice, indicating a fractional quantum Hall-type behavior, while the charge pumping value is zero if the 1D lattice filling is commensurate, indicating a Mott insulator behavior. The charge-density-wave order is also discussed. © 2015 American Physical Society.

The exact relationship between nucleosome positioning and methylation of CpG islands in human pathogenesis is unknown. In the present study, we characterized the nucleosome position within the p16 CpG island and established a seeding methylation-specific PCR (sMSP) assay based on bisulfite modification to enrich the p16 alleles containing methylated-CpG at the methylation "seeding" sites within its intron-1 in gastric carcinogenesis. The sMSP-positive rate in primary gastric carcinoma (GC) samples (36/40) was significantly higher than that observed in gastritis (19/45) or normal samples (7/13) (P<0.01). Extensive clone sequencing of these sMSP products showed that the density of methylated-CpGs in p16 CpG islands increased gradually along with the severity of pathological changes in gastric tissues. In gastritis lesions the methylation was frequently observed in the region corresponding to the exon-1 coding-nucleosome and the 5'UTR-nucleosome; the methylation was further extended to the region corresponding to the promoter-nucleosome in GC samples. Only few methylated-CpG sites were randomly detected within p16 CpG islands in normal tissues. The significantly inversed relationship between the p16 exon-1 methylation and its transcription was observed in GC samples. An exact p16 promoter-specific 83 bp-MSP assay confirms the result of sMSP (33/55 vs. 1/6, P<0.01). In addition, p16 methylation in chronic gastritis lesions significantly correlated with H. pylori infection; however, such correlation was not observed in GC specimens. It was determined that de novo methylation was initiated in the coding region of p16 exon-1 in gastritis, then progressed to its 5'UTR, and ultimately to the proximal promoter in GCs. Nucleosomes may function as the basic extension/progression unit of de novo methylation of p16 CpG islands in vivo.

Gipson C.D.,Medical University of South Carolina | Kupchik Y.M.,Medical University of South Carolina | Shen H.,Peking University | Reissner K.J.,Medical University of South Carolina | And 2 more authors.
Neuron | Year: 2013

Cocaine addiction is characterized by long-lasting vulnerability to relapse arising because neutral environmental stimuli become associated with drug use and then act as cues that induce relapse. It is not known how cues elicit cocaine seeking, and why cocaine seeking is more difficult to regulate than seeking a natural reward. We found that cocaineassociated cues initiate cocaine seeking by inducing a rapid, transient increase in dendritic spine size and synaptic strength in the nucleus accumbens. These changes required neural activity in the prefrontal cortex. This is not the case when identical cues were associated with obtaining sucrose, which did not elicit changes in spine size or synaptic strength. The marked cue-induced synaptic changes in the accumbens were correlated with the intensity of cocaine, but not sucrose seeking, and may explain the difficulty addicts experience in managing relapse to cocaine use. © 2013 Elsevier Inc.

Jiang M.-Y.,Peking University
Advanced Nonlinear Studies | Year: 2010

Positive periodic solutions of the equation ẍ + x = g(t)xp-1 are considered with continuous and T-periodic g. Some existence results of solutions are obtained by variational method.

Chen J.,National University of Singapore | Zhang G.,Peking University | Li B.,Peking University | Li B.,National University of Singapore
Nano Letters | Year: 2010

We propose to reduce the thermal conductivity of silicon nanowires (SiNWs) by introducing a small hole at the center, i.e., construct a silicon nanotube (SiNT) structure. Our numerical results demonstrate that a very small hole (only 1% reduction in cross section area) can induce a 35% reduction in room temperature thermal conductivity. Moreover, with the same cross section area, thermal conductivity of SiNT is only about 33% of that of SiNW at room temperature. The spatial distribution of vibrational energy reveals that localization modes are concentrated on the inner and outer surfaces of SiNTs. The enhanced surface-to-volume ratio in SiNTs reduces the percentage of delocalized modes, which is believed to be responsible for the reduction of thermal conductivity. Our study suggests SiNT is a promising thermoelectric material with low thermal conductivity. © 2010 American Chemical Society.

He Q.Y.,Peking University | Gong Q.H.,Peking University | Reid M.D.,Swinburne University of Technology
Physical Review Letters | Year: 2015

Using Venn diagrams, we classify the different types of two-mode Gaussian continuous variable quantum correlation including directional entanglement and Einstein-Podolsky-Rosen (EPR) steering. We establish unified signatures for one- and two-way quantum steering, entanglement, and discord beyond entanglement in terms of an EPR-type variance. By focusing on Gaussian states, we link an optimized condition for entanglement based on an EPR variance to the Simon-Peres condition. This allows us to quantify the asymmetry of the Gaussian entanglement, and to relate the asymmetry to a directional quantum teleportation protocol where Alice and Bob possess asymmetrically noisy channels. Our analysis enables a determination of the type and direction of quantum correlation in a way that is easily measured in experiment. We also find that for symmetric states, when discord exceeds a certain threshold, the states are necessarily steerable. © 2015 American Physical Society.

PURPOSE: To evaluate and compare the thickness and the morphology of femtosecond and mechanical microkeratome LASIK fl aps using anterior segment optical coherence tomography (AS-OCT). METHODS: Bilateral LASIK was performed in 132 eyes from 61 myopic patients. Flaps were created in 72 eyes using the WaveLight FS200 femtosecond laser (Wave- Light GmbH, Erlangen, Germany) and in 50 eyes using the Moria microkeratome (Moria SA, Antony, France). AS-OCT was used 1 week postoperatively to evaluate the thickness of 17 points across each fl ap, which were 0, 2, and 3.5 mm to the corneal vertex on the horizontal, vertical, 45°, and 135° meridians. RESULTS: The mean central fl ap thickness was 105.53 ± 5.86 μm in the WaveLight group and 132.96 ± 13.91 μm in the Moria group (P < .001). The difference between the achieved and the intended fl ap thickness (accuracy) was 6.17 ± 3.98 and 23.60 ± 12.64 μm, respectively (P < .001). The standard deviation within individual fl ap (uniformity) was smaller in the WaveLight group. The symmetry and regularity were also better in the WaveLight group. Flap morphology showed a more regular planar shape in the WaveLight group and a meniscus shape in the Moria group. CONCLUSIONS: AS-OCT showed that the fl aps created by the WaveLight femtosecond laser were more accurate, reproducible, and uniform than those created by the Moria microkeratome. Copyright © SLACK Incorporated.

Liu X.,Peking University
Advances in dental research | Year: 2011

As an opportunistic infection, candidiasis is common among individuals infected with HIV. About 90% of patients develop oral and/or oropharyngeal candidiasis in various stages of AIDS. Triazole antifungal agents, such as fluconazole and itraconazole, are considered to be first-choice agents for treatment and prevention because of their relatively low side effects and high effectiveness on mucosal infections. However, with prolonged exposure to azoles, drug resistance becomes a challenge for clinicians and patients alike. In traditional Chinese medicine, more than 300 herbs have been discovered to have "pesticidal" activities, and some of these have been used as antifungal agents in clinical practice for many years. Crude extracts from a number of medicinal herbs have been shown to exhibit antifungal activities in vitro. These include cortex moutan, cortex pseudolaricis, rhizoma alpiniae officinarum, rhizoma coptidis, clove and cinnamon, anemarrhena cortex phellodendri, ramulus cinnamomi, and Chinese gall. The effective anti-Candida principals were identified to be berberine, palmatine, allincin, pseudolaric acid A and B, magnolol, honokiol, and galangin. Thus, traditional Chinese medicinal herbs provide abundant choices for the treatment of refractory candidiasis commonly seen in HIV/AIDS patients. However, there remains a need for further screening of effective extracts and for study of the antifungal mechanisms involved. Importantly, ahead of clinical application, the safety of these compounds must be firmly established.

Zhang B.,University of Nevada, Las Vegas | Yan H.,Peking University | Yan H.,University of Arizona
Astrophysical Journal | Year: 2011

The recent Fermi observation of GRB 080916C shows that the bright photosphere emission associated with a putative fireball is missing, which suggests that the central engine likely launches a Poynting-flux-dominated (PFD) outflow.We propose a model of gamma-ray burst (GRB) prompt emission in the PFD regime, namely, the Internal-Collision-induced MAgnetic Reconnection and Turbulence (ICMART) model. It is envisaged that the GRB central engine launches an intermittent, magnetically dominated wind, and that in the GRB emission region, the ejecta is still moderately magnetized (e.g., 1 ≲ σ ≲ 100). Similar to the internal shock (IS) model, the mini-shells interact internally at the radius RIS ∼ σ2cδt. Most of these early collisions, however, have little energy dissipation, but serve to distort the ordered magnetic field lines entrained in the ejecta. At a certain point, the distortion of magnetic field configuration reaches the critical condition to allow fast reconnection seeds to occur, which induce relativistic MHD turbulence in the interaction regions. The turbulence further distorts field lines easing additional magnetic reconnections, resulting in a runway release of the stored magnetic field energy (an ICMART event). Particles are accelerated either directly in the reconnection zone, or stochastically in the turbulent regions, which radiate synchrotron photons that power the observed gamma rays. Each ICMART event corresponds to a broad pulse in the GRB light curve, and a GRB is composed of multiple ICMART events. This model retains the merits of IS and other models, but may overcome several difficulties/issues faced by the IS model (e.g., low efficiency, fast cooling, electron number excess, Amati/Yonetoku relation inconsistency, and missing bright photosphere). Within this model, the observed GRB variability timescales could have two components, one slow component associated with the central engine time history, and another fast component associated with relativistic magnetic turbulence in the emission region. The model predicts a decrease of gamma-ray polarization degree and Ep in each ICMART event (broad pulse) during the prompt GRB phase, as well as a moderately magnetized external reverse shock. The model may be applied to the GRBs that have time-resolved, featureless Band-function spectra, such as GRB 080916C and most GRBs detected by Fermi LAT. © 2011 The American Astronomical Society. All rights reserved.

Chen G.Q.,Peking University | Wu Z.,Peking University
International Journal of Heat and Mass Transfer | Year: 2012

Heterogeneity of media distribution in a packed tube plays an important role on scalar dispersion by enhancing the transverse non-uniformity of the flow velocity. Presented in this paper is a theoretical analysis for an instantaneous release of scalar substance into a fully developed flow through a long tube of two zones distinctively packed with porous media. The velocity distribution of the flow through the tube is derived, with the known solution for a single zone tube flow included as a special case. Mei's perturbation analysis for scalar dispersion in a single phase fluid flow is rigorously generalized for the two-zone case of a tube flow to develop a dispersion model by averaging the concentration transport equation. Corresponding dispersivity is analytically determined, and Taylor's well-known result for a single-zone tube flow is recovered by setting corresponding parameters as unity. The enhancement of the dispersion by the heterogeneity and the dependence of the enhanced dispersion on the tube radius are illustrated and characterized by relevant dimensionless parameters. © 2011 Elsevier Ltd. All rights reserved.

We predict an intrinsic thermo-spin Hall effect, namely, that a transverse spin current is generated by the temperature gradient and the heat current in a disorder-free two-dimensional electron gas (2DEG) with finite spin-orbit coupling. There exist two classes of contributions to the thermal spin Hall effect, corresponding to a 2DEG contacting two reservoirs at different temperatures and to a 2DEG separated from the reservoirs by insulating spacers, respectively. It is shown that the thermal spin Hall current can be generated not only by the temperature gradient directly but also by the thermoelectric effect. © 2009 Elsevier Ltd. All rights reserved.

Zhang C.,Peking University | Jiao N.,Peking University | Jiao N.,East China Normal University
Angewandte Chemie - International Edition | Year: 2010

In the air tonight: A novel approach to symmetric and unsymmetric aromatic azo compounds from simple anilines catalyzed by inexpensive CuBr has been disclosed. Air (or dioxygen) was used as an oxidant under mild reaction conditions, with H2O as the byproduct, to make this transformation environmentally benign and very easy to handle. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhao J.,Peking University | Tang H.,Peking University
Journal of Computational Physics | Year: 2013

This paper develops the P K-based Runge-Kutta discontinuous Galerkin (RKDG) methods with WENO limiter for the one- and two-dimensional special relativistic hydrodynamics, K = 1, 2, 3, which is an extension of the work [J.X. Qiu, C.-W. Shu, Runge-Kutta discontinuous Galerkin method using WENO limiters, SIAM J. Sci. Comput. 26 (2005) 907-929]. The WENO limiter for the RKDG method is adaptively implemented via two following steps: the "troubled" cells are first identified by using a TVB modified minmod function, and then a new polynomial solution inside the "troubled" cells is locally reconstructed to replace the RKDG solution by using the WENO technique based on the cell average values of the RKDG solution in the neighboring cells as well as the original cell averages of the "troubled" cells. Several test problems in one and two dimensions are computed using the developed RKDG methods with WENO limiter. The computations demonstrate that our methods are stable, accurate, and robust in maintaining accuracy for simulating flows in the special relativistic hydrodynamics. © 2013 Elsevier Inc.

Gao Y.Q.,Peking University
Journal of Physical Chemistry B | Year: 2012

Elucidating the interactions of cosolvents and cosolutes, for example, urea and inorganic salts, with proteins plays a very important role in understanding protein structure formation, solubility, and dynamics. In a recent study, we rationalized the experimentally observed salt effects on water/air surface tension and showed the potential importance of cation/anion association/ cooperativity. In this paper, we focus on salt effects on the solvation of simple model compounds such as peptides and benzene, hoping to obtain a more general and simple understanding of the Hofmeister series. We show here that preferred cation binding to the carbonyl and anion to the apolar surface of model polypeptides can help explain the experimentally observed salt effects on polypeptide activity coefficient in water. The effects of ions on the solvation of amide group can be both direct and indirect, which together attribute to an effective change of the proton donor/acceptor equilibrium in aqueous solutions. We show that such an argument can be used to understand not only the salt effects on solubility of amides but also why some organic compounds are protein secondary structure denaturants whereas others are protectants. (Graph Presented) © 2012 American Chemical Society.

Zeng Z.,Peking University
World Journal of Gastroenterology | Year: 2014

Persistent hepatitis B virus (HBV) infection is a significant public health problem because it is a major cause of chronic liver disease, cirrhosis, and hepatocellular carcinoma (HCC). Roughly one-third of the world population has been infected with HBV and there are about 350 million (5%-6%) persistent carriers. HBV causes 80% of all liver cancer cases and is the second most important carcinogen, after smoking tobacco. There is an approximate 90% risk of becoming a persistent carrier following perinatal infection in infants born to e antigen positive carrier mothers and a 30% risk in pre-school children. Only 5%-10% of adults become persistent carriers following infection. Of individuals persistently infected with HBV, 10%-30% will develop liver cirrhosis and HCC. These highly variable outcomes in both clearance rates and disease outcomes in persistently infected individuals cannot be fully explained by differences in immunological, viral or environmental factors. Thus, differences in host genetic factors may affect the natural history of hepatitis B. © 2014 Baishideng Publishing Group Inc. All rights reserved.

Yu S.,Stanford University | Chen H.-Y.,Stanford University | Gao B.,Peking University | Kang J.,Peking University | Wong H.-S.P.,Stanford University
ACS Nano | Year: 2013

The three-dimensional (3D) cross-point array architecture is attractive for future ultra-high-density nonvolatile memory application. A bit-cost-effective technology path toward the 3D integration that requires only one critical lithography step or mask for reducing the bit-cost is demonstrated in this work. A double-layer HfOx-based vertical resistive switching random access memory (RRAM) is fabricated and characterized. The HfOx thin film is deposited at the sidewall of the predefined trench by atomic layer deposition, forming a vertical memory structure. Electrode/oxide interface engineering with a TiON interfacial layer results in nonlinear I-V suitable for the selectorless array. The fabricated HfOx vertical RRAM shows excellent performances such as reset current (<50 μA), switching speed (<100 ns), switching endurance (>108 cycles), read disturbance immunity (>10 9 cycles), and data retention time (>105 s @ 125 C). © 2013 American Chemical Society.

Wei T.,Fujian Agriculture and forestry University | Li Y.,Peking University
Annual Review of Phytopathology | Year: 2016

Rice reoviruses, transmitted by leafhopper or planthopper vectors in a persistent propagative manner, seriously threaten the stability of rice production in Asia. Understanding the mechanisms that enable viral transmission by insect vectors is a key to controlling these viral diseases. This review describes current understanding of replication cycles of rice reoviruses in vector cell lines, transmission barriers, and molecular determinants of vector competence and persistent infection. Despite recent breakthroughs, such as the discoveries of actin-based tubule motility exploited by viruses to overcome transmission barriers and mutually beneficial relationships between viruses and bacterial symbionts, there are still many gaps in our knowledge of transmission mechanisms. Advances in genome sequencing, reverse genetics systems, and molecular technologies will help to address these problems. Investigating the multiple interaction systems among the virus, insect vector, insect symbiont, and plant during natural infection in the field is a central topic for future research on rice reoviruses. © 2016 by Annual Reviews. All rights reserved.

Zhao P.,Peking University
Urban Studies | Year: 2014

This paper aims to contribute to existing literature on the effects of the built environment on bicycle commuting, examining the case of Beijing. A group of city-wide random samples is analysed. The analysis shows that bicycle commuting is significantly associated with some features of the built environment when many demographic and socioeconomic factors are taken into account. Higher destination accessibility, a higher number of exclusive bicycle lanes, a mixed environment and greater connectivity between local streets tend to increase the use of the bicycle. These effects differ across gender, age and income groups. However, residential density has no significant effects on the use of a bicycle for commuting, while higher levels of public transit services tends to decrease rather than increase bicycle commuting. The results imply that the drastic changes in the built environment are a major reason for the demise of 'the kingdom of bicycles' in China. © 2013 Urban Studies Journal Limited.

Ge H.,Fudan University | Qian M.,Peking University | Qian H.,University of Washington
Physics Reports | Year: 2012

The mathematical theory of nonequilibrium steady state (NESS) has a natural application in open biochemical systems which have sustained source(s) and sink(s) in terms of a difference in their chemical potentials. After a brief introduction in Section 1, in Part II of this review, we present the widely studied biochemical enzyme kinetics, the workhorse of biochemical dynamic modeling, in terms of the theory of NESS (Section 2.1). We then show that several phenomena in enzyme kinetics, including a newly discovered activation-inhibition switching (Section 2.2) and the well-known non-Michaelis-Menten-cooperativity (Section 2.3) and kinetic proofreading (Section 2.4), are all consequences of the NESS of driven biochemical systems with associated cycle fluxes. Section 3 is focused on nonlinear and nonequilibrium systems of biochemical reactions. We use the phosphorylation-dephosphorylation cycle (PdPC), one of the most important biochemical signaling networks, as an example (Section 3.1). It starts with a brief introduction of the Delbrück-Gillespie process approach to mesoscopic biochemical kinetics (Sections 3.2 and 3.3). We shall discuss the zeroth-order ultrasensitivity of PdPC in terms of a new concept - the temporal cooperativity (Sections 3.4 and 3.5), as well as PdPC with feedback which leads to biochemical nonlinear bistability (Section 3.6). Also, both are nonequilibrium phenomena. PdPC with a nonlinear feedback is kinetically isomorphic to a self-regulating gene expression network, hence the theory of NESS discussed here could have wide applications to many other biochemical systems. © 2011 Elsevier B.V.

Zhang X.-J.,Zhejiang Normal University | Qian H.,University of Washington | Qian M.,Peking University
Physics Reports | Year: 2012

The concepts of equilibrium and nonequilibrium steady states are introduced in the present review as mathematical concepts associated with stationary Markov processes. For both discrete stochastic systems with master equations and continuous diffusion processes with Fokker-Planck equations, the nonequilibrium steady state (NESS) is characterized in terms of several key notions which are originated from nonequilibrium physics: time irreversibility, breakdown of detailed balance, free energy dissipation, and positive entropy production rate. After presenting this NESS theory in pedagogically accessible mathematical terms that require only a minimal amount of prerequisites in nonlinear differential equations and the theory of probability, it is applied, in Part I, to two widely studied problems: the stochastic resonance (also known as coherent resonance) and molecular motors (also known as Brownian ratchet). Although both areas have advanced rapidly on their own with a vast amount of literature, the theory of NESS provides them with a unifying mathematical foundation. Part II of this review contains applications of the NESS theory to processes from cellular biochemistry, ranging from enzyme catalyzed reactions, kinetic proofreading, to zeroth-order ultrasensitivity. © 2011 Elsevier B.V.

Zhang G.,Peking University
Nanoscale | Year: 2011

By using molecular dynamics simulations, we have studied heat flux in graphene Y junctions with lengths of 16.7 nm. It is found that the heat flux runs preferentially from the branches to the stem, which demonstrates an obvious thermal rectification effect in these asymmetric graphene ribbons. More interesting, compared to single-layer graphene Y junctions, a larger rectification ratio can be achieved in double-layer structures, due to the presence of layer-layer interactions. Combined with the availability of high quality few-layer graphene materials, our results shed light on heat conduction in graphene nanoribbons and may open up few-layer graphene applications in thermal management of nano electronics.

Long term opioid treatment results in hyperalgesia and tolerance, which is a troublesome phenomenon in clinic application. Recent studies have revealed a critical role of toll-like receptor 4 (TLR4) in the neuropathological process of opioid-induced hyperalgesia and tolerance. TLR4 is predominantly expressed by microglial cells and is a key modulator in the activation of the innate immune system. Activation of TLR4 may initiate the activation of microglia and hence a number of neurotransmitters and neuromodulators that could enhance neuronal excitability are released. Blockade of TLR4 activation by its antagonists alleviate neuropathic pain. We hypothesized that opioid antagonists such as naloxone and naltrexone, which were also demonstrated to be TLR4 antagonist, may have clinic application value in attenuation of opioid-induced hyperalgesia and tolerance. © 2012 Elsevier Ltd.

Qiao J.,Peking University | Yan X.,Peking University
Clinical Ophthalmology | Year: 2013

Meibomian gland dysfunction (MGD) is one of the most common diseases observed in clinics; it influences a great number of people, and is the leading cause of evaporative dry eye. Given the increased recognition of the importance of MGD, a great amount of attention has been paid to therapies targeting this condition. The traditional treatments of MGD consist of warm compresses and lid hygiene for removing an obstructed meibum, as well as antibiotics and anti-inflammatory agents to improve the quality of the meibum. However, each of these treatments has a different shortcoming and the treatment of MGD remains challenging. Despite the numerous possible treatment options for MGD, it is still difficult to obtain complete relief of signs and symptoms. This review focuses on current emerging treatment options for MGD including intraductal meibomian gland probing, emulsion eye drops containing lipids, the LipiFlow® thermal pulsation system, N-acetyl-cysteine, azithromycin, oral supplementation with omega-3 essential fatty acids, and cyclosporine A. © 2013 Qiao and Yan.

Wang L.,Peking University | Xiao F.,Beijing Institute of Technology
IEEE Transactions on Automatic Control | Year: 2010

In this note, we discuss finite-time state consensus problems for multi-agent systems and present one framework for constructing effective distributed protocols, which are continuous state feedbacks. By employing the theory of finite-time stability, we investigate both the bidirectional interaction case and the unidirectional interaction case, and prove that if the sum of time intervals, in which the interaction topology is connected, is sufficiently large, the proposed protocols will solve the finite-time consensus problems. © 2006 IEEE.

Hartmann L.,University of Michigan | Herczeg G.,Peking University | Calvet N.,University of Michigan
Annual Review of Astronomy and Astrophysics | Year: 2016

Accretion through circumstellar disks plays an important role in star formation and in establishing the properties of the regions in which planets form and migrate. The mechanisms by which protostellar and protoplanetary disks accrete onto low-mass stars are not clear; angular momentum transport by magnetic fields is thought to be involved, but the low-ionization conditions in major regions of protoplanetary disks lead to a variety of complex nonideal magnetohydrodynamic effects whose implications are not fully understood. Accretion in pre-main-sequence stars of masses ≤1Mo (and in at least some 2-3-Mo systems) is generally funneled by the stellar magnetic field, which disrupts the disk at scales typically of order a few stellar radii. Matter moving at near free-fall velocities shocks at the stellar surface; the resulting accretion luminosities from the dissipation of kinetic energy indicate that mass addition during the T Tauri phase over the typical disk lifetime ∼3 Myr is modest in terms of stellar evolution, but is comparable to total disk reservoirs as estimated from millimeter-wave dust emission (∼10-2 Mo). Pre-main-sequence accretion is not steady, encompassing timescales ranging from approximately hours to a century, with longer-timescale variations tending to be the largest. Accretion during the protostellar phase--while the protostellar envelope is still falling onto the disk--is much less well understood, mostly because the properties of the central obscured protostar are difficult to estimate. Kinematic measurements of protostellar masses with new interfometric facilities should improve estimates of accretion rates during the earliest phases of star formation. © 2016 by Annual Reviews.

Liu T.,Peking University | Wu Y.,Peking University | Zhang H.,Peking University
Astrophysical Journal, Supplement Series | Year: 2012

A mapping survey of 51 Planck cold clumps projected on the Orion complex was performed with J = 1-0 lines of 12CO and 13CO with the 13.7m telescope at the Purple Mountain Observatory. The mean column densities of the Planck gas clumps range from 0.5 to 9.5 × 10 21cm -2, with an average value of (2.9 ± 1.9) × 10 21cm -2. The mean excitation temperatures of these clumps range from 7.4 to 21.1K, with an average value of 12.1 ± 3.0K and the average three-dimensional velocity dispersion σ 3D in these molecular clumps is 0.66 ± 0.24kms -1. Most of the clumps have σ NT larger than or comparable to σ Therm. The H 2 column density of the molecular clumps calculated from molecular lines correlates with the aperture flux at 857GHz of the dust emission. By analyzing the distributions of the physical parameters, we suggest that turbulent flows can shape the clump structure and dominate their density distribution on large scales, but not function on small scales due to local fluctuations. Eighty-two dense cores are identified in the molecular clumps. The dense cores have an average radius and local thermal equilibrium (LTE) mass of 0.34 ± 0.14pc and 38 +5 -30 M ⊙, respectively. The structures of low column density cores are more affected by turbulence, while the structures of high column density cores are more affected by other factors, especially by gravity. The correlation of velocity dispersion versus core size is very weak for the dense cores. The dense cores are found to be most likely gravitationally bounded rather than pressure confined. The relationship between M vir and M LTE can be well fitted with a power law. The core mass function here is much flatter than the stellar initial mass function. The lognormal behavior of the core mass distribution is most likely determined by internal turbulence. © 2012. The American Astronomical Society. All rights reserved.

Zhang R.,Texas A&M University | Zhang R.,Fudan University | Zhang R.,Peking University | Khalizov A.,Texas A&M University | And 3 more authors.
Chemical Reviews | Year: 2012

Recent findings related to nucleation and growth of atmospheric nanoparticles, with an emphasis on the understanding of these processes at a fundamental molecular level, are assessed. A laminar flow chamber with continuous formation of the nucleating vapors has been introduced for studying binary and ternary nucleation of atmospherically important sulfuric acid, which is subject to particularly severe wall loss. Reviews by Curtius, Holmes, and Kulmala and Kerminen provided an update on most recent field studies and also discussed the findings of atmospheric measurements in relation to the current laboratory and modeling work on atmospheric nucleation. Recently, Zhao et al. used a sensitive atmospheric pressure CIMS with two alternative charged/neutral cluster separation methods to measure low concentrations of neutral clusters formed during nucleation events, extending the instrumentation for measuring sulfuric acid in the atmosphere and sulfate clusters in the laboratory.

Qin Y.,Peking University | Xie S.D.,Peking University
Atmospheric Chemistry and Physics | Year: 2012

Multi-year inventories of anthropogenic black carbon emissions, including both fuel consumption and biomass open burning, at a high spatial resolution of 0.25°×0.25 have been constructed in China using GIS methodology for the period 1980-2009, based on official statistical data and time-varying emission factors. Results show that black carbon emissions increased from 0.87 Tg in 1980 to 1.88 Tg in 2009 with a peak in about 1995, and had been continually increasing in the first decade of the 21 century. Residential contribution to the total BC emissions declined from 82.03% in 1980 to 42.33% in 2009 at a continuous diminishing trend, but had always been the dominant contributor in China. While contributions from industry and transportation sectors had increased notably. BC emissions were mainly concentrated in the central eastern districts, the three northeastern provinces and the Sichuan Basin, covering 22.30% of China's territory, but were responsible for 43.02%, 50.47%, 50.69% and 54.30% of the national black carbon emissions in 1985, 1995, 2005 and 2009, respectively. Besides, China made up 70%-85% of BC emissions in East Asia, half of the emissions in Asia, and accounted for averagely 18.97% of the global BC emissions during the estimation period. © 2012 Author(s).

Peng L.-M.,Peking University | Zhang Z.,Peking University | Wang S.,Peking University
Materials Today | Year: 2014

Carbon nanotubes (CNTs) are quasi-one-dimensional materials with unique properties and are ideal materials for applications in electronic devices. Significant progress has been made on CNT electronics, and a doping-free approach has emerged from this research. This approach utilizes the contact control on the properties of field-effect transistors (FETs), preserving the perfect lattice of the CNT making it possible for CNT FETs to outperform state-of-the-art Si devices. Both n-type and p-type CNT FETs with near ballistic performance limits have been fabricated, symmetric CMOS devices have been demonstrated, and pass-transistor-logic, a circuit configuration that is more efficient than CMOS is being explored. © 2014 Elsevier Ltd. All rights reserved.

Uhm Z.L.,Peking University | Uhm Z.L.,University of Nevada, Las Vegas | Zhang B.,Peking University | Zhang B.,University of Nevada, Las Vegas
Nature Physics | Year: 2014

Synchrotron radiation of relativistic electrons is an important radiation mechanism in many astrophysical sources. In the sources where the synchrotron cooling timescale is shorter than the dynamical timescale, electrons are cooled down below the minimum injection energy. It has been believed that such 'fast cooling' electrons have a power-law distribution in energy with an index -2, and their synchrotron radiation has a photon spectral index1 -'1.5. On the other hand, in a transient expanding astrophysical source, such as a γ-ray burst (GRB), the magnetic field strength in the emission region continuously decreases with radius. Here we study such a system, and find that in a certain parameter regime, the fast-cooling electrons can have a harder energy spectrum. We apply this new physical regime to GRBs, and suggest that the GRB prompt emission spectra whose low-energy photon spectral index has a typical value2-5-1 could be due to synchrotron radiation in this moderately fast-cooling regime. © 2014 Macmillan Publishers Limited.

Li X.T.,Peking University
Advanced Materials Research | Year: 2014

Seismic attributes analysis were used to predict the sand distribution in this paper. Spectral decomposition technique was carried out in frequency domain. Spectral seismic attributes made an identification of target geological-mass from time domain to frequency domain in Lower U sandstone of HMO 3D area. The 40hz frequency attribute was the best attribute to predict sand distribution. Seismic waveform classification for Lower U sandstone with the time window from -7ms to +7ms of Lower U sandstone had a good relationship with the sandstone distribution. With the comprehansive analysis of borehole oil and gas distribution and seismic attributes characteristics, a prospective oil and gas area target was determined. © (2014) Trans Tech Publications, Switzerland.

