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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.

Duan X.,Peking University | Lieber C.M.,Harvard University
Nano Research | Year: 2015

This review describes work presented in the 2014 inaugural Tsinghua University Press-Springer Nano Research Award lecture, as well as current and future opportunities for nanoscience research at the interface with brain science. First, we briefly summarize some of the considerations and the research journey that has led to our focus on bottom-up nanoscale science and technology. Second, we recapitulate the motivation for and our seminal contributions to nanowirebased nanoscience and technology, including the rational design and synthesis of increasingly complex nanowire structures, and the corresponding broad range of “applications” enabled by the capability to control structure, composition and size from the atomic level upwards. Third, we describe in more detail nanowire-based electronic devices as revolutionary tools for brain science, including (i) motivation for nanoelectronics in brain science, (ii) demonstration of nanowire nanoelectronic arrays for high-spatial/high-temporal resolution extracellular recording, (iii) the development of fundamentally-new intracellular nanoelectronic devices that approach the sizes of single ion channels, (iv) the introduction and demonstration of a new paradigm for innervating cell networks with addressable nanoelectronic arrays in three-dimensions. Last, we conclude with a brief discussion of the exciting and potentially transformative advances expected to come from work at the nanoelectronics-brain interface.[Figure not available: see fulltext.] © 2014 Tsinghua University Press and Springer-Verlag Berlin Heidelberg

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.

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.

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.

Schulze A.,Peking University | Schulze A.,University of Tokyo | Wisotzki L.,Leibniz Institute for Astrophysics Potsdam
Monthly Notices of the Royal Astronomical Society | Year: 2014

The redshift evolution of the black hole-bulge relations is an essential observational constraint for models of black hole-galaxy coevolution. In addition to the observational challenges for these studies, conclusions are complicated by the influence of selection effects. We demonstrate that there is presently no statistical significant evidence for cosmological evolution in the M•-bulge relations, once these selection effects are taken into account and corrected for. We present a fitting method, based on the bivariate distribution of black hole mass and galaxy property, that accounts for the selection function in the fitting and is therefore able to recover the intrinsic black hole-bulge relation unbiased. While prior knowledge is restricted to a minimum, we at least require knowledge of either the sample selection function and the mass dependence of the active fraction, or the spheroid distribution function and the intrinsic scatter in the black hole-bulge relation. We employed our fitting routine to existing studies of the M•-bulge relation at z ∼ 1.5 and z ∼ 6, using our current best knowledge of the distribution functions. There is no statistical significant evidence for positive evolution in the M•-M* ratio out to z ∼ 2. At z ∼ 6 the current constraints are less strong, but we demonstrate that the large observed apparent offset from the local M•-bulge relation at z ∼ 6 is fully consistent with no intrinsic offset. The method outlined here provides a tool to obtain more reliable constraints on black hole-galaxy co-evolution in the future. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Sun Y.,Nanjing University | Wang C.,CAS Academy of Mathematics and Systems Science | Zhang Z.,Peking University
Archive for Rational Mechanics and Analysis | Year: 2011

We prove a blow-up criterion in terms of the upper bound of (ρ, ρ-1, θ) for a strong solution to three dimensional compressible viscous heat-conductive flows. The main ingredient of the proof is an a priori estimate for a quantity independently introduced in Haspot (Regularity of weak solutions of the compressible isentropic Navier-Stokes equation, arXiv:1001. 1581, 2010) and Sun et al. (J Math Pure Appl 95:36-47, 2011), whose divergence can be viewed as the effective viscous flux. © 2011 Springer-Verlag.

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.

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.

Liu C.-C.,CAS Institute of Physics | Jiang H.,Peking University | Yao Y.,CAS Institute of Physics | Yao Y.,Beijing Institute of Technology
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

Starting from symmetry considerations and the tight-binding method in combination with first-principles calculation, we systematically derive the low-energy effective Hamiltonian involving spin-orbit coupling (SOC) for silicene. This Hamiltonian is very general because it applies not only to silicene itself but also to the low-buckled counterparts of graphene for the other group-IVA elements Ge and Sn, as well as to graphene when the structure returns to the planar geometry. The effective Hamitonian is the analog to the graphene quantum spin Hall effect (QSHE) Hamiltonian. As in the graphene model, the effective SOC in low-buckled geometry opens a gap at the Dirac points and establishes the QSHE. The effective SOC actually contains the first order in the atomic intrinsic SOC strength ξ0, while this leading-order contribution of SOC vanishes in the planar structure. Therefore, silicene, as well as the low-buckled counterparts of graphene for the other group-IVA elements Ge and Sn, has a much larger gap opened by the effective SOC at the Dirac points than graphene, due to the low-buckled geometry and larger atomic intrinsic SOC strength. Further, the more buckled is the structure, the greater is the gap. Therefore, the QSHE can be observed in low-buckled Si, Ge, and Sn systems in an experimentally accessible temperature regime. In addition, the Rashba SOC in silicene is intrinsic due to its own low-buckled geometry, which vanishes at the Dirac point K, while it has a nonzero value with deviation of k from the K point. Therefore, the QSHE in silicene is robust against the intrinsic Rashba SOC. © 2011 American Physical Society.

Cheng R.,University of Texas at Austin | Niu Q.,University of Texas at Austin | Niu Q.,Peking University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Adiabatic dynamics of conduction electrons in antiferromagnetic (AFM) materials with slowly varying spin texture is developed. Quite different from the ferromagnetic (FM) case, adiabaticity in AFM texture does not imply perfect alignment of conduction electron spins with background profile, instead, it introduces an internal dynamics between degenerate bands. As a result, the orbital motion of conduction electrons becomes spin dependent and is affected by two emergent gauge fields: one of them is the non-Abelian version of what has been discovered in FM systems; the other leads to an anomalous velocity that has no FM counterpart. Two examples with experimental predictions are provided. © 2012 American Physical Society.

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.

Guo X.,Peking University
Acta biochimica et biophysica Sinica | Year: 2012

Abnormal expression of histone demethylase Jumonji domain-containing protein 1A (JMJD1A) is associated with many kinds of cancers. JMJD1A is also a hypoxic response gene and its expression is regulated by hypoxia-inducible factor-1α (HIF-1α). In this study, we determined the role of JMJD1A in development and hypoxia pathway. We also measured the expression of JMJD1A and two hypoxia factors glucose transporter 1 (GLUT1) and vascular endothelial growth factor (VEGF) in 786-0 and HEK293 cells treated with different concentrations of NiCl(2) (2.5-100 μM) for 24 h, and found that JMJD1A mRNA and protein were up-regulated with increased concentrations of NiCl(2). We then observed that ascorbate could retard the up-regulated effect of NiCl(2)-induced JMJD1A expression in a dose-dependent manner through decreasing the stability of HIF-1α protein. Immunohistochemical analysis further demonstrated ascorbate antagonized Ni(2+)-induced up-regulation of JMJD1A expression in 786-0, HEK293, and OS-RC-2 cells. These findings suggest that both Ni(2+) and ascorbate can regulate the expression of histone demethylase JMJD1A, which is important for cancer development or inhibition.

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.

Anttu N.,Lund University | Xu H.Q.,Lund University | Xu H.Q.,Peking University
Physical Review B - Condensed Matter and Materials Physics | Year: 2011

We present the formulation of a scattering matrix method for the study of light-scattering properties of metal films. The method is employed for the study of the optical excitation of surface plasmons in a gold film of 15-230 nm thickness, patterned periodically with subwavelength nanoholes. The gold film is placed on a thick SiO2 wafer, and the nanoholes as well as the top side of the gold film are filled with H2O. Light is incident on the gold film from either the SiO2 or the H2O side. The extinction and reflectance spectra of the system, as well as the electromagnetic field distributions at certain characteristic wavelengths, are calculated. The extinction spectra show, depending on system parameters, one or several peaks in the visible wavelength range. The extinction peaks are found to be caused by surface plasmons. A simple model based on the dispersion relation for surface plasmons in an unperforated gold film is shown to predict the peak positions of the extinction for thick perforated films very well. Even for thin films, this simple model, which includes coupling of surface plasmons on both surfaces of the film, predicts peak positions of the extinction well if the hole diameter is small enough. As the hole diameter increases, the extinction peaks of thin films show redshifts. Extinction peaks caused by surface plasmons at the SiO2/Au interface in thick films exhibit strong redshifts when the film thickness is decreased. However, the extinction peaks caused by surface plasmons at the H2O/Au interface in thick films show a completely different behavior. In this case, the extinction peaks do not move noticeably when the film thickness is decreased. Instead, they are weakened and finally disappear. It is also found that each extinction peak is accompanied by an extinction dip and that a reflectance dip is located in the wavelength between the extinction peak and the dip. This arrangement of an extinction peak, a reflectance dip, and an extinction dip is a general property of the surface-plasmon excitation. The calculated electromagnetic field distributions in both thick and thin films show clearly the signature of the excitation of surface plasmons at the extinction peaks, the extinction dips, and the reflectance dips. In thick films with small holes, the electric-field strength in the vicinity of the holes is weak at wavelengths for which surface plasmons are excited. In contrast to this, for thin films at the surface-plasmon excitations, a much stronger electric field is seen in the vicinity of the holes. © 2011 American Physical Society.

Qian Z.,Peking University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

The asymptotic structure of the Kohn-Sham exchange potential v x(r) in the classically forbidden region of a metal surface is investigated, together with that of the Slater exchange potential VxS(r) and those of the approximate Krieger-Li-Iafrate VxKLI(r) and Harbola-Sahni W x(r) exchange potentials. Particularly, the former is shown to have the form of v x(z→∞)=-α x/z with α x a constant dependent only of bulk electron density. The same result in previous work is thus confirmed; in the meanwhile, a controversy raised recently gets resolved. The structure of the exchange hole ρ x(r,r ′) is examined, and the delocalization of it in the metal bulk when the electron is at large distance from the metal surface is demonstrated with analytical expressions. The asymptotic structures of v x(r), VxS(r), VxKLI(r), and W x(r) at a slab metal surface are also investigated. Particularly, v x(z→∞)=-1/z in the slab case. The distinction, in this respect, between the semi-infinite and the slab metal surfaces is elucidated. © 2012 American Physical Society.

Li S.,University of Science and Technology of China | Sun W.,Peking University
Journal of Hazardous Materials | Year: 2011

The aggregation/sedimentation potentials of TiO 2 nanoparticles were studied in mono- and binary systems of Suwannee River fulvic acids (SRFA) and Fe(III) at different pH values. SRFA adsorption significantly enhanced the stability of TiO 2 nanoparticles at pH 4, 6 and 8, mainly due to the dramatic increase in negative surface charges. The presence of Fe(III) stabilized aggregation/sedimentation of TiO 2 nanoparticles at pH 4 due to the increasing positive charges after Fe(III) sorption, but destabilized aggregation/sedimentation at pH 6 and 8 attributed to the bridging effect of Fe(III)-hydroxy. The formation of COO-Fe(III) complex was found in binary system of SRFA and Fe(III). Thus, the positive charges that Fe(III) imparted to nanoparticles were neutralized by SRFA. Compared with those in mono-system of Fe(III), SRFA enhanced aggregation/sedimentation at pH 4, while stabilized TiO 2 nanoparticles at higher pH in binary system of SRFA and Fe(III). The sedimentation rates of TiO 2 nanoparticles showed relatively lower coefficient with zeta potentials (-0.883, P<0.01) than with hydrodynamic particle sizes (0.964, P<0.01), due to the steric hindrance of SRFA and the bridging effect of Fe(III)-hydroxy, which was confirmed by DLVO calculation. These results have important implications for prediction of the stability and fate of nanoparticles in natural water. © 2011 Elsevier B.V.

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.

Shu L.,Peking University
Communications in Mathematical Physics | Year: 2010

We establish the exact dimensional property of an ergodic hyperbolic measure for a C2 non-invertible but non-degenerate endomorphism on a compact Riemannian manifold without boundary. Based on this, we give a new formula of Lyapunov dimension of ergodic measures and show it coincides with the dimension of hyperbolic ergodic measures in a setting of random endomorphisms. Our results extend several well known theorems of Barreira et al. (Ann Math 149:755-783, 1999) and Ledrappier and Young [Commun Math Phys 117(4):529-548, 1988] for diffeomorphisms to the case of endomorphisms. © 2010 Springer-Verlag.

Zhang B.,Chinese Academy of Sciences | Zhang Y.,Peking University | Zhu D.,Chinese Academy of Sciences
Chemical Communications | Year: 2012

An organic-inorganic hybrid combining a semiconducting BEDT-TTF layer and a Jahn-Teller distorted oxalato-bridged honeycomb antiferromagnetic layer [Cu2(C2O4)3 2-] n was obtained and characterized.

Wang W.,Peking University
Advanced Nonlinear Studies | Year: 2010

In this article, let σ R2n be a compact convex hypersurface which is (r, R)- pinched with R/r < √3/2. Then σ carries at least two strictly elliptic closed characteristics; moreover, σ carries at least 2[n+2/4] non-hyperbolic closed characteristics.

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..

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.

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.

Liu X.-W.,Peking University | Zhao G.,CAS National Astronomical Observatories | Hou J.-L.,Chinese Academy of Sciences
Research in Astronomy and Astrophysics | Year: 2015

By the time of this writing, the ongoing LAMOST Galactic surveys have collected approximately 4.5 million stellar spectra with signal-to-noise ratios better than 10 per pixel. This special issue is devoted to early results from the surveys, mostly based on the LAMOST Data Release 1 (DR1; Luo et al., this volume) that contains data secured by May 2013, the end of the first year of regular surveys, although a few studies have made use of data collected in the second year of regular surveys. LAMOST DR1 was released to the Chinese astronomical community and international partners in August 2013 and made public to the whole world in March 2015. Here we briefly review the scope and motivation, data reduction and release, as well as early results of the surveys. As the project advances, one can expect that these surveys will yield an exquisite description of the distribution, kinematics and chemistry of Galactic stellar populations, especially those within a few kpc of the Sun, a robust measurement of the local dark matter density, and, consequently, shed light on how our Galaxy, and other galaxies in general, form and evolve. © 2015 National Astronomical Observatories, Chinese Academy of Sciences and IOP Publishing Ltd.

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.

Dong S.,Peking University | Dong S.,Institute for Advanced Study | Katz B.,Institute for Advanced Study | Socrates A.,Institute for Advanced Study
Astrophysical Journal Letters | Year: 2014

We propose a stringent observational test on the formation of warm Jupiters (gas-giant planets with 10 days ≲ P ≲ 100 days) by high-eccentricity (high-e) migration mechanisms. Unlike hot Jupiters, the majority of observed warm Jupiters have pericenter distances too large to allow efficient tidal dissipation to induce migration. To access the close pericenter required for migration during a Kozai-Lidov cycle, they must be accompanied by a strong enough perturber to overcome the precession caused by general relativity, placing a strong upper limit on the perturber's separation. For a warm Jupiter at a 0.2 AU, a Jupiter-mass (solar-mass) perturber is required to be ≲ 3 AU (≲ 30 AU) and can be identified observationally. Among warm Jupiters detected by radial velocities (RVs), ≳ 50% (5 out of 9) with large eccentricities (e ≳ 0.4) have known Jovian companions satisfying this necessary condition for high-e migration. In contrast, ≲ 20% (3 out of 17) of the low-e (e ≲ 0.2) warm Jupiters have detected additional Jovian companions, suggesting that high-e migration with planetary perturbers may not be the dominant formation channel. Complete, long-term RV follow-ups of the warm-Jupiter population will allow a firm upper limit to be put on the fraction of these planets formed by high-e migration. Transiting warm Jupiters showing spin-orbit misalignments will be interesting to apply our test. If the misalignments are solely due to high-e migration as commonly suggested, we expect that the majority of warm Jupiters with low-e (e ≲ 0.2) are not misaligned, in contrast with low-e hot Jupiters. © 2014. The American Astronomical Society. All rights reserved..

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

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

Agnor C.B.,Queen Mary, University of London | Lin D.N.C.,University of California at Santa Cruz | Lin D.N.C.,Peking University
Astrophysical Journal | Year: 2012

We examine how the late divergent migration of Jupiter and Saturn may have perturbed the terrestrial planets. Using a modified secular model we have identified six secular resonances between the ν5 frequency of Jupiter and Saturn and the four apsidal eigenfrequencies of the terrestrial planets (g 1-4). We derive analytic upper limits on the eccentricity and orbital migration timescale of Jupiter and Saturn when these resonances were encountered to avoid perturbing the eccentricities of the terrestrial planets to values larger than the observed ones. Because of the small amplitudes of the j = 2, 3 terrestrial eigenmodes the g 2 - ν5 and g 3 - ν5 resonances provide the strongest constraints on giant planet migration. If Jupiter and Saturn migrated with eccentricities comparable to their present-day values, smooth migration with exponential timescales characteristic of planetesimal-driven migration (τ ∼ 5-10 Myr) would have perturbed the eccentricities of the terrestrial planets to values greatly exceeding the observed ones. This excitation may be mitigated if the eccentricity of Jupiter was small during the migration epoch, migration was very rapid (e.g., τ ≲ 0.5 Myr perhaps via planet-planet scattering or instability-driven migration) or the observed small eccentricity amplitudes of the j = 2, 3 terrestrial modes result from low probability cancellation of several large amplitude contributions. Results of orbital integrations show that very short migration timescales (τ < 0.5 Myr), characteristic of instability-driven migration, may also perturb the terrestrial planets' eccentricities by amounts comparable to their observed values. We discuss the implications of these constraints for the relative timing of terrestrial planet formation, giant planet migration, and the origin of the so-called Late Heavy Bombardment of the Moon 3.9 ± 0.1 Ga ago. We suggest that the simplest way to satisfy these dynamical constraints may be for the bulk of any giant planet migration to be complete in the first 30-100Myr of solar system history. © 2012. The American Astronomical Society. All rights reserved.