Huang X.-J.,Peking University
Best Practice and Research: Clinical Haematology | Year: 2011

Currently, human leukocyte antigen (HLA)-mismatched/haploidentical allografts have been validated as an alternative stem cell source for patients who have no immediate access to an HLA-matched related or unrelated donor. However, relapse remains a challenge after HLA-mismatched/haploidentical hematopoietic stem cell transplantation (HSCT) that is employed in the treatment of patients with hematological malignancies. In recent years, newly developed immunomodulatory strategies, which include prophylactic and therapeutic donor lymphocyte/natural killer (NK) cell infusion, donor selection based on NK alloreactivity/non-inherited maternal antigen (NIMA), immune reconstitution promotion, and application of exogenous cytokines, have made it possible to decrease the relapse rate and improve outcomes following haploidentical HSCT. Further elucidation of the underlying mechanisms that govern leukemia stem cell escape from immunosurveillance after haploidentical HSCT may broaden our understanding and lead to therapies that control relapse. © 2011 Elsevier Ltd. All rights reserved.

Sun Y.,University of Jinan | Wang L.,Peking University
Systems and Control Letters | Year: 2012

This paper is concerned with the problem of consensus in the H ∞ sense for second-order continuous-time multi-agent systems with multiple asymmetric time-varying delays. By using a model transformation approach and matrix theory, we establish several conditions in terms of linear matrix inequalities such that consensus of multi-agent systems can be achieved in the H ∞ sense. The feasibility of the consensus conditions is also analyzed. As an application, we consider the case of intermittent measurement between agents. Numerical examples are presented to illustrate the theoretical results which can be applied to the case of negative information weights. © 2012 Elsevier B.V. All rights reserved.

Sun Q.,Peking University
Journal of Chemical Physics | Year: 2010

In this work, the Raman spectra of aqueous C12E5 solutions are recorded and utilized to demonstrate the existence of single donator-single acceptor (DA) hydrogen bonding in water. From Raman OH stretching bands of aqueous C12E5 solutions, the relative intensity of 3430 cm-1 subband increases with C12E5 concentrations. For confined water, the DA hydrogen bonding can be expected to be the important hydrogen bonding species. Therefore, the 3430 cm-1 component can be ascribed to OH vibration engaged in DA hydrogen bonding. This is in agreement with our recent explanation on Raman OH stretching band of water. For water at ambient conditions, the double donor-double acceptor (DDAA) and DA should be the dominant hydrogen bonding species, the ratio of DDAA to DA can be approximately to be 0.75:1, and the mean hydrogen bonding can be determined to be 2.75. © 2010 American Institute of Physics.

Methylation of CpG islands inactivates transcription of tumor suppressor genes including p16 (CDKN2A). Inhibitors of DNA methylation and histone deacylation are recognized as useful cancer therapeutic chemicals through reactivation of the expression of methylated genes. However, these inhibitors are not target gene-specific, so that they lead to serious side effects as regular cytotoxic chemotherapy agents. To explore the feasibility of methylated gene-specific reactivation by artificial transcription factors, we engineered a set of Sp1-like seven-finger zinc-finger proteins (7ZFPs) targeted to a 21-bp sequence of the p16 promoter and found that these 7ZFPs could bind specifically to the target p16 promoter probe. Then the p16-specific artificial transcription factors (p16ATFs) were made from these 7ZFPs and the transcription activator VP64. Results showed that transient transfection of some p16ATFs selectively up-regulated the endogenous p16 expression in the p16-active 293T cells. Moreover, the transient transfection of the representative p16ATF-6I specifically reactivated p16 expression in the p16-methylated H1299 and AGS cells pretreated with a nontoxic amount of 5'-aza-deoxycytidine (20 and 80 nM, respectively). In addition, stable transfection of the p16ATF induced demethylation of p16 CpG island and trimethylation of histone H3K4, and inhibited recruitment of DNA methyltransferase 1 and trimethylation of H3K9 and H3K27 in the p16 promoter in H1299 cells without 5'-aza-deoxycytidine pretreatment. Notably, inhibition of cell migration and invasion was observed in these p16-reactivated cells induced by transient and stable p16ATF transfection. These results demonstrate that p16ATF not only specifically reactivates p16 expression through demethylation of CpG islands, but also restores methylated p16 function.

Wang T.,Peking University | Jiao N.,Peking University
Accounts of Chemical Research | Year: 2014

ConspectusBecause of the importance of nitrogen-containing compounds in chemistry and biology, organic chemists have long focused on the development of novel methodologies for their synthesis. For example, nitrogen-containing compounds show up within functional materials, as top-selling drugs, and as bioactive molecules. To synthesize these compounds in a green and sustainable way, researchers have focused on the direct functionalization of hydrocarbons via C-H or C-C bond cleavage. Although researchers have made significant progress in the direct functionalization of simple hydrocarbons, direct C-N bond formation via C-H or C-C bond cleavage remains challenging, in part because of the unstable character of some N-nucleophiles under oxidative conditions.The nitriles are versatile building blocks and precursors in organic synthesis. Recently, chemists have achieved the direct C-H cyanation with toxic cyanide salts in the presence of stoichiometric metal oxidants. In this Account, we describe recent progress made by our group in nitrile synthesis. C-H or C-C bond cleavage is a key process in our strategy, and azides or DMF serve as the nitrogen source. In these reactions, we successfully realized direct nitrile synthesis using a variety of hydrocarbon groups as nitrile precursors, including methyl, alkenyl, and alkynyl groups. We could carry out Csp3-H functionalization on benzylic, allylic, and propargylic C-H bonds to produce diverse valuable synthetic nitriles. Mild oxidation of C=C double-bonds and C≡C triple-bonds also produced nitriles.The incorporation of nitrogen within the carbon skeleton typically involved the participation of azide reagents. Although some mechanistic details remain unclear, studies of these nitrogenation reactions implicate the involvement of a cation or radical intermediate, and an oxidative rearrangement of azide intermediate produced the nitrile. We also explored environmentally friendly oxidants, such as molecular oxygen, to make our synthetic strategy more attractive. Our direct nitrile synthesis methodologies have potential applications in the synthesis of biologically active molecules and drug candidates. © 2014 American Chemical Society.

Chang D.,Peking University | Song Y.,Peking University
Atmospheric Chemistry and Physics | Year: 2010

Biomass burning in tropical Asia emits large amounts of trace gases and particulate matter into the atmosphere, which has significant implications for atmospheric chemistry and climatic change. In this study, emissions from open biomass burning over tropical Asia were evaluated during seven fire years from 2000 to 2006 (1 March 2000-31 February 2007). The size of the burned areas was estimated from newly published 1-km L3JRC and 500-m MODIS burned area products (MCD45A1). Available fuel loads and emission factors were assigned to each vegetation type in a GlobCover characterisation map, and fuel moisture content was taken into account when calculating combustion factors. Over the whole period, both burned areas and fire emissions showed clear spatial and seasonal variations. The size of the L3JRC burned areas ranged from 36 031 km2 in fire year 2005 to 52 303 km2 in 2001, and the MCD45A1 burned areas ranged from 54 790 km2 in fire year 2001 to 148 967 km 2 in 2004. Comparisons of L3JRC and MCD45A1 burned areas using ground-based measurements and other satellite data were made in several major burning regions, and the results suggest that MCD45A1 generally performed better than L3JRC, although with a certain degree of underestimation in forest areas. The average annual L3JRC-based emissions were 123 (102-152), 12 (9-15), 1.0 (0.7-1.3), 1.9 (1.4-2.6), 0.11 (0.09-0.12), 0.89 (0.63-1.21), 0.043 (0.036-0.053), 0.021 (0.021-0.023), 0.41 (0.34-0.52), 3.4 (2.6-4.3), and 3.6 (2.8-4.7) Tg yr-1 for CO2, CO, CH4, NMHCs, NOx, NH3, SO2, BC, OC, PM2.5, and PM10, respectively, whereas MCD45A1-based emissions were 122 (108-144), 9.3 (7.7-11.7), 0.63 (0.46-0.86), 1.1 (0.8-1.6), 0.11 (0.10-0.13), 0.54 (0.38-0.76), 0.043 (0.038-0.051), 0.033 (0.032-0.037), 0.39 (0.34-0.47), 3.0 (2.6-3.7), and 3.3 (2.8-4.0) Tg yr-1. Forest burning was identified as the major source of the fire emissions due to its high carbon density. Although agricultural burning was the second highest contributor, it is possible that some crop residue combustion was missed by satellite observations. This possibility is supported by comparisons with previously published data, and this result may be due to the small size of the field crop residue burning. Fire emissions were mainly concentrated in Indonesia, India, Myanmar, and Cambodia. Furthermore, the peak in the size of the burned area was generally found in the early fire season, whereas the maximum fire emissions often occurred in the late fire season.

Bian Y.,Peking University | Gong Q.,Peking University
Optics Express | Year: 2013

A hybrid plasmonic structure comprising a silicon slot waveguide separated from an inverse metal ridge by a thin low-index insulator gap is proposed and investigated. Owing to its symmetric hybrid configuration containing closely spaced silicon rails near the metal ridge, the fundamental symmetric hybrid slot mode supported by the structure is demonstrated to be capable of simultaneously achieving low propagation loss and subwavelength field confinement within a wide range of physical dimensions at the telecom wavelength. Comprehensive numerical investigations regarding the effects of key geometric parameters on the guided modes' properties, including the slot sizes, the shape and dimension of the silicon rails, the width of the gap region as well as the height of metallic nanoridge, have been conducted. It is revealed that the propagation distance of the symmetric mode can be more than several millimeters (even up to the centimeter range), while simultaneously achieving a subwavelength mode size and tight field confinement inside the gap region. In addition to the studies on the modal characteristics, excitation strategies of the guided hybrid modes and the conversion between dielectric slot and hybrid slot modes are also numerically demonstrated. The studied platform potentially combines the advantages of silicon slot and plasmonic structures, which might lay important groundwork for future hybrid integrated photonic components and circuits. © 2013 Optical Society of America.

Cai H.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We explore the Higgs couplings to gauge bosons in the minimal SO(5)/SO(4) 4D composite Higgs model. The pion scatterings put unitary constraints on the couplings and therefore determine the branching ratios of various Higgs decays. Through fine-tuning the parameters, enhancement of Higgs to diphoton rate is possible to be achieved with the existence of vector meson fields. © 2013 American Physical Society.

Liu X.,Peking University | Lee C.-S.,Peking University
Organic Letters | Year: 2012

A concise enantioselective synthesis of (-)-teucvidin has been achieved. Our synthetic strategy involved the diastereoselective Michael/Conia-ene cascade cyclization reaction for rapid establishment of the cis-decalin skeleton with three new stereogenic centers in one pot (72%, single diastereomer), the epoxidation/dealkoxycarbonylation protocol for construction of the fused furanone moiety, and the O-allylation/Claisen rearrangement protocol for construction of the all-carbon quaternary center at C9 of the clerodane skeleton. © 2012 American Chemical Society.

Our objective was to examine whether high blood pressure in the preconception period was associated with low birth weight (LBW) and small-for-gestational age (SGA) in Chinese women. Data were obtained from the China–US Collaborative Project for Neural Tube Defects Prevention, a large population-based cohort study. We included 43 718 singleton live births delivered at gestational ages of 28−45 weeks to women who were registered before pregnancy in 7 counties in southern China. Blood pressure was measured during registration by trained healthcare workers, and other health-related information was recorded prospectively. We used logistic regression to evaluate the associations between preconception blood pressure and the risk of LBW and SGA, adjusting for potential confounders. The prevalence of hypertension in the preconception study population was 4.62% (2019/43 718). The incidences of LBW and SGA were 2.33% and 5.05% for the hypertension group and 2.01% and 5.68% for the nonhypertension group. Compared with the nonhypertension group, the hypertension group did not show significantly increased risk for LBW overall (adjusted risk ratio =1.16, 95% confidence interval 0.86−1.57) or SGA (adjusted risk ratio =0.89, 95% confidence interval 0.73−1.09). When participants with normal blood pressure were used as the reference, the adjusted risk ratio of SGA for prehypertensive women was 1.13 (95% confidence interval 1.03−1.25). Our results do not support an association between hypertension or higher blood pressure before pregnancy and increased risk of LBW or SGA. © 2016 American Heart Association, Inc

Qiu H.,Peking University
Communications in Mathematical Physics | Year: 2011

Let M be a smooth Riemannian manifold. We show that for C1 generic f ∈ Diff1(M), if f has a hyperbolic attractor Λf, then there exists a unique SRB measure supported on Λf. Moreover, the SRB measure happens to be the unique equilibrium state of potential function ψf ∈ C0(Λf) defined by ψf(x) = -log {pipe}det(Df{pipe}Eu x){pipe}, x ∈ Λf, where Eu x is the unstable space of TxM. © 2010 Springer-Verlag.

Li H.-T.,Peking University | Zhou Y.-B.,Peking University | Liu J.-M.,Peking University
International Journal of Obesity | Year: 2013

Studies have reported inconsistent results concerning the association of cesarean section with offspring obesity. We performed a systematic review and meta-analysis to examine whether cesarean section increases the risk of later overweight and obesity. Pubmed, Embase and Web of Science were searched using different combinations of two groups of keywords: 'cesarean' and 'overweight/obesity'. Cohort or case-control studies that reported the association of cesarean section with childhood (3-8 years), adolescence (9-18 years) and/or adult (>19 years) overweight/obesity were eligible. Where possible, adjusted risk estimates were pooled using a random effects model; otherwise unadjusted estimates were pooled. Statistical heterogeneity was assessed with I2 statistics; the values of 25%, 50% and 75% were considered to indicate low, medium and high heterogeneity, respectively. We conducted a subgroup analysis to identify the sources of heterogeneity according to study quality defined on the basis of the Newcastle-Ottawa Scale. In total, two case-control and seven cohort studies were identified for the literature review and 15 separate risk estimates were included in the meta-analysis. The overall pooled odds ratio (OR) of overweight/obesity for offspring delivered by cesarean section compared with those born vaginally was 1.33 (95% confidence interval (CI) 1.19, 1.48; I2 =63%); the OR was 1.32 (1.15, 1.51) for children, 1.24 (1.00, 1.54) for adolescents and 1.50 (1.02, 2.20) for adults. In subgroup analysis, the overall pooled OR was 1.18 (1.09, 1.27; I2 =29%) for high-quality studies and 1.78 (1.43, 2.22; I2 =24%) for medium-quality (P for interaction=0.0005); no low-quality studies were identified. The ORs for children, adolescents and adults all tended to be lower for high-quality studies compared with medium-quality studies. Our results indicated that cesarean section was moderately associated with offspring overweight and obesity. This finding has public health implications, given the increase in cesarean births in many countries. © 2013 Macmillan Publishers Limited.

Gu B.,Peking University | Zhu W.-G.,Peking University
International Journal of Biological Sciences | Year: 2012

Among the human genome, p53 is one of the first tumor suppressor genes to be discovered. It has a wide range of functions covering cell cycle control, apoptosis, genome integrity maintenance, metabolism, fertility, cellular reprogramming and autophagy. Although different possible underlying mechanisms for p53 regulation have been proposed for decades, none of them is conclusive. While much literature focuses on the importance of individual post-translational modifications, further explorations indicate a new layer of p53 coordination through the interplay of the modifications, which builds up a complex 'network'. This review focuses on the necessity, characteristics and mechanisms of the crosstalk among post-translational modifications and its effects on the precise and selective behavior of p53. © Ivyspring International Publisher.

Xu C.,Peking University | Tao D.,Intelligent Systems Technology, Inc.
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2015

It is practical to assume that an individual view is unlikely to be sufficient for effective multi-view learning. Therefore, integration of multi-view information is both valuable and necessary. In this paper, we propose the Multi-view Intact Space Learning (MISL) algorithm, which integrates the encoded complementary information in multiple views to discover a latent intact representation of the data. Even though each view on its own is insufficient, we show theoretically that by combing multiple views we can obtain abundant information for latent intact space learning. Employing the Cauchy loss (a technique used in statistical learning) as the error measurement strengthens robustness to outliers. We propose a new definition of multi-view stability and then derive the generalization error bound based on multi-view stability and Rademacher complexity, and show that the complementarity between multiple views is beneficial for the stability and generalization. MISL is efficiently optimized using a novel Iteratively Reweight Residuals (IRR) technique, whose convergence is theoretically analyzed. Experiments on synthetic data and real-world datasets demonstrate that MISL is an effective and promising algorithm for practical applications. © 2015 IEEE.

Xu Z.,Peking University | Zhang C.,Peking University | Jiao N.,Peking University | Jiao N.,Chinese Academy of Sciences
Angewandte Chemie - International Edition | Year: 2012

A fragment-assembling strategy is used to form oxazoles from aryl acetaldehydes, amines, and molecular oxygen under mild conditions (see scheme). The transformation is highly efficient with the removal of six hydrogen atoms, including the cleavage of four C(sp3)-H bonds. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yang J.,Peking University | Zhang J.,Peking University
Optics Express | Year: 2013

We propose a nano-polarization-converter made of a resonant Lshaped slot antenna in a gold film and study its optical properties using the finite-difference time-domain method. Phase retardation between the fast and slow axes of the nano-polarization-converter originates from the simultaneous excitation of both single-surface first-order magnetic plasmon resonance mode and second-order magnetic plasmon resonance mode at the working wavelength. By adjusting the size of the slot antenna, which is still much smaller than the wavelength, the working wavelength can be tuned within a large wavelength range. © 2013 Optical Society of America.

Tao G.,Peking University
Journal of Physical Chemistry C | Year: 2014

Interactions between electronic states and the environmental phonon bath in singlet fission plays a vital role in understanding the underlying mechanisms. In this work we apply the symmetrical quasiclassical nonadiabatic molecular dynamics simulation method [Cotton, S. J.; Miller, W. H. J. Phys. Chem. A 2013, 117, 7190 and Meyer, H. D.; Miller, W. H. J. Chem. Phys. 1979, 70, 3214] to a model system of singlet fission materials and examine the dependence of fission dynamics on some key factors in the bath modeling, such as, functional form of spectra density, characteristic frequencies, reorganization energy, and bath temperatures. Possible schemes of engineering the phonon spectrum to control fi ssion dynamics have been discussed. (Graph Presented). © 2014 American Chemical Society.

Li W.,Peking University | Huntsinger L.,University of California at Berkeley
Ecology and Society | Year: 2011

Northern China's grasslands have been losing productivity since the 1980s, when a policy known as the "grassland contracting policy" allocated commonly used grazing lands to individual herder households. Examined here is the connection between implementation of the grassland contracting policy and the loss of grassland production using the analytic concepts of ability to benefit and community failure. A gacha (village) of the Sunite Left Banner of the Xilingol League in Inner Mongolia is used as a case study to compare herder ability to benefit from rangeland resources during adverse climate events before and after policy implementation. Social-ecological resilience, access to social and ecological assets, and institutions supporting crisis relief have been affected. We find that the privatization of grassland use rights has weakened pastoralist ability to benefit from rangelands by weakening or dismantling what are identified as the rights-, structure-, and relations-based abilities that enabled pastoralists to cope with nonequilibrium conditions. This has led to a community failure that engenders feedbacks of increased impoverishment and environmental deterioration. The inflexible boundaries of quasi-private household property rights have caused the pastoral system to lose capacity to respond to drought and weather events through the flexibility of "otor" and other forms of herd movement, increasing vulnerability to environmental change. © 2011 by the author(s).

Zhang C.,Peking University | Hao R.,Peking University | Liao H.,Peking University | Hou Y.,Peking University
Nano Energy | Year: 2013

Nitrogen-containing graphene is a promising candidate for oxygen reduction reaction (ORR) in fuel cells. However, there are still some challenges in further application and modification of N-graphene and in understanding the roles of various nitrogen states on electrocatalysis. Herein, we design a simple and effective solvothermal method to synthesize amino-functionalized graphene (AG) from graphite oxide (GO) only in the presence of ammonia solution. Having a significant amount of amino species with the total nitrogen content of up to 10.6% (atom%), the resultant product can act as an efficient metal-free catalyst, exhibiting enhanced electrocatalytic properties for ORR. Furthermore, a combination of X-ray photoelectron spectroscopy (XPS) and electrochemical measurements was used to investigate the roles of various nitrogen states in ORR, and the contribution of amino group has been demonstrated for the first time. Our experiments show that the graphitic- and amino-type of nitrogen components determine the onset potential and electron transfer number, while the total content of graphitic and pyridinic nitrogen atoms is the key factor to enhance the current density in the electrocatalytic activity for ORR. This work could lead to economical synthesis of AG as efficient ORR electrocatalyst in fuel cells, and help to understand the catalytic mechanism of various nitrogen states towards ORR. © 2012 Elsevier Ltd.

Chen Y.,Peking University
Computers, Environment and Urban Systems | Year: 2011

The relationships between the size, scale, shape, and dimension of urban settlements are basic problems remained to be further resolved, and this paper provides an available perspective for understanding these problems. Based on the standard circle, the relations between the fractal dimension of urban boundary and the compactness ratios of urban shape were derived from a geometric measure relation in a simple way. The compactness ratios proved to be the exponential functions of the reciprocal of the boundary dimension. The results can be generalized and applied to the common indices of shape including circularity ratio, ellipticity index, and form ratio, which are defined by urban area, perimeter, or Feret's diameter. The mathematical models are empirically verified by the remote sensing data of China's 31 mega-cities in 1990 and 2000 and lend support to the assumption that urban boundaries are pre-fractals rather than real fractals. A conclusion can be drawn that there exist certain functional relations between the shape indices and the boundary dimension, and within certain range of scales, the fractal parameters can be indirectly estimated by the ratios of size measurements to reflect the features of urban shapes. © 2011 Elsevier Ltd.

Lin Y.,CAS Beijing National Laboratory for Molecular | Lin Y.,University of Chinese Academy of Sciences | Li Y.,CAS Beijing National Laboratory for Molecular | Zhan X.,CAS Beijing National Laboratory for Molecular | Zhan X.,Peking University
Advanced Energy Materials | Year: 2013

A novel linear non-fullerene acceptor (DBS-2DPP) based on dibenzosilole and diketopyrrolopyrrole is designed and synthesized. DBS-2DPP exhibits strong and broad absorption and appropriate energy levels matching with P3HT. Solution-processed BHJ OSCs based on P3HT:DBS-2DPP show PCEs as high as 2.05%. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wang J.,Peking University
Journal of experimental & clinical cancer research : CR | Year: 2013

To assess the efficacy of intraoperative ultrasound-guided implantation of 125I seeds for the treatment of unresectable pancreatic carcinoma, and analyze the associated prognostic factors. Twenty-eight patients with pancreatic carcinoma who underwent laparotomy and were considered to have unresectable tumors were included in this study. Nine patients were pathologically diagnosed with Stage II disease, and nineteen patients with Stage III disease. Twenty-eight patients received intraoperative ultrasound-guided 125I seed implantation and received a D90 (at least 90% of the tumor volume received the reference dose) ranging from 60 to 163 Gy, with a median of 120 Gy. Seven patients received an additional 35-50 Gy external beam radiotherapy after seed implantation, and ten patients received two to ten cycles of chemotherapy. Overall survival of the patients was calculated and prognostic factors were evaluated. Of the patients, 94.1% (16/17) achieved good to medium pain relief. The tumor response rate was 78.6% (22/28), and local control was achieved in 85.7% (24/28) of patients. The 1-, 2- and 3-year survival rates were 30%, 11% and 4%, and the median survival was 10.1 months (95% CI: 9.0-10.9). Analysis using the Cox proportional hazards model suggested that patients younger than 60 years and patients who received a D90 higher than 110 Gy may survive for a longer period. I seed implantation provides a safe and effective method to relieve pain, control local tumor growth and, to some extent, prolong the survival of patients with stage II and III pancreatic disease, without additional complications. Age and accumulated dose may be factors predictive of a favorable outcome for patients with unresectable pancreatic carcinoma treated with 125I seeds. These findings need to be validated by conducting further studies with larger cohorts.

Tao G.,Peking University
Journal of Physical Chemistry C | Year: 2014

The recently developed symmetrical quasi-classical (SQC) method (Cotton, S. J.; Miller, W. H. J. Phys. Chem. A, 2013, 117, 7190) has been applied to a model system for molecular dimers of polyacenes, a family of organic materials for highly efficient solar energy conversion by using singlet fission (SF). Our results describe the electronic-nuclear coupled dynamics of singlet fission very well for the model system, in good agreement with those recently obtained by using Redfield theory. The quantum interference between the charge transfer mediated pathway and the direct pathway of singlet fission has been investigated, and we found that pathway coherence may change the short-time SF dynamics quite a lot, even though the direct pathway itself may be very slow. The SQC method performs very efficiently in treating the model system with up to several thousand degrees of freedom and therefore shows a potential to be implemented to real complex molecular systems, such as singlet fission materials. © 2014 American Chemical Society.

Tumor necrosis factor-α is a key mediator in the pathogenesis of psoriasis. Infliximab is a monoclonal antibody that specifically binds to tumor necrosis factor-α. The purpose of this study was to validate the efficacy and safety of 5 mg/kg infliximab therapy in Chinese patients with moderate to severe plaque psoriasis. In this multicenter, double-blind, placebo-controlled trial, 129 patients with moderate-to-severe psoriasis were randomized to the induction therapy (weeks 0, 2 and 6) with infliximab 5 mg/kg (n = 84) or placebo (n = 45), followed with infliximab 5 mg/kg scheduled at week 14 and week 22 in the infliximab group, and infliximab 5 mg/kg scheduled at weeks 10, 12 and 16 in the placebo group. The primary end point was the proportion of patients who achieved at least 75% improvement in Psoriasis Area and Severity Index (PASI 75 response rate) from baseline at week 10. At week 10, 81.0% of patients treated with infliximab (5 mg/kg) achieved a 75% or greater improvement compared with 2.2% of patients treated with placebo (P < 0.001). A significant improvement in PASI, Physician's Global Assessment (PGA) and Dermatology Life Quality Index (DLQI), was seen from week 6 through week 14 in the infliximab group compared with the placebo group. Through week 22, PASI, PGA, DLQI were well maintained. The incidence of adverse events for the infliximab treatment group was slightly higher in comparison to the placebo treatment group during the first 10 weeks without statistical significance. However, there were 3 cases of tuberculosis that developed during the 26 weeks treatment with infliximal. Infliximab treatment was effective as induction and maintenance treatments for Chinese patients with moderate to severe plaque psoriasis. Most drug-induced adverse events were mild to moderate, and well tolerated. Screening for tuberculosis is essential and prophylactic treatment should be given if necessary.

Li C.,Peking University
Mathematics of Operations Research | Year: 2014

Enlightened by the theory of Watanabe [Watanabe S (1987) Analysis of Wiener functionals (Malliavin calculus) and its applications to heat kernels. Ann. Probab. 15:1-39] for analyzing generalized random variables and its further development in Yoshida [Yoshida N (1992a) Asymptotic expansions for statistics related to small diffusions. J. Japan Statist. Soc. 22: 139-159], Takahashi [Takahashi A (1995) Essays on the valuation problems of contingent claims. Ph.D. thesis, Haas School of Business, University of California, Berkeley, Takahashi A (1999) An asymptotic expansion approach to pricing contingent claims. Asia-Pacific Financial Markets 6:115-151] as well as Kunitomo and Takahashi [Kunitomo N, Takahashi A (2001) The asymptotic expansion approach to the valuation of interest rate contingent claims. Math. Finance 11(1):117-151, Kunitomo N, Takahashi A (2003) On validity of the asymptotic expansion approach in contingent claim analysis. Ann. Appl. Probab. 13(3):914-952] etc., we focus on a wide range of multivariate diffusion models and propose a general probabilistic method of small-time asymptotic expansions for approximating option price in simple closed-form up to an arbitrary order. To explicitly construct correction terms, we introduce an efficient algorithm and novel closed-form formulas for calculating conditional expectation of multiplication of iterated stochastic integrals, which are potentially useful in a wider range of topics in applied probability and stochastic modeling for operations research. The performance of our method is illustrated through various models nested in constant elasticity of variance type processes. With an application in pricing options on VIX under GARCH diffusion and its multifactor generalization to the Gatheral double lognormal stochastic volatility models, we demonstrate the versatility of our method in dealing with analytically intractable non-Lévy and non-affine models. The robustness of the method is theoretically supported by justifying uniform convergence of the expansion over the whole set of parameters. © 2014 INFORMS.

Xu C.,Peking University | Tao D.,University of Technology, Sydney
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2014

In this paper, we extend the theory of the information bottleneck (IB) to learning from examples represented by multi-view features. We formulate the problem as one of encoding a communication system with multiple senders, each of which represents one view of the data. Based on the precise components filtered out from multiple information sources through a 'bottleneck', a margin maximization approach is then used to strengthen the discrimination of the encoder by improving the code distance within the frame of coding theory. The resulting algorithm therefore inherits all the merits of the IB principle and coding theory. It has two distinct advantages over existing algorithms, namely, that our method finds a tradeoff between the accuracy and complexity of the multi-view model, and that the encoded multi-view data retains sufficient discrimination for classification. We also derive the robustness and generalization error bound of the proposed algorithm, and reveal the specific properties of multi-view learning. First, the complementarity of multi-view features guarantees the robustness of the algorithm. Second, the consensus of multi-view features reduces the empirical Rademacher complexity of the objective function, enhances the accuracy of the solution, and improves the generalization error bound of the algorithm. The resulting objective function is solved efficiently using the alternating direction method. Experimental results on annotation, classification and recognition tasks demonstrate that the proposed algorithm is promising for practical applications. © 1979-2012 IEEE.

Certain cancer genes contribute to tumorigenesis in a manner of either co-occurring or mutually exclusive (anti-cooccurring) mutations; however, the global picture of when, where and how these functional interactions occur remains unclear. This study presents a systems biology approach for this purpose. After applying this method to cancer gene mutation data generated from large-scale and whole genome sequencing of cancer samples, a network of cancer genes with co-occurring and anti-co-occurring mutations was constructed. Analysis of this network revealed that genes with cooccurring mutations prefer direct signaling transductions and that the interaction relations among cancer genes in the network are related with their functional similarity. It was also revealed that genes with co-occurring mutations tend to have similar mutation frequencies, whereas genes with anti-co-occurring mutations tend to have different mutation frequencies. Moreover, genes with more exons tend to have more co-occurring mutations with other genes, and genes having lower local coherent network structures tend to have higher mutation frequency. The network showed two complementary modules that have distinct functions and have different roles in tumorigenesis. This study presented a framework for the analysis of cancer genome sequencing outputs. The presented data and uncovered patterns are helpful for understanding the contribution of gene mutations to tumorigenesis and valuable in the identification of key biomarkers and drug targets for cancer. © 2010 Qinghua Cui.