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.

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.

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.

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.

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.

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.

Chen H.-X.,Beijing University of Technology | Chen H.-X.,Beihang University | Chen W.,University of Saskatchewan | Liu X.,Lanzhou University | And 2 more authors.
Physics Reports | Year: 2016

In the past decade many charmonium-like states were observed experimentally. Especially those charged charmonium-like Zc states and bottomonium-like Zb states cannot be accommodated within the naive quark model. These charged Zc states are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. Recently, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. We list the puzzles and theoretical challenges of these models when confronted with the experimental data. We also discuss possible future measurements which may distinguish the theoretical schemes on the underlying structures of the hidden-charm multiquark states. © 2016 Elsevier B.V..

Lin Y.,CAS Beijing National Laboratory for Molecular | Lin Y.,University of Chinese Academy of Sciences | Zhan X.,Peking University
Materials Horizons | Year: 2014

Although fullerenes and their derivatives, such as PCBM, have been the dominant electron-acceptor materials in organic photovoltaic cells (OPVs), they suffer from some disadvantages, such as weak absorption in the visible spectral region, limited spectral breadth and difficulty in variably tuning the band gap. It is necessary to explore non-fullerene electron acceptors that will not only retain the favorable electron-accepting and transporting properties of fullerenes but also overcome their insufficiencies. After a decade of mediocrity, non-fullerene acceptors are undergoing rapid development and are emerging as a hot area of focus in the field of organic semiconductors. Solution-processed bulk heterojunction (BHJ) OPVs based on non-fullerene acceptors have shown encouraging power conversion efficiencies of over 4%. This article reviews recent developments in several classes of solution-processable non-fullerene acceptors for BHJ OPVs. The remaining problems and challenges along with the key research directions in the near future are discussed. © The Royal Society of Chemistry 2014.

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.

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.

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.

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.

Chen Y.,Peking University
Microelectronic Engineering | Year: 2012

Self-aligned triple patterning (SATP) technology offers both improved resolution and design flexibility for scaling integrated circuits down to sub-15 nm half pitch. By keeping and designing mandrel patterns which further define the route of the following spacers, SATP process represents a prospective trend that not only drives up the feature density, but also relaxes the overlay requirement with fewer masks and allows quasi-2D design flexibility. In this paper, we shall present the latest research progress made in optimization of existing SATP process to improve its lithographic performance such as CDU and line width roughness. In addition to solving the previously reported problems of etching small mandrels and sacrificial spacers, we also address the issue of reducing SATP process complexity/cost. © 2012 Elsevier B.V. All rights reserved.

Ma Y.L.,Peking University
Zhonghua jie he he hu xi za zhi = Zhonghua jiehe he huxi zazhi = Chinese journal of tuberculosis and respiratory diseases | Year: 2011

To evaluate the frequency of sensitization to Aspergillus antigens and the prevalence of allergic bronchopulmonary aspergillosis (ABPA) in asthmatic patients. Two hundred consecutive non-smoking outpatients with asthma (≥ 18 years) underwent skin testing with aeroallergens, peripheral eosinophil counting, measurements of total serum IgE level and specific IgE against Aspergillus fumigatus, radiologic investigations and pulmonary function tests. Eleven patients (5.5%) had a positive skin reactivity to Aspergillus antigens. Five of these 11 patients (45.5%) met the diagnostic criteria of ABPA, an overall prevalence of 2.5% (5/200). There were 2 males and 3 females, aging from 19 to 62 years, with a disease duration from 15 to 40 years. All of the patients had asthmatic symptoms such as cough and wheeze. Moderate to severe obstructive ventilatory defect was found in 4 patients. Total serum IgE levels and specific IgE against Aspergillus fumigates were elevated significantly in all the patients, and elevated eosinophil count was found in 3 patients. Three cases were diagnosed as ABPA-CB because of the presence of central bronchiectasis on HRCT. The prevalence of ABPA in Chinese patients with asthma was underestimated. Clinical features of ABPA were similar to asthma alone, but with longer duration and more severe lung function defect. Sensitization to Aspergillus, increased eosinophils and total serum IgE levels were important indicators for the diagnosis of ABPA.

Zhang Z.,Peking University
Guangxue Xuebao/Acta Optica Sinica | Year: 2011

The development of femtosecond fiber lasers is briefly reviewed, and the recent advances in the high repetition rate femtosecond fiber lasers are reported. With the simulation, It's demonstrated that the output pulse width is a function of the pulse repetition rate or the fiber length. With properly selected optical components and the dispersion management, Er3+-doped fiber laser of 330 MHz repetition rate, dispersion Yb3+-doped fiber laser of 490 MHz repetition rate, all-normal dispersion Yb3+-doped laser of 600 MHz repetition rate are developed. Those kinds of fiber lasers can be excellent optical sources for astro-combs.

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.

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.

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.

Zhu Y.B.,Peking University
Zhonghua wei chang wai ke za zhi = Chinese journal of gastrointestinal surgery | Year: 2012

To investigate the clinical value of tumor markers CEA, CA19-9, CA72-4 and CA242 in the diagnosis and prognosis of patients with gastric cancer. One hundred and sixty gastric cancer patients who had received treatment from 2002 to 2007 at the Beijing Cancer Hospital were retrospectively analyzed. Blood samples were taken from patients upon admission to the hospital, and CEA, CA19-9, CA72-4, CA242 levels were detected. Statistical analysis was performed to identify the clinical value of these tumor markers in diagnosis and prognosis. On initial diagnosis, the positive rates of CEA, CA19-9, CA72-4 and CA242 were 37.7%, 26.7%, 37.6% and 21.3%, respectively, and the positive rate of combined detection was 62.9%. CEA was more frequently positive in patients with lymph node metastasis (P=0.029); CA72-4 was more frequently positive in patients with vascular involvement and advanced stage (P=0.039, P=0.011). Multivaraite analysis showed that CA72-4 was an independent prognostic factor (P=0.012). Patients with positive CA72-4 carried a 2.147-fold increased risk of death than those with negative CA72-4. Kaplan-Meier analysis showed that patients with positive CA19-9 or positive CA72-4 had worse survival than those with negative CA19-9 or CA72-4 (P=0.006, P=0.002). Tumor markers including CEA, CA19-9, CA72-4 and CA242 have clinical significance and prognostic value in patients with gastric cancer. Combined detection of four tumor markers can increase the positive rate. CA72-4 is an independent prognostic factor. CA19-9 and CA72-4 are associated with the prognosis of patients with gastric cancer.

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.

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.

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.

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

We show that the observed pattern of quark flavor mixing, such as |V us|≃|Vcd|, |Vcb|≃|Vts|, |Vcd/Vtd|≃|Vcs/Vts|≃ |Vtb/Vcb|, and |Vub/Vcb|<|V td/Vts|, can essentially be understood in the chiral and heavy quark mass limits. In particular, the phenomenologically successful relations |Vub/Vcb|∼√mu/mc and |Vtd/Vts|≃√md/ms can be reasonably conjectured in the mb→∞ and m t→∞ limits, respectively. We stress that the strength of weak CP violation in the quark sector is determined by the moduli of the four corner elements of the Cabibbo-Kobayashi-Maskawa matrix. A comparison between strong and weak CP-violating effects in the standard model is also made. © 2012 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.

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.

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.

Chen H.-Y.,University of Tasmania | Chen Y.-J.,Peking University | Baker M.,University of Tasmania
Chemical Geology | Year: 2012

The Sawayaerdun gold deposit is hosted by Carbonaceous metasediments and is considered to be the largest Muruntau-type gold deposit in the Chinese Tianshan metallogenic belt. Gold mineralization at Sawayaerdun occurs in quartz veins associated with three major hydrothermal events: an early, barren quartz vein stage, middle stage mineralized quartz veins with pyrite and late carbonate (-quartz) veins. The isotopic compositions of quartz and sulfides from the Sawayaerdun gold deposit show some variation but are generally comparable to those of other orogenic-type gold deposits. Fluids trapped in early-stage quartz have a δ 18O range of 13.6‰ to 15.4‰, δD of -48‰ to -75‰, δ 13C of 0.5‰ to 4.2‰ and δ 30Si of -0.2‰ to 0‰. In contrast, isotopic compositions of fluids trapped in middle-stage quartz have δ 18O values of 6.7‰ to 14.7‰, δD of -56‰ to -110‰, δ 13C of 0.4‰ to 10.1‰ and δ 30Si of -0.3‰ to 0‰. Diagenetic and hydrothermal pyrite have similar sulfur (-1.8‰ to 0.9‰) and Pb isotopic values that are associated with host rock compositions. The early-stage, 18O and 13C-rich fluids are probably derived from metamorphic decarbonation of the sedimentary host rock at depth, leading to the precipitation of early barren quartz veins. In the middle stage, a decrease in the regional pressure and temperature regime could have resulted in the incorporation of external fluids into the ore-forming system. These external fluids with isotopic signatures similar to that of the host rock and generally rich in 34S and radiogenic Pb mixed with original ore-forming fluids to generate extensive metal precipitation. Late-stage fluids trapped by calcite veins show isotopic compositions similar to meteoric water, indicating the cessation of hydrothermal fluid circulation at Sawayaerdun occurred at this time. The metallogenetic model illustrated by stable and Pb isotopes is also consistent with fluid inclusion studies in Sawayaerdun. The development of mineralization at Sawayaerdun is strongly linked to fluid mixing, as witnessed by the isotopic signatures of fluids from identified ore-bearing zones. The isotopic compositions of other anomalous zones at Sawayaerdun are similar to those of the mineralized zones, suggesting a high potential for further exploration. © 2012 Elsevier B.V.

Wang X.-Y.,Peking University | Chen H.-S.,Beijing Key Laboratory of Hepatitis C and Immunotherapy for Liver Diseases
World Journal of Gastroenterology | Year: 2014

Chronic infection with hepatitis B virus (HBV) constitutes a major global public health threat, causing substantial disease burdens such as liver cirrhosis and hepatocellular carcinoma, thus representing high unmet medical needs. Currently available therapies are safe, well tolerated, and highly effective in decreasing viremia and improving measured clinical outcomes with low rates of antiviral resistance. However, long-term management remains a clinical challenge, mainly due to the slow kinetics of HBV surface antigen clearance. In this article, we review emerging antivirals directed at novel targets derived from mechanisms of viral cellular entry, viral replication, viral assembly, and the host immune response, leading to preclinical and clinical trials for possible future therapeutic intervention. The recent therapeutic advances in the development of all categories of HBV inhibitors may pave the way for regimens of finite duration that result in long-lasting control of chronic hepatitis B infection. © 2014 Baishideng Publishing Group Inc. All rights reserved.

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.

He Q.Y.,Swinburne University of Technology | He Q.Y.,Peking University | Reid M.D.,Swinburne University of Technology
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We describe how to generate an Einstein-Podolsky-Rosen (EPR) paradox between a mesoscopic mechanical oscillator and an optical pulse. We find two types of paradox, defined by whether it is the oscillator or the pulse that shows the effect Schrödinger called "steering". Only the oscillator paradox addresses the question of mesoscopic local reality for a massive system. In that case, EPR's "elements of reality" are defined for the oscillator, and it is these elements of reality that are falsified (if quantum mechanics is complete). For this sort of paradox, we show that a thermal barrier exists, meaning that a threshold level of pulse-oscillator interaction is required for a given thermal occupation n0 of the oscillator. We find there is no equivalent thermal barrier for the entanglement of the pulse with the oscillator or for the EPR paradox that addresses the local reality of the optical system. Finally, we examine the possibility of an EPR paradox between two entangled oscillators. Our work highlights the asymmetrical effect of thermal noise on quantum nonlocality. © 2013 American Physical Society.

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.

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.

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.

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.

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.

Huang Z.-P.,Peking University
Journal of Applied Mechanics, Transactions ASME | Year: 2014

The objective of this paper is to present a new framework to formulate thermoelastic constitutive relations for initially isotropic rubberlike materials undergoing finite deformations. The strain-energy function for incompressible materials is extended to include the effects of compressibility and temperature changes. The novelty of this framework is that only a few material functions and material parameters to be fitted with the experimental data are required, and these functions and parameters have clear physical meaning. In order to validate the proposed formulation, the Gent-Gent model for incompressible rubbers is chosen as an illustrative example. A new expression of the Helmholtz free energy of rubberlike materials, which takes into account the material compressibility and thermal effect, is then derived. In this generalized Gent-Gent model, only one material function and six material parameters are introduced. It is shown that the generalized Gent-Gent model can be used to predict the stress-strain behavior over the entire range of deformation. Even for incompressible materials, the strain-energy function in this paper is different from that given by Gent himself. The generalized Gent-Gent model can also adequately describe the thermal-mechanical coupling effect, in which thermoelastic inversion phenomena occur. © 2014 by ASME.

Huang Z.,Peking University | Gibb A.J.,University College London
Journal of Physiology | Year: 2014

Native NMDA receptors (NMDARs) are tetrameric channels formed by two GluN1 and two GluN2 subunits. So far, seven NMDARs subunits have been identified and they can form diheteromeric or triheteromeric NMDARs (more than one type of GluN2 subunit). Extracellular Mg2+ is an important regulator of NMDARs, and particularly the voltage dependence of Mg2+ block is crucial to the roles of NMDARs in synaptic plasticity and the integration of synaptic activity with neuronal activity. Although the Mg2+ block properties of diheteromeric NMDARs are fully investigated, properties of triheteromeric NMDARs are still not clear. Our previous data suggested that dopaminergic neurones expressed triheteromeric GluN1-GluN2B-GluN2D NMDARs. Here, using NMDARs in dopaminergic neurones from postnatal day 7 (P7) rats as a model system, we characterize the voltage-dependent Mg2+ block properties of triheteromeric NMDARs. In control conditions, external Mg2+ significantly inhibits the whole cell NMDA-evoked current in a voltage-dependent manner with IC50 values of 20.9 μm, 53.3 μm and 173 μm at -90 mV, -70 mV and -50 mV, respectively. When the GluN2B-selective antagonist ifenprodil was applied, the Mg2+ sensitivity of the residual NMDA-mediated currents (which is mainly carried by GluN1-GluN2B-GluN2D NMDARs) is reduced to IC50 values of 45.9 μm (-90 mV), 104 μm (-70 mV) and 276 μm (-50 mV), suggesting that triheteromeric GluN1-GluN2B-GluN2D NMDARs have less affinity for external Mg2+ than GluN1-GluN2B receptors. In addition, fitting INMDA-V curves with a trapping Mg2+ block model shows the triheteromeric GluN1-GluN2B-GluN2D NMDARs have weaker voltage-dependent Mg2+ block (δ = 0.56) than GluN1-GluN2B NMDARs. Finally, our concentration jump and single channel recordings suggest that GluN1-GluN2B-GluN2D rather than GluN1-GluN2D NMDARs are present. These data provide information relevant to Mg2+ block characteristics of triheteromeric NMDARs and may help to better understand synaptic plasticity, which is dependent on these triheteromeric NMDARs. © 2014 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological 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.

Stempien J.P.,Nanyang Technological University | Sun Q.,Peking University | Chan S.H.,Nanyang Technological University
Energy | Year: 2013

Parametric study of a power plant extension system based on solid-oxide electrolyzer cell (SOEC) system was conducted. Parameters involved in the analysis include temperature, amount of exhaust gas recirculation (EGR) and mole flux. Three limiting steps for reactant gases conversion were identified. An attempt has been made to explain the twin effects of EGR on the system performance. Increased performance of CO2 conversion at lower temperatures has been observed. Significant effects of mole flux and temperature on CO2 and H2O conversion have been confirmed. For the system configuration under study, 46.2% of electricity-to-syngas efficiency has been achieved. Maximum CO2 removal performance of ~2.57molCO2/kWh was predicted at the temperature of 500°C. Conversion ratio of 50-100% of CO2 is achievable depending on the operating conditions. Recommendations have been made for incorporating SOEC system into a power plant to mitigate CO2 and improve efficiency and flexibility of electricity production. © 2013 Elsevier Ltd.

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.

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.

Mandal D.,University of Maryland University College | Quan H.T.,University of Maryland University College | Quan H.T.,Peking University | Jarzynski C.,University of Maryland University College
Physical Review Letters | Year: 2013

We describe a simple and solvable model of a device that - like the "neat-fingered being" in Maxwell's famous thought experiment - transfers energy from a cold system to a hot system by rectifying thermal fluctuations. In order to accomplish this task, our device requires a memory register to which it can write information: the increase in the Shannon entropy of the memory compensates the decrease in the thermodynamic entropy arising from the flow of heat against a thermal gradient. We construct the nonequilibrium phase diagram for this device, and find that it can alternatively act as an eraser of information. We discuss our model in the context of the second law of thermodynamics. © 2013 American Physical Society.

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.

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.