Perets H.B.,Harvard - Smithsonian Center for Astrophysics | Kouwenhoven M.B.N.,Peking University
Astrophysical Journal | Year: 2012

In recent years, several planets have been discovered at wide orbits (>100AU) around their host stars. Theoretical studies encounter difficulties in explaining their formation and origin. Here we propose a novel scenario for the production of planetary systems at such orbits, through the dynamical recapture of free floating planets (FFPs) in dispersing stellar clusters and stellar associations. This process is a natural extension of the recently suggested scenario for the formation of wide stellar binaries. We use N-body simulations of dispersing clusters with 10-1000 stars and comparable numbers of FFPs to study this process. We find that planets are captured into wide orbits in the typical range few × 100-106AU and have a wide range of eccentricities (thermal distribution). Typically, 3-6 × (f FFP/1)% of all stars capture a planetary companion with such properties (where f FFP is the number of FFP per star in the birth clusters). The planetary capture efficiency is comparable to that of capture-formed stellar binaries, and shows a similar dependence on the cluster size and structure. It is almost independent of the specific planetary mass; planets as well as substellar companions of any mass can be captured. The capture efficiency decreases with increasing cluster size, and for a given cluster size it increases with the host/primary mass. We also find that more than one planet can be captured around the same host through independent consecutive captures; similarly, planets can be captured into binary systems, both in circumstellar and circumbinary orbits. We also expect planets to be captured into pre-existing planetary (and protoplanetary systems) as well as into orbits around black holes and massive white dwarfs, if these formed early enough before the cluster dispersal. In particular, stellar black holes have a high capture efficiency (>50% and 5-10 × (f FFP/1)% for capture of stars and planetary companions, respectively) due to their large mass. Finally, although rare, two FFPs or brown dwarfs can become bound and form an FFP-binary system with no stellar host. © © 2012. The American Astronomical Society. All rights reserved.

Wang C.,Peking University | Chen H.,Peking University | Wang Z.,Peking University | Chen J.,Peking University | Huang Y.,Peking University
Angewandte Chemie - International Edition | Year: 2012

Diverse opportunities: A Rhodium(III)-catalyzed ortho-selective olefination of arenes using a novel triazene as a directing group is reported. This method exhibits substantial post-functionalization synthetic versatility, overcoming a vital limitation in Ca spa 2-H activation/functionalization products: restricted structural diversity. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Khan Z.H.,Peking University
International Journal of Heat and Mass Transfer | Year: 2014

The instability of the liquid-vapour front in a geothermal system with a cooling flux at the liquid boundary is investigated by introducing a small perturbation at the front. The mechanisms contributing to the stability and instability of such systems are analysed using a separate-phase model with a sharp interface between liquid and vapour. The governing equations representing incompressibility, Darcy's law and energy conservation for each phase are linearised about suitable base state and the stability of this state is investigated. A conditional expression for the critical modified Rayleigh number depending on the different physical parameters has been found. It has been shown that advection is not essential for instability, but it encourages the unstable behaviour. © 2013 Elsevier Ltd. All rights reserved.

Ding S.,Peking University | Jiao N.,Peking University | Jiao N.,Chinese Academy of Sciences
Angewandte Chemie - International Edition | Year: 2012

Often used as a common solvent for chemical reations and utilized widely in industry as a reagent, N,N-dimethylformamide (DMF) has played an important role in organic synthesis for a long time. Numerous highly useful articles and reviews discussing its utilizations have been published. With a focus on the performance of DMF as a multipurpose precursor for various units in numerous reactions, this Minireview summarizes recent developments in the employment of DMF in the fields of formylation, aminocarbonylation, amination, amidation, and cyanation, as well as its reaction with arynes. © 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yi C.,Peking University | Yi C.,Peking Tsinghua Center for Life science | He C.,University of Chicago
Cold Spring Harbor Perspectives in Biology | Year: 2013

Endogenous and exogenous factors constantly challenge cellular DNA, generating cytotoxic and/or mutagenic DNA adducts. As a result, organisms have evolved different mechanisms to defend against the deleterious effects of DNA damage. Among these diverse repair pathways, direct DNA-repair systems provide cells with simple yet efficient solutions to reverse covalentDNA adducts. In this review,we focus on recent advances in the field of directDNA repair, namely, photolyase-, alkyltransferase-, and dioxygenase-mediated repair processes. We present specific examples to describe new findings of known enzymes and appealing discoveries of new proteins. At the end of this article, we also briefly discuss the influence of direct DNA repair on other fields of biology and its implication on the discovery of new biology. © 2013 Cold Spring Harbor Laboratory Press; all rights reserved.

Chong S.,Harvard University | Chen C.,Harvard University | Ge H.,Peking University | Xie X.S.,Harvard University | Xie X.S.,Peking University
Cell | Year: 2014

Transcription of highly expressed genes has been shown to occur in stochastic bursts. But the origin of such ubiquitous phenomenon has not been understood. Here, we present the mechanism in bacteria. We developed a high-throughput, in vitro, single-molecule assay to follow transcription on individual DNA templates in real time. We showed that positive supercoiling buildup on a DNA segment by transcription slows down transcription elongation and eventually stops transcription initiation. Transcription can be resumed upon gyrase binding to the DNA segment. Furthermore, using single-cell mRNA counting fluorescence in situ hybridization (FISH), we found that duty cycles of transcriptional bursting depend on the intracellular gyrase concentration. Together, these findings prove that transcriptional bursting of highly expressed genes in bacteria is primarily caused by reversible gyrase dissociation from and rebinding to a DNA segment, changing the supercoiling level of the segment. © 2014 Elsevier Inc.

Liu J.,Peking University
Pattern Recognition | Year: 2010

To find the best partition of a large and complex network into a small number of clusters has been addressed in many different ways. However, the probabilistic setting in which each node has a certain probability of belonging to a certain cluster has been scarcely discussed. In this paper, a fuzzy partitioning formulation, which is extended from a deterministic framework for network partition based on the optimal prediction of a random walker Markovian dynamics, is derived to solve this problem. The algorithms are constructed to minimize the objective function under this framework. It is demonstrated by the simulation experiments that our algorithms can efficiently determine the probabilities with which a node belongs to different clusters during the learning process. Moreover, they are successfully applied to two real-world networks, including the social interactions between members of a karate club and the relationships of some books on American politics bought from © 2009 Elsevier Ltd. All rights reserved.

Saliva diagnostics has become an attractive field utilizing nanotechnology and molecular technologies for pSS (primary Sjögren's syndrome). However, no specific methods have been established. To refine the diagnostic power of the saliva peptide finger print for the early detection of pSS, we screened the expression spectrum of salivary peptides in pSS patients by using mass spectrometry MALDI-TOF-MS (matrix-assisted laser-desorption ionization-time-of-flight MS) combined with magnetic bead. The present study was comprised 12 pSS patients and 13 healthy controls and broken down to two different phases. In the initial 'exploratory phase', we enrolled seven pSS patients with eight age- and sex-matched healthy volunteers. Proteomics analysis of the unstimulated salivary samples was conducted to generate proportional peptide mass fingerprints. A diagnostic model was established. The testing cohort of the second 'validation phase' was represented by five pSS patients and five age- and sex-matched healthy controls. The diagnostic power of this diagnostic panel was then validated. The results showed seven m/z (mass-to-charge) ratio peaks with significant differences. Five peptides were up-regulated and two down-regulated in the pSS patients compared with matched healthy subjects. In the validation phase, four out of five pSS patients were diagnosed as pSS, and four of the five healthy controls were diagnosed as healthy controls, respectively. Potential biomarkers were also primarily predicted. The novel diagnostic proteomic model with m/z peaks 1068.1 Da, 1196.2 Da, 1738.4 Da, 3375.3 Da, 3429.3 Da, 3449.7 Da and 3490.6 Da is of certain value for early diagnosis of pSS.

To evaluate the efficacy and safety of trastuzumab in combination with chemotherapy versus chemotherapy alone in the first-line treatment of HER-2-positive advanced gastric or gastro-oesophageal junction cancer. Fifteen Chinese research centers are involved in the BO18255 (ToGA) study. Patients with gastric or gastro-oesophageal junction cancer were eligible for inclusion if their tumor showed overexpression of HER-2 protein by immunohistochemistry +++ or FISH-positive. Patients were randomly assigned in a 1:1 ratio to receive a chemotherapy regimen consisting of capecitabine or 5-FU plus cisplatin or chemotherapy in combination with intravenous trastuzumab. The primary endpoint was overall survival. Eighty-five Chinese patients were enrolled in this study, of whom 84 were included in the primary analysis: trastuzumab plus chemotherapy (FP/H) (n = 36) and chemotherapy alone (FP)(n = 48). The median follow-up was 15.2 months in the FP/H group and 14.2 months in the FP group. The median survival time was 12.6 months in the FP/H group compared with 9.7 months in the FP group [hazard ratio 0.72, 95%CI (0.40; 1.29)]. Grade 3/4 adverse events were higher in the FP/H(63.9%)than FP (47.9%) groups, including neutropenia, vomiting and nausea. Two mild cardiac adverse events occurred in the FP/H group. Severe adverse events occurred in 3 cases of both two groups, respectively. Addition of trastuzumab to chemotherapy is well tolerated and shows improved survival in Chinese patients with advanced gastric or gastro-oesophageal junction cancer. These results are consistent with the results of ToGA whole population trial. Trastuzumab in combination with chemotherapy can be considered as a new option for patients with HER-2-positive advanced gastric or gastro-oesophageal junction cancer.

Chen Y.,Peking University
PLoS ONE | Year: 2013

Spatial autocorrelation plays an important role in geographical analysis; however, there is still room for improvement of this method. The formula for Moran's index is complicated, and several basic problems remain to be solved. Therefore, I will reconstruct its mathematical framework using mathematical derivation based on linear algebra and present four simple approaches to calculating Moran's index. Moran's scatterplot will be ameliorated, and new test methods will be proposed. The relationship between the global Moran's index and Geary's coefficient will be discussed from two different vantage points: spatial population and spatial sample. The sphere of applications for both Moran's index and Geary's coefficient will be clarified and defined. One of theoretical findings is that Moran's index is a characteristic parameter of spatial weight matrices, so the selection of weight functions is very significant for autocorrelation analysis of geographical systems. A case study of 29 Chinese cities in 2000 will be employed to validate the innovatory models and methods. This work is a methodological study, which will simplify the process of autocorrelation analysis. The results of this study will lay the foundation for the scaling analysis of spatial autocorrelation. © 2013 Yanguang Chen.

Lin S.,Peking University
Human reproduction (Oxford, England) | Year: 2013

Does the type of media used to culture embryos for IVF influence the birthweight and length of neonates? No significant differences were observed in birthweight and length among the three embryo culture media used for in vitro embryo culture. Since the establishment of IVF as an assisted reproductive technology (ART), many different culture systems have been used for the development of human embryos. Some studies have shown that the types of culture media influence the newborn birthweight; however, other studies have shown no effect. To further explore this contradictory issue, we compared the birthweight and length of neonates born after the transfer of embryos cultured in one of three commercially available media. This retrospective analysis of birthweight and length of newborns included 1201 women who delivered singletons and 445 women who delivered twins. The following three commercially available culture media were used: G5™, Global and Quinn's advantage media. Women who underwent IVF-ET cycles between 2008 and 2010 were analyzed. Patients younger than 40 years of age with a body mass index (BMI) <30 kg/m(2) were analyzed. Only data from singletons and twins born alive after the 20th week of gestation were included in the data analysis. Patients who received preimplantation genetic diagnosis (PGD) and donor oocytes were excluded. The analysis of 1201 singletons and 445 sets of twins showed no significant association between mean birthweight or mean birth length and the type of embryo culture medium. Inter-twin mean birthweight and length disparities were analyzed, but were not shown to be significantly different. Multiple linear regression analysis showed that maternal weight, maternal height, gestational age and infant gender were significantly related to birthweight, and paternal height, gestational age and newborn complications were significantly associated with birth length. The current study showed that birthweight and length of newborns were not associated with the embryo culture medium. More research needs to be performed to analyze the effects of other culture medium formulations and to evaluate the long-term effects of embryo culture medium on the health of children conceived through ART. WIDER IMPLICATIONS OF THESE FINDINGS: Our retrospective study suggests that embryo culture medium does not influence neonatal birthweight and length; however, the effects of culture medium on epigenetic variation of embryos need to be studied further.

The relative effects of climate and geometric constraints on geographic diversity patterns have long been controversial. We developed a new method to assess the role of geometric constraints in shaping altitudinal richness patterns. We showed how plant species richness on four mountains in southwest China are shaped by geometric constraints and environmental gradients together. Contrary to previous studies, our results suggested that: 1) small- and large-ranged species richness were largely controlled by the same environmental gradients, and differed mainly in the effect of geometric constraints. 2) The contribution of geometric constraints (in addition to environmental gradients) to explaining species richness was greater when species richness peaked at low altitudes than at mid-altitudes, suggesting that geometric constraints may be very important when richness peaks are far away from mid-domains. 3) Relating species richness directly to environmental factors (the most widely used method in biodiversity studies) may be misleading when geometric constraints may be affecting the richness pattern, because this method may overestimate the effect of environmental factors by failing to distinguish the confounding effect of geometric constraints. Instead, the effect of environmental factors can be evaluated with an underlying gradient derived from small-ranged species. 4) The geometric constraints effect cannot be fully evaluated by pure geometric constraints models, and is better evaluated with range-based models constrained with environmental gradients. 5) If the generality of our findings is supported for other taxa on other gradients, then many previous studies on the effects of climate and of geometric constraints on geographic diversity patterns may need to be re-visited. © 2012 The Authors. Ecography © 2012 Nordic Society Oikos.

Niu J.,Peking University
PloS one | Year: 2012

The slip-flow and heat transfer of a non-Newtonian nanofluid in a microtube is theoretically studied. The power-law rheology is adopted to describe the non-Newtonian characteristics of the flow, in which the fluid consistency coefficient and the flow behavior index depend on the nanoparticle volume fraction. The velocity profile, volumetric flow rate and local Nusselt number are calculated for different values of nanoparticle volume fraction and slip length. The results show that the influence of nanoparticle volume fraction on the flow of the nanofluid depends on the pressure gradient, which is quite different from that of the Newtonian nanofluid. Increase of the nanoparticle volume fraction has the effect to impede the flow at a small pressure gradient, but it changes to facilitate the flow when the pressure gradient is large enough. This remarkable phenomenon is observed when the tube radius shrinks to micrometer scale. On the other hand, we find that increase of the slip length always results in larger flow rate of the nanofluid. Furthermore, the heat transfer rate of the nanofluid in the microtube can be enhanced due to the non-Newtonian rheology and slip boundary effects. The thermally fully developed heat transfer rate under constant wall temperature and constant heat flux boundary conditions is also compared.

Sun Y.,Peking University | Liu Y.,Beihang University
IEEE Signal Processing Magazine | Year: 2012

The Internet has created vast opportunities to interact with strangers. The interactions can be fun, informative, and even profitable [1]. However, there is also risk involved. Will an eBay seller ship the product in time? Is the advice from a self-proclaimed expert on trustworthy? Does a product from have high quality as described? © 2012 IEEE.

Wang X.,Peking University | Wang D.Z.,Peking University
Tetrahedron | Year: 2011

We reported herein new reactivities and possible mechanistic implications of a simplest oxidant (NaH/air) uncovered on a broad range of useful transformations, including aerobic alcohol oxidations, allylic alcohol isomerizations and oxidations, cyclopropyl alcohol fragmentations, and direct aryl aldehyde oxidative amidations. These readily implementable transition-metal-free processes feature exceptional material accessibility, operational simplicity, and environmental compatibility, and add new dimensions to its synthetic utilities that are fairly robust yet had not previously been fully realized and systematically explored. © 2011 Published by Elsevier Ltd.

Antidepressants are effective in treating interferon-α/ribavirin (IFN-α/RBV)-associated depression during or after treatment of chronic hepatitis C (CHC). Whether antidepressant prophylaxis is necessary in this population remains under debate. Comprehensive searches were performed in Medline, Embase, Cochrane Controlled Trials Register and PubMed. Reference lists were searched manually. The methodology was in accordance with the 2009 PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) Statement. We identified six randomized, double-blind, placebo-controlled trials involving 522 CHC patients treated with pegylated (PEG)-IFN-α plus RBV. The antidepressants used were escitalopram, citalopram, and paroxetine, which are selective serotonin reuptake inhibitors (SSRIs). The rates of depression (17.9% vs. 31.0%, P = 0.0005), and rescue therapy (27.4% vs. 42.7%, P<0.0001) in the SSRI group were significantly lower than those in the placebo group. The rate of sustained virological response (SVR) (56.8% vs. 50.0%, P = 0.60) and drug discontinuation (18.7% vs. 21.1%, P = 0.63) in the SSRI group did not differ significantly to those in the placebo group. In terms of safety, the incidence of muscle and joint pain (40.8% vs. 52.4%, P = 0.03) and respiratory problems (29.3% vs. 40.1%, P = 0.03) were lower, but the incidence of dizziness was significantly higher (22.3% vs. 10.2%, P = 0.001) in the SSRI group. Prophylactic SSRI antidepressants can significantly reduce the incidence of PEG-IFN-α/RBV-associated depression in patients with CHC, with good safety and tolerability, without reduction of SVR.

Ju Y.,Beijing Institute of Technology | Wang A.,Peking University
Expert Systems with Applications | Year: 2012

How to select suitable emergency alternative is critical to emergency management and has attracted much attention for both researchers and practitioners. In the process of evaluating emergency alternative problems, there usually exists incomplete and uncertain information, and the decision makers can not easily express their judgments on the candiates with exact and crisp values. The Dempster-Shafer theory (DST) is well suited for dealing with such problems and can generate comprehensive assessments for different alternatives. In this paper, the DS/AHP method and extended TOPSIS method are incorporated to solve group multi-criteria decision making (GMCDM) problems with incomplete information. The proposed method involves three steps: (1) Identify the focal elements of each decision maker according to the group decision matrix. (2) Construct the group weighted normalized belief interval decision matrix using Dempster's rule of combination. (3) Propose the Extended TOPSIS approach for group interval data to rank the emergency alternatives. In this method, the positive ideal solution vector is defined as the maximum plausibility of all emergency alternatives with respect to each criterion, and the negative ideal solution vector is defined as the minimum belief of all emergency alternatives with respect to each criterion. An emergency alternative evaluation selection problem is taken as an illustrative example to demonstrate the feasibility and practicability of the proposed methods for group decision making in emergency management. © 2011 Elsevier Ltd. All rights reserved.

Liang J.,Peking University | Zhang G.,Peking University
ACS Applied Materials and Interfaces | Year: 2012

In contrast to the main-stream strategy of growing convex nanostructures upward from the substrates and using them as cold electron sources, it is illustrated in this article that growing concave nanostructures downward into substrates also results in configurations suitable for field emission. Well-ordered TiO2 nanotube arrays were developed on the titanium foils in two-step anodizations. Simultaneously, arrays of sharp nanotips, which resembled the Spindt emitter arrays in appearance, also manifested themselves on the outmost surface of the foils. These nanotips were actually the remainder of the titanium foil surfaces that survived dissolution during anodization. Annealing transformed the amorphous TiO2 nanotips into anatase crystals and further to rutile. Despite the lack of an overall large aspect ratio, the sharpness of these nanotips guaranteed sufficiently strong electric fields for electron extraction. As a result, field emission was readily obtained from the TiO2 nanotip arrays, either before or after annealing. Photoelectron spectroscopy of the samples demonstrated that the majority of the emitted electrons came from local states in the band gap. Annealing at an appropriate temperature increased these local states and improved the field-emission capability of the samples. © 2012 American Chemical Society.

Ma D.,Peking University
The British journal of nutrition | Year: 2013

To evaluate the effect of treatment with β-conglycinin, a major soyabean protein, on blood lipids in menopausal women, we recruited 100 hyperlipidaemic women aged 40-60 years old. Participants were randomly allocated to three groups: placebo group (n 34, four casein tablets/d); low dose group (n 33, four tablets containing 2·3 g β-conglycinin/d); high-dose group (n 33, eight tablets containing 4·6 g β-conglycinin/d). The mean serum TAG concentration was significantly reduced after 6 and 12 weeks of β-conglycinin intervention by 0·44 (sd 0·20) and 0·78 (sd 1·03) mmol/l in the low-dose group, and by 0·46 (sd 0·17) and 1·25 (sd 1·06) mmol/l in the high-dose group, respectively. One-way ANOVA revealed that serum TAG concentrations in the low-dose and high-dose groups were significantly lowered compared with the placebo group at weeks 6 and 12 (P< 0·05). The low dose and high dose consumptions of β-conglycinin significantly decreased the LDL-cholesterol concentration by 0·46 (sd 0·72) and 0·52 (sd 0·97) mmol/l at week 12, respectively (P< 0·05). Compared with the changes from baseline in the placebo group, apoB and NEFA were significantly lowered in both the low-dose and high-dose β-conglycinin groups (P< 0·05). In conclusion, the results suggest that β-conglycinin intake significantly decreases serum TAG and LDL-cholesterol levels.

Cai K.,Peking University | Yan Q.,Peking University | Zhao D.,Peking University
Chemical Science | Year: 2012

A series of dihydro- and tetrahydro-tetraazaacene diimides containing 6 or 7 laterally fused six-membered rings were synthesized. Halochromic and redox-switchable vis-NIR optical characteristics were exhibited. Quinonoid tautomers of dihydrotetraazaacene derivatives were obtained and characterized, which exhibited adequate stability and existed in equilibrium with the more commonly observed benzenoid tautomer. © 2012 The Royal Society of Chemistry.

Liang J.,Tianjin Medical University | Liang J.,Peking University | Shang Y.,Tianjin Medical University | Shang Y.,Peking University
Annual Review of Physiology | Year: 2013

Estrogen exhibits a broad spectrum of physiological functions ranging from regulation of the menstrual cycle and reproduction to modulation of bone density, brain function, and cholesterol mobilization. Despite the beneficial actions of endogenous estrogen, sustained exposure to exogenous estrogen is a well-established risk factor for various cancers. We summarize our current understanding of the molecular mechanisms of estrogen signaling in normal and cancer cells and discuss the major challenges to existing antiestrogen therapies. Copyright © 2013 by Annual Reviews. All rights reserved.

Luan J.Y.,Peking University | Li X.,Peking University
European Journal of Vascular and Endovascular Surgery | Year: 2013

Objectives To analyze computed tomography (CT) imaging features of isolated dissection of the superior mesenteric artery (SMA). Methods The imaging findings of 20 consecutive patients with isolated dissection of the SMA were retrospectively evaluated and categorized according to a new imaging classification: Type A, dissections localized at the curved part of the SMA and extended proximally; Type B, dissections limited to the curved part; Type C or D, dissections localized at the curved part and extended distally without or with involved ileocolic or distal ileal arteries. The relationship between classification and symptoms and treatment effect is discussed, and prior reported cases where CT images were available were classified and analyzed. Results The dissections were around the curved part of the SMA in all 20 patients. In symptomatic patients, the true lumen was more stenosed, the dissection started nearer the SMA ostium, and the dissection was longer. The best effect of conservative treatment was achieved in Type B cases. When dissection extended distally, the effect progressively worsened from Type B to Type D. Conclusions The new classification is useful for describing the imaging features of isolated dissection of the SMA. © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

The γ-rays from gamma-ray bursts (GRBs) are believed to be produced by internal shocks driven by small timescale, ∼1 ms, variation in the GRB outflows, and a pair-production spectral cutoff is generally expected around the GeV range. However, the observed optical flashes accompanying GRBs suggest that the delayed residual collisions due to large timescale variation continue to accelerate electrons. We show here that the inverse-Compton (IC) scattering of the prompt γ-rays by these residual internal shock electrons leads to a high-energy emission beyond the previously thought spectral cutoff, in agreement with the previous detections of GeV photons by EGRET in several GRBs in conjunction with MeV emission. We expect a spectral break due to the transition from the primary to residual internal shock emission at the previously thought spectral cutoff and expect systematic time delays of high-energy photons relative to MeV emission, the discovery of which would provide stringent constraint on the outflow properties, but requires large enough collection of high-energy photons by, e.g., Fermi and AGILE satellites. The recent Fermi-detected bright GRB 080916c unambiguously shows the shifting of the prompt emission toward later times as the photon energy increases. The second-scale shifting at >100MeV is much longer than the MeV variability time, as predicted in the residual collision model. The observations imply that there should be emission above 70 GeV in the source frame, which may not be produced by primary internal shocks but by IC emission in residual collisions. With the method involving time delays of high-energy emission, the bulk Lorentz factor of GRB 080916c is determined to be Γ 300. © 2010. The American Astronomical Society. All rights reserved.

Magnetic nanoparticles (MNPs) modified simultaneously with amorphous Fe and Mn oxides (Mag-Fe-Mn) were synthesized to remove arsenite [As(III)] from water. Mag-Fe-Mn particles were fabricated through heterogeneous nucleation technique by employing the maghemite as the magnetic core and Fe-Mn binary oxide (FMBO) as the coating materials. Powder X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy were utilized to characterize the hybrid material. With a saturation magnetization of 23.2emu/g, Mag-Fe-Mn particles with size of 20-50nm could be easily separated from solutions with a simple magnetic process in short time (within 5min). At pH 7.0, 200μg/L of As(III) could be easily decreased to below 10μg/L by Mag-Fe-Mn particles (0.1g/L) within 20min. As(III) could be effectively removed by Mag-Fe-Mn particles at initial pH range from 4 to 8 and the residual As was completely oxidized to less toxic arsenate [As(V)]. The co-occurring redox reactions between Mn oxide and As(III) was confirmed by XPS analysis. Chloride, sulfate, bicarbonate, and nitrate at common concentration range had negligible influence on As(III) removal, whereas, silicate and phosphate reduced the As(III) removal by competing with arsenic species for adsorption sites. As(III) removal was not obviously affected by natural organic matter (up to 8mg/L as TOC). Mag-Fe-Mn could be regenerated with ternary solution of NaOH, NaCl, and NaClO. Throughout five consecutive cycles, the adsorption and desorption efficiencies maintained above 98% and 87%, respectively. Mag-Fe-Mn had a larger adsorption capacity for As(III) (47.76mg/g) and could remove trace As(III) more thoroughly than MNPs modified solely with either Fe or Mn oxide due to the synergistic effect of the coating Fe and Mn oxides. This research extended the potential applicability of FMBO to a great extent and provided a convenient approach to efficiently remove trace As(III) from water. © 2013 Elsevier Ltd.

Ye L.-H.,Peking University
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

The Kohn-Sham orbital kinetic energy density τσ(r)= iwiσ| ψiσ(r)|2 is one fundamental quantity for constructing metageneralized gradient approximations (meta-GGAs) for use by density functional theory. We present a computational scheme of τσ(r) for the full-potential linearized augmented plane-wave (FLAPW) method. Our scheme is highly accurate and efficient and easy to implement with existing computer codes. To illustrate its performance, we construct the Becke-Johnson meta-GGA exchange potentials for Be, Ne, Mg, Ar, Ca, Zn, Kr, and Cd atoms, which are in very good agreement with the original results. For bulk solids, we construct the Tran-Blaha modified Becke-Johnson potential (mBJ) and confirm its capability to calculate band gaps with the reported bad convergence of the mBJ potential being substantially improved. The present computational scheme of τσ(r) should also be valuable for developing other meta-GGAs in the FLAPW as well as in similar methods utilizing atom centered basis functions. © 2015 American Physical Society.

Men Y.,Peking University
International journal of nanomedicine | Year: 2011

Multidrug resistance (MDR) of cancers can be circumvented by inducing programmed cell death, which is known as apoptosis. Mitochondria play a crucial role in apoptosis. Mitochondria-specific therapy would provide an efficient strategy for treating resistant cancers. A strategy was proposed here to overcome MDR by designing cancer mitochondria-specific drug-loaded liposomes, namely, antiresistant epirubicin mitosomes, aimed at treating resistant leukemia by targeting mitochondria. Evaluations were performed on human chronic leukemia K562, MDR K562/ADR cells, and female BALB/c nude mice xenografted with MDR K562/ADR cells. The liposomes were characterized through assays of cytotoxicity, mitochondrial targeting, caspase-9 and caspase-3, antitumor activities, and TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) analysis. The average size of antiresistant epirubicin mitosomes was in the range of 105-115 nm. Antiresistant epirubicin mitosomes were effective in inhibiting proliferation of MDR K562/ADR cells in vitro and selectively accumulated into the mitochondria. Caspase-9 and caspase-3 activity was increased after applying antiresistant epirubicin mitosomes. In xenografted resistant MDR K562/ADR tumor in nude mice, antiresistant tumor effect of antiresistant epirubicin mitosomes was evidently observed. Apoptotic inducing effects by antiresistant epirubicin mitosomes were noticeably evidenced via mitochondrial pathway. Antiresistant epirubicin mitosomes had significant inhibitory effect against resistant leukemia in vitro and in vivo, hence providing a promising strategy for improving therapeutic efficacy in resistant human leukemia.

Wei Y.,Peking University
Biomedical materials (Bristol, England) | Year: 2011

In recent years, interest in magnetic biomimetic scaffolds for tissue engineering has increased considerably. The aim of this study is to develop magnetic biodegradable fibrous materials with potential use in bone regeneration. Magnetic biodegradable Fe(3)O(4)/chitosan (CS)/poly vinyl alcohol (PVA) nanofibrous membranes were achieved by electrospinning with average fiber diameters ranging from 230 to 380 nm and porosity of 83.9-85.1%. The influences of polymer concentration, applied voltage and Fe(3)O(4) nanoparticles loading on the fabrication of nanofibers were investigated. The polymer concentration of 4.5 wt%, applied voltage of 20 kV and Fe(3)O(4) nanoparticles loading of lower than 5 wt% could produce homogeneous, smooth and continuous Fe(3)O(4)/CS/PVA nanofibrous membranes. X-ray diffraction (XRD) data confirmed that the crystalline structure of the Fe(3)O(4), CS and PVA were maintained during electrospinning process. Fourier transform infrared spectroscopy (FT-IR) demonstrated that the Fe(3)O(4) loading up to 5 wt% did not change the functional groups of CS/PVA greatly. Transmission electron microscopy (TEM) showed islets of Fe(3)O(4) nanoparticles evenly distributed in the fibers. Weak ferrimagnetic behaviors of membranes were revealed by vibrating sample magnetometer (VSM) test. Tensile test exhibited Young's modulus of membranes that were gradually enhanced with the increase of Fe(3)O(4) nanoparticles loading, while ultimate tensile stress and ultimate strain were slightly reduced by Fe(3)O(4) nanoparticles loading of 5%. Additionally, MG63 human osteoblast-like cells were seeded on the magnetic nanofibrous membranes to evaluate their bone biocompatibility. Cell growth dynamics according to MTT assay and scanning electron microscopy (SEM) observation exhibited good cell adhesion and proliferation, suggesting that this magnetic biodegradable Fe(3)O(4)/CS/PVA nanofibrous membranes can be one of promising biomaterials for facilitation of osteogenesis.

Zhao C.,Peking University | Zhang J.,Peking University
ACS Nano | Year: 2010

Two-dimensional plasmonic demultiplexers for surface plasmon polaritons (SPPs), which consist of concentric grooves on a gold film, are proposed and experimentally demonstrated to realize light-SPP coupling, effective dispersion, and multiple-channel SPP guiding. A resolution as high as 10 nm is obtained. The leakage radiation microscopy imaging shows that the SPPs of different wavelengths are focused and routed into different SPP strip waveguides. The plasmonic demultiplexer can thus serve as a wavelength division multiplexing element for an integrated plasmonic circuit and also as a plasmonic spectroscopy or filter. © 2010 American Chemical Society.

Careful analysis of experimental data showed that the salt aqueous solution/air surface tension depends on a rather complicated manner of salt composition and points to the importance of ion cooperativity. In this short article, we include the selective binding of anions over cations at interfaces (as revealed from molecular dynamics simulations, spectroscopic measurements, and Record's analysis of the surface tension data) and the anion-cation association (based on the observation of matching water affinity) in a simple theoretical model to understand salt effects on surface tension. The introduction of the surface effect and ion association provides a qualitative explanation of the experimental data, in particular, the strong anion dependence of the cations? rank according to their ability of increasing water surface tension. We hope that the physical insight provided by this study can be used to point to new directions for more detailed studies. © 2011 American Chemical Society.

Zheng W.,Peking University
Diabetes Research and Clinical Practice | Year: 2011

Objective: To investigate factors related to diabetic retinopathy (DR). Method: Clinical data of 603 Chinese diabetic patients were analyzed retrospectively. On the basis of its severity, DR was graded as non-diabetic retinopathy (NDR), non proliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR). Factor analysis was conducted and factor scores were used as independent variables in both Logistic and Ordinal regression models to identify the predictors of the development and/or progression of DR. Result: After factor analysis, 21 original variables were finally reduced to eight unique factors, representing obesity, glycemic, C peptide, lipids, time, renal, blood pressure and metabolic factors. Logistic regression revealed that female (OR = 2.208, 95%CI 1.328-3.671), comorbidity of peripheral atherosclerosis (PA) (OR = 2.690, 95%CI 1.000-7.238), time factor (OR = 1.838, 95%CI 1.421-2.377) and renal factor (OR = 2.444, 95%CI 1.757-3.400) were positively associated with DR, while C peptide factor (OR = 0.469, 95%CI 0.365-0.604) was negatively associated with DR. Besides another negatively related obesity factor (OR = 0.777), Ordinal regression revealed similarly related factors, but ruled out the influence of gender and PA. Conclusion: Female, macrovascular complications, time and renal factors are predictors of DR, while C peptide factor is negatively associated with the development and/or progression of DR. © 2011 Elsevier Ireland Ltd.

Sun Q.,Peking University
Vibrational Spectroscopy | Year: 2012

Raman spectroscopy was utilized to investigate the effects of dissolved NaCl on water structure. For aqueous NaCl solutions, the difference spectra indicate a clear isosbestic point at 3345 cm -1 and a weak isosbestic point around 3625 cm -1. According to our explanation on Raman OH stretching band of water, it can be inferred that the addition of NaCl primarily breaks the tetrahedral hydrogen bonding and promotes formation of the donor hydrogen bonding in water, and slightly lowers the amount of free OH bonds. This is different from the effects of pressure and temperature on water structure. For liquid water, a water molecule interacts with neighboring water molecules through various local hydrogen bonded networks. Additionally, the enthalpy change of hydrogen bonding in water can be determined to be 11.35 kJ/mol. © 2012 Elsevier B.V.

He H.,Peking University | Magi-Galluzzi C.,Cleveland Clinic
Advances in Anatomic Pathology | Year: 2014

Epithelial-to-mesenchymal transition (EMT) describes a phenotypical change induced in epithelial cells that lose their cell-cell basement membrane contacts and their structural polarity to become spindle-shaped and morphologically similar to mesenchymal/myofibroblast cell. The abnormal induction of EMT has been demonstrated to contribute to cancer dissemination and progression. Renal cell carcinoma (RCC) with sarcomatoid differentiation (sarcomatoid RCC) represents a good example of EMT both morphologically and immunohistochemically. Early spindle cell changes can at times be identified in RCC and likely represent an early step toward EMT. Herein, we present a review of the current understanding of EMT in renal neoplasms including some known signaling regulation, the association of sarcomatoid differentiation in RCC with aggressive behavior and dismal prognosis, and EMT-related tumor biology in sarcomatoid RCC. A better perception of the EMT may contribute toward an improved understanding of the development of sarcomatoid RCC. In addition, a distinct signature for sarcomatoid RCC may have utility in the differential diagnosis for prognostic stratification as well as in identifying novel genes and pathway targets for therapeutic intervention. © 2014 by Lippincott Williams & Wilkins.

Wu X.,Peking University | Liu H.,Peking University
Global Change Biology | Year: 2013

Understanding spring phenology changes in response to the rapid climate change at biome-level is crucial for projecting regional ecosystem carbon exchange and climate-biosphere interactions. In this study, we assessed the long-term changes and responses to changing climate of the spring phenology in six temperate biomes of China by analyzing the global inventory monitoring and modeling studies (GIMMS) NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) and concurrent mean temperature and precipitation data for 1982-2006. Results show that the spring phenology trends in the six temperate biomes are not continuous throughout the 25 year period. The spring phenology in most areas of the six biomes showed obvious advancing trends (ranging from -0.09 to -0.65 day/yr) during the 1980s and early 1990s, but has subsequently suffered consistently delaying trends (ranging from 0.22 to 1.22 day/yr). Changes in spring (February-April) temperature are the dominating factor governing the pattern of spring vegetation phenology in the temperate biomes of China. The recently delayed spring phenology in these temperate biomes has been mainly triggered by the stalling or reversal of the warming trend in spring temperatures. Results in this study also reveal that precipitation during November-January can explain 16.1% (P < 0.05), 20.9% (P < 0.05) and 14.2% (P < 0.05) of the variations in temperate deciduous forest (TDF), temperate steppe (TS), temperate desert (TD) respectively, highlighting the important role of winter precipitation in regulating changes in the spring vegetation phenology of water-limited biomes. © 2012 Blackwell Publishing Ltd.

Wang W.,Peking University
Ageing Research Reviews | Year: 2012

The expression of senescence-associated genes, which governs the progression and the maintenance of senescence, is regulated at multiple levels. Apart from the transcriptional mechanisms that control cellular senescence, studies over the past decade have revealed that post-transcriptional gene regulation, especially through changes in mRNA turnover and translation, critically influences protein expression patterns in the senescent cell. Among the post-transcriptional regulatory factors, RNA-binding proteins (RBPs) are particularly influential in the establishment of senescence-associated protein profiles. In this review, I discuss the current knowledge of the role of RBPs in cellular senescence and the molecular mechanisms that regulate their function. © 2012 Elsevier B.V.

The burden of disability, analgesia, and health services use associated with knee pain and osteoarthritis (OA) in developing countries is relatively unknown, despite a high proportion of these populations required to be engaged in heavy occupational physical activity throughout their life span. The aim of this survey was to estimate the burden of disability, analgesia, and health services use associated with knee pain in rural China. This was a population-based cross-sectional survey among residents, aged 50 years and older, of Wuchuan County, Inner Mongolia. Participants completed an interviewer-based questionnaire, evaluating knee pain and associated disability, analgesia, and health services use, and obtained bilateral standardized weight-bearing knee radiographs. Of the 1,027 participants, 513 (50%) reported knee pain on most days of at least 1 month in the past year, with 109 (21%) also demonstrating radiographic OA (Kellgren-Lawrence grade ≥2) in the symptomatic knee. Adjusting for age, gender, body mass index (BMI), education, and back pain, the presence of knee pain was associated with significantly greater difficulty in walking, climbing 10 steps, stooping, completing cleaning chores, and preparing meals. Among the 513 subjects with knee pain, the additional presence of radiographic evidence of OA was significantly associated with more occasions of "unbearable" pain (59% versus 36%) and restricted activity (64% versus 39%), as well as increased use of nonsteroidal antiinflammatory drugs (NSAIDs) (88% versus 78%) and the reported number of doctor visits (59% versus 33%) in the past year. The use of paracetamol for knee pain was rare (6% versus 2%). Knee pain is highly prevalent in rural northern China. The associated significant disability and marked preferential use of NSAIDs as analgesia should be of concern in these communities reliant on heavy occupational physical activity for their livelihood. The findings will be useful to guide the distribution of future health care resources and preventive strategies.

Zemp M.,Peking University
Astrophysical Journal | Year: 2014

It is common practice to describe formal size and mass scales of dark matter halos as spherical overdensities with respect to an evolving density threshold. Here, we critically investigate the evolutionary effects of several such commonly used definitions and compare them to the halo evolution within fixed physical scales as well as to the evolution of other intrinsic physical properties of dark matter halos. It is shown that, in general, the traditional way of characterizing sizes and masses of halos dramatically overpredicts the degree of evolution in the last 10 Gyr, especially for low-mass halos. This pseudo-evolution leads to the illusion of growth even though there are no major changes within fixed physical scales. Such formal size definitions also serve as proxies for the virialized region of a halo in the literature. In general, those spherical overdensity scales do not coincide with the virialized region. A physically more precise nomenclature would be to simply characterize them by their very definition instead of calling such formal size and mass definitions "virial." In general, we find a discrepancy between the evolution of the underlying physical structure of dark matter halos seen in cosmological structure formation simulations and pseudo-evolving formal virial quantities. We question the importance of the role of formal virial quantities currently ubiquitously used in descriptions, models, and relations that involve properties of dark matter structures. Concepts and relations based on pseudo-evolving formal virial quantities do not properly reflect the actual evolution of dark matter halos and lead to an inaccurate picture of the physical evolution of our universe. © 2014. The American Astronomical Society. All rights reserved..

Zhao Q.,Peking University | Guo H.-W.,Peking University
Molecular Plant | Year: 2011

Phytohormone ethylene plays pivotal roles in plant response to developmental and environmental signals. During the past few years, the emerging evidence has led us to a new understanding of the signaling mechanisms and regulatory networks of the ethylene action. In this review, we focus on the major advances made in the past three years, particularly the findings leading to new paradigms and the observations under debate. With the recent demonstration of the regulation of the protein stability of numerous key signaling components including EIN3, EIL1, EIN2, ETR2, EBF1/EBF2, and ETP1/ETP2, we highlight proteasome-dependent protein degradation as an essential regulatory mechanism that is widely adopted in the ethylene signaling pathway. We also discuss the implication of the negative feedback mechanism in the ethylene signaling pathway in light of ethylene-induced ETR2 and EBF2 gene expression. Meanwhile, we summarize the controversy on the involvement of MKK9-MPK3/6 cascade in the ethylene signaling versus biosynthesis pathway, and discuss the possible role of this MAPK module in the ethylene action. Finally, we describe the complex interactions between ethylene and other signaling pathways including auxin, light, and plant innate immunity, and propose that EIN3/EIL1 act as a convergence point in the ethylene-initiated signaling network. © 2011 The Author.

Meng Z.,Peking University | Zhang F.,Pennsylvania State University
Monthly Weather Review | Year: 2011

Ensemble-based data assimilation is a state estimation technique that uses short-term ensemble forecasts to estimate flow-dependent background error covariance and is best known by varying forms of ensemble Kalman filters (EnKFs). The EnKF has recently emerged as one of the primary alternatives to the variational data assimilation methods widely used in both global and limited-area numerical weather prediction models. In addition to comparing the EnKF with variational methods, this article reviews recent advances and challenges in the development and applications of the EnKF, including its hybrid with variational methods, in limited-area models that resolve weather systems from convective to meso- and regional scales. © 2011 American Meteorological Society.

Wang H.,Peking University
Biometrika | Year: 2012

We propose a method of factor profiled sure independence screening for ultrahigh-dimensional variable selection. The objective of this method is to identify nonzero components consistently from a sparse coefficient vector. The new method assumes that the correlation structure of the high-dimensional data can be well represented by a set of low-dimensional latent factors, which can be estimated consistently by eigenvalue-eigenvector decomposition. The estimated latent factors should then be profiled out from both the response and the predictors. Such an operation, referred to as factor profiling, produces uncorrelated predictors. Therefore, sure independence screening can be applied subsequently and the resulting screening result is consistent for model selection, a major advantage that standard sure independence screening does not share. We refer to the new method as factor profiled sure independence screening. Numerical studies confirm its outstanding performance. © 2011 Biometrika Trust.

Qin Y.-M.,Peking University | Zhu Y.-X.,Peking University
Current Opinion in Plant Biology | Year: 2011

Cotton fibers (cotton lint) are single-celled trichomes that differentiate from the ovule epidermis. Unidirectional and fast-growing cells generally expand at the dome-shaped apical zone (tip-growth mode); however, previous studies suggest that elongating fiber cells expand via a diffuse-growth mode. Tip-localized Ca 2+ gradient and active secretary vesicle trafficking are two important phenomena of tip-growth. Recently, a high Ca 2+ gradient is found in the cytoplasm of fast-elongating cotton fiber cells near the growing tip. Several protein coding genes participating in vesicle coating and transport are highly expressed in elongating fiber cells. Taken together with the observation that ethylene acts as a positive regulator for cotton fiber and several Arabidopsis tissues that are known to elongate via tip growth prompted us to propose a linear-growth mode for similar cell types. © 2010 Elsevier Ltd.

Jiang Z.,Peking University
American Journal of Epidemiology | Year: 2015

Assessment of indirect effects is useful for epidemiologists interested in understanding the mechanisms of exposure-outcome relationships. A traditional way of estimating indirect effects is to use the "difference method," which is based on regression analysis in which one adds a possible mediator to the regression model and examines whether the coefficient for the exposure changes. The difference method has been criticized for lacking a causal interpretation when it is used with logistic regression. In this article, we use the counterfactual framework to define the natural indirect effect (NIE) and assess the relationship between the NIE and the difference method. We show that under appropriate assumptions, the difference method consistently estimates the NIE for continuous outcomes and is always conservative for binary outcomes. Thus, the difference method can be used to provide evidence for the presence of mediation but not for the absence of mediation. © 2015 The Author 2015. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved.

Yang M.,Peking University | Li R.,Peking University | Chu T.,Peking University
Automatica | Year: 2013

We investigate a type of disturbance decoupling problem (DDP) of Boolean control networks. Using the semi-tensor product of matrices, the dynamics of a Boolean control network is expressed in its algebraic form. Under the framework of output-friendly subspace, we give a necessary and sufficient condition for the solvability of DDP by analyzing the redundant variables, and we present a computationally feasible method to construct all the valid feedback control matrices. The logical functions of each controller can be recovered from the obtained feedback control matrix. Finally, an example is provided to show the effectiveness of the proposed method. © 2012 Elsevier Ltd. All rights reserved.

Sun Y.,University of Jinan | Wang L.,Peking University
Automatica | Year: 2013

This note is focused on the stability analysis for a class of switched nonlinear systems with disturbance input and delay. Sufficient conditions in terms of linear inequalities are presented such that the switched system is asymptotically stable for arbitrary switching, any admissible sector nonlinearities and disturbances, and any constant delay. We not only drop a condition of one result given in Aleksandrov, Chen, Platonov, and Zhang (2011), but also extend the main result to a more general switched nonlinear system with disturbance input and delay. © 2012 Elsevier Ltd. All rights reserved.

Xu S.,Peking University | Yan H.,Peking University
Astrophysical Journal | Year: 2013

A correct description of cosmic-ray (CR) diffusion in turbulent plasma is essential for many astrophysical and heliospheric problems. This paper aims to present the physical diffusion behavior of CRs in actual turbulent magnetic fields, a model of which has been numerically tested. We perform test particle simulations in compressible magnetohydrodynamic turbulence. We obtain scattering and spatial diffusion coefficients by tracing particle trajectories. We find no resonance gap for pitch-angle scattering at 90°. Our result confirms the dominance of mirror interaction with compressible modes for most pitch angles, as revealed by the nonlinear theory. For crossfield transport, our results are consistent with normal diffusion predicted earlier for large scales. The diffusion behavior strongly depends on the AlfvénicMach number and the particle's parallel mean free path.We, for the first time, numerically derive the dependence of M4A for the perpendicular diffusion coefficient with respect to the mean magnetic field.We conclude that CR diffusion coefficients are spatially correlated to the local turbulence properties. On scales smaller than the injection scale, we find that CRs are superdiffusive. We emphasize the importance of our results in a wide range of astrophysical processes, including magnetic reconnection. © 2013. The American Astronomical Society. All rights reserved. Printed in the U.S.A.

Liu B.,Peking University | Showman A.P.,University of Arizona
Astrophysical Journal | Year: 2013

The ongoing characterization of hot Jupiters has motivated a variety of circulation models of their atmospheres. Such models must be integrated starting from an assumed initial state, which is typically taken to be a wind-free, rest state. Here, we investigate the sensitivity of hot-Jupiter atmospheric circulation to initial conditions with shallow-water models and full three-dimensional models. Those models are initialized with zonal jets, and we explore a variety of different initial jet profiles. We demonstrate that, in both classes of models, the final, equilibrated state is independent of initial condition - as long as frictional drag near the bottom of the domain and/or interaction with a specified planetary interior are included so that the atmosphere can adjust angular momentum over time relative to the interior. When such mechanisms are included, otherwise identical models initialized with vastly different initial conditions all converge to the same statistical steady state. In some cases, the models exhibit modest time variability; this variability results in random fluctuations about the statistical steady state, but we emphasize that, even in these cases, the statistical steady state itself does not depend on initial conditions. Although the outcome of hot-Jupiter circulation models depend on details of the radiative forcing and frictional drag, aspects of which remain uncertain, we conclude that the specification of initial conditions is not a source of uncertainty, at least over the parameter range explored in most current models. © 2013. The American Astronomical Society. All rights reserved.

Wang T.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

Motivated by Verlinde's theory of entropic gravity, we give a tentative explanation to the Coulomb's law with an entropic force. When trying to do this, we find the equipartition rule should be extended to charges and the concept of temperature should be reinterpreted. If one accepts the holographic principle as well as our generalizations and reinterpretations, then Coulomb's law, the Poisson equation, and the Maxwell equations can be derived smoothly. Our attempt can be regarded as a new way to unify the electromagnetic force with gravity, from the entropic origin. Possibly some of our postulates are related to the D-brane picture of black hole thermodynamics. © 2010 The American Physical Society.

Zhao H.,Peking University | Ma D.,Peking University
Journal of the American Chemical Society | Year: 2012

Iron carbide nanoparticles have long been considered to have great potential in new energy conversion, nanomagnets, and nanomedicines. However, the conventional relatively harsh synthetic conditions of iron carbide hindered its wide applications. In this article, we present a facile wet-chemical route for the synthesis of Hägg iron carbide (Fe 5C 2) nanoparticles, in which bromide was found to be the key inducing agent for the conversion of Fe(CO) 5 to Fe 5C 2 in the synthetic process. Furthermore, the as-synthesized Fe 5C 2 nanoparticles were applied in the Fischer-Tropsch synthesis (FTS) and exhibited intrinsic catalytic activity in FTS, demonstrating that Fe 5C 2 is an active phase for FTS. Compared with a conventional reduced-hematite catalyst, the Fe 5C 2 nanoparticles showed enhanced catalytic performance in terms of CO conversion and product selectivity. © 2012 American Chemical Society.

Wang C.,Peking University | Sun H.,Peking University | Fang Y.,Peking University | Huang Y.,Peking University
Angewandte Chemie - International Edition | Year: 2013

Unprotected indoles are prepared with the title method, which has a wide scope for alkynes. Excellent regioselectivity was accomplished for aryl-alkyl and alkyl-alkyl disubstituted acetylenes. This reaction features an unusual 1,2 rhodium migration and ring-contraction-triggered N-N bond cleavage. It allows rapid conversion of the reaction products into several functional molecules. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chao W.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

A simple extension of the standard model providing a TeV-scale seesaw mechanism is presented. Beside the standard model particles and right-handed Majorana neutrinos, the model contains a singly charged scalar, an extra Higgs doublet, and three vectorlike singly charged fermions. In our model, Dirac neutrino mass matrix raises only at the loop level. Small but nonzero Majorana neutrino masses come from integrating out heavy Majorana neutrinos, which can be at the TeV-scale. The phenomenologies of the model are investigated, including scalar mass spectrum, neutrino masses and mixings, lepton flavor violations, heavy neutrino magnetic moments as well as possible collider signatures of the model at the LHC. © 2010 The American Physical Society.

Chen W.,Beijing University of Technology | Zhu S.-L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

After constructing all the tetraquark interpolating currents with JPC=1-+, 1-, 1++ and 1 +- in a systematic way, we investigate the two-point correlation functions to extract the masses of the charmoniumlike states with QCD sum rule. For the 1- qcq̄c̄ charmoniumlike state, mX=4.6∼4.7GeV, which implies a possible tetraquark interpretation for the state Y(4660). The masses for both the 1++ qcq̄c̄ and scs̄c̄ charmoniumlike states are around 4.0∼4.2GeV, which are slightly above the mass of X(3872). For the 1-+ and 1 +- qcq̄c̄ charmoniumlike states, the extracted masses are around 4.5∼4.7GeV and 4.0∼4.2GeV, respectively. As a by-product, the bottomoniumlike states are also studied. We also discuss the possible decay modes and experimental search of the charmoniumlike states. © 2011 American Physical Society.

Atmospheric turbulence is a major limiting factor in an optical wireless communication (OWC) link. The turbulence distorts the phase of the propagating optical fields and limits the focusing capabilities of the telescope antennas. Hence, a detector array is required to capture the widespread signal energy in the focal-plane. This paper addresses the biterror rate (BER) performance of optical wireless communication (OWC) systems employing a detector array in the presence of turbulence. Here, considering the gamma-gamma turbulence model, we propose a blind estimation scheme that provides the closed-form expression of the BER by exploiting the information of the data output of each pixel, which is based on the singular value decomposition of the sample matrix of the received signals after the code-matched filter. Instead of assuming spatially white additive noise, we consider the case where the noise spatial covariance matrix is unknown. The new method can be applied to either the single transmitter or the multi-transmitter cases. Simulation results for different Rytov variances are presented, which conform closely to the results of the proposed model. © 2011 Optical Society of America.

Wang J.,Peking University
Industrial and Engineering Chemistry Research | Year: 2013

This paper proposes a closed-loop compensation method to remove oscillations caused by control valve stiction. With the control loop operating at the auto mode, the proposed method adds a short-time rectangular wave to the reference to introduce two movements for the control valve to arrive at a desired position. A systematic way to design the parameters of the short-time rectangular wave is developed. The proposed method is robust against modeling errors and measurement noises. The effectiveness of the proposed method is illustrated by laboratory and simulation examples. © 2013 American Chemical Society.

Hu F.,Peking University | Yi H.,Peking University | Zhou Z.,Peking University
Optics Letters | Year: 2011

A compact wavelength demultiplexing structure based on arrayed metal-insulator-metal (MIM) slot cavities is proposed and demonstrated numerically. The structure consists of a bus waveguide perpendicularly coupled with a series of slot cavities, each of which captures SPPs at the resonance frequency from the bus waveguide and tunes the transmission wavelength by changing its geometrical parameters. A cavity theory model is used to design the operating wavelengths of the structure. Moreover, single band transmission of each channel and the adjustable transmission bandwidth can be obtained by altering the drop waveguide positions and the coupling distance. The proposed arrayed slot cavity-based structure could be utilized to develop ultracompact optical wavelength demultiplexing device for large-scale photonic integration. © 2011 Optical Society of America.

Wang J.-H.,Peking University | Wang J.-H.,Dana-Farber Cancer Institute
Cell Research | Year: 2012

The inside-out signaling of integrins regulates the ligand-binding affinity of the cell surface receptors in response to changes in the environment for cell survival. The specific binding to the cytoplasmic tail of integrin's β subunit by the intracellular protein talin is the key step of inside-out signaling. A pull-push mechanism has been proposed to explain how the PIP2-enriched membrane disrupts the dual auto-inhibition of the N-terminal talin-FERM domain by the C-terminal talin-rod domain such that activated talin-FERM can reach the β-tail for integrin activation. © 2012 IBCB, SIBS, CAS All rights reserved.

Tang H.,Peking University
Cochrane database of systematic reviews (Online) | Year: 2012

Ovarian hyperstimulation syndrome (OHSS) is a complication resulting from administration of human chorionic gonadotrophin (hCG) in assisted reproduction technology (ART) treatment. Most case are mild, but forms of moderate or severe OHSS appear in 3% to 8% of in vitro fertilisation (IVF) cycles. Recently, the dopamine agonist cabergoline has been introduced as a secondary prevention intervention for OHSS in women at high risk of OHSS who are undergoing ART treatment. To assess the effectiveness and safety of cabergoline in preventing ovarian hyperstimulation syndrome (OHSS) in high-risk women undergoing ART treatment. Major medical databases (Cochrane Menstrual Disorders and Subfertility Group Specialised Register of trials, CENTRAL (The Cochrane Library), MEDLINE, EMBASE and PsycINFO) were systematically searched for randomised controlled trials (RCTs) assessing the effect of cabergoline in preventing OHSS. Databases were searched up to September 2011. Registers of clinical trials, abstracts of scientific meetings and reference lists of included studies were searched. No language restrictions were applied. RCTs which compared cabergoline with placebo, no treatment or another intervention for preventing OHSS in high-risk women were considered for inclusion. Primary outcome measures included incidence of moderate or severe OHSS and live birth rate. Secondary endpoints were clinical pregnancy rate, multiple pregnancy rate, miscarriage rate and any other adverse effects of the treatment. Two authors independently screened titles, abstracts and the full text of publications; extracted data; and assessed risk of bias. Any disagreements were resolved by consensus. Pooled results were reported as odds ratio (OR) and 95% confidence interval (95% CI) by the Mantel-Haenszel method. Only two trials involving 230 women met the inclusion criteria. Both studies had a moderate risk of bias. Oral cabergoline, 0.5 mg daily, was given as an intervention and compared with a matched placebo. A statistically significant reduction in OHSS was observed in the cabergoline treated group (OR 0.40, 95% CI 0.20 to 0.77; 2 RCTs, 230 women) with a number needed to treat (NTT) of 7. There was a statistically significant difference in the incidence of moderate OHSS, favouring cabergoline (OR 0.38, 95% CI 0.19 to 0.78; 2 RCTs, 230 women) but not in severe OHSS (OR 0.77, 95% CI 0.24 to 2.45; 2 RCTs, 230 women). There was no significant difference in the clinical pregnancy rate (OR 0.94, 95% CI 0.56 to 1.59; 2 RCTs, 230 women), miscarriage rate (OR 0.31, 95% CI 0.03 to 3.07; 1 RCT, 163 women) or any other adverse effects of the treatment (OR 2.07, 95% CI 0.56 to 7.70; 1 RCT, 67 women). However, no data on multiple pregnancy rate or live birth rate were reported in either trial. Cabergoline appears to reduce the risk of OHSS in high-risk women, especially for moderate OHSS. The use of cabergoline does not affect the pregnancy outcome (clinical pregnancy rate, miscarriage rate), nor is there an increased risk of adverse events. Further research should consider the risk of administering cabergoline and the comparison between cabergoline and established treatments (such as intravenous albumin and coasting). Large, well-designed and well-executed RCTs that involve more clinical endpoints are necessary to further evaluate the role of cabergoline in OHSS prevention.

Ma X.,Peking University | Chen B.,Peking University | Yang M.,Peking University
Gondwana Research | Year: 2013

Many Cu-Mo-Au deposits are considered to be related to adakitic porphyries formed in non-arc settings, e.g., in collisional orogenic zones and intra-plate environments, but their genesis is still under discussion. The Aolunhua porphyry complex and its related Mo-Cu deposit from the eastern Central Asian Orogenic Belt (CAOB) provide important insights into this issue. The porphyries are characterized by high Sr (496-705ppm) and Sr/Y and La/Yb ratios similar to those of typical adakitic rocks, and low ISr ratios (0.7049-0.7052) and positive εNd(t) (+0.5 to +1.4) and εHf(t) (+3.5 to +9.8) values. These features, along with the occurrence of mafic microgranular enclaves (MMEs), compositional and textural disequilibrium of plagioclase phenocrysts and relatively high Mg# values (45-52), indicate that they were derived from mixing of felsic magma from partial melting of a juvenile arc-type lower crust and mafic magma from a lithospheric mantle previously metasomatized by subduction zone fluids/melts. High Sr/Y and La/Yb ratios are indicative of contribution from enriched mantle-derived materials (with high LILEs; e.g., Sr, La), which were strengthened by subsequent fractionation of ferromagnesian phases such as pyroxene and hornblende. MMEs hosted by the ore-bearing porphyry have zircon U-Pb ages of ca. 132Ma, similar to those of the host rocks. The enclaves have elevated Mg# (56-63), LILEs (e.g., Sr=660-891ppm), LREE (LaN=68-150, (La/Sm)N=3.0-4.0, (La/Yb)N=12.0-19.6) and ratios of radiogenic isotopes of Nd- and Hf (εNd=+0.7 to +1.6; εHf=+3.3 to +10.9), suggesting that their parental magmas were derived from the metasomatized mantle source. The Mo-Cu mineralization was probably related to the high water content, high oxygen and sulfur fugacity of hybrid magma. Formation of the adakitic porphyries and related Mo-Cu deposits of the eastern CAOB could be related to the Early Cretaceous lithospheric extension, caused by the subduction of the Paleo-Pacific plate and its induced reactivation of juvenile arc-type lower crust. © 2013 International Association for Gondwana Research.

Fa W.,Peking University
Journal of Applied Geophysics | Year: 2013

Ground penetrating radar (GPR) is currently within the scope of China's Chang-E 3 lunar mission, to study the shallow subsurface of the Moon. In this study, key factors that could affect a lunar GPR performance, such as frequency, range resolution, and antenna directivity, are discussed firstly. Geometrical optics and ray tracing techniques are used to model GPR echoes, considering the transmission, attenuation, reflection, geometrical spreading of radar waves, and the antenna directivity. The influence on A-scope GPR echoes and on the simulated radargrams for the Sinus Iridum region by surface and subsurface roughness, dielectric loss of the lunar regolith, radar frequency and bandwidth, and the distance between the transmit and receive antennas are discussed. Finally, potential scientific return about lunar subsurface properties from GPR echoes is also discussed. Simulation results suggest that subsurface structure from several to hundreds of meters can be studied from GPR echoes at P and VHF bands, and information about dielectric permittivity and thickness of subsurface layers can be estimated from GPR echoes in combination with regolith composition data. © 2013 Elsevier B.V.