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

We investigate the possible molecules composed of two heavy flavor baryons such as "A QB Q" (Q=b, c) within the one-pion-exchange model (OPE). Our results indicate that the long-range π exchange force is strong enough to form molecules such as [Σ QΞQ′]S=1I=1/2 (Q=b, c), [Σ QΛ Q]S=1I=1 (Q=b, c), [Σ bΞb′]S=1I=3/2, and [Ξ bΞb′]S=1I=0 where the S-D mixing plays an important role. In contrast, the π exchange does not form the spin-singlet A QB Q bound states. If we consider the heavier scalar and vector meson exchanges as well as the pion exchange, some loosely bound spin-singlet S-wave states appear while results of the spin-triplet A QB Q system do not change significantly, which implies the pion exchange plays an dominant role in forming the spin-triplet molecules. Moreover, we perform an extensive coupled channel analysis of the Λ QΛ Q system within the OPE and one-boson-exchange framework and find that there exist loosely bound states of Λ QΛ Q (Q=b, c) with quantum numbers I(JP)=0(0 +), 0(0 -), and 0(1 -). The binding solutions of Λ QΛ Q system mainly come from the coupled-channel effect in the flavor space. Besides the OPE force, the medium- and short-range attractive force also plays a significant role in the formation of the loosely bound Λ cΛ c and Λ bΛ b states. Once produced, they will be very stable because such a system decays via weak interaction with a very long lifetime around 10 -13-10 -12s. © 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.

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.

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.

OBJECTIVE: To compare efficacy and tolerability of 7-day standard triple therapy versus 7-day levofloxacin-based triple therapy in first-line treatment for Helicobacter pylori (H. pylori) infection. METHODS: Three hundred consecutive H.pylori positive patients were randomized to receive: clarithromycin, amoxicillin, lansoprazole (Group A: n = 150); or amoxicillin, levofloxacin, lansoprazole (Group B: n = 150). H. pylori status was rechecked by (13)C-urea breath test 4 weeks after the end of therapy. RESULTS: The eradication rates in intention to treat (ITT) and per protocol (PP) analyses were: Group A, 74.5% (111/149) and 78.2% (111/142); and Group B, 82.4% (122/148) and 83.0%(122/147). Although the eradication rate achieved with levofloxacin-based triple therapy was higher than that with standard therapies in either ITT or PP analysis, but no significantly difference was found between the two triple therapies. The incidence of side effects was similar among groups. CONCLUSIONS: A 7-day levofloxacin-based triple therapy can achieve higher H.pylori eradication rate than standard regimen. The levofloxacin-based regimen can be one effective therapy for the first-line anti-H.pylori treatment.

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.

Chen X.,University of Pennsylvania | Wang L.,Peking University | Cao R.,Beijing Normal University
Child Development | Year: 2011

The purpose of this study was to examine how shyness-sensitivity and unsociability were associated with social, school, and psychological adjustment in rural Chinese children. Participants were third- to fifth-grade students (N = 820; M age=10years) in rural schools in P. R. China. Data on shyness-sensitivity, unsociability, and adjustment were obtained from multiple sources including peer assessments, sociometric nominations, teacher ratings, self-reports, and school records. It was found that unsociability was associated with social, school, and psychological problems, whereas shyness was generally associated with indexes of adjustment such as social status, teacher-rated competence, and academic achievement. The results indicate that rural Chinese context may play an important role in defining the functional meanings of children's social behaviors. © 2011 The Authors. Child Development © 2011 Society for Research in Child Development, Inc.

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.

Zha D.,Peking University
Pacific Review | Year: 2013

Abstract Food is a tireless referent in international relations studies about China and its ties with the rest of the world. This paper addresses two contemporary issues. First, why is China so sensitive about grain self-sufficiency? Second, why does there seem to be a lack of effective dialogue between epistemic communities in China and outside over China's overseas agricultural activities? The first part of the paper reviews the development of China's agricultural sector and underlines the importance of China's contribution in stabilizing the world food markets. Next, it explores the ideational sources of Chinese food insecurity, in spite of its success in attaining high levels of self-sufficiency in grain. The third part of the paper reviews the evolution of China's overseas agricultural activities and analyzes the factors that contribute to a mismatch of understanding about the political implications therein. The paper concludes by proposing a couple of conceptual road maps for securitizing food as a referent in debates about China's security environment and Chinese international relations. © 2013 © 2013 Taylor & Francis.

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.

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.

Wang H.,Beijing Normal University | Zhang T.-J.,Beijing Normal University | Zhang T.-J.,Peking University
Astrophysical Journal | Year: 2012

We use the observational Hubble parameter data (OHD), both the latest observational data set (Stern et al.; referred to as SJVKS) and the simulated data sets, to constrain Lematre-Tolman-Bondi (LTB) void models. The necessity of the consistency check on OHD itself in the LTB cosmology is stressed. Three voids are chosen as test models and are constrained using the Union2 data set of SN Ia as well as OHD. Despite their different parameterization, the results from our test models show some similarities; e.g., the best-fit voids obtained from OHD are all considerably broader than those from SN Ia. Due to the small size of the SJVKS data set, the constraints are not conclusive. The constraining power of the future OHD observations are therefore investigated through a figure of merit (FoM) analysis based on the Monte Carlo simulated data. We found that, in the case that the future OHD become more consistent with SN Ia, the results from the test models are almost unanimous: (1) as many as 32 OHD data points at the SJVKS-like uncertainty level are needed to give a higher FoM than the Union2 data set of SN Ia, (2) precise observation helps reduce this required number, (3) increasing the survey depth does not always increase the FoM. On the other hand, if the future OHD and the Union2 data set keep favoring different voids, in a similar manner as they do at present, the 1σ confidence regions obtained from the two probes should finally separate. We test this conjecture and find that the minimum observational requirement (the size of the data set, the uncertainty level, and the survey depth) for this inconsistency to emerge depends strongly on the void model. © 2012. The American Astronomical Society. All rights reserved.

Zhang X.,CAS National Astronomical Observatories | Lu Y.,CAS National Astronomical Observatories | Yu Q.,Peking University
Astrophysical Journal | Year: 2012

We study observational constraints on the cosmic evolution of the relationships between massive black hole (MBH) mass (M •) and stellar mass (M *, sph; or velocity dispersion σ) of a host galaxy/spheroid. Assuming that the M •-M *, sph (or M •-σ) relation evolves with redshift as ∝(1 + z) Γ, the MBH mass density can be obtained from either the observationally determined galaxy stellar mass functions or velocity dispersion distribution functions over redshift z ∼ 0-1.2 for any given Γ. The MBH mass density at different redshifts can also be inferred from the luminosity function of QSOs/active galactic nuclei (AGNs) provided the radiative efficiency ε is known. By matching the MBH density inferred from galaxies to that obtained from QSOs/AGNs, we find that Γ = 0.64+0.27 - 0.29 for the M •-M *, sph relation and Γ = -0.21+0.28 - 0.33 for the M •- σ relation, and ε = 0.11+0.04 - 0.03. Our results suggest that MBH mass growth precedes bulge mass growth but that the galaxy velocity dispersion does not increase with the mass growth of the bulge after nuclear activity is quenched, which is roughly consistent with the two-phase galaxy formation scenario proposed by Oser et al. in which a galaxy roughly doubles its mass after z = 1 due to accretion and minor mergers while its velocity dispersion drops slightly. © 2012. The American Astronomical Society. All rights reserved..

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.

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.

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.

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.

Ge X.-M.,Nanyang Technological University | Chan S.-H.,Nanyang Technological University | Liu Q.-L.,Nanyang Technological University | Sun Q.,Nanyang Technological University | Sun Q.,Peking University
Advanced Energy Materials | Year: 2012

Solid oxide fuel cells (SOFC) are highly effi cient energy conversion devices with the advantage of directly utilizing hydrocarbon fuels. Starting with a short introduction about the fuel challenges and early achievements in this fi eld, this review paper focuses on advances in oxygen-ion conducting electrolyte-based SOFC during the last 15 years. Robust anodes immune to carbon deposition are a prerequisite for direct hydrocarbon SOFC. In this paper, direct hydrocarbon SOFC anode materials are classifi ed into three general categories: Ni-cermet, Cu-cermet, and oxide-based anodes. Oxide anodes are further classifi ed in terms of their crystalline structures, namely fl uorite, rutile, tungsten bronze, pyrochlore, perovskite, and double perovskite. Achievements and recent advances on these SOFC anodes are reviewed and discussed. The concluding remarks summarize the pros and cons of direct hydrocarbon SOFC anode materials along with the perspective of future research trends. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

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.

Evoli C.,University of Hamburg | Yan H.,Peking University
Astrophysical Journal | Year: 2014

We revisit propagation of galactic cosmic rays (CRs) in light of recent advances in CR diffusion theory in realistic interstellar turbulence. We use a tested model of turbulence in which it has been shown that fast modes dominate scattering of CRs. As a result, propagation becomes inhomogeneous and environment dependent. By adopting the formalism of the nonlinear theory developed by Yan & Lazarian, we calculate the diffusion of CRs self-consistently from first principles. We assume a two-phase model for the Galaxy to account for different damping mechanisms of the fast modes, and we find that the energy dependence of the diffusion coefficient is mainly affected by medium properties. We show that it gives a correct framework to interpret some of the recent CR puzzles. © 2014. The American Astronomical Society. 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.