Su Y.,Peking University | Sun X.,Peking University | Wu G.,Peking University | Jiao N.,Peking University | Jiao N.,East China Normal University
Angewandte Chemie - International Edition | Year: 2013

Oxygen? That's radical! A method for the direct synthesis of substituted alcohols, ketones, and diketones through a catalyst-controlled highly chemoselective coupling and oxygenation of olefins has been developed. The method is simple and practical, can be switched by the selection of different catalysts, and employs molecular oxygen as both an oxidant and a reagent. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lv H.,Peking University | Cai Y.-B.,Peking University | Zhang J.-L.,Peking University
Angewandte Chemie - International Edition | Year: 2013

Breaking bad: Efficient copper-catalyzed C-F bond activation has been achieved by replacing fluorine with hydrogen. A copper hydride is proposed as the active intermediate, which proceeds through a nucleophilic attack on the fluorocarbon, as determined by experimental and theoretical results (see structure; C gray, H white, Cu light red, F light blue; distances in Å). © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Objective: To monitor hypertension prevalence, awareness, treatment and control in China two to three years after major reform of the health system. Methods: Data from a national survey conducted in 2011-2012 among Chinese people aged 45 years or older - which included detailed anthropometric measurements - were used to estimate the prevalence of hypertension and the percentages of hypertensive individuals who were unaware of, receiving no treatment for, and/or not controlling their hypertension well. Modified Poisson regressions were used to estimate relative risks (RRs). Findings: At the time of the survey, nearly 40% of Chinese people aged 45 years or older had a hypertensive disorder. Of the individuals with hypertension, more than 40% were unaware of their condition, about 50% were receiving no medication for it and about 80% were not controlling it well. Compared with the other hypertensive individuals, those who were members of insurance schemes that covered the costs of outpatient care were more likely to be aware of their hypertension (adjusted RR, aRR: 0.737; 95% confidence interval, CI: 0.619-0.878) to be receiving treatment for it (aRR: 0.795; 95% CI: 0.680-0.929) and to be controlling it effectively (aRR: 0.903; 95% CI: 0.817-0.996). Conclusion: In China many cases of hypertension are going undetected and untreated, even though the health system appears to deliver effective care to individuals who are aware of their hypertension. A reduction in the costs of outpatient care to patients would probably improve the management of hypertension in China.

Skin integrity is essential for protection from external stress and trauma. Defects in structural proteins such as keratins cause skin fragility, epitomized by epidermolysis bullosa (EB), a life-threatening disorder. Here we show that dominant mutations of KLHL24, encoding a cullin 3–RBX1 ubiquitin ligase substrate receptor, cause EB. We have identified start-codon mutations in the KLHL24 gene in five patients with EB. These mutations lead to truncated KLHL24 protein lacking the initial 28 amino acids (KLHL24-ΔN28). KLHL24-ΔN28 is more stable than its wild-type counterpart owing to abolished autoubiquitination. We have further identified keratin 14 (KRT14) as a KLHL24 substrate and found that KLHL24-ΔN28 induces excessive ubiquitination and degradation of KRT14. Using a knock-in mouse model, we have confirmed that the Klhl24 mutations lead to stabilized Klhl24-ΔN28 and cause Krt14 degradation. Our findings identify a new disease-causing mechanism due to dysregulation of autoubiquitination and open new avenues for the treatment of related disorders. © 2016 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.

Dong S.,Institute for Advanced Study | Dong S.,Peking University | Zhu Z.,Princeton University
Astrophysical Journal | Year: 2013

We infer the period (P) and size (Rp ) distribution of Kepler transiting planet candidates with Rp ≥ 1 R ⊕ and P < 250 days hosted by solar-type stars. The planet detection efficiency is computed by using measured noise and the observed time spans of the light curves for ∼120,000 Kepler target stars. We focus on deriving the shape of planet periods and radius distribution functions. We find that for orbital periods P > 10 days, the planet frequency dNp /dlog P for "Neptune-size" planets (Rp = 4-8 R ⊕) increases with period as P 0.7 ± 0.1. In contrast, dN p /dlog P for "super-Earth-size" (2-4 R ⊕) as well as "Earth-size" (1-2 R ⊕) planets are consistent with a nearly flat distribution as a function of period (P 0.11 ± 0.05 and P -0.10 ± 0.12, respectively), and the normalizations are remarkably similar (within a factor of ∼1.5 at 50 days). Planet size distribution evolves with period, and generally the relative fractions for big planets (∼3-10 R ⊕) increase with period. The shape of the distribution function is not sensitive to changes in the selection criteria of the sample. The implied nearly flat or rising planet frequency at long periods appears to be in disagreement with the sharp decline at ∼100 days in planet frequency for low-mass planets (planet mass mp < 30 M ⊕) recently suggested by the HARPS survey. Within 250 days, the cumulative frequencies for Earth-size and super-Earth-size planets are remarkably similar (∼28% and 25%), while Neptune-size and Jupiter-size planets are ∼7% and ∼3%, respectively. A major potential uncertainty arises from the unphysical impact parameter distribution of the candidates. © 2013. The American Astronomical Society. All rights reserved.

The biological function of MAGEC2, a cancer/testis antigen highly expressed in various cancers, remains largely unknown. Here we demonstrate that expression of MAGEC2 induces rounded morphology and amoeboid-like movement of tumor cells in vitro and promotes tumor metastasis in vivo. The pro-metastasis effect of MAGEC2 was mediated by signal transducer and activator of transcription 3 (STAT3) activation. Mechanistically, MAGEC2 interacts with STAT3 and inhibits the polyubiquitination and proteasomal degradation of STAT3 in the nucleus of tumor cells, resulting in accumulation of phosphorylated STAT3 and enhanced transcriptional activity. Notably, expression levels of MAGEC2 and phosphorylated STAT3 are positively correlated and both are associated with incidence of metastasis in human hepatocellular carcinoma. This study not only reveals a previously unappreciated role of MAGEC2 in promoting tumor metastasis, but also identifies a new molecular mechanism by which MAGEC2 sustains hyperactivation of STAT3 in the nucleus of tumor cells. Thus, MAGEC2 may represent a new antitumor metastasis target for treatment of cancer.Oncogene advance online publication, 24 October 2016; doi:10.1038/onc.2016.314. © 2016 Macmillan Publishers Limited, part of Springer Nature.

Wang Z.,Peking University | Li X.,Peking University | Huang Y.,Peking University
Angewandte Chemie - International Edition | Year: 2013

Carbonyl-substituted allenes are highly important synthetic intermediates for a number of heterocycles and strained-ring systems. However, chemistry of allenyl aldehydes has not been explored as extensively as their ketone, ester, or amide analogues because of a lack of general synthetic methods. Described herein is the first direct α-vinylidenation of aldehydes and an α-vinylidenation/γ-functionalization cascade to access tri- and tetrasubstituted allenyl aldehydes using a combination of a gold catalyst and an secondary amine. The reactive enamine intermediate of an aldehyde reacts with the gold-activated hypervalent silylethynyl benziodoxolone to selectively generate the corresponding trisubstituted allenyl aldehyde. The allenyl aldehyde can further react with another equivalent of the alkynylation reagent or other electrophiles to afford tetrasubstituted allenes bearing an aldehyde group, an acetylene, and a halogen functionality. This method enables rapid access to polysubstituted furans from aldehydes. Gold and amine team up: Gold and an amine catalyst work synergistically to promote either an α-vinylidenation or an α-vinylidenation/γ-functionalization of aldehydes to generate tri- and tetrasubstituted allenes. The allene products also undergo an additional reaction to generate polysubstituted furans. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang B.,Peking University | Zhang B.,University of Nevada, Las Vegas
Astrophysical Journal Letters | Year: 2013

Double neutron star mergers are strong sources of gravitational waves. The upcoming advanced gravitational wave detectors are expected to make the first detection of gravitational wave bursts (GWBs) associated with these sources. Proposed electromagnetic counterparts of a GWB include a short gamma-ray burst, an optical macronova, and a long-lasting radio afterglow. Here we suggest that at least some GWBs could be followed by an early afterglow lasting for thousands of seconds, if the post-merger product is a highly magnetized, rapidly rotating, massive neutron star rather than a black hole. This afterglow is powered by dissipation of a proto-magnetar wind. The X-ray flux is estimated to be as bright as (10-8-10-7) erg s-1 cm -2. The optical flux is subject to large uncertainties but could be as bright as 17th magnitude in R band. We provide observational hints of such a scenario, and discuss the challenge and strategy to detect these signals. © 2013. The American Astronomical Society. All rights reserved.

Chen X.,Peking University | Liu F.K.,Peking University
Astrophysical Journal | Year: 2013

It has been suggested that an intermediate-massive black hole (IMBH) with mass 103-5 M could fall into the galactic center (GC) and form a massive black hole binary (MBHB) with the central supermassive black hole, but current observations are not sensitive to constrain all mass and distance ranges. Motivated by the recent discovery that MBHBs could enhance the rate of tidal-disruption events (TDEs) of stellar objects, we investigate the prospect of using stellar-disruption rate to probe IMBHs in the GC. We incorporated the perturbation by an IMBH into the loss-cone theory and calculated the stellar-disruption rates in the GC. We found that an IMBH heavier than 2000 M could distinguishably enhance the stellar-disruption rate. By comparing observations of Sgr A* with the fall-back model for stellar debris, we suggested that the TDE rate in our Galaxy should not significantly exceed 0.002 yr-1, therefore a fraction of the parameter space for the IMBH, concentrating at the high-mass end, can already be excluded. To derive constraint in the remaining parameter space, it is crucial to observationally confirm or reject the stellar-disruption rate between 10-4 and 10-2 yr-1, and we discussed possible strategies to make such measurements. © 2013. The American Astronomical Society. All rights reserved..

Luo Y.,Peking University
Circulation Research | Year: 2016

RATIONALE:: Vascular endothelial inflammation, including the expression of intercellular adhesion molecule 1 (ICAM-1), is a key event in vascular diseases. However, the mechanisms underlying the regulation of ICAM-1 are largely unknown. OBJECTIVE:: To investigate the mechanisms on the regulation of ICAM-1 by NSun2-mediated mRNA methylation and the impact of NSun2-ICAM-1 regulatory process in vascular inflammation and allograft arteriosclerosis. METHODS AND RESULTS:: By using in vitro, in cells and in vivo methylation assays, we showed that the tRNA methyltransferase NSun2 methylated the ICAM-1 mRNA. Methylation by NSun2 promoted the translation of ICAM-1, thereby increasing the adhesion of leukocytes to endothelial cells. TNFα or homocysteine (Hcy) activated the methyltransferase activity of NSun2 by repressing the phosphorylation of NSun2 by Aurora-B. The levels of ICAM-1 induction and of leukocyte adhesion to vascular endothelium observed with Hcy treatment in wild type rats were markedly decreased in NSun2 -/- rats. In a rat model of aortic allograft, the lack of donor NSun2 impaired the formation of allograft arteriosclerosis. CONCLUSIONS:: NSun2 upregulates the expression of ICAM-1 by methylating ICAM-1 mRNA. This regulatory process impacts on vascular inflammation and allograft arteriosclerosis. © 2016 American Heart Association, Inc.

Zhang G.,Peking University | Zhang H.,Peking University
Nanoscale | Year: 2011

By using molecular dynamics simulations, we have studied heat flux in graphene Y junctions with lengths of 16.7 nm. It is found that the heat flux runs preferentially from the branches to the stem, which demonstrates an obvious thermal rectification effect in these asymmetric graphene ribbons. More interesting, compared to single-layer graphene Y junctions, a larger rectification ratio can be achieved in double-layer structures, due to the presence of layer-layer interactions. Combined with the availability of high quality few-layer graphene materials, our results shed light on heat conduction in graphene nanoribbons and may open up few-layer graphene applications in thermal management of nano electronics. © 2011 The Royal Society of Chemistry.

Vertical column densities (VCDs) of tropospheric nitrogen dioxide (NO 2) retrieved from space provide valuable information to estimate emissions of nitrogen oxides (NOx) inversely. Accurate emission attribution to individual sources, important both for understanding the global biogeochemical cycling of nitrogen and for emission control, remains difficult. This study presents a regression-based multi-step inversion approach to estimate emissions of NOx from anthropogenic, lightning and soil sources individually for 2006 over East China on a 0.25° long × 0.25° lat grid, employing the DOMINO product version 2 retrieved from the Ozone Monitoring Instrument. The inversion is done gridbox by gridbox to derive the respective emissions, taking advantage of differences in seasonality between anthropogenic and natural sources. Lightning and soil emissions are combined together for any given gridbox due to their similar seasonality; and their different spatial distributions are used implicitly for source separation to some extent. The nested GEOS-Chem model for East Asia is used to simulate the seasonal variations of different emission sources and impacts on VCDs of NO2 for the inversion purpose. Sensitivity tests are conducted to evaluate key assumptions embedded in the inversion process. The inverse estimate suggests annual budgets of about 7.1 TgN (plusmn;39%), 0.21 TgN (plusmn;61%), and 0.38 TgN (plusmn;65%) for the a posteriori anthropogenic, lightning and soil emissions, respectively, about 18-23% higher than the respective a priori values. The enhancements in anthropogenic emissions are largest in cities and areas with extensive use of coal, particularly in the north in winter, as evident on the high-resolution grid. Derived soil emissions are consistent with recent bottom-up estimates. They are less than 6% of anthropogenic emissions annually, increasing to about 13% for July. Derived lightning emissions are about 3% of anthropogenic emissions annually and about 10% in July. Overall, anthropogenic emissions are found to be the dominant source of NOx over East China with important implications for nitrogen control. © Author(s) 2012.

Zhou L.,Peking University
Differential Geometry and its Application | Year: 2010

We first compute Riemannian curvature and Ricci curvature of (α, β) metrics. Then we apply these formulae to discuss a special class (α, β) metrics F = α (1 + frac(β, α)) p (| p | ≥ 1) which have constant flag curvature. We obtain the sufficient and necessary conditions that F = frac((α + β) 2, α) have constant flag curvature. Then we prove that such metrics must be locally projectively flat and complete their local classification. Using the same method we find a necessary condition that flag curvature of F = frac(α 2, α + β) is constant and proved that there are no non-trivial Matsumoto metrics. Furthermore, we give a negative answer whether there are non-trivial metrics F = α (1 + frac(β, α)) p (| p | ≥ 1) of constant flag curvature when β is closed. © 2009 Elsevier B.V. All rights reserved.

Jin Y.,Peking University
Journal of hazardous materials | Year: 2012

Cetyltrimethylammonium bromide (CTAB) modified magnetic nanoparticles (Fe(3)O(4)@CTAB) were synthesized and used to remove arsenate from water. Fe(3)O(4)@CTAB was prepared by a modified simple co-precipitation process with cheap and environmental friendly iron salts and cationic surfactant CTAB. Powder X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infra-red spectroscopy were utilized to characterize the prepared adsorbent (Fe(3)O(4)@CTAB). Transmission electron microscopy (TEM) image showed that Fe(3)O(4)@CTAB particles were approximately spherical with the core size of 10 nm. With a saturation magnetization of 67.2 emu g(-1), the Fe(3)O(4)@CTAB nanoparticles could be easily separated from solutions with a simple magnetic process in very short time (within 5 min). Adsorption of arsenate on Fe(3)O(4)@CTAB reached equilibrium within 2 min at pH 6. Arsenate adsorption agreed well with pseudo-second order kinetic model and two-site Langmuir isotherm model with the arsenate adsorption capacity of 23.07 mg g(-l), which was twice greater than that of pure Fe(3)O(4). Arsenate removal rate was over 90% at a wide pH range from 3 to 9 and the removal of arsenate was not obviously affected by the presence of dissolved natural organic matter (up to 10 mg L(-1) as TOC) and competitive anions (sulfate, bicarbonate, and silicate up to 20 mg L(-1), and phosphate up to 5 mg L(-1)) in solutions. Fe(3)O(4)@CTAB could be regenerated in alkali solutions and more than 85% As(V) was removed even in fifth regeneration/reuse cycle. Copyright © 2012 Elsevier B.V. All rights reserved.

Li T.,Peking University
Molecular & cellular proteomics : MCP | Year: 2012

Lysine acetylation is a well-studied post-translational modification on both histone and nonhistone proteins. More than 2000 acetylated proteins and 4000 lysine acetylation sites have been identified by large scale mass spectrometry or traditional experimental methods. Although over 20 lysine (K)-acetyl-transferases (KATs) have been characterized, which KAT is responsible for a given protein or lysine site acetylation is mostly unknown. In this work, we collected KAT-specific acetylation sites manually and analyzed sequence features surrounding the acetylated lysine of substrates from three main KAT families (CBP/p300, GCN5/PCAF, and the MYST family). We found that each of the three KAT families acetylates lysines with different sequence features. Based on these differences, we developed a computer program, Acetylation Set Enrichment Based method to predict which KAT-families are responsible for acetylation of a given protein or lysine site. Finally, we evaluated the efficiency of our method, and experimentally detected four proteins that were predicted to be acetylated by two KAT families when one representative member of the KAT family is over expressed. We conclude that our approach, combined with more traditional experimental methods, may be useful for identifying KAT families responsible for acetylated substrates proteome-wide.

Hou G.,Peking University
Geoscience Frontiers | Year: 2012

This study proposes three models to explain the mechanism of the three major types of mafic dyke swarms. Parallel dyke swarms form in response to a regional stress field, e.g. the mafic dyke swarms in the North China Craton, whereas small radiating dyke swarm forms due to stress constructions around a plutonic or volcanic edifice, such as the dyke swarm at Spanish Peak, USA. The third type of radiating dyke swarm is giant fan-shaped dyke swarm such as the Mackenzie dyke swarm. Fractures that formed prior to magmatism may play a vital role in dictating the dyke swarm geometry. In most of the cases, the pre-existing fractures are induced by tectonic stresses and not by magma injection though magma injection can increase the fracture size by propagation at the dyke tip. © 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

Liew S.-L.,University of Southern California | Han S.,Peking University | Aziz-Zadeh L.,University of Southern California
Human Brain Mapping | Year: 2011

Recent research suggests that the inference of others' intentions from their observed actions is supported by two neural systems that perform complementary roles. The human putative mirror neuron system (pMNS) is thought to support automatic motor simulations of observed actions, with increased activity for previously experienced actions, whereas the mentalizing system provides reflective, non-intuitive reasoning of others' perspectives, particularly in the absence of prior experience. In the current fMRI study, we show how motor familiarity with an action and perceptual familiarity with the race of an actor uniquely modulate these two systems. Chinese participants were asked to infer the intentions of actors performing symbolic gestures, an important form of non-verbal communication that has been shown to activate both mentalizing and mirror neuron regions. Stimuli were manipulated along two dimensions: (1) actor's race (Caucasian vs. Chinese actors) and (2) participants' level of experience with the gestures (familiar or unfamiliar). We found that observing all gestures compared to observing still images was associated with increased activity in key regions of both the pMNS and mentalizing systems. In addition, observations of one's same race generated greater activity in the posterior pMNS-related regions and the insula than observations of a different race. Surprisingly, however, familiar gestures more strongly activated regions associated with mentalizing, while unfamiliar gestures more strongly activated the posterior region of the pMNS, a finding that is contrary to prior literature and demonstrates the powerful modulatory effects of both motor and perceptual familiarity on pMNS and mentalizing regions when asked to infer the intentions of intransitive gestures. © 2010 Wiley-Liss, Inc.

Meng Z.,Peking University | Zhang Y.,Peking University
Monthly Weather Review | Year: 2012

Based on a 3-yr (2007-09) mosaic of radar reflectivity and conventional surface and synoptic radiosonde observations, the general features of squall lines preceding landfalling tropical cyclones (TCs) (pre-TC) in China are examined and compared with their midlatitude and subtropical counterparts. The results show that about 40% of landfalling TCs are associated with pre-TC squall lines with high-occurring frequency in August and from late afternoon to midnight. Most pre-TC squall lines form in a broken-line mode with a trailingstratiform organization. On average, they occur about 600 km from the TC center in the front-right quadrant with a maximum length of 220 km, a maximum radar reflectivity of 57-62 dBZ, a life span of 4 h, and a moving speed of 12.5 m s -1. Pre-TC squall lines are generally shorter in lifetime and length than typical midlatitude squall lines. Pre-TC squall lines tend to form in the transition area between the parent TC and subtropical high in a moist environment and with a weaker cold pool than their midlatitude counterparts. The environmental 0-3-km vertical shear is around 10 m s -1 and generally normal to the orientation of the squall lines. This weak shear makes pre-TC squall lines in a suboptimal condition according to the Rottuno-Klemp-Weisman (RKW) theory. Convection is likely initiated by low-level mesoscale frontogenesis, convergence, and/or confluence instead of synoptic-scale forcing. The parent TC may contribute to (i) the development of convection by enhancing conditional instability and low-level moisture supply, and (ii) the linear organization of discrete convection through the interaction between the TC and the neighboring environmental system. © 2012 American Meteorological Society.

Human CMTM is a novel gene family consisting of CKLF and CMTM1-8. CMTM4 is the most conserved gene and has three RNA splicing forms designated as CMTM4-v1, -v2 and -v3, but in many types of tissue and cell lines, only CMTM4-v1 and -v2 could be detected. CMTM4-v2 is the full length cDNA product, which has been highly conserved during evolution. CMTM4-v1 and -v2 are broadly expressed in normal types of tissue. They are distributed on the cell membrane and across the cytoplasm in a speckled pattern. Overexpression of CMTM4-v1 and -v2 can inhibit HeLa cell growth via G2/M phase accumulation without inducing apoptosis. Therefore, CMTM4 might be an important gene involved in cell growth and cell cycle regulation.

Ji X.,Peking University
Ecological Modelling | Year: 2015

Pulsing paradigm is regarded general for all scales of ecosystem. The pulsing succession view insists that a resource-dependent system will approach its peak through intensive consumption of resources, then move towards recession and get ready for the next cycle. Urban economy, as an open and resource-dependent subsystem in the whole ecosystem may pulse, and its quantitative growth in physical scale will be limited by the finite ecosystem eventually. This raises one problem: what would be the future of urban economy when it gets to the physical climax under the ecological constraint? Modelling is a feasible approach to simulate and reveal the pulse of a large scale system whose wave length is too long for individuals to witness. In this study, systems ecology-modelling, as a combination of ecological modelling and theories of systems ecology, is applied to take the pulse of urban economy. Cosmic emergy is applied to synthesize the material, energy, information, currency and population flows and stocks, which greatly facilitates and simplifies the simulation. Taking Beijing city as a case, the systems ecology-modelling is carried out, and the pulses of Beijing's economy and its components are partly observed. Suggestions on urban management are proposed accordingly. © 2015 Elsevier B.V.

Yang L.,Peking University | Yang J.,Peking University
International Journal of Robust and Nonlinear Control | Year: 2011

This paper investigates fast finite-time control of nonlinear dynamics using terminal sliding-mode (TSM) scheme. Some new norms of fast TSM strategies are proposed, and a faster convergence rate is established in comparison with the conventional fast TSM. A novel concept of nonsingular fast TSM, which is able to avoid the possible singularity during the control phase, is adopted in the robust high-precision control of uncertain nonlinear systems. Numerical simulation on a two-link rigid robot manipulator demonstrates the effectiveness of the proposed algorithm. © 2010 John Wiley & Sons, Ltd.

Li R.,Peking University | Chu T.,Peking University
IEEE Transactions on Neural Networks and Learning Systems | Year: 2012

We examine complete synchronization of two deterministic Boolean networks (BNs) coupled unidirectionally in the drive-response configuration. A necessary and sufficient criterion is presented in terms of algebraic representations of BNs. As a consequence, we show that complete synchronization can occur only between two conditionally identical BNs when the transition matrix of the drive network is nonsingular. Two examples are worked out to illustrate the obtained results. © 2012 IEEE.

Lazarian A.,University of Wisconsin - Madison | Yan H.,Peking University
Astrophysical Journal | Year: 2014

Diffusion of cosmic rays (CRs) is the key process for understanding their propagation and acceleration. We employ the description of spatial separation of magnetic field lines in magnetohydrodynamic turbulence in Lazarian & Vishniac to quantify the divergence of the magnetic field on scales less than the injection scale of turbulence and show that this divergence induces superdiffusion of CR in the direction perpendicular to the mean magnetic field. The perpendicular displacement squared increases, not as the distance x along the magnetic field, which is the case for a regular diffusion, but as the x 3 for freely streaming CRs. The dependence changes to x 3/2 for the CRs propagating diffusively along the magnetic field. In the latter case, we show that it is important to distinguish the perpendicular displacement with respect to the mean field and to the local magnetic field. We consider how superdiffusion changes the acceleration of CRs in shocks and show how it decreases efficiency of the CRs acceleration in perpendicular shocks. We also demonstrate that in the case when the small-scale magnetic field is generated in the pre-shock region, an efficient acceleration can take place for the CRs streaming without collisions along the magnetic loops. © 2014. The American Astronomical Society. All rights reserved..

Dewan S.,University of California at Irvine | Ren F.,Peking University
Information Systems Research | Year: 2011

In this paper, we empirically investigate the impact of information technology (IT) investment on firm return and risk financial performance, emphasizing the moderating role of the firm boundary strategies of diversification and vertical integration. Our results indicate a sharp contrast between the direct and interactive effects of IT on both the return (profitability) and risk (variability of returns) dimensions. Although the direct effect of IT capital is to increase firm risk for a given level of return, we find that suitable boundary strategies can moderate the impact of IT on firm performance in a way that increases return and decreases risk, at the margin. This interaction effect is strongest in service firms, in firms with high levels of IT investment intensity, and in more recent time periods. Our results are robust to alternative proxies for firm risk, including an ex ante risk measure (variability of analysts' earnings estimates), and alternative risk-return specifications. Put together, our results provide new insights into how IT and firm boundary strategies interact to affect the risk and return performance of firms. © 2011 INFORMS.

Yang R.,Peking University
PloS one | Year: 2011

Due to recent leaps forward in DNA synthesis and sequencing technology, DNA manipulation has been extended to the level of whole-genome synthesis. Bacteriophages occupy a special niche in the micro-organic ecosystem and have potential as a tool for therapeutic agent. The purpose of this study was to carry out chemical synthesis of the bacteriophage G4 and the study of its infectivity. Full-sized genomes of bacteriophage G4 molecules were completed from short overlapping synthetic oligonucleotides by direct assembly polymerase chain reaction and ligase chain reaction followed by fusion polymerase chain reaction with flanking primers. Three novel restriction endonuclease sites were introduced to distinguish the synthetic G4 from the wild type. G4 particles were recovered after electroporation into Escherichia coli and were efficient enough to infect another strain. The phage was validated by electron microscope. Specific polymerase chain reaction assay and restriction analyses of the plaques verified the accuracy of the chemical synthetic genomes. Our results showed that the bacteriophage G4 obtained is synthetic rather than a wild type. Our study demonstrated that a phage can be synthesized and manipulated genetically according to the sequences, and can be efficient enough to infect the Escherichia coli, showing the potential use of synthetic biology in medical application.

Du W.,Peking University | Fan Z.,Peking University
Astrophysical Journal | Year: 2014

With the halo catalog from the Millennium Simulation, we analyze the weak-lensing measured density profiles for clusters of galaxies, paying attention to the determination of the concentration-mass (c-M) relation, which can be biased by the center offset, selection effect, and shape noise from intrinsic ellipticities of background galaxies. Several different methods of locating the center of a cluster from weak-lensing effects alone are explored. We find that, for intermediate redshift clusters, the highest peak from our newly proposed two-scale smoothing method applied to the reconstructed convergence field, first with a smoothing scale of 2′ and then 0.′5, corresponds best to the true center. Assuming the parameterized Navarro-Frenk-White profile, we fit the reduced tangential shear signals around different centers identified by different methods. It is shown that, for the ensemble median values, a center offset larger than one scale radius r s can bias the derived mass and concentration significantly lower than the true values, especially for low-mass halos. However, the existence of noise can compensate for the offset effect and reduce the systematic bias, although the scatter of mass and concentration becomes considerably larger. Statistically, the bias effect of center offset on the c-M relation is insignificant if an appropriate center finding method is adopted. On the other hand, noise from intrinsic ellipticities can bias the c-M relation derived from a sample of weak-lensing analyzed clusters if a simple χ2 fitting method is used. To properly account for the scatter and covariance between c and M, we apply a Bayesian method to improve the statistical analysis of the c-M relation. It is shown that this new method allows us to derive the c-M relation with significantly reduced biases. © 2014. The American Astronomical Society. All rights reserved..

Yao X.,Peking University
Library Collections, Acquisition and Technical Services | Year: 2012

CALIS is a nationwide academic library consortium in China. By coordinating, guiding, and organizing academic libraries, CALIS aims to minimize spending while obtaining foreign resources with the best prices and services. It also aims to meet the demands of teaching and research via the CALIS cooperative purchase service. Since 2005, there has been a customer satisfaction survey to evaluate this cooperative purchase service and the databases subscribed to by the CALIS consortium during the CALIS annual "imported database training week". 494 staff members from 246 libraries took part in the fourth such survey to evaluate 87 databases cooperatively purchased in 2009. According to the survey, CALIS releases database usage reports and database evaluation rankings to help libraries analysis costs and make more informed collection developments decisions. Such survey activities provide a win-win situation, not only for CALIS and its member libraries, but also for database vendors. Survey results and usage reports help libraries analyze the quality of resources and provide evidence for libraries to choose among different purchasing options. Also, more promotional work has been done to enhance understanding, solve libraries' problems, and improve service quality. Finally, survey results and database evaluation rankings have been used to urge database vendors and publishers to make improvements relevant to libraries' development strategies. © 2012 Elsevier Ltd.

Chai Y.,Peking University
Annals of the Association of American Geographers | Year: 2013

The space-time behavior approach has become an influential methodology in Chinese urban geography. In this article I provide an overview of space-time behavior research in China, focusing on theoretical and methodological progress as well as key themes and findings from recent empirical studies. I argue that space-time behavior research offers a new perspective for understanding the complexity and diversity of human behavior patterns during the large-scale spatial and institutional transition in Chinese cities. Yet although Chinese urban geographers have made more methodological progress in data collection and analytic tools, theoretical development still lags behind compared to the space-time behavior approach in the West. The article concludes by discussing key theoretical and practical challenges for future development of space-time activity research in China. © 2013 Copyright Taylor and Francis Group, LLC.

Lin Q.,Peking University | Labuz J.F.,University of Minnesota
International Journal of Rock Mechanics and Mining Sciences | Year: 2013

Evaluation of mode I fracture characteristics, such as critical opening displacement and process-zone length, is fundamental for the analysis and prediction of crack growth. To identify deformation with micron-scale resolution, experiments were performed using digital image correlation, where displacement is determined through a comparison of a pair of digital images by matching a small area from the image before deformation to the image after deformation. The matching process uses a cross-correlation algorithm, and within this study, the correlation is based on a Fast Fourier Transform method. Mode I fracture tests were performed on Berea sandstone using three-point bending. Twelve specimens, of three types, were fabricated: six center notch (0.5mm radius), three smooth boundary, and three reduced-section (6 or 12mm radius notch). The characteristics of tensile fracture, namely opening displacement and crack length, were extracted from detailed displacement measurements. At the onset of unstable propagation (peak load) for the center notch specimens, the critical opening displacement ωc=30μm at the notch tip, and as the crack propagated, the known position of ωc allowed the identification of the process zone throughout the post-peak response. Incremental displacement contours established the tip of the effective crack, and the length of the process zone lp=5-7mm, about 10 times the maximum grain size. In addition, it was observed that the process zone maintained a constant length with constant critical opening for all tests. © 2013 Elsevier Ltd.

In this paper, an experimental work is carried out to investigate the characteristics of solar thermal collection using supercritical CO2. This solar thermal conversion is based on supercritical CO2 natural convection, which is much easily induced because a small change in temperature can result in large change in density close to the critical point. In addition, its critical temperature is 31.1°C and low enough to be easily reached in the low-temperature solar thermal conversion system. The obtained results show that the supercritical CO2 flow rate is smooth curve and not affected by the sudden variation of the solar radiation. The solar thermal conversion operation process can be divided into three periods: starting-up, transition, and stable period. When the system reaches the stable period, the CO2 flow rate will keep at a high value even if the solar radiation stays at a low level. It is also found that the smaller local solar radiation variation is, the better ability of keeping the flow rate near the peak level the supercritical CO2 fluid owns. It is also found that a small pressure difference can drive a supercritical CO2 flow with high flow rate. Furthermore, high solar thermal conversion efficiency is found at a high mass flow rate and under operation pressure near the critical point. © 2012 John Wiley & Sons, Ltd.

Li J.S.,Peking University | Chen G.Q.,Peking University | Chen G.Q.,King Abdulaziz University
Renewable and Sustainable Energy Reviews | Year: 2013

Although Macao is one of the individual members of the Kyoto Protocol, a holistic picture to draw its energy consumption and GHG emissions has been lacking. A comprehensive review of energy consumption as well as GHG emissions is presented in this study for Macao since the handover of sovereignty to China. The results show that the Macao's energy consumption and its related GHG emissions were 32,700 Terajoules (Tj) and 3.70E+06 t CO2 e. in 2010, increased by 31.10% and 100.34% over those of 2000, respectively. The results also indicate that electricity is the biggest contributor to GHG emissions, and induced a large amount of GHG emissions in other places. Energy intensity and per capita GHG emission also witnessed growth from 2000 to 2010. In terms of sectors of the economy, the service industry, commerce, restaurants and hotels, transportation and households are the leading four energy users and GHG emission inducers. Our analysis also suggests that decision-makers should take indirect emissions from energy consumption into consideration to support Macao's energy, climate and sustainability initiatives. © 2012 Elsevier Ltd.

Huang Y.-H.,Peking University | Liu X.-Y.,Peking University | Du X.-X.,Peking University | Jiang Z.-F.,Peking University | Su X.-D.,Peking University
Nature Structural and Molecular Biology | Year: 2012

STING (stimulator of interferon genes) is an essential signaling adaptor that mediates cytokine production in response to microbial invasion by directly sensing bacterial secondary messengers such as the cyclic dinucleotide bis-(3′-5′)-cyclic dimeric GMP (c-di-GMP). STING's structure and its binding mechanism to cyclic dinucleotides were unknown. We report here the crystal structures of the STING cytoplasmic domain and its complex with c-di-GMP, thus providing the structural basis for understanding STING function. © 2012 Nature America, Inc. All rights reserved.

Zhang C.,Peking University | Lai L.,Peking University
Proteins: Structure, Function and Bioinformatics | Year: 2012

Proteins perform their functions mainly via active sites, whereas other parts of the proteins comprise the scaffolds, which support the active sites. One strategy for protein functional design is transplanting active sites, such as catalytic sites for enzyme or binding hot spots for protein-protein interactions, onto a new scaffold. AutoMatch is a new program designed for efficiently elucidating suitable scaffolds and potential sites on the scaffolds. Backrub motions are used to treat backbone flexibility during the design process. A step-by-step checking strategy and cluster-representation examination strategy were developed to solve the large combinatorial problem for the matching of active-site conformations. In addition, a grid-based binding energy scoring method was used to filter the solutions. An enzyme design benchmark and a protein-protein interaction design benchmark were built to test the algorithm. AutoMatch could identify the hot spots in the nonbinding protein and rank them within the top five results for 8 of 10 target-binding protein design cases. In addition, among the 15 enzymes tested, AutoMatch can identify the catalytic active sites in the apoprotein and rank them within the top five results for 13 cases. AutoMatch was also tested for screening scaffold library in designing binding proteins targeting influenza hemagglutinin, HIV gp120, and epidermal growth factor receptor kinase, respectively. AutoMatch, and the two test sets, ActApo and ActFree, are available for noncommercial applications at. © 2011 Wiley Periodicals, Inc.

Yin W.,Peking University | Wang C.,Peking University | Huang Y.,Peking University
Organic Letters | Year: 2013

A mild, aerobic, catalytic process for obtaining nitriles directly from alcohols and aqueous ammonia is described. The reaction proceeds via a dehydrogenation cascade mediated by catalytic CuI, bpy, and TEMPO in the presence of O2. The substrate scope is broad including various functionalized aromatic and aliphatic alcohols. This protocol enabled the one-pot synthesis of various biaryl heterocycles directly from commercially available alcohols. © 2013 American Chemical Society.

Suzuki W.A.,New York University | Naya Y.,Peking University
Annual Review of Neuroscience | Year: 2014

Anatomically, the perirhinal cortex sits at the boundary between the medial temporal lobe and the ventral visual pathway. It has prominent interconnections not only with both these systems, but also with a wide range of unimodal and polymodal association areas. Consistent with these diverse projections, neurophysiological studies reveal a multidimensional set of mnemonic signals that include stimulus familiarity, within- and between-domain associations, associative recall, and delay-based persistence. This wide range of perirhinal memory signals not only includes signals that are largely unique to the perirhinal cortex (i.e., object familiarity), consistent with dual-process theories, but also includes a range of signals (i.e., associative flexibility and recall) that are strongly associated with the hippocampus, consistent with single-process theories. These neurophysiological findings have important implications for bridging the gap between single-process and dual-process models of medial temporal lobe function. © Copyright ©2014 by Annual Reviews. All rights reserved.

Wang C.,Peking University | Huang Y.,Peking University
Organic Letters | Year: 2013

A general protocol for the synthesis of N-alkyl indoles has been developed via a redox neutral C-H activation strategy using a traceless nitroso directing group. A broad scope of substituted N-alkyl indoles has been prepared in good to excellent yields using a very simple Rh catalyst system in the absence of an external oxidant or any other additive. Good to excellent regioselectivity has been achieved for asymmetrically disubstituted acetylenes. © 2013 American Chemical Society.

Large discrepancies between the laminar flame speeds and Markstein lengths measured in experiments and those predicted by simulations for ultra-lean methane/air mixtures bring a great concern for kinetic mechanism validation. In order to quantitatively explain these discrepancies, a computational study is performed for propagating spherical flames of lean methane/air mixtures in different spherical chambers using different radiation models. The emphasis is focused on the effects of radiation and compression. It is found that the spherical flame propagation speed is greatly reduced by the coupling between thermal effect (change of flame temperature or unburned gas temperature) and flow effect (inward flow of burned gas) induced by radiation and/or compression. As a result, for methane/air mixtures near the lean flammability limit, the radiation and compression cause large amounts of under-prediction of the laminar flame speeds and Markstein lengths extracted from propagating spherical flames. Since radiation and compression both exist in the experiments on ultra-lean methane/air mixtures reported in the literature, the measured laminar flame speeds and Markstein lengths are much lower than results from simulation and thus cannot be used for kinetic mechanism validation. © 2010 The Combustion Institute.

Jia C.,CAS Beijing National Laboratory for Molecular | Guo X.,CAS Beijing National Laboratory for Molecular | Guo X.,Peking University
Chemical Society Reviews | Year: 2013

Understanding charge transport of single molecules or a small collection of molecules sandwiched between electrodes is of fundamental importance for molecular electronics. This requires the fabrication of reliable devices, which depend on several factors including the testbed architectures used, the molecule number and defect density being tested, and the nature of the molecule-electrode interface. On the basis of significant progresses achieved in both experiments and theory over the past decade, in this tutorial review, we focus on new insights into the influence of the nature of the molecule-electrode interface, the most critical issue hindering the development of reliable devices, on the conducting properties of molecules. We summarize the strategies developed for controlling the interfacial properties and how the coupling strength between the molecules and the electrodes modulates the device properties. These analyses should be valuable for deeply understanding the relationship between the contact interface and the charge transport mechanism, which is of crucial importance for the development of molecular electronics, organic electronics, nanoelectronics, and other interface-related optoelectronic devices. © 2013 The Royal Society of Chemistry.

Yang W.,Peking University | Hu X.,Peking University
Physical Review Letters | Year: 2011

A Comment on the Letter by Sung Won Hwang et al., Phys. Rev. Lett.PRLTAO0031-9007 105, 127403 (2010)10.1103/PhysRevLett.105.127403. The authors of the Letter offer a Reply. © 2011 American Physical Society.

Chen Z.,CAS Institute of Physics | Wu B.,Peking University
Physical Review Letters | Year: 2011

Mean-field Bloch bands of a Bose-Einstein condensate in a honeycomb optical lattice are computed. We find that the topological structure of the Bloch bands at the Dirac point is changed completely by atomic interaction of arbitrary small strength: the Dirac point is extended into a closed curve and an intersecting tube structure arises around the original Dirac point. These tubed Bloch bands are caused by the superfluidity of the system. Furthermore, they imply the inadequacy of the tight-binding model to describe an interacting Boson system around the Dirac point and the breakdown of adiabaticity by interaction of arbitrary small strength. © 2011 American Physical Society.

Yu S.-L.,Nanjing University | Xie X.C.,Peking University | Xie X.C.,Oklahoma State University | Li J.-X.,Nanjing University
Physical Review Letters | Year: 2011

We investigate the interplay between the strong correlation and the spin-orbit coupling in the Kane-Mele-Hubbard model and obtain the qualitative phase diagram via the variational cluster approach. We identify, through an increase of the Hubbard U, the transition from the topological band insulator to either the spin liquid phase or the easy-plane antiferromagnetic insulating phase, depending on the strength of the spin-orbit coupling. A nontrivial evolution of the bulk bands in the topological quantum phase transition is also demonstrated. © 2011 American Physical Society.

Xie W.J.,Peking University | Gao Y.Q.,Peking University
Journal of Physical Chemistry Letters | Year: 2013

In cells, biological molecules function in an aqueous solution. Electrolytes and other small molecules play important roles in keeping the osmotic pressure of the cellular environment as well as the structure formation and function of biomolecules. The observed empirical rules such as Hofmeister series are still waiting for molecular interpretations. In this Perspective, we will discuss a simple and self-consistent theory that takes into account the cooperative effects of cations and anions in affecting water/air surface tension, water activity, and the solubility of model compounds including polypeptides. Molecular dynamics simulations used to test these theoretical models will also be discussed. © 2013 American Chemical Society.

Yin Y.,Peking University | Zhao X.S.,Peking University
Accounts of Chemical Research | Year: 2011

DNA hybridization, wherein strands of DNA form duplex or larger hybrids through noncovalent, sequence-specific interactions, is one of the most fundamental processes in biology. Developing a better understanding of the kinetic and dynamic properties of DNA hybridization will thus help in the elucidation of molecular mechanisms involved in numerous biochemical processes. Moreover, because DNA hybridization has been widely adapted in biotechnology, its study is invaluable to the development of a range of commercially important processes. In this Account, we examine recent studies of the kinetics and dynamics of DNA hybridization, including (i) intramolecular collision of random coil, single-stranded DNA (ssDNA), (ii) nucleic acid hairpin folding, and (iii) considerations of DNA hybridization from both a global view and a detailed base-by-base view. We also examine the spontaneous single-base-pair flipping in duplex DNA because of its importance to both DNA hybridization and repair.Intramolecular collision of random coil ssDNA, with chemical relaxation times ranging from hundreds of nanoseconds to a few microseconds, is investigated both theoretically and experimentally. The first passage time theory of Szabo, Schulten, and Schulten, which determines the average reaction time of the intrachain collision, was tested. Although it was found to provide an acceptable approximation, a more sophisticated theoretical treatment is desirable.Nucleic acid hairpin folding has been extensively investigated as an important model system of DNA hybridization. The relaxation time of hairpin folding and unfolding strongly depends on the stem length, and it may range from hundreds of microseconds to hundreds of milliseconds. The traditional two-state model has been revised to a multistate model as a result of new experimental observations and theoretical study, and partially folded intermediate states have been introduced to the folding energy landscape. On the other hand, new techniques are needed to provide more accurate and detailed information on the dynamics of DNA hairpin folding in the time domain of sub-milliseconds to tens of milliseconds.From a global view, the hybridization of unstructured ssDNA goes through an entropy-controlled nucleation step, whereas the hybridization of ssDNA with a hairpin structure must overcome an extra, enthalpy-controlled energy barrier to eliminate the hairpin. From a detailed base-by-base view, however, there exist many intermediate states. The average single-base-pair hybridization and dehybridization rates in a duplex DNA formation have been determined to be on the order of a millisecond. Meanwhile, accurate information on the early stages of hybridization, such as the dynamics of nucleation, is still lacking.The investigation of spontaneous flipping of a single base in a mismatched base pair in a duplex DNA, although very important, has only recently been initiated because of the earlier lack of suitable probing tools. In sum, the study of DNA hybridization offers a rich range of research opportunities; recent progress is highlighting areas that are ripe for more detailed investigation. © 2011 American Chemical Society.

Lu H.-Z.,University of Hong Kong | Shi J.,Peking University | Shen S.-Q.,University of Hong Kong
Physical Review Letters | Year: 2011

A magnetoconductivity formula is presented for the surface states of a magnetically doped topological insulator. It reveals a competing effect of weak localization and weak antilocalization in quantum transport when an energy gap is opened at the Dirac point by magnetic doping. It is found that, while random magnetic scattering always drives the system from the symplectic to the unitary class, the gap could induce a crossover from weak antilocalization to weak localization, tunable by the Fermi energy or the gap. This crossover presents a unique feature characterizing the surface states of a topological insulator with the gap opened at the Dirac point in the quantum diffusion regime. © 2011 American Physical Society.

Chen B.,Peking University | Jahn B.-M.,National Taiwan University | Suzuki K.,Japan Agency for Marin Earth Science and Technology
Geology | Year: 2013

The Mesozoic high-Mg dioritic rocks in the North China Craton have been suggested to be part of adakitic rocks. The origin of the high-Mg diorites has been attributed to equilibration of partial melts from delaminated mafi c crust (eclogite) with mantle peridotite. Here we present petrological and Os isotopic data against the delamination model, and propose a process of magma mixing between siliceous crustal melts and basaltic magma from metasomatized mantle in a post-kinematic setting for their origin. The magma mixing process is supported by (1) euhedral overgrowths of high-Ca plagioclase and high-Mg pyroxene over low-Ca plagioclase and low-Mg pyroxene, respectively, and (2) highly radiogenic Os isotopic compositions, and negatively correlated Nd and Sr isotopic ratios. Our proposed model is probably applicable to the general mode of origin and tectonic settings of high-Mg adakitic magmas. © 2012 Geological Society of America.

Liu S.,Peking University | Guo X.,Peking University
NPG Asia Materials | Year: 2012

Carbon nanomaterials field-effect transistor (FET)-based electrical biosensors provide significant advantages over the current gold standards, holding great potential for realizing direct, label-free, real-time electrical detection of biomolecules in a multiplexed manner with ultrahigh sensitivity and excellent selectivity. The feasibility of integrating them with current complementary metal oxide semiconductor platform and a fluid handling module using standard microfabrication technology opens up new opportunities for the development of low-cost, low-noise, portable electrical biosensors for use in practical future devices. In this article, we review recent progress in the rapidly developing area of biomolecular interaction detection using FET-based biosensors based on the carbon nanomaterials single-walled carbon nanotubes (SWNTs) and graphene. Detection scenarios include DNA-DNA hybridization, DNA-protein interaction, protein function and cellular activity. In particular, we will highlight an amazing property of SWNT- or graphene-FETs in biosensing: their ability to detect biomolecules at the single-molecule level or at the single-cell level. This is due to the size comparability and the surface compatibility of the carbon nanomaterials with biological molecules. We also summarize some current challenges the scientific community is facing, including device-to-device heterogeneity and the lack of system integration for uniform device array mass production. © 2012 Nature Japan K.K. All rights reserved 1884-4057/12.

Li Z.,Peking University
Geophysical Prospecting for Petroleum | Year: 2013

With prestack elastic impedance inversion, we can get elastic wave impedance with different incidence angles, and it can better distinguish lithology of underground reservoir and fluid properties but fails to solve multi-solution problem. In this paper, we combine actual seismic data with drilling, logging and geological data, and build a fracture-cavity type reservoir seismic-geological model, which coincides with the actual underground condtions. In terms of forward modeling we analyze seismic wave field characteristics of target reservoir. On the basis of the above research, we apply prestack elastic impedance inversion on the result of forward modeling and actual seismic data. The effective combination of forward modeling and elastic inversion helps to recognize the lithology and fluid characteristics of fracture-cavity type reservoir and improve the accuracy of reservoir prediction.

Varnum M.E.W.,Peking University
PLoS ONE | Year: 2013

Numerous studies have documented the effects of social class on psychological and behavioral variables. However, lay beliefs about how social class affects these dimensions have not been systematically tested. Studies 1 and 2 assessed lay beliefs about the association between social class and 8 variables (including psychological and behavioral tendencies and cognitive ability). Study 3 assessed lay beliefs about the Big five personality traits and social class, and study 4 reframed the 8 variables from study 1 in opposite terms and yielded similar results. Study 5 contained the variables framed as in both studies 1 and 4, and replicated those results suggesting that framing effects were not responsible for the effects observed. Interestingly, for the most part lay beliefs about social class did not differ as a function of participants' own social class. In general people held relatively accurate and consistent stereotypes about the relationship between social class and well-being, health, intelligence, and neuroticism. In contrast lay beliefs regarding social class and reasoning styles, as well as relational, social, and emotional tendencies were less consistent and coherent. This work suggests that on the whole people's beliefs about social class are not particularly accurate, and further that in some domains there are contradictory stereotypes about the consequences of social class. © 2013 Varnum et al.

Tian Z.L.,Peking University | Wei C.J.,Peking University
Journal of Metamorphic Geology | Year: 2013

Eclogites from the Kebuerte Valley, Chinese South Tianshan, consist of garnet, omphacite, phengite, paragonite, glaucophane, hornblendic amphibole, epidote, quartz and accessory rutile, titanite, apatite and carbonate minerals with occasional presence of coesite or quartz pseudomorphs after coesite. The eclogites are grouped into two: type I contains porphyroblastic garnet, epidote, paragonite and glaucophane in a matrix dominated by omphacite where the proportion of omphacite and garnet is >50 vol.%; and type II contains porphyroblastic epidote in a matrix consisting mainly of fine-grained garnet, omphacite and glaucophane where the proportion of omphacite and garnet is <50 vol.%. Garnet in both types of eclogites mostly exhibits core-rim zoning with increasing grossular (Xgr) and pyrope (Xpy) contents, but a few porphyroblastic garnet grains in type I eclogite shows core-mantle zoning with increasing Xpy and a slight decrease in Xgr, and mantle-rim zoning with increases in both Xgr and Xpy. Garnet rims in type I eclogite have higher Xpy than in type II. Petrographic observations and phase equilibria modelling with pseudosections calculated using thermocalc in the NCKMnFMASHO system for three representative samples suggest that the eclogites have experienced four stages of metamorphism: stage I is the pre-peak temperature prograde heating to the pressure peak (Pmax) which was recognized by the garnet core-mantle zoning with increasing Xpy and decreasing Xgr. The P-T conditions at Pmax constrained from garnet mantle or core compositions with minimum Xgr content are 29-30kbar at 526-540°C for type I and 28.2kbar at 518°C for type II, suggesting an apparent thermal gradient of ∼5.5°Ckm-1. Stage II is the post-Pmax decompression and heating to the temperature peak (Tmax), which was modelled from the garnet zoning with increasing Xgr and Xpy contents. The P-T conditions at Tmax, defined using the garnet rim compositions with maximum Xpy content and the Si content in phengite, are 24-27kbar at 590°C for type I and 22kbar at 540°C for type II. Stage III is the post-Tmax isothermal decompression characterized by the decomposition of lawsonite, which may have resulted in the release of a large amount of fluid bound in the rocks, leading to the formation of epidote, paragonite and glaucophane porphyroblasts. Stage IV is the late retrograde evolution characterized by the overprint of hornblendic amphibole in eclogite and the occurrence of epidote-amphibole facies mineral assemblages in the margins or in the strongly foliated domains of eclogite blocks due to fluid infiltration. The P-T estimates obtained from conventional garnet-clinopyroxene-phengite thermobarometry for the Tianshan eclogites are roughly consistent with the P-T conditions of stage II at Tmax, but with large uncertainties in temperature. On the basis of these metamorphic stages or P-T paths, we reinterpreted that the recently reported zircon U-Pb ages for eclogite may date the Tmax stage or the later decompression stage, and the widely distributed (rutile-bearing) quartz veins in the eclogite terrane may have originated from the lawsonite decomposition during the decompression stage rather than from the transition from blueschist to eclogite as previously proposed. © 2012 Blackwell Publishing Ltd.

Despite playing a crucial role in the world economy and in any framework for policy cooperation, there is little awareness among policy-makers in developed countries of China's views and policy directions. Aimed to address this gap, this article attempts to integrate the different views of mainstream Chinese experts and scholars who have influence in shaping the country's foreign economic policy. The author suggests that differentiating between the two concepts of current account imbalance and international currency power imbalance can offer a persuasive explanation of China's positions on international policy coordination, and help advance the global debate on the issue of global economic rebalancing. Chinese analysts generally resist the one-off rapid appreciation of the RMB exchange rate, but they support international collaboration for rebalancing the global economy and emphasize the implementation of China's own obligations by carrying forward domestic structural reforms of the Chinese economy. © The Author 2013. Published by Oxford University Press.

Chao W.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

A possible extension of the Standard Model to include lepton number as local gauge symmetry is investigated. In such a model, anomalies are canceled by two extra fermions doublet. After leptonic gauge symmetry spontaneously broken, three active neutrinos may acquire non-zero Majorana masses through the modified Type-II seesaw mechanism. Constraints on the model from electro-weak precision measurements are studied. Due to the Z2 discrete flavor symmetry, right-handed Majorana neutrinos can serve as cold dark matter candidate of the Universe. Constraint from dark matter relic abundance is calculated. © 2010 Elsevier B.V.

Ma Y.-Q.,Beijing University of Technology | Wang K.,Beijing University of Technology | Chao K.-T.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review Letters | Year: 2011

We present a complete evaluation for J/ψ(ψ′) prompt production at the Tevatron and LHC at next-to-leading order in nonrelativistic QCD, including color-singlet, color-octet, and higher charmonia feeddown contributions. The short-distance coefficients of PJ[8]3 at next-to-leading order are found to be larger than leading order by more than an order of magnitude but with a minus sign at high transverse momentum pT. Two new linear combinations of color-octet matrix elements are obtained from the CDF data, and used to predict J/ψ production at the LHC, which agrees with the CMS data. The possibility of S0[8]1 dominance and the J/ψ polarization puzzle are also discussed. © 2011 American Physical Society.

Chen W.,Peking University | Chen W.,University of California at Davis | D'Souza R.M.,University of California at Davis | D'Souza R.M.,Santa Fe Institute
Physical Review Letters | Year: 2011

We generalize the random graph evolution process of Bohman, Frieze, and Wormald. Potential edges, sampled uniformly at random from the complete graph, are considered one at a time and either added to the graph or rejected provided that the fraction of accepted edges is never smaller than a decreasing function asymptotically approaching the value α=1/2. We show that multiple giant components appear simultaneously in a strongly discontinuous percolation transition and remain distinct. Furthermore, tuning the value of α determines the number of such components with smaller α leading to an increasingly delayed and more explosive transition. The location of the critical point and strongly discontinuous nature are not affected if only edges which span components are sampled. © 2011 American Physical Society.

Bian Y.,Peking University | Gong Q.,Peking University
Laser and Photonics Reviews | Year: 2014

The goal of confining light at the deep-subwavelength scale while retaining moderate attenuation has been pursued for years in the field of plasmonics. However, few feasible configurations at present are excellent at balancing the tradeoff between confinement and loss. This work proposes to overcome the above limitation by using hybrid wedge structures, which consist of triangular metal wedges loaded with nanometric low/high-index dielectric claddings. Owing to the superior guiding properties of wedge plasmons in conjunction with high refractive index contrast near wedge tips, the modal sizes can be squeezed into significantly smaller spaces than those of their conventional wedge and planar hybrid counterparts, while simultaneously featuring propagation distances over tens of micrometers at telecommunication wavelengths. Studies on the evolution from a single metallic wedge to semiconductor-insulator-metal wedge(s) reveal strategies for continuous improvement of the optical performance. Discussions concerning practical issues including crosstalk and mode excitation have further elucidated their potential in building high-performance nanophotonic components. © 2014 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Liu Z.,Peking University | Wang F.,Peking University
Current Molecular Medicine | Year: 2013

The cell adhesion molecule integrin αvβ3 is an important player in the process of angiogenesis. In the last decades, a series of radiolabeled Arg-Gly-Asp (RGD) peptides targeting integrin αvβ3 has been prepared and optimized for positron emission tomography (PET) and single-photon-emission computed tomography (SPECT) imaging of integrin αvβ3 expression. Several promising radiotracers have been tested in clinical trials. In this review, we will introduce strategies that have been used to optimize and accelerate RGD radiotracers towards clinical translation; illustrate RGD-based radiotracers that have been investigated in clinical trials; and discuss the other applications of RGD radiotracers aside from tumor detection. © 2013 Bentham Science Publishers.

Xing G.-G.,Peking University
Brain Research | Year: 2010

The descending serotonergic (5-HT) system is shown to be plastically altered under pathological conditions such as inflammation or peripheral nerve lesion. Although much evidence indicates that the potentiation of descending facilitatory 5-HT pathways may contribute to the development of chronic pain, the inhibition of descending inhibitory 5-HT system may be functionally more important to the development of central sensitization and neuropathic pain. In the present study, we observed that the inhibitory effects of 5-HT and its receptor agonists including 1A, 1B, 3,4, and probably 2C receptor agonists, on the C-fiber responses of dorsal horn wide dynamic range (WDR) neurons in the spinal cord decreased significantly following spinal nerve ligation (SNL). Furthermore, we found that the antagonistic effects of 5-HT 1B, 2C, 3, and 4 receptor antagonists on the 5-HT-induced inhibition of C-fiber responses of WDR neurons were also attenuated after SNL. In consistent with these observations, we also found an obvious decrease in the content of 5-HT and 5-HIAA, and a marked increase in the turnover rate of 5-HT (5-HIAA/5-HT) in the ipsilateral dorsal half of the lumbar spinal cord after SNL. These data indicate that a loss or decrease in the descending inhibitory 5-HT system upon the spinal processing of nociceptive information appears to occur following spinal nerve injury, and this kind of decrease in the descending inhibitory 5-HT system is proposed to be involved in the development of central sensitization and ultimately to the nerve injury-induced neuropathic pain. © 2010 Elsevier B.V. All rights reserved.

Wang L.-G.,Peking University | Gu J.,Peking University
Cancer Epidemiology | Year: 2012

Background: Colorectal cancer (CRC) metastasis occurs in various organs, most frequently in liver. Serological examination including tumor and biochemical markers for liver function evaluation is routinely performed, though its accuracy is not high. MicroRNAs (miRNAs) have been implicated in a variety of human diseases including cancer, and have many characteristics of an ideal biomarker most notably their inherent stability and resilience. Recently, several studies have indicated that circulating miRNAs hold much potential as novel noninvasive biomarkers for cancer and other disease processes. The objective of this study was to investigate the potential of serum miRNAs as novel biomarkers for CRC with liver metastasis. Methods: This study was divided into three phases: (I) 3 candidate serum miRNAs were detected by using real-time RT-PCR, corresponding 38 CRC patients with liver metastasis and 36 CRC patients without metastasis. (II) Marker validation by real-time RT-PCR on a similar cohort of age- and sex-matched CRC patients without (n= 20) and with liver metastasis (n= 20). (III) We examined the correlation between the expressions of candidate serum miRNAs with clinical parameters of CRC patients. Results: Serum miR-29a was significantly higher in colorectal liver metastasis (CRLM) patients than in CRC patients. This marker yielded a receiver operating characteristic curve area of 80.3%. At a cutoff value of 0.155, the sensitivity was 75% and the specificity was 75% in discriminating metastatic from non-metastatic patients. In addition, increased levels of miR-29a expression were also observed in colorectal tumors from CRLM patients compared with CRC patients. No significant difference was observed in the levels of serum miR-92a between metastatic and non-metastatic patients. Conclusions: These findings suggest that serum miR-29a has strong potential as a novel noninvasive biomarker for early detection of CRC with liver metastasis. © 2011.

Wang F.,Peking University | Kivelson S.A.,Stanford University | Lee D.-H.,University of California at Berkeley | Lee D.-H.,Lawrence Berkeley National Laboratory
Nature Physics | Year: 2015

In common with other iron-based high-temperature superconductors, FeSe exhibits a transition to a nematic phase below 90 K in which the crystal rotation symmetry is spontaneously broken. However, the absence of strong low-frequency magnetic fluctuations near or above the transition has been interpreted as implying the primacy of orbital ordering. In contrast, we establish that quantum fluctuations of spin-1 local moments with strongly frustrated exchange interactions can lead to a nematic quantum paramagnetic phase consistent with the observations in FeSe. We show that this phase is a fundamental expression of the existence of a Berry s phase associated with the topological defects of a Néel antiferromagnet, in a manner analogous to that which gives rise to valence bond crystal order for spin-1/2 systems. We present an exactly solvable model realizing the nematic quantum paramagnetic phase, discuss its relation with the spin-1 J 1 -J 2 model, and construct a field theory of the Landau-forbidden transition between the Néel state and this nematic quantum paramagnet. © 2015 Macmillan Publishers Limited. All rights reserved.

Wang B.,Peking University | Zhang Q.,Peking University
Journal of Cancer Research and Clinical Oncology | Year: 2012

Purpose: MicroRNA-21 (miR-21) was reported as being overexpressed in various human cancerous tissues, but its expression in cancerous serum was not unanimous in different laboratories. On the base of optimizing experimental design and improving trial protocol, we wanted to know whether the circulating microRNA-21 was dysregulated in the common solid cancers. Methods: Using SYBR green real-time quantitative reverse transcription-PCR, we detected the expression of circulating miR-21 in 174 patients with solid cancers and 39 normal control subjects, including breast cancer, esophageal cancer, gastric cancer, colorectal cancer, lung cancer. Furthermore, we analyzed the associations between miR-21 expression and clinical features of patients. Results: miR-21 was significantly overexpressed in human solid cancerous serum relative to normal control (P < 0.001), and its sensitivity and specificity were significantly higher than the currently used tumor markers. High miR-21 expression was not correlated with gender, age, clinical stage, and lymph node metastasis status. Conclusion: Circulating miR-21 could serve as a potential broad-spectrum serum-based biomarker for the detection of some solid cancers. © Springer-Verlag 2012.