Jiang J.J.,Peking University
Genetics and molecular research : GMR | Year: 2012

We investigated the association between the LOC387715/ARMS2 polymorphism (rs10490924 G>T) and susceptibility to polypoidal choroidal vasculopathy (PCV) through a meta-analysis of 1446 cases and 3255 controls from eight case-control studies. The genetic effect of the LOC387715/ARMS2 rs10490924 G>T polymorphism on PCV was assessed by calculating pooled odds ratios (ORs) with 95% confidence intervals (95%CIs). We found that elevated PCV risk was significantly associated with the GG genotype (GG vs TT, OR = 4.23, 95%CI = 3.53-5.06), and heterozygous genotype TG appeared to have a minor effect on PCV risk (TG vs TT, OR = 1.47, 95%CI = 1.26-1.71). Patients with the T allele were 2.09 times more likely to have PCV than those with the G allele (95%CI = 1.906-2.288). A further subgroup analysis by ages also showed that the genetic effect of the LOC387715/ARMS2 rs10490924 G>T polymorphism on PCV is stronger among patients with mean age <73 years. Our meta-analysis strengthened the evidence that the LOC387715/ARMS2 rs10490924 G>T polymorphism plays an important role in PCV susceptibility.

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 Epinion.com trustworthy? Does a product from Amazon.com have high quality as described? © 2012 IEEE.

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.

Chen J.,Peking University
The Journal of the Acoustical Society of America | Year: 2012

This study investigated whether speech-like maskers without linguistic content produce informational masking of speech. The target stimuli were nonsense Chinese Mandarin sentences. In experiment I, the masker contained harmonics the fundamental frequency (F0) of which was sinusoidally modulated and the mean F0 of which was varied. The magnitude of informational masking was evaluated by measuring the change in intelligibility (releasing effect) produced by inducing a perceived spatial separation of the target speech and masker via the precedence effect. The releasing effect was small and was only clear when the target and masker had the same mean F0, suggesting that informational masking was small. Performance with the harmonic maskers was better than with a steady speech-shaped noise (SSN) masker. In experiments II and III, the maskers were speech-like synthesized signals, alternating between segments with harmonic structure and segments composed of SSN. Performance was much worse than for experiment I, and worse than when an SSN masker was used, suggesting that substantial informational masking occurred. The similarity of the F0 contours of the target and masker had little effect. The informational masking effect was not influenced by whether or not the noise-like segments of the masker were synchronous with the unvoiced segments of the target speech.

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.

Boxberg F.,Lund University | SaOndergaard N.,Lund University | Xu H.Q.,Peking University | Xu H.Q.,Lund University
Advanced Materials | Year: 2012

The elastic and piezoelectric properties of zincblende and wurtzite crystalline InAs/InP nanowire heterostructures have been studied using electro-elastically coupled continuum elasticity theory. A comprehensive comparison of strains, piezoelectric potentials and piezoelectric fields in the two crystal types of nanowire heterostructures is presented. For each crystal type, three different forms of heterostructures-core-shell, axial superlattice, and quantum dot nanowire heterostructures-are considered. In the studied nanowire heterostructures, the principal strains are found to be insensitive to the change in the crystal structure. However, the shear strains in the zincblende and wurtzite nanowire heterostructures can be very different. All the studied nanowire heterostructures are found to exhibit a piezoelectric field along the nanowire axis. The piezoelectric field is in general much stronger in a wurtzite nanowire heterostructure than in its corresponding zincblende heterostructure. Our results are expected to be particularly important for analyzing and understanding the properties of epitaxially grown nanowire heterostructures and for applications in nanowire electronics, optoelectronics, and biochemical sensing. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chen D.,Columbia University | Shan J.,Columbia University | Zhu W.-G.,Peking University | Qin J.,Baylor College of Medicine | Gu W.,Columbia University
Nature | Year: 2010

The tumour suppressor ARF is specifically required for p53 activation under oncogenic stress. Recent studies showed that p53 activation mediated by ARF, but not that induced by DNA damage, acts as a major protection against tumorigenesis in vivo under certain biological settings, suggesting that the ARF-p53 axis has more fundamental functions in tumour suppression than originally thought. Because ARF is a very stable protein in most human cell lines, it has been widely assumed that ARF induction is mediated mainly at the transcriptional level and that activation of the ARF-p53 pathway by oncogenes is a much slower and largely irreversible process by comparison with p53 activation after DNA damage. Here we report that ARF is very unstable in normal human cells but that its degradation is inhibited in cancerous cells. Through biochemical purification, we identified a specific ubiquitin ligase for ARF and named it ULF. ULF interacts with ARF both in vitro and in vivo and promotes the lysine-independent ubiquitylation and degradation of ARF. ULF knockdown stabilizes ARF in normal human cells, triggering ARF-dependent, p53-mediated growth arrest. Moreover, nucleophosmin (NPM) and c-Myc, both of which are commonly overexpressed in cancer cells, are capable of abrogating ULF-mediated ARF ubiquitylation through distinct mechanisms, and thereby promote ARF stabilization in cancer cells. These findings reveal the dynamic feature of the ARF-p53 pathway and suggest that transcription-independent mechanisms are critically involved in ARF regulation during responses to oncogenic stress. © 2010 Macmillan Publishers Limited. All rights reserved.

Wu J.,CAS Beijing National Laboratory for Molecular | Hou Y.,Peking University | Gao S.,CAS Beijing National Laboratory for Molecular
Nano Research | Year: 2011

In this work, FePt-Au heterostructured nanocrystals (HNCs) such as tadpole-, dumbbell-, bead-, and necklace-like nanostructures were synthesized by a facile heteroepitaxial growth of Au NCs onto FePt nanorods (NRs). A study of the growth mechanism revealed that the morphology control of the final products can be correlated with the adsorption sites of hydrogen onto the FePt NRs, which can be manipulated by the amount of the forming gas (Ar/7% H2) added. Not only the optical characteristic and magnetic properties of the intrinsic materials were retained in the products, but also the FePt-Au HNCs showed the tunable multifunctional properties resulted from the interactions between Au and FePt. Moreover, for methanol oxidation, the FePt-Au HNCs exhibited enhanced catalytic activity and CO tolerance on the catalyst surface compared to commercial Pt catalysts. It is worth noting that as multifunctional units, the FePt-Au HNCs also possess a heterogeneous surface, which could potentially enable their site-specific functionalization for targeting or imaging purposes in biomedical applications. More interestingly, the catalytic properties of the FePt-Au HNCs also endow this material with application potentials in nanocatalysis. © 2011 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

Xue Y.,East Carolina University | Liang H.,East Carolina University | Wu L.,Peking University
Information Systems Research | Year: 2011

This paper aims to understand the influence of punishment and perceived justice on user compliance with mandatory information technology (IT) policies. Drawing on punishment research and justice theory, a research model is developed. Data collected from a field survey of enterprise resource planning (ERP) users are analyzed to test the proposed hypotheses. The results indicate that IT compliance intention is strongly influenced by perceived justice of punishment, which is negatively influenced by actual punishment. When perceived justice of punishment is considered, the effect of satisfaction on compliance intention decreases and that of perceived usefulness becomes insignificant. This paper contributes to information systems (IS) research and practice by drawing attention to the importance of punishment, particularly perceived justice of punishment, in mandatory IT settings. It delineates the relationships among actual punishment, punishment expectancy, perceived justice of punishment, and IT compliance intention, and thus provides a better understanding of user compliance behavior in mandatory IT settings. © 2011 INFORMS.

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.

Nude mice are important in vivo model for characterization of cell malignancy behavior; however, many cancer cells fail to form tumors in it. Understanding this defective mechanism may provide novel insights into tumorigenesis and how tumor cells escape innate immunity. Whole-genome sequencing was conducted on two gastric cancer (GC) cells, BGC823 and AGS, which do and do not form tumors in nude mice, to identify their genomic differences relevant to natural killer (NK) cells. We found that the tumorigenic capacity of human GC cell lines was dependent on the recruitment and activation of NK cells in xenograft tumors. We used whole-genome sequence (WGS) on GC cell lines to identify potential genes controlling susceptibility to NK-mediated killing. The tumorigenic cell line BGC823 expressed high levels of HLA-I because of copy gain and was resistant to NK cell killing. In contrast, another cell line AGS expressing low levels of HLA-I with activated NKp30/MAPK/IL-12 (interleukin-12) or IL-2 (interleukin-2) pathway was susceptible to NK lysis. Treatment of tumor bearing mice with systemic administration of IL-12 in combination with intratumor injection of anti-HLA-I antibody significantly increased NK cell recruitment into xenograft tumors, which became sensitive to NK killing, resulting in reduced tumor progression. In human GC specimens, decreased HLA-I expression and increased NK cells surrounding tumor cells were correlated with decreased metastasis potential and better prognosis of patients. Our results provide a mechanistic basis for GC cells to escape NK lysis and a promising prospect of NK immunotherapy for GC cells.Oncogene advance online publication, 14 September 2015; doi:10.1038/onc.2015.324. © 2015 Macmillan Publishers Limited