Li L.,Peking University | Lu P.,Microsoft | Yin Y.,Nanjing University
Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms | Year: 2013

We give a complete characterization of the two-state anti-ferromagnetic spin systems which exhibit strong spatial mixing on general graphs. We show that a two-state anti-ferromagnetic spin system exhibits strong spatial mixing on all graphs of maximum degree at most Δ if and only if the system has a unique Gibbs measure on infinite regular trees of degree up to Δ, where Δ can be either bounded or unbounded. As a consequence, there exists an FPTAS for the partition function of a two-state anti-ferromagnetic spin system on graphs of maximum degree at most Δ when the uniqueness condition is satisfied on infinite regular trees of degree up to Δ. In particular, an FPTAS exists for arbitrary graphs if the uniqueness is satisfied on all infinite regular trees. This covers as special cases all previous algorithmic results for two-state anti-ferromagnetic systems on general-structure graphs. Combining with the FPRAS for two-state ferromagnetic spin systems of Jerrum-Sinclair and Goldberg-Jerrum-Paterson, and the very recent hardness results of Sly-Sun and independently of Galanis-Štefankovic-Vigoda, this gives a complete classification, except at the phase transition boundary, of the approximability of all two-state spin systems, on either degree-bounded families of graphs or family of all graphs. Copyright © SIAM.

Guo J.,CAS Institute of Theoretical Physics | Kang Z.,Korea Institute for Advanced Study | Kang Z.,Peking University
Nuclear Physics B | Year: 2015

Extending the spacetime symmetries of standard model (SM) by scale invariance (SI) may address the Higgs naturalness problem. In this article we attempt to embed accidental dark matter (DM) into SISM, requiring that the symmetry protecting DM stability is accidental due to the model structure rather than imposed by hand. In this framework, if the light SM-like Higgs boson is the pseudo Goldstone boson of SI spontaneously breaking, we can even pine down the model, two-Higgs-doublets plus a real singlet: The singlet is the DM candidate and the extra Higgs doublet triggers electroweak symmetry breaking via the Coleman-Weinberg mechanism; Moreover, it dominates DM dynamics. We study spontaneously breaking of SI using the Gillard-Weinberg approach and find that the second doublet should acquire vacuum expectation value near the weak scale. Moreover, its components should acquire masses around 380 GeV except for a light CP-odd Higgs boson. Based on these features, we explore viable ways to achieve the correct relic density of DM, facing stringent constraints from direct detections of DM. For instance, DM annihilates into bb- near the SM-like Higgs boson pole, or into a pair of CP-odd Higgs boson with mass above that pole. © 2015 The Authors.

Guo Q.,University of California at Merced | Liu Y.,Peking University
Ecography | Year: 2010

ModEco is a software package for ecological niche modeling. It integrates a range of niche modeling methods within a geographical information system. ModEco provides a user friendly platform that enables users to explore, analyze, and model species distribution data with relative ease. ModEco has several unique features: 1) it deals with different types of ecological observation data, such as presence and absence data, presence-only data, and abundance data; 2) it provides a range of models when dealing with presence-only data, such as presence-only models, pseudo-absence models, background vs presence data models, and ensemble models; and 3) it includes relatively comprehensive tools for data visualization, feature selection, and accuracy assessment. © 2010 The Authors.

Peng Y.,Peking University | Xu R.,Peking University | Zheng X.,Peking University
PLoS Pathogens | Year: 2014

RIG-I like receptors (RLRs) recognize cytosolic viral RNA and initiate innate immunity; they increase the production of type I interferon (IFN) and the transcription of a series of antiviral genes to protect the host organism. Accurate regulation of the RLR pathway is important for avoiding tissue injury induced by excessive immune response. HSCARG is a newly reported negative regulator of NF-κB. Here we demonstrated that HSCARG participates in innate immunity. HSCARG inhibited the cellular antiviral response in an NF-κB independent manner, whereas deficiency of HSCARG had an opposite effect. After viral infection, HSCARG interacted with tumor necrosis receptor-associated factor 3 (TRAF3) and inhibited its ubiquitination by promoting the recruitment of OTUB1 to TRAF3. Knockout of HSCARG attenuated the de-ubiquitination of TRAF3 by OTUB1, and knockdown of OTUB1 abolished the effect of HSCARG. HSCARG also interacted with Ikappa-B kinase epsilon (IKKε) after viral infection and impaired the association between TRAF3 and IKKε, which further decreased the phosphorylation of IKKε and interferon response factor 3 (IRF3), thus suppressed the dimerization and nuclear translocation of IRF3. Moreover, knockdown of TRAF3 dampened the inhibitory effect of IFN-β transcription by HSCARG, suggesting that TRAF3 is necessary for HSCARG to down-regulate RLR pathway. This study demonstrated that HSCARG is a negative regulator that enables balanced antiviral innate immunity. © 2014 Peng et al.

Bankir L.,French Institute of Health and Medical Research | Yang B.,Peking University | Yang B.,Key Laboratory of Molecular Cardiovascular science
Kidney International | Year: 2012

The mechanism by which urine is concentrated in the mammalian kidney remains incompletely understood. Urea is the dominant urinary osmole in most mammals and may be concentrated a 100-fold above its plasma level in humans and even more in rodents. Several facilitated urea transporters have been cloned. The phenotypes of mice with deletion of the transporters expressed in the kidney have challenged two previously well-accepted paradigms regarding urea and sodium handling in the renal medulla but have provided no alternative explanation for the accumulation of solutes that occurs in the inner medulla. In this review, we present evidence supporting the existence of an active urea secretion in the pars recta of the proximal tubule and explain how it changes our views regarding intrarenal urea handling and UT-A2 function. The transporter responsible for this secretion could be SGLT1, a sodium-glucose cotransporter that also transports urea. Glucagon may have a role in the regulation of this secretion. Further, we describe a possible transfer of osmotic energy from the outer to the inner medulla via an intrarenal Cori cycle converting glucose to lactate and back. Finally, we propose that an active urea transporter, expressed in the urothelium, may continuously reclaim urea that diffuses out of the ureter and bladder. These hypotheses are all based on published findings. They may not all be confirmed later on, but we hope they will stimulate further research in new directions. © 2012 International Society of Nephrology.

Transcription factor 21 (TCF21) has been identified as a candidate tumor suppressor at 6q23-q24 that is epigenetically inactivated in many types of human cancers. We recently found that TCF21 methylation level was significantly increased in clear cell renal cell carcinoma (ccRCC). The purpose of this study was to investigate the prognostic impact of TCF21 expression in ccRCC and analyze the relationship between TCF21 expression and methylation level. We used real-time PCR and immunohistochemical staining to detect the expression of TCF21, and used methylation specific-PCR (MS-PCR) to determine the methylation status of TCF21 in ccRCC samples and cell line 786-O. The results showed that TCF21 expression level in ccRCC samples was significantly lower than in normal adjacent tissue samples (NAT samples). The Kaplan-Meier survival analysis demonstrated that TCF21 was a significant prognosticator of cancer-specific survival (p=0.001). Furthermore, the DNA demethylating agent 5'-azacytidine restored part of TCF21 expression by suppressing TCF21 methylation in 786-O. The methylation level of TCF21 in ccRCC samples was much higher than in NAT samples. These results suggest that the expression of TCF21 was an independent prognostic factor for poor survival in patients with ccRCC. Aberrant methylation was an important reason for the down-regulation the expression of TCF21, and may be associated with tumorigenesis in ccRCC.

Li M.,Peking University | Li M.,University of Michigan | Yu X.,University of Michigan
Oncogene | Year: 2015

DNA damage is a deleterious threat, but occurs daily in all types of cells. In response to DNA damage, poly(ADP-ribosyl)ation, a unique post-translational modification, is immediately catalyzed by poly(ADP-ribose) polymerases (PARPs) at DNA lesions, which facilitates DNA damage repair. Recent studies suggest that poly(ADP-ribosyl)ation is one of the first steps of cellular DNA damage response and governs early DNA damage response pathways. Suppression of DNA damage-induced poly(ADP-ribosyl)ation by PARP inhibitors impairs early DNA damage response events. Moreover, PARP inhibitors are emerging as anti-cancer drugs in phase III clinical trials for BRCA-deficient tumors. In this review, we discuss recent findings on poly(ADP-ribosyl)ation in DNA damage response as well as the molecular mechanism by which PARP inhibitors selectively kill tumor cells with BRCA mutations. © 2015 Macmillan Publishers Limited All rights reserved.

The authors conducted a 2-year follow-up of 40 cardiovascular disease patients (mean age = 65.6 years (standard deviation, 5.8)) who underwent repeated measurements of cardiovascular response before and during the 2008 Beijing Olympics (Beijing, China), when air pollution was strictly controlled. Ambient levels of particulate matter with an aerodynamic diameter less than 2.5 μm (PM(2.5)), black carbon, nitrogen dioxide, sulfur dioxide, ozone, and carbon monoxide were measured continuously, with validation of concurrent real-time measurements of personal exposure to PM(2.5) and carbon monoxide. Linear mixed-effects models were used with adjustment for individual risk factors, time-varying factors, and meteorologic effects. Significant heart rate variability reduction and blood pressure elevation were observed in association with exposure to air pollution. Specifically, interquartile-range increases of 51.8 μg/m(3), 2.02 μg/m(3), and 13.7 ppb in prior 4-hour exposure to PM(2.5), black carbon, and nitrogen dioxide were associated with significant reductions in the standard deviation of the normal-to-normal intervals of 4.2% (95% confidence interval (CI): 1.9, 6.4), 4.2% (95% CI: 1.8, 6.6), and 3.9% (95% CI: 2.2, 5.7), respectively. Greater heart rate variability declines were observed among subjects with C-reactive protein values above the 90th percentile, subjects with a body mass index greater than 25, and females. The authors conclude that autonomic and vascular dysfunction may be one of the mechanisms through which air pollution exposure can increase cardiovascular disease risk, especially among persons with systemic inflammation and overweight.

Xu W.,Peking University | Xiao J.,Peking University | Chen Y.,Peking University | Ling X.,Peking University | Zhang J.,Peking University
Advanced Materials | Year: 2013

Graphene is exploited to serve as a seamless and inert veil to fabricate a surface-enhanced Raman spectroscopy (SERS) substrate with a passivated surface. This novel approach inherits the concept of metal-molecule isolation (for more well-defined surface interactions) and results in a few superiorities. We find the SERS performance of a graphene-veiled substrate is highly morphology-dependent, and the dynamic process of thermal annealing is investigated in detail by in-situ Raman spectroscopy. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhu C.,Peking University | Yi C.,Peking University
Angewandte Chemie - International Edition | Year: 2014

The AlkB family demethylases AlkB, FTO, and ALKBH5 recognize differentially methylated RNA/DNA substrates, which results in their distinct biological roles. Here we identify key active-site residues that contribute to their substrate specificity. Swapping such active-site residues between the demethylases leads to partially switched demethylation activities. Combined evidence from X-ray structures and enzyme kinetics suggests a role of the active-site residues in substrate recognition. Such a divergent active-site sequence may aid the design of selective inhibitors that can discriminate these homologue RNA/DNA demethylases. Exchange program: Divergent active-site residues contribute to the substrate recognition and demethylation specificity of RNA/DNA demethylases AlkB, FTO, and ALKBH5. Swapping these residues results in partially switched demethylation activities (see picture). In the implicated inhibitor design principle, such divergent active-site sequences could aid the design of selective inhibitors that discriminate these demethylases. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang C.,CAS Beijing National Laboratory for Molecular | Lai L.,Peking University
Biochemical Society Transactions | Year: 2011

Structure-based drug design for chemical molecules has been widely used in drug discovery in the last 30 years. Many successful applications have been reported, especially in the field of virtual screening based on molecular docking. Recently, there has been much progress in fragment-based as well as de novo drug discovery. As many protein-protein interactions can be used as key targets for drug design, one of the solutions is to design protein drugs based directly on the protein complexes or the target structure. Compared with protein-ligand interactions, protein-protein interactions are more complicated and present more challenges for design. Over the last decade, both sampling efficiency and scoring accuracy of protein-protein docking have increased significantly. We have developed several strategies for structurebased protein drug design. A grafting strategy for key interaction residues has been developed and successfully applied in designing erythropoietin receptor-binding proteins. Similarly to small-molecule design, we also tested de novo protein-binder design and a virtual screen of protein binders using protein-protein docking calculations. In comparison with the development of structure-based small-molecule drug design, we believe that structure-based protein drug design has come of age. ©The Authors Journal compilation ©2011 Biochemical Society.

Chen J.,National University of Singapore | Zhang G.,Peking University | Li B.,National University of Singapore | Li B.,Tongji University
Nano Letters | Year: 2012

By using nonequilibrium molecular dynamics simulations, we demonstrated that thermal conductivity of germanium nanowires can be reduced more than 25% at room temperature by atomistic coating. There is a critical coating thickness beyond which thermal conductivity of the coated nanowire is larger than that of the host nanowire. The diameter-dependent critical coating thickness and minimum thermal conductivity are explored. Moreover, we found that interface roughness can induce further reduction of thermal conductivity in coated nanowires. From the vibrational eigenmode analysis, it is found that coating induces localization for low-frequency phonons, while interface roughness localizes the high-frequency phonons. Our results provide an available approach to tune thermal conductivity of nanowires by atomic layer coating. © 2012 American Chemical Society.

Guo X.,Peking University
Advanced Materials | Year: 2013

Interactions between biological molecules are fundamental to biology. Probing the complex behaviors of biological systems at the molecular level provides new opportunities to uncover the wealth of molecular information that is usually hidden in conventional ensemble experiments and address the "unanswerable" questions in the physical, chemical and biological sciences. Nanometer-scale materials are particularly well matched with biomolecular interactions due to their biocompatibility, size comparability, and remarkable electrical properties, thus setting the basis for biological sensing with ultrahigh sensitivity. This brief review aims to highlight the recent progress of the burgeoning field of single-molecule electrical biosensors based on nanomaterials, with a particular focus on single-walled carbon nanotubes (SWNTs), for better understanding of the molecular structure, interacting dynamics, and molecular functions. The perspectives and key issues that will be critical to the success of next-generation single-molecule biosensors toward practical applications are also discussed, such as the device reproducibility, system integration, and theoretical simulation. Recent progress in the development of single-molecule electrical biosensors based on nanomaterials is highlighted. Particular focus is given to single-walled carbon nanotubes (SWNTs), for better understanding of the molecular structure, interacting dynamics, and molecular functions. Key issues that will be critical to the success of next-generation single-molecule biosensors toward practical applications are also discussed, such as the device reproducibility, system integration, and theoretical simulation. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen Y.,Peking University
Physica A: Statistical Mechanics and its Applications | Year: 2014

Central place systems have been demonstrated to possess self-similarity in both the theoretical and empirical perspectives. A central place model can be treated as a monofractal with a single scaling process. However, a real system of human settlements is a complex network with multi-scaling processes. The simple fractal central place models are not enough to interpret the spatial patterns and evolutive processes of urban systems. It is necessary to construct multi-scaling fractal models of urban places. Based on the postulates of intermittent space filling and unequal probability of urban growth, two typical multifractal models of central places are proposed in this paper. One model is put forward to reflect the process of spatial concentration (convergence), and the generalized correlation dimension varies from 0.7306 to 1.3181; the other model is presented to describe the process of spatial deconcentration (divergence), the generalized correlation dimension ranges from 1.6523 to 1.7118. An empirical analysis was made by the cities and towns of Central Plains, China, and an analogy is drawn between the real system of urban places and the theoretical models. A finding is that urban systems take on multifractal form, and can be modeled with multi-scaling fractals. This is a preliminary attempt to develop the theory of fractal central places, and the results are helpful for understanding the similarities and differences between the dynamical process of spatial concentration and that of spatial deconcentration. © 2014 Elsevier B.V.

Chen Y.,Peking University
Physica A: Statistical Mechanics and its Applications | Year: 2014

Replacements resulting from competition are ubiquitous phenomena in both nature and society. The evolution of a self-organized system is always a physical process substituting one type of components for another type of components. A logistic model of replacement dynamics has been proposed in terms of technical innovation and urbanization, but it fails to arouse widespread attention in the academia. This paper is devoted to laying the foundations of general replacement principle by using analogy and induction. The empirical base of this study is urban replacement, including urbanization and urban growth. The sigmoid functions can be employed to model various processes of replacement. Many mathematical methods such as allometric scaling and head/tail breaks can be applied to analyzing the processes and patterns of replacement. Among varied sigmoid functions, the logistic function is the basic and the simplest model of replacement dynamics. A new finding is that replacement can be associated with chaos in a nonlinear system, e.g., urban chaos is just a part of replacement dynamics. The aim of developing replacement theory is at understanding complex interaction and conversion. This theory provides a new way of looking at urbanization, technological innovation and diffusion, Volterra-Lotka's predator-prey interaction, man-land relation, and dynastic changes resulting from peasant uprising, and all that. Especially, the periodic oscillations and chaos of replacement dynamics can be used to explain and predict the catastrophic occurrences in the physical and human systems. © 2014 Elsevier B.V. All rights reserved.

Encouraging results from a small sample of patients with myelodysplastic syndrome (MDS) undergoing haploidentical donor (HID) hematopoietic stem cell transplantation (HSCT) must be extended. Furthermore, an algorithm derived from a comparison of the outcomes of HID and identical-sibling donor (ISD) HSCT must be established. Therefore, the outcomes of 454 MDS patients who underwent HSCT from HIDs (n=226) or ISDs (n=228) between 2003 and 2013 that were reported to the Chinese Bone Marrow Transplantation Registry were analyzed. Among the 3/6 HID (n=136), 4–5/6 HID (n=90) and ISD patient groups, the 4-year adjusted cumulative incidences of non-relapse mortality were 34, 29 and 16%, respectively (overall P=0.004), and of relapse were 6, 7 and 10%, respectively (overall P=0.36). The 4-year adjusted probabilities of overall survival were 58, 63 and 73%, respectively (overall P=0.07), and of relapse-free-survival were 58, 63 and 71%, respectively (overall P=0.14); pairwise comparison showed that the difference was only statistically significant in the 3/6 HID vs ISD pair. The data suggest that ISDs remain the best donor source for MDS patients while HIDs (perhaps 4–5/6 HID in particular) could be a valid alternative when an ISD is not available; human leukocyte antigen disparity had no effect on survival among the HID patients.Leukemia advance online publication, 20 May 2016; doi:10.1038/leu.2016.110. © 2016 Macmillan Publishers Limited

Zhi W.,Peking University | Ji G.,Peking University
Science of the Total Environment | Year: 2012

This study explores a bibliometric approach to quantitatively evaluate global scientific constructed wetlands research, and statistically assess current trends, and future directions using the Science Citation Index Expanded (SCI-EXPANDED) database from 1991 to 2011. Articles referencing constructed wetlands were analyzed by accessing the following: publication language, output characteristics, publication performance by country and institution, author keywords, title words, and KeyWords Plus. Synthetically analyzing three keyword types, we concluded that the dominant constructed wetlands research hotspots from 1991 to 2011 included water, nutrients, plants, and flow. These four hotspots remained the most dominant research areas throughout our study period, and are predicted to remain the top research emphases in the near future. "Soil" also exhibited a notable increase since 2005, and is likely to become another notable area of research interest in the future. "Phytoremediation" and "horizontal" were not identified in 1991-1995, but exhibited marked increases from 136th (0.5%) and 169th (0.7%) in 1996-2000, to 9th (3.8%) and 11th (4.3%) in 2006-2011, respectively. Therefore, given the heightened attention during the last 15. years, these topics are likely to become a primary research focus in upcoming years. © 2012 Elsevier B.V.

Li L.,Peking University
Public Health | Year: 2011

China is in the process of a new round of healthcare reforms. The Chinese Government has launched ambitious healthcare reforms aiming to achieve equitable access to basic health services; and to build a safe, effective, convenient and inexpensive healthcare system for both urban and rural residents. This paper will provide a brief overview of China's healthcare reforms, and describe the challenges and opportunities facing these reforms. © 2010 The Royal Society for Public Health.

Meng Y.,Peking University
Oncogene | Year: 2016

The oncogene Lysosome-associated protein transmembrane-4β (LAPTM4B) gene was identified, and the polymorphism region in the 5′-UTR of this gene was certified to be associated with tumor susceptibility. LAPTM4B-35 protein was found to be highly expressed in various solid tumors and could be a poor prognosis marker. The functions of LAPTM4B in solid tumors were also explored. It is suggested that LAPTM4B could promote the proliferation of tumor cells, boost invasion and metastasis, resist apoptosis, initiate autophagy and assist drug resistance.Oncogene advance online publication, 23 May 2016; doi:10.1038/onc.2016.189. © 2016 Macmillan Publishers Limited

Zha Z.,Harbin Institute of Technology | Yue X.,Harbin Institute of Technology | Ren Q.,Peking University | Dai Z.,Harbin Institute of Technology
Advanced Materials | Year: 2013

Uniform polypyrrole (PPy) nanoparticles are fabricated from a facile one-step aqueous dispersion polymerization. Owing to their high photothermal conversion efficiency and photostability compared with the well-known Au nanorods, as well as their good colloidal stability and biocompatibility, the resulting PPy nanoparticles can used as a novel promising photothermal ablation coupling agent for targeted treatment of cancer. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang C.,Peking University | Tang C.,Peking University | Jiao N.,Peking University | Jiao N.,East China Normal University
Chemical Society Reviews | Year: 2012

Copper salts have been developed as versatile catalysts for oxidative coupling reactions in organic synthesis. During these processes, Cu-catalysts are often proposed to serve as a one-electron oxidant to promote the single-electron transfer process. Recently, the transition-metal catalyzed direct dehydrogenative transformation has attracted considerable attention. This tutorial review summarizes the recent advances in the copper-catalyzed dehydrogenative functionalization via a single electron transfer (SET) process achieving C-C, C-N, C-O, C-halogen atoms, C-P, and N-N bond formation. © The Royal Society of Chemistry 2012.

Shi Z.,Peking University | Zhang C.,Peking University | Tang C.,Peking University | Jiao N.,Peking University | Jiao N.,Chinese Academy of Sciences
Chemical Society Reviews | Year: 2012

For green and sustainable chemistry, molecular oxygen is considered as an ideal oxidant due to its natural, inexpensive, and environmentally friendly characteristics, and therefore offers attractive academic and industrial prospects. This critical review introduces the recent advances over the past 5 years in transition-metal catalyzed reactions using molecular oxygen as the oxidant. This review highlights the scope and limitations, as well as the mechanisms of these oxidation reactions (184 references). © 2012 The Royal Society of Chemistry.

Zhan-Ming C.,Renmin University of China | Chen G.Q.,Peking University
Ecological Indicators | Year: 2013

This study investigates the virtual water profile of the world in 2004 based on a multi-region input-output model. The water footprints of 112 nation-level regions are calculated and the footprint compositions of major water consumers are analyzed. Less than 35% of the global virtual water requirement is provided by agricultural products, in spite of the fact that 69% of the total water withdrawal is associated with agricultural sector. At the national scale, India, the United States, and mainland China are the world's largest virtual water consumers. Per capita water footprint varies from 30 m3 for Rest of South Central Africa to 3290 m3 for Luxembourg. As one of the major determinants of national footprint, international virtual water trade sums up to 30% of the direct water withdrawal of the world. Meanwhile, results show that 57% of the international virtual water flows is embodied in non-food trade, confirming the importance to take not only food product but also non-food product into account when overall water budget is considered. Mainland China is the world's leading exporter and deficit receiver in terms of virtual water trade (204 Gm3 and 142 Gm3, respectively), in contrast to the United States as the leading importer (178 Gm3) and Japan as the leading surplus receiver (77 Gm3). Finally, the virtual water trade connections of China and the United States with their major trading partners are revealed via introducing the index of virtual water dependency. Results presented in this study are of essential implications for policy making regarding water using pattern adjustment and water security enhancement.© © 2012 Elsevier Ltd.

Mahmood N.,Peking University | Zhang C.,Peking University | Liu F.,Peking University | Zhu J.,Peking University | Hou Y.,Peking University
ACS Nano | Year: 2013

A facile strategy was designed for the fabrication of hybrid of Co 3Sn2@Co nanoparticles (NPs) and nitrogen-doped graphene (NG) sheets through a hydrothermal synthesis, followed by annealing process. Core-shell architecture of Co3Sn2@Co pin on NG is designed for the dual encapsulation of Co3Sn2 with adaptable ensembles of Co and NG to address the structural and interfacial stability concerns facing tin-based anodes. In the resulted unique architecture of Co 3Sn2@Co-NG hybrid, the sealed cobalt cover prevents the direct exposer of Sn with electrolyte because of encapsulated structure and keeps the structural and interfacial integrity of Co3Sn2. However, the elastically strong, flexible and conductive NG overcoat accommodates the volume changes and therefore brings the structural and electrical stabilization of Co3Sn2@Co NPs. As a result, Co3Sn2@Co-NG hybrid exhibits extraordinary reversible capacity of 1615 mAh/g at 250 mA/g after 100 cycles with excellent capacity retention of 102%. The hybrid bears superior rate capability with reversible capacity of 793.9 mAh/g at 2500 mA/g and Coulombic efficiency nearly 100%. © 2013 American Chemical Society.

Song C.-X.,University of Chicago | Yi C.,Peking University | Yi C.,Peking Tsinghua Center for Life science | He C.,University of Chicago
Nature Biotechnology | Year: 2012

Nucleotide variants, especially those related to epigenetic functions, provide critical regulatory information beyond simple genomic sequence, and they define cell status in higher organisms. 5-methylcytosine, which is found in DNA, was until recently the only nucleotide variant studied in terms of epigenetics in eukaryotes. However, 5-methylcytosine has turned out to be just one component of a dynamic DNA epigenetic regulatory network that also includes 5-hydroxymethylcytosine, 5-formylcytosine and 5-carboxylcytosine. Recently, reversible methylation of N 6 -methyladenosine in RNA has also been demonstrated. The discovery of these new nucleotide variants triggered an explosion of new information in the epigenetics field. This rapid research progress has benefited significantly from timely developments of new technologies that specifically recognize, enrich and sequence nucleotide modifications, as evidenced by the wide application of the bisulfite sequencing of 5-methylcytosine and very recent modifications of bisulfite sequencing to resolve 5-hydroxymethylcytosine from 5-methylcytosine with base-resolution information. © 2012 Nature America, Inc.

Meng Y.,CAS National Center for Nanoscience and Technology | Meng Y.,Peking University | Wang K.,CAS National Center for Nanoscience and Technology | Zhang Y.,CAS National Center for Nanoscience and Technology | Wei Z.,CAS National Center for Nanoscience and Technology
Advanced Materials | Year: 2013

A highly flexible graphene free-standing film with hierarchical structure is prepared by a facile template method. With a porous structure, the film can be easily bent and cut, and forms a composite with another material as a scaffold. The 3D graphene film exhibits excellent rate capability and its capacitance is further improved by forming a composite with polyaniline nanowire arrays. The flexible hierarchical composite proves to be an excellent electrode material for flexible supercapacitors. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ni H.-G.,Peking University | Zeng H.,Peking University
Science of the Total Environment | Year: 2013

Hexabromocyclododecane diastereoisomers (α, β, and γ-HBCD) and tetrabromobisphenol A (TBBPA) were investigated in air conditioning filter dust (designated as particulate phase of indoor air, PPIA) collected from an office building in Shenzhen, China in 2009. Concentrations of σHBCD (sum of α-, β-, and γ-HBCD) ranged from 652 to 122, 973ng/g in PPIA. Generally, γ-HBCD was the most abundant diastereomer. Concentrations of TBBPA ranged from 30 to 59, 140ng/g in PPIA. According to our results, approximate 61.9pg/kg body weight/day (pg/kg/d) PM2.5 bound σHBCD can be inhaled deep into the lungs and 31.3pg/kg/d PM10 bound σHBCD tends to be deposited in the upper parts of the respiratory system, and those values of TBBPA were 28.7pg/kg/d and 14.5pg/kg/d for the lower and upper respiratory tracts, respectively. The average intakes of σHBCD via dust inhalation and ingestion were 37.92pg/kg/d and 2, 079pg/kg/d for adults, and those data of TBBPA were 17.62pg/kg/d and 966.2pg/kg/d, respectively. Our research found that exposure via indoor dust inhalation and ingestion contributed more than dietary pathway. Sensitivity analysis result suggests that the concentration of HBCD and TBBPA is the most significant parameter governing estimated results, and the other parameters, such as body weight and inhalation rate, do not affect the outcome much. © 2013 Elsevier B.V.

Gao Y.,Peking University
Pflugers Archiv European Journal of Physiology | Year: 2010

Studies in the last two decades have firmly established that nitric oxide (NO) exerts a broad range of effects on bodily functions including muscle contractility, platelet aggregation, metabolism, neuronal activity, and immune responses. The underlying mechanisms rely primarily on elevating guanosine 3′,5′-cyclic monophosphate due to the stimulation of soluble guanylyl cyclase, inhibiting mitochondria respiration by the action on cytochrome C oxidase, and nitrosylating proteins and enzymes. Under pathophysiological conditions, an increased production of NO concurrently with an enhanced generation of superoxide leads to the formation of peroxynitrite, a potent oxidative agent, and thus tissue injuries. This article intends to provide a brief review on the effects of NO in the modulations of muscle contractility, platelet aggregation, metabolism, neuronal activity, and immune responses. The actions of NO vary depending on the interactions between this gaseous molecule, its derivates, and their effectors as well as the local redox environments. Considering the complexity of these interactions and the widespread presence of NO in various body systems and cell types, there is no doubt that this area of research will remain very challenging and rewarding in the foreseeable future. © 2009 Springer-Verlag.

Feng F.,Peking University
Computer Physics Communications | Year: 2012

We have generalized the Mathematica function Apart from 1 to N dimensions: the generalized function $Apart can decompose any linear dependent elements in Vx* to irreducible ones. The elements in Vx* can be viewed as the corresponding propagators which involve loop momenta, and the decomposition will be useful when one tries to perform loop calculations using packages such as Fire and Reduze, which have implemented the integration by parts (IBP) identities and Lorentz invariance (LI) identities. A description on how to use this package, combined with Fire, FeynArts, and FeynCalc packages, to do one-loop calculations in double quarkonium production in e+ e- colliders is given, and the full source code for a specific process ( e+e-→Jψ+ ηc) is also available. © 2012 Elsevier B.V. All rights reserved.

Deng M.T.,Lund University | Yu C.L.,Lund University | Huang G.Y.,Lund University | Larsson M.,Lund University | And 3 more authors.
Nano Letters | Year: 2012

Semiconductor InSb nanowires are expected to provide an excellent material platform for the study of Majorana fermions in solid state systems. Here, we report on the realization of a Nb-InSb nanowire-Nb hybrid quantum device and the observation of a zero-bias conductance peak structure in the device. An InSb nanowire quantum dot is formed in the device between the two Nb contacts. Due to the proximity effect, the InSb nanowire segments covered by the superconductor Nb contacts turn to superconductors with a superconducting energy gap ΔInSb ∼ 0.25 meV. A tunable critical supercurrent is observed in the device in high back gate voltage regions in which the Fermi level in the InSb nanowire is located above the tunneling barriers of the quantum dot and the device is open to conduction. When a perpendicular magnetic field is applied to the devices, the critical supercurrent is seen to decrease as the magnetic field increases. However, at sufficiently low back gate voltages, the device shows the quasi-particle Coulomb blockade characteristics and the supercurrent is strongly suppressed even at zero magnetic field. This transport characteristic changes when a perpendicular magnetic field stronger than a critical value, at which the Zeeman energy in the InSb nanowire is E z ∼ ΔInSb, is applied to the device. In this case, the transport measurements show a conductance peak at the zero bias voltage and the entire InSb nanowire in the device behaves as in a topological superconductor phase. We also show that this zero-bias conductance peak structure can persist over a large range of applied magnetic fields and could be interpreted as a transport signature of Majorana fermions in the InSb nanowire. © 2012 American Chemical Society.

Qiao J.,Peking University | Feng H.L.,North Shore University Hospital
Human Reproduction Update | Year: 2011

Background: Polycystic ovary syndrome (PCOS) is a common metabolic dysfunction and heterogeneous endocrine disorder in women of reproductive age. Although patients with PCOS are typically characterized by increased numbers of oocytes retrieved during IVF, they are often of poor quality, leading to lower fertilization, cleavage and implantation rates, and a higher miscarriage rate. METHODS: For this review, we searched the database Medline: (1950 to January 2010) and Google for all full texts and/or abstract articles published in English with content related to oocyte maturation and embryo developmental competence. Results: The search showed that alteration of many factors may directly or indirectly impair the competence of maturating oocytes through endocrine and local paracrine/autocrine actions, resulting in a lower pregnancy rate in patients with PCOS. The extra-ovarian factors identified included gonadotrophins, hyperandrogenemia and hyperinsulinemia, although intra-ovarian factors included members of the epidermal, fibroblast, insulin-like and neurotrophin families of growth factors, as well as the cytokines. Conclusions: Any abnormality in the extra- and/or intra-ovarian factors may negatively affect the granulosa cell-oocyte interaction, oocyte maturation and potential embryonic developmental competence, contributing to unsuccessful outcomes for patients with PCOS who are undergoing assisted reproduction. © The Author 2010. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology.

Zhang C.,Peking University | Feng P.,Peking University | Jiao N.,Peking University | Jiao N.,Chinese Academy of Sciences
Journal of the American Chemical Society | Year: 2013

The Cu-catalyzed novel aerobic oxidative esterification reaction of 1,3-diones for the synthesis of α-ketoesters has been developed. This method combines C-C σ-bond cleavage, dioxygen activation and oxidative C-H bond functionalization, as well as provides a practical, neutral, and mild synthetic approach to α-ketoesters which are important units in many biologically active compounds and useful precursors in a variety of functional group transformations. A plausible radical process is proposed on the basis of mechanistic studies. © 2013 American Chemical Society.

Luo C.,Peking University | Huang Y.,Peking University
Journal of the American Chemical Society | Year: 2013

Tetrahydroquinolines containing two quaternary stereogenic centers were synthesized with excellent ee and dr via a four-component cyclization reaction catalyzed by a chiral phosphoric acid. High chemoselectivity was achieved by differentiating anilines with similar reactivities to yield diverse "hybrid" products. The chirality of the quaternary C4 atom of the 4-aminotetrahydroquinoline products was found to undergo highly stereoselective inversion, enabling facile functionalization using a wide range of nucleophiles (C, O, N, and S). © 2013 American Chemical Society.

Zhang L.,University of Texas at Austin | Niu Q.,University of Texas at Austin | Niu Q.,Peking University
Physical Review Letters | Year: 2014

We study the angular momentum of phonons in a magnetic crystal. In the presence of a spin-phonon interaction, we obtain a nonzero angular momentum of phonons, which is an odd function of magnetization. At zero temperature, a phonon has a zero-point angular momentum in addition to a zero-point energy. With increasing temperature, the total phonon angular momentum diminishes and approaches zero in the classical limit. The nonzero phonon angular momentum can have a significant impact on the Einstein-de Haas effect. To obtain the change of angular momentum of electrons, the change of the phonon angular momentum needs to be subtracted from the opposite change of the lattice angular momentum. Furthermore, the finding of the phonon angular momentum gives a potential method to study the spin-phonon interaction. Possible experiments on phonon angular momentum are also discussed. © 2014 American Physical Society.

Cheng P.,CAS Beijing National Laboratory for Molecular | Cheng P.,University of Chinese Academy of Sciences | Li Y.,CAS Beijing National Laboratory for Molecular | Zhan X.,Peking University
Energy and Environmental Science | Year: 2014

Indene-C60 bisadduct (ICBA) is used as an electron-cascade acceptor material in poly{4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′] dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b] thiophene-4,6-diyl} (PTB7):[6,6]-phenyl-C71-butyric-acid-methyl-ester (PC 71BM) blend to fabricate ternary blend polymer solar cells (PSCs). Due to higher lowest unoccupied molecular orbital (LUMO) energy levels of ICBA relative to PC71BM, the open circuit voltage (VOC) increases with the addition of ICBA. ICBA plays a bridging role between PTB7 and PC71BM, thus providing more routes for charge transfer at the donor/acceptor (D/A) interface. When the ICBA content is much smaller than the PC71BM content, the morphology of the ternary blend active layer is similar to that of the PTB7:PC71BM blend, which guarantees suitable phase separation and efficient charge transport. Ternary blend devices with 15% ICBA content exhibit an average power conversion efficiency (PCE) of 8.13%, higher than that (7.23%) of the PTB7:PC71BM binary blend. Without any further device work (such as interlayer, invert structure and tandem cells), the ternary blend PSCs exhibit PCEs as high as 8.24%, which is the highest reported for ternary blend PSCs and ICBA-related PSCs. This journal is © the Partner Organisations 2014.

Shao L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

In the pure-gravity sector of the minimal standard-model extension, nine Lorentz-violating coefficients of a vacuum-condensed tensor field describe dominant observable deviations from general relativity, out of which eight were already severely constrained by precision experiments with lunar laser ranging, atom interferometry, and pulsars. However, the time-time component of the tensor field, s¯TT, dose not enter into these experiments, and was only very recently constrained by Gravity Probe B. Here we propose a novel idea of using the Lorentz boost between different frames to mix different components of the tensor field, and thereby obtain a stringent limit of s¯TT from binary pulsars. We perform various tests with the state-of-the-art white dwarf optical spectroscopy and pulsar radio timing observations, in order to get new robust limits of s¯TT. With the isotropic cosmic microwave background as a preferred frame, we get |s¯TT|<1.6×10-5 (95% C.L.), and without assuming the existence of a preferred frame, we get |s¯TT|<2.8×10-4 (95% C.L.). These two limits are respectively about 500 times and 30 times better than the current best limit. © 2014 American Physical Society.

Gong M.,Peking University | Li S.,Peking University
Journal of Experimental Psychology: Human Perception and Performance | Year: 2014

Statistical regularities in the natural environment play a central role in adaptive behavior. Among other regularities, reward association is potentially the most prominent factor that influences our daily life. Recent studies have suggested that pre-established reward association yields strong influence on the spatial allocation of attention. Here we show that reward association can also improve visual working memory (VWM) performance when the reward-associated feature is task-irrelevant. We established the reward association during a visual search training session, and investigated the representation of reward-associated features in VWM by the application of a change detection task before and after the training. The results showed that the improvement in VWM was significantly greater for items in the color associated with high reward than for those in low reward-associated or nonrewarded colors. In particular, the results from control experiments demonstrate that the observed reward effect in VWM could not be sufficiently accounted for by attentional capture toward the high reward-associated item. This was further confirmed when the effect of attentional capture was minimized by presenting the items in the sample and test displays of the change detection task with the same color. The results showed significantly larger improvement in VWM performance when the items in a display were in the high reward-associated color than those in the low reward-associated or nonrewarded colors. Our findings suggest that, apart from inducing space-based attentional capture, the learned reward association could also facilitate the perceptual representation of high reward-associated items through feature-based attentional modulation. © 2014 American Psychological Association.

Zhang G.-P.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

The inclusive hadronic production of ηQ (ηc or ηb) pair is proposed to extract the transverse momentum-dependent (TMD) gluon distribution functions. We use nonrelativistic QCD (NRQCD) for the production of ηQ. Under the nonrelativistic limit, the TMD factorization for this process is assumed to make a lowest-order calculation. For unpolarized initial hadrons, unpolarized and linearly polarized gluon distributions can be extracted by studying different angular distributions. © 2014 American Physical Society.

Foreman M.R.,Max Planck Institute for the Science of Light | Jin W.-L.,Peking University | Vollmer F.,Max Planck Institute for the Science of Light
Optics Express | Year: 2014

A theoretical analysis of detection limits in swept-frequency whispering gallery mode biosensing modalities is presented based on application of the Cramér-Rao lower bound. Measurement acuity factors are derived assuming the presence of uncoloured and 1/f Gaussian technical noise. Frequency fluctuations, for example arising from laser jitter or thermorefractive noise, are also considered. Determination of acuity factors for arbitrary coloured noise by means of the asymptotic Fisher information matrix is highlighted. Quantification and comparison of detection sensitivity for both resonance shift and broadening sensing modalities are subsequently given. Optimal cavity and coupling geometries are furthermore identified, whereby it is found that slightly under-coupled cavities outperform critically and over coupled ones. © 2014 Optical Society of America.

Li Y.-H.,Northeastern University China | Zhang X.,Northeastern University China | Zhang X.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Dark energy might interact with cold dark matter in a direct, nongravitational way. However, the usual interacting dark energy models (with constant w) suffer from some catastrophic difficulties. For example, the Qρc model leads to an early-time large-scale instability, and the Qρde model gives rise to the future unphysical result for cold dark matter density (in the case of a positive coupling). In order to overcome these fatal flaws, we propose in this paper an interacting dark energy model (with constant w) in which the interaction term is carefully designed to realize that Qρde at the early times and Qρc in the future, simultaneously solving the early-time superhorizon instability and future unphysical ρc problems. The concrete form of the interaction term in this model is Q= 3βHρdeρcρde+ρc, where β is the dimensionless coupling constant. We show that this model is actually equivalent to the decomposed new generalized Chaplygin gas (NGCG) model, with the relation β=-αw. We calculate the cosmological perturbations in this model in a gauge-invariant way and show that the cosmological perturbations are stable during the whole expansion history provided that β>0. Furthermore, we use the Planck data in conjunction with other astrophysical data to place stringent constraints on this model (with eight parameters), and we find that indeed β>0 is supported by the joint constraint at more than 1σ level. The excellent theoretical features and the support from observations all indicate that the decomposed NGCG model deserves more attention and further investigation. © 2014 American Physical Society.

Wen L.,Peking University | Tang F.,Peking University
Cell | Year: 2014

Techniques for profiling individual cells are rapidly advancing and are providing an unprecedented opportunity for studying the genetic regulation of development and disease. In this issue, Durruthy-Durruthy et al. analyze gene expression at the single-cell level for a simple but highly organized three-dimensional structure, the mouse otocyst. © 2014 Elsevier Inc.

Fu X.,Peking University
Acta Biochimica et Biophysica Sinica | Year: 2014

Small heat-shock proteins (sHSPs) are ubiquitous ATP-independent molecular chaperones that play crucial roles in protein quality control in cells. They are able to prevent the aggregation and/or inactivation of various non-native substrate proteins and assist the refolding of these substrates independently or under the help of other ATP-dependent chaperones. Substrate recognition and binding by sHSPs are essential for their chaperone functions. This review focuses on what natural substrate proteins an sHSP protects and how it binds the substrates in cells under fluctuating conditions. It appears that sHSPs of prokaryotes, although being able to bind a wide range of cellular proteins, preferentially protect certain classes of functional proteins, such as translation-related proteins and metabolic enzymes, which may well explain why they could increase the resistance of host cells against various stresses. Mechanistically, the sHSPs of prokaryotes appear to possess numerous multi-type substrate-binding residues and are able to hierarchically activate these residues in a temperature-dependent manner, and thus act as temperature- regulated chaperones. The mechanism of hierarchical activation of substrate-binding residues is also discussed regarding its implication for eukaryotic sHSPs. © 2014 © The Author 2014.

Wen L.,Peking University | Tang F.,Peking University
Genomics | Year: 2014

DNA methylation (5-methylcytosine, 5mC) is involved in many cellular processes and emerges as an important epigenetic player in brain development and memory formation. The recent discovery that 5mC can be oxidized to 5-hydroxymethylcytosine (5hmC) by TET (Ten-Eleven-Translocation) proteins provides novel insights into the dynamic character of 5mC in the brain. The content of 5hmC is remarkably high in the brain, adding further complexity. In this review, we discuss how recent advances have improved our understanding of the possible biological roles of 5hmC and TET proteins in the brain. These advances attribute to various approaches, including the genome-wide approach to map 5hmC in different genomic contexts, the gene knockout/knockdown approach to elucidate the functions of TET proteins and 5hmC, and the biochemical approach to uncover potential 5hmC readers. © 2014 Elsevier Inc.

Phosphatase of regenerating liver-3 (PRL-3 or PTP4A3) has been implicated in controlling cancer cell proliferation, motility, metastasis, and angiogenesis. Deregulated expression of PRL-3 is highly correlated with cancer progression and predicts poor survival. Although PRL-3 was categorized as a tyrosine phosphatase, its cellular substrates remain largely unknown. We demonstrated that PRL-3 interacts with integrin β1 in cancer cells. Recombinant PRL-3 associates with the intracellular domain of integrin β1 in vitro. Silencing of integrin α1 enhances PRL-3-integrin β1 interaction. Furthermore, PRL-3 diminishes tyrosine phosphorylation of integrin β1 in vitro and in vivo. With site-specific anti-phosphotyrosine antibodies against residues in the intracellular domain of integrin β1, tyrosine-783, but not tyrosine-795, is shown to be dephosphorylated by PRL-3 in a catalytic activity-dependant manner. Phosphorylation of Y783 is potentiated by ablation of PRL-3 or by treatment with a chemical inhibitor of PRL-3. Conversely, depletion of integrin α1 decreases the phosphorylation of this site. Our results revealed a direct interaction between PRL-3 and integrin β1 and characterized Y783 of integrin β1 as a bona fide substrate of PRL-3, which is negatively regulated by integrin α1.

Liu Y.,Peking University | Hong T.,Peking University
Diabetes, Obesity and Metabolism | Year: 2014

The main pathogenesis of type 2 diabetes mellitus (T2DM) includes insulin resistance and pancreatic islet dysfunction. Metformin, which attenuates insulin resistance, has been recommended as the first-line antidiabetic medication. Dipeptidyl peptidase-4 (DPP-4) inhibitors are novel oral hypoglycaemic agents that protect glucagon-like peptide-1 (GLP-1) from degradation, maintain the bioactivity of endogenous GLP-1, and thus improve islet dysfunction. Results from clinical trials have shown that the combination therapy of DPP-4 inhibitors and metformin [as an add-on, an initial combination or a fixed-dose combination (FDC)] provides excellent efficacy and safety in patients with T2DM. Moreover, recent studies have suggested that metformin enhances the biological effect of GLP-1 by increasing GLP-1 secretion, suppressing activity of DPP-4 and upregulating the expression of GLP-1 receptor in pancreatic β-cells. Conversely, DPP-4 inhibitors have a favourable effect on insulin sensitivity in patients with T2DM. Therefore, the combination of DPP-4 inhibitors and metformin provides an additive or even synergistic effect on metabolic control in patients with T2DM. This article provides an overview of clinical evidence and discusses the rationale for the combination therapy of DPP-4 inhibitors and metformin. © 2013 John Wiley & Sons Ltd.

Li L.-X.,Peking University
General Relativity and Gravitation | Year: 2016

Maxwell’s equations cannot describe a homogeneous and isotropic universe with a uniformly distributed net charge, because the electromagnetic field tensor in such a universe must be vanishing everywhere. For a closed universe with a nonzero net charge, Maxwell’s equations always fail regardless of the spacetime symmetry and the charge distribution. The two paradoxes indicate that Maxwell’s equations need be modified to be applicable to the universe as a whole. We consider two types of modified Maxwell equations, both can address the paradoxes. One is the Proca-type equation which contains a photon mass term. This type of electromagnetic field equations can naturally arise from spontaneous symmetry breaking and the Higgs mechanism in quantum field theory, where photons acquire a mass by eating massless Goldstone bosons. However, photons loose their mass again when the symmetry is restored, and the paradoxes reappear. The other type of modified Maxwell equations, which are more attractive in our opinions, contain a term with the electromagnetic field potential vector coupled to the spacetime curvature tensor. This type of electromagnetic field equations do not introduce a new dimensional parameter and return to Maxwell’s equations in a flat or Ricci-flat spacetime. We show that the curvature-coupled term can naturally arise from the ambiguity in extending Maxwell’s equations from a flat spacetime to a curved spacetime through the “minimal substitution rule”. Some consequences of the modified Maxwell equations are investigated. The results show that for reasonable parameters the modification does not affect existing experiments and observations. However, we argue that, the field equations with a curvature-coupled term can be testable in astrophysical environments where the mass density is high or the gravity of electromagnetic radiations plays a dominant role in dynamics, e.g., the interior of neutron stars and the early universe. © 2016, Springer Science+Business Media New York.

Fang Z.,Peking University | Zhu X.,National Center for Nanosciences and Technology of China
Advanced Materials | Year: 2013

Plasmonics has developed into one of the rapidly growing research topics for nanophotonics. With advanced nanofabrication techniques, a broad variety of nanostructures can be designed and fabricated for plasmonic devices at nanoscale. Fundamental properties for both surface plasmon polaritons (SPP) and localized surface plasmons (LSP) arise a new insight and understanding for the electro-optical device investigations, such as plasmonic nanofocusing, low-loss plasmon waveguide and active plasmonic detectors for energy harvesting. Here, we review some typical functional plasmonic nanostructures and nanosmart devices emerging from our individual and collaborative research works. Plasmonics has developed into one of the rapidly growing research topics for nanophotonics. With advanced nanofabrication techniques, a broad variety of plasmonic nanostructures have been designed and fabricated. Combining the merits of both surface plasmons and graphene, the graphene photodetection can be greatly enhanced, leading to a new research area as graphene plasmonics. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Liu W.,Peking University
Pharmaceutical research | Year: 2012

To clarify sotalol's classification in the BCS versus BDDCS systems through cellular, rat everted sac and PAMPA permeability studies. Studies were carried out in Madin Darby canine kidney (MDCK) and MDR1-transfected MDCK (MDCK-MDR1) cell lines, rat everted gut sacs and the Parallel Artificial Membrane Permeability Assay (PAMPA) system. Three-hour transport studies were conducted in MDCK cell lines (with apical pH changes) and MDCK-MDR1 cells (with and without the P-glycoprotein inhibitor GG918); male Sprague-Dawley rats (300~350 g) were used to prepare everted sacs. In the PAMPA studies, drug solutions at different pH's were dosed in each well and incubated for 5 h. Samples were measured by LC-MS/MS, or liquid scintillation counting and apparent permeability (P(app)) was calculated. Sotalol showed low permeability in all of the cultured-cell lines, everted sacs and PAMPA systems. It might be a border line P-glycoprotein substrate. The PAMPA study showed that sotalol's permeability increased with a higher apical pH, while much less change was found in MDCK cells. The low permeability rate for sotalol correlates with its Class 3 BDDCS assignment and lack of in vivo metabolism.

Meng T.,Tsinghua University | Chen H.,Peking University
Health and Place | Year: 2014

We investigate relationship between social capital and self-rated health (SRH) in urban and rural China. Using a nationally representative data collected in 2005, we performed multilevel analyses. The social capital indicators include bonding trust, bridging trust, social participation and Chinese Communist Party membership. Results showed that only trust was beneficial for SRH in China. Bonding trust mainly promoted SRH at individual level and bridging trust mainly at county level. Moreover, the individual-level bridging trust was only positively associated with SRH of urban residents, which mirrored the urban-rural dual structure in China. We also found a cross-level interaction effect of bonding trust in urban area. In a county with high level of bonding trust, high-bonding-trust individuals obtained more health benefit than others; in a county with low level of bonding trust, the situation was the opposite. © 2014 Elsevier Ltd.

Deng Z.-H.,Peking University
Expert Systems with Applications | Year: 2014

Mining Top-Rank-k frequent patterns is an emerging topic in frequent pattern mining in recent years. In this paper, we propose a new mining algorithm, NTK, to mining Top-Rank-k frequent patterns. The NTK algorithm employs a data structure, Node-list, to represent patterns. The Node-list structure makes the mining process much efficient. We have experimentally evaluated our algorithm against two representative algorithms on four real datasets. The experimental results show that the NTK algorithm is efficient and is at least two orders of magnitude faster than the FAE algorithm and also remarkably faster than the VTK algorithm, the recently reported state-of-the-art algorithm for mining Top-Rank-k frequent patterns. © 2013 Elsevier Ltd. All rights reserved.

Yang Y.,Peking University | Zhang Y.,Peking University | Wang J.,Peking University
Organic Letters | Year: 2011

BF 3•OEt 2-catalyzed direct cyanation of indoles and pyrroles using a less toxic, bench-stable, and easily handled electrophilic cyanating agent N-cyano-N-phenyl-para-toluenesulfonamide (NCTS) affords 3-cyanoindoles and 2-cyanopyrroles in good yields with excellent regioselectivity. The substrate scope is broad with respect to indoles and pyrroles. © 2011 American Chemical Society.

Chang Y.-J.,Peking University | Huang X.-J.,Peking University
Seminars in Oncology | Year: 2012

Approaches for haploidentical bone marrow transplantation (BMT) without T-cell depletion have been designed using new transplant strategies, including anti-thymocyte globulin (ATG) preparative regimens, granulocyte colony-stimulating factor-primed grafts, post-transplantation rapamycin, or high-dose cyclophosphamide (Cy) in combination with other immunosuppressive agents for graft-versus-host disease (GVHD) prophylaxis. These strategies ensured fast hematologic engraftment across the human leukocyte antigen (HLA) barrier with an acceptable incidence of GVHD. Long-term follow-up results from different transplant centers suggest that unmanipulated transplantation may provide an alternative strategy in the haploidentical setting without requiring the technical expertise and cost of ex vivo T-cell depletion. This review discusses immune reconstitution and factors associated with clinical outcomes following unmanipulated haploidentical hematopoietic stem cell transplantation (HSCT), and compares outcomes between unmanipulated haploidentical transplant versus HLA-matched sibling donor (MSD) transplantation, HLA-matched unrelated donor (MUD) transplantation, or unrelated double umbilical cord blood (dUCB) transplantation. Advantages and disadvantages of unmanipulated haploidentical HSCT and strategies to improve outome after haploidentical BMT without ex vivo T-cell depletion are discussed. © 2012 Elsevier Inc. All rights reserved.

Chang Y.-J.,Peking University | Huang X.-J.,Peking University
Current Opinion in Hematology | Year: 2012

Purpose of Review: This article summarizes recent improvements and progress with unmanipulated haploidentical blood and marrow transplantation (HBMT) and discusses the difference in outcomes between patients receiving HBMT and those receiving unmanipulated granulocyte colony stimulating factor (G-CSF) mobilized haploidentical peripheral blood (G-PB) grafts as allografts. Recent Findings: Long-term follow-up confirmed that unmanipulated HBMT is a promising protocol that can be successfully extended to treat severe aplastic anemia. Recent observations regarding immune recovery, infections, and strategy for modified donor lymphocyte infusions have provided insight into the prevention of infections and the decrease in relapse after HBMT. Extensive chronic graft-versus-host disease (GVHD) strongly and negatively impacts patient health-related quality of life, suggesting that it should be successfully controlled. A prospective study suggested the inclusion of HBMT in treatment algorithms as a viable option for adults with acute myeloid leukemia with unfavorable cytogenetics who lack a matched donor. Randomized clinical trials are warranted to investigate whether mixture grafts of G-CSF-mobilized blood and marrow or G-PB alone should be chosen as allografts in haploidentical settings. Summary: Unmanipulated HBMT is a reliable protocol. New strategies should be investigated to decrease the incidences of GVHD and relapse. Novel mobilization regimens such as AMD3100 alone or G-CSF+AMD3100 for allograft engineering may improve transplant outcomes following HBMT. © 2012 Wolters Kluwer Health | Lippincott Williams and Wilkins.

Ge H.,Peking University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

Nonequilibrium thermodynamics of a general second-order stochastic system is investigated. We prove that at steady state, under inversion of velocities, the condition of time reversibility over the phase space is equivalent to the antisymmetry of spatial flux and the symmetry of velocity flux. Then we show that the condition of time reversibility alone cannot always guarantee the Maxwell-Boltzmann distribution. Comparing the two conditions together, we find that the frictional force naturally emerges as the unique odd term of the total force at thermodynamic equilibrium, and is followed by the Einstein relation. The two conditions respectively correspond to two previously reported different entropy production rates. In the case where the external force is only position dependent, the two entropy production rates become one. We prove that such an entropy production rate can be decomposed into two non-negative terms, expressed respectively by the conditional mean and variance of the thermodynamic force associated with the irreversible velocity flux at any given spatial coordinate. In the small inertia limit, the former term becomes the entropy production rate of the corresponding overdamped dynamics, while the anomalous entropy production rate originates from the latter term. Furthermore, regarding the connection between the first law and second law, we find that in the steady state of such a limit, the anomalous entropy production rate is also the leading order of the Boltzmann-factor weighted difference between the spatial heat dissipation densities of the underdamped and overdamped dynamics, while their unweighted difference always tends to vanish. © 2014 American Physical Society.

Zhang L.,Peking University
Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association | Year: 2012

Uric acid may be associated with kidney damage through multiple pathways. Previous cohort studies revealed inconsistent results, and research among the non-hypertensive and non-diabetic population are extremely limited. This prospective cohort study included 1410 residents aged 59.1 ± 9.4 years from an urban district of Beijing, China. All participants had an estimated glomerular filtration rate >60 mL/min/1.73m(2). Plasma uric acid was assessed at baseline; and its relation with renal function decline after 4 years' follow-up was analyzed. During 4 years (5630 person-years) of follow-up, 168 patients (11.9%) developed renal function decline. After adjusting for potential confounders including baseline renal function, plasma uric acid levels were independently associated with an increased risk of renal function decline, with a fully adjusted odds ratio (OR) of 1.19 [per 1 mg/dL increase; 95% confidence interval (CI) 1.04-1.38]. Analysis among 615 hypertension-free and diabetes-free participants yielded similar results, with an adjusted OR of 1.50 (per 1 mg/dL increase; 95% CI 1.13-1.98). Our prospective cohort study revealed that plasma uric acid level is independently associated with an increasing likelihood of renal function decline.

Zhang C.,Peking University | Mahmood N.,Peking University | Yin H.,Peking University | Liu F.,Peking University | Hou Y.,Peking University
Advanced Materials | Year: 2013

We develop a simple and economical thermal annealing method for the synthesis of phosphorus-doped graphene, which exhibits remarkable electrocatalytic activity towards the oxygen reduction reaction and enhances the electrochemical performance as an anode material for lithium ion batteries. The experimental results suggest the significant role of phosphorus atoms in graphene. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Liu J.,Peking University
European Physical Journal B | Year: 2010

To find the fuzzy community structure in a complex network, in which each node has a certain probability of belonging to a certain community, is a hard problem and not yet satisfactorily solved over the past years. In this paper, an extension of modularity, the fuzzy modularity is proposed, which can provide a measure of goodness for the fuzzy community structure in networks. The simulated annealing strategy is used to maximize the fuzzy modularity function, associating with an alternating iteration based on our previous work. The proposed algorithm can efficiently identify the probabilities of each node belonging to different communities with random initial fuzzy partition during the cooling process. An appropriate number of communities can be automatically determined without any prior knowledge about the community structure. The computational results on several artificial and real-world networks confirm the capability of the algorithm. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2010.

Zhang J.-F.,Northeastern University China | Li Y.-H.,Northeastern University China | Zhang X.,Northeastern University China | Zhang X.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

We show that involving a sterile neutrino species in the ΛCDM + r model can help relieve the tension about the tensor-to-scalar ratio r between the Planck temperature data and the BICEP2 B-mode polarization data. Such a model is called the ΛCDM + r + νs model in this paper. Compared to the ΛCDM + r model, there are two extra parameters, Neff and mν,sterileeff, in the ΛCDM + r + νs model. We show that in this model the tension between Planck and BICEP2 can be greatly relieved at the cost of the increase of ns. However, comparing with the ΛCDM + r + dns/d lnk model that can significantly reduce the tension between Planck and BICEP2 but also makes trouble to inflation due to the large running of the spectral index of the order 10-2 produced, the ΛCDM + r + νs model is much better for inflation. By including a sterile neutrino species in the standard cosmology, besides the tension with BICEP2, the other tensions of Planck with other astrophysical data, such as the H0 direct measurement, the Sunyaev-Zeldovich cluster counts, and the galaxy shear data, can all be significantly relieved. So, this model seems to be an economical choice. Combining the Planck temperature data, the WMAP-9 polarization data, and the baryon acoustic oscillation data with all these astrophysical data (including BICEP2), we find that in the ΛCDM + r + νs model ns=0.999 ± 0.011, r=0.21-0.05 + 0.04, Neff=3.95 ± 0.33 and mν,sterile eff = 0.51-0.13 +0.12eV. Thus, our results prefer δNeff>0 at the 2.7σ level and a nonzero mass of sterile neutrino at the 3.9σ level. © 2014 The Authors.

Chen Z.-Q.,Peking University | Bian Z.-Q.,Peking University | Huang C.-H.,Peking University
Advanced Materials | Year: 2010

Iridium complexes are drawing great interest because they exhibit high phosphorescence quantum efficiency. Extensive efforts have been devoted to the molecular design of ligands to achieve phosphorescent emission over a wide range of wavelengths that is compatible with many applications. In this research news article, we focus on materials design to improve the performance of phosphorescent IrIII complexes for organic light-emitting diodes (OLEDs), luminescence sensitizers, and biological imaging. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.

Shen T.,Peking University | Yuan Y.,Peking University | Jiao N.,Peking University | Jiao N.,Chinese Academy of Sciences
Chemical Communications | Year: 2014

A novel and direct metal-free nitro-carbocyclization of activated alkenes leading to valuable nitro-containing oxindoles via cascade C-N and C-C bond formation has been developed. The mechanistic study indicates that the initial NO and NO2 radical addition and the following C-H functionalization processes are involved in this transformation. This journal is © The Royal Society of Chemistry 2014.