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN), an important tumour-suppressor gene, is mutated, downregulated or dysfunctional in many tumours. The phosphatase activity of PTEN depends on membrane translocation (activation). As promising anti-cancer agents, histone deacetylase (HDAC) inhibitors, particularly trichostatin A (TSA), can promote PTEN membrane translocation, but the underlying mechanism remains unknown. In this study, we revealed that non-selective HDAC inhibitors, namely, TSA or suberoylanilide hydroxamic acid (SAHA), induced PTEN membrane translocation through PTEN acetylation at K163 by inhibiting HDAC6. K163 acetylation inhibited the interaction of the PTEN C-tail with the remaining part of PTEN, resulting in PTEN membrane translocation. Overexpression of wild-type PTEN, but not K163-mutated PTEN, facilitated the inhibition of cell proliferation, migration and invasion, as well as xenograft tumour growth, induced by SAHA or tubastatin A, an HDAC6-specific inhibitor. These results indicated that PTEN activation by inhibiting HDAC6 significantly contributed to tumour inhibition. Therefore, non-selective HDAC or HDAC6-specific inhibitors may be more clinically suitable to treat tumours without PTEN mutations or deletions.Oncogene advance online publication, 17 August 2015; doi:10.1038/onc.2015.293. © 2015 Macmillan Publishers Limited

Lin Y.,CAS Beijing National Laboratory for Molecular | Ma L.,University of Chinese Academy of Sciences | Li Y.,Peking University | Liu Y.,CAS Beijing National Laboratory for Molecular | And 2 more authors.
Advanced Energy Materials | Year: 2014

An oligothiophene-based molecule (BDT-3T-CA) using a molecular engineering approach is applied to solution-processed layer-by-layer solar cells. The solar cells based on BDT-3T-CA/PC61BM (a fullerene derivative) exhibit power conversion efficiency (PCE) values as high as 4.16% and fill factor (FF) values up to 0.75. The FF of 0.75 is the highest value reported for solution processed small molecule solar cells. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Han S.,Peking University
Current Opinion in Behavioral Sciences | Year: 2015

Cultural differences in human behavior have been widely documented and interpreted by various psychological theories that emphasize cognitive or affective mechanisms. However, it remains a challenge to provide a coherent neuroscience understanding of culturally discrepant behaviors. Cultural neuroscience research has shown increasing evidence for culturally specific patterns of brain activity such as stronger activity in the dorsal medial prefrontal cortex, lateral frontal cortex and temporoparietal junction in East Asians but stronger activity in the anterior cingulate, ventral medial prefrontal cortex, bilateral insula and temporal pole in Westerners. These findings help to create a coherent neural account of behavior differences between Western and East Asian cultures. © 2015 Elsevier Ltd.

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.

Ida S.,Tokyo Institute of Technology | Lin D.N.C.,University of California at Santa Cruz | Lin D.N.C.,Peking University
Astrophysical Journal | Year: 2010

Radial velocity and transit surveys indicate that solar-type stars bear super-Earths, with masses up to ∼20M⊕ and periods up to a few months, that are more common than those with Jupiter-mass gas giants. In many cases, these super-Earths are members of multiple-planet systems in which their mutual dynamical interaction has influenced their formation and evolution. In this paper, we modify an existing numerical population synthesis scheme to take into account protoplanetary embryos' interaction with their evolving natal gaseous disks, as well as their close scatterings and resonant interaction with each other. We show that it is possible for a group of compact embryos to emerge interior to the ice line, grow, migrate, and congregate into closely packed convoys which stall in the proximity of their host stars. After the disk-gas depletion, they undergo orbit crossing, close scattering, and giant impacts to form multiple rocky Earths or super-Earths in non-resonant orbits around ∼0.1 AU with moderate eccentricities of ∼0.01-0.1. We suggest that most refractory super-Earths with periods in the range of a few days to weeks may have formed through this process. These super-Earths differ from Neptune-like ice giants by their compact sizes and lack of a substantial gaseous envelope. © 2010. The American Astronomical Society. All rights reserved.

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.

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.

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.

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.

Sun Y.,Nanjing University | Zhang Z.,Peking University
Communications in Mathematical Physics | Year: 2011

In this paper, we establish new a priori estimates for the coupled 2D Navier-Stokes equations and Fokker-Planck equation. As its applications, we prove the global existence of smooth solutions for the coupled 2D micro-macro models for polymeric fluids in the bounded domain. © 2010 Springer-Verlag.

Yue J.,Beijing University of Technology | Zhao X.,Beijing University of Technology | Xia D.,Peking University
Electrochemistry Communications | Year: 2012

A novel C/Co composite with Co nanoparticles embedded in carbon matrix is synthesized firstly by pyrolysis of polymeric cobalt phthalocyanine (PcCo) at 700 °C in argon atmosphere. This composite is investigated as an anode material for lithium ion batteries, indicating high tap density and excellent electrochemical performance. The C/Co electrode can retain a higher reversible capacity of over 600 mAh g - 1 at a current of 50 mA g - 1 after 40 cycles and shows better rate capability and less hysteresis in comparison to carbon not containing Co. The significant improvement is attributed to the Co nanoparticles grown in-situ reaction with catalytic activity and high electrical conductivity. © 2012 Elsevier B.V.

Wang T.,Peking University
Zhonghua wai ke za zhi [Chinese journal of surgery] | Year: 2011

To report the experience for the precision osteoid osteoma resection using computer navigation system. Between January 2008 and December 2009, 26 surgical resections were performed for 26 patients who had osteoid osteoma with computer navigation system. There were 23 males and 3 females with an average age of 18 years (7 to 35). Tumors were located at femoral shaft 9, femoral trochanter 4, femoral neck 2, tibial shaft 5, metaphysic of proximal tibia 1, acetabulum 2, pubis 1, vertebral appendix 1 and radial shaft 1. Pre-operative X-ray and CT of each patient was performed to confirm the diagnosis. It was carried out intraoperatively the process of CT-based navigation in 4 cases and intraoperative Iso-C three-dimensional navigation in 22 cases. The Navigation System software was Spine Navigation 1.2 in all cases. The Pointer was helpful to localize the lesion and precisely resected the lesion without removal of any excess bone. All the navigation operations were finished successfully with curettage for 12 and En Bloc resection for 14. Bone grafting was made in 21 cases and none in 3 cases. The completely clearance of nidus by intraoperative visual inspection and Pointer confirmation, postoperative X-ray and(or) CT scan was performed in all cases. All cases had histopathology diagnosis of osteoid osteoma and immediate pain relief after surgery. All cases were followed up for 20.6 months averaged (12 to 35 months). No local recurrence and pain relapse occurred. The navigation system is very helpful for the precision tumor resection of nidus. Especially for the patients with osteoid osteoma located at diaphysis, Intraoperative Iso-C three-dimensional navigation is more useful.

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.

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.

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.

In the present paper, some multiplicity results for semilinear resonant elliptic problems with discontinuous nonlinearities are obtained by using our extended double linking theorem. © 2009 Springer Science+Business Media, LLC.

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.

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.

Ye L.-H.,Peking University
Physical Review B - Condensed Matter and Materials Physics | Year: 2016

Despite its huge successes in total-energy-related applications, the Kohn-Sham scheme of density functional theory cannot get reliable single-particle excitation energies for solids. In particular, it has not been able to calculate the ionization potential (IP), one of the most important material parameters, for semiconductors. We illustrate that an approximate exact-exchange optimized effective potential (EXX-OEP), the Becke-Johnson exchange, can be used to largely solve this long-standing problem. For a group of 17 semiconductors, we have obtained the IPs to an accuracy similar to that of the much more sophisticated GW approximation (GWA), with the computational cost of only local-density approximation/generalized gradient approximation. The EXX-OEP, therefore, is likely as useful for solids as for finite systems. For solid surfaces, the asymptotic behavior of the vxc has effects similar to those of finite systems which, when neglected, typically cause the semiconductor IPs to be underestimated. This may partially explain why standard GWA systematically underestimates the IPs and why using the same GWA procedures has not been able to get an accurate IP and band gap at the same time. © 2016 American Physical 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.

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 Amazon.com. © 2009 Elsevier Ltd. All rights reserved.

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.

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.

Song L.,Peking University | Niyato D.,Nanyang Technological University | Han Z.,University of Houston | Hossain E.,University of Manitoba
IEEE Wireless Communications | Year: 2014

Device-to-device communication underlaying cellular networks allows mobile devices such as smartphones and tablets to use the licensed spectrum allocated to cellular services for direct peer-to-peer transmission. D2D communication can use either one-hop transmission (i.e. D2D direct communication) or multi-hop clusterbased transmission (i.e. in D2D local area networks). The D2D devices can compete or cooperate with each other to reuse the radio resources in D2D networks. Therefore, resource allocation and access for D2D communication can be treated as games. The theories behind these games provide a variety of mathematical tools to effectively model and analyze the individual or group behaviors of D2D users. In addition, game models can provide distributed solutions to the resource allocation problems for D2D communication. The aim of this article is to demonstrate the applications of game-theoretic models to study the radio resource allocation issues in D2D communication. The article also outlines several key open research directions. © 2002-2012 IEEE.

Liang H.,East Carolina University | Xue Y.,East Carolina University | Wu L.,Peking University
Information Systems Research | Year: 2013

With reward (carrot) and punishment (stick) widely applied by organizations to regulate mandatory IT usage, it is imperative to understand how these incentives influence employee compliance behavior. Drawing upon control theory and regulatory focus theory, this study investigates the relationships among regulatory focus, reward, punishment, and compliance behavior in mandatory IT settings. Survey data were collected from 186 employees in companies where enterprise resource planning (ERP) compliance was mandated. Analyses reveal that punishment expectancy is a strong determinant of compliance behavior, whereas the main effect of reward expectancy is not significant. Moreover, the relationship between reward expectancy and compliance behavior is moderated by promotion focus and the relationship between punishment expectancy and compliance behavior is moderated by prevention focus. This study provides an in-depth understanding of reward and punishment in mandatory IT settings and suggests that regulatory focus plays an important role in affecting employees' compliance with organizational controls. © 2013 INFORMS.

With the development of information technology, integrated circuits (IC) and system which target high performance and low power consumption have widely penetrated to all the aspects of national economy, national defense construction and people's life. With the continuous increase in IC integration density, the power consumption is becoming the limiting factor. It turns out that the driving force of the future IC and system development is the reduction of the power consumption and improvement of the performance/power ratio. The Moore's Law is inherently the law for the technology and economic development, and has served as the guideline of the IC development for half a century. However, with the scaling down of IC feature size and the corresponding increased integration density, it is progressively approaching the physical limitation. Moore's Law will gradually complete its historic mission and it will be replaced by a law of reducing the power consumption while ensuring the performance requirements for IC, SoC and SiP performance, law of improving the performance/power ratio. This paper will discuss the related research topics on Green micro/nanoelectronics, including low-power design, novel low-power devices, manufacturing processes for low power applications and related micro/nano electromechanical systems. © Science China Press and Springer-Verlag Berlin Heidelberg 2011.

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.

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.

Cao J.,Peking University
Beijing da xue xue bao. Yi xue ban = Journal of Peking University. Health sciences | Year: 2013

To develop a novel method for obtaining the clear visualization of the gingival profile by cone-beam computed tomography (CBCT) that consistently allows the measurements of gingival thickness and use it to explore the relationship between the gingival thickness and gingival biotype, and the gingival thickness and underlying alveolar bone thickness in the maxillary anterior region. In this study, 15 volunteers with healthy gingiva in the maxillary anterior teeth were involved, and a special preparation was done before CBCT scans including making impression with the contrast agent. The tissue biotypes were assessed clinically with the probe, The thickness of both gingiva and bone and the gingival thickness of the cemento-enamel junction (CEJ) were measured radiographically with cone-beam computed tomography scans. All data analyses were performed using SPSS 16.0. The CBCT image showed clear visualization of the gingival profile. The average gingival thickness of the CEJ was (1.22±0.32) mm. A correlation was observed between the tissue biotypes and the gingival thickness (r=0.449,P<0.05). The labial gingival thickness was negative associated with the underlying bone thickness measured with CBCT in the maxillary anterior region (r=-0.31, P=0.021). A method was established for measuring gingival thickness based on cone-beam computed tomography. The gingival biotypes had a positive correlation with gingival thickness of the CEJ.

Jung J.,University of Texas at Austin | Qiao Z.,University of Texas at Austin | Niu Q.,University of Texas at Austin | Niu Q.,Peking University | MacDonald A.H.,University of Texas at Austin
Nano Letters | Year: 2012

We demonstrate that the one-dimensional (1D) transport channels that appear in the gap when graphene nanoroads are embedded in boron nitride (BN) sheets are more robust when they are inserted at AB/BA grain boundaries. Our conclusions are based on ab initio electronic structure calculations for a variety of different crystal orientations and bonding arrangements at the BN/C interfaces. This property is related to the valley Hall conductivity present in the BN band structure and to the topologically protected kink states that appear in continuum Dirac models with position-dependent masses. © 2012 American Chemical Society.

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.

Liu Y.P.,Peking University
Zhonghua er ke za zhi. Chinese journal of pediatrics | Year: 2012

Methylmalonic aciduria is the most common disorder of organic acidurias in the mainland of China. It is also the one of treatable metabolic disorders. The clinical spectrum of the patients varies from severe neonatal-onset forms with neonatal brain injury and high mortality to milder forms with adult-onset. The clinical manifestations of neonates with methylmalonic aciduria are non-specific. Early diagnosis and adequate treatment contribute a lot to improving the prognosis of the patients. In this study, the abnormal clinical and laboratory findings in neonatal period of 160 Chinese patients with early-onset methylmalonic aciduria were investigated. From 1996 to 2011, a total of 398 patients with methylmalonic aciduria were diagnosed in our hospital; 286 (71.9%) patients had early-onset before 1 year of age. Among 286 patients, 160 (55.9%) presented symptoms in neonatal period. Their urine organic acids were analyzed by gas chromatography-mass spectrometry. Blood amino acids and acylcarnitine profiles were determined by liquid chromatography tandem mass spectrometry. Serum and urine total homocysteine were measured using a fluorescence polarization immunoassay. In some patients, gene analysis was performed. Based on the disease types and general condition, individual dietary and medical interventions were started soon after diagnosis. Out of the 160 patients, 131 (81.9%) had combined methylmalonic aciduria and homocysteinemia. Isolated methylmalonic aciduria was found in 29 cases (18.1%). The common presentations in neonatal period were feeding difficulty, seizures, lethargy and dyspnea. Megaloblastic anemia, liver dysfunction, hyperammonemia and metabolic acidosis were the frequent findings in the routine laboratory test. The most common initial clinical diagnosis was suspected hypoxic-ischemic encephalopathy. Even in 36 cases with abnormal family history, only 3 patients were admitted with suspected inborn errors of metabolism. Five cases (3.1%) were diagnosed by postmortem metabolic examination; 7 cases (4.4%) were detected by newborn screening. In 148 cases (92.5%), the diagnosis was much delayed to the age of one month to 8 years and 5 months (mean 13 months). Methylmalonic aciduria combined with homocysteinemia (MMACHC) gene analyses were performed in 31 cases with combined methylmalonic aciduria. CblC defect was confirmed. The patients with isolated methylmalonic aciduria were treated with protein-restricted diet, cobalamin and L-carnitine. The patients of methylmalonic aciduria combined with homocysteinemia were treated with cobalamin, L-carnitine, calcium folinate, betaine and common diet. Seven patients died without treatment. Clinical improvement was observed in 153 patients. Only 2 patients detected by newborn screening had normal mental and physical development. Mild to severe psychomotor retardation was observed in 151 cases. High mortality and disability rates were observed in the patients with early-onset methylmalonic aciduria. Combined methylmalonic aciduria and homocysteinemia is the common type of methylmalonic aciduria. The clinical manifestation in neonatal period of the patients with early-onset methylmalonic aciduria is complex. Feeding difficulty, seizures, lethargy and dyspnea are the common symptoms in neonatal period of the patients. Megaloblastic anemia, liver dysfunction, hyperammonemia and metabolic acidosis were the frequent laboratory findings.

Feng G.,Health Elements | Feng G.,Peking University | Leem Y.-E.,Health Elements | Levin H.L.,Health Elements
Nucleic Acids Research | Year: 2013

Transposable elements possess specific patterns of integration. The biological impact of these integration profiles is not well understood. Tf1, a long-terminal repeat retrotransposon in Schizosaccharomyces pombe, integrates into promoters with a preference for the promoters of stress response genes. To determine the biological significance of Tf1 integration, we took advantage of saturated maps of insertion activity and studied how integration at hot spots affected the expression of the adjacent genes. Our study revealed that Tf1 integration did not reduce gene expression. Importantly, the insertions activated the expression of 6 of 32 genes tested. We found that Tf1 increased gene expression by inserting enhancer activity. Interestingly, the enhancer activity of Tf1 could be limited by Abp1, a host surveillance factor that sequesters transposon sequences into structures containing histone deacetylases. We found the Tf1 promoter was activated by heat treatment and, remarkably, only genes that themselves were induced by heat could be activated by Tf1 integration, suggesting a synergy of Tf1 enhancer sequence with the stress response elements of target promoters. We propose that the integration preference of Tf1 for the promoters of stress response genes and the ability of Tf1 to enhance the expression of these genes co-evolved to promote the survival of cells under stress. © 2012 The Author(s).

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.

Watkins M.,University College London | Pan D.,CAS Institute of Physics | Wang E.G.,Peking University | Michaelides A.,University College London | And 2 more authors.
Nature Materials | Year: 2011

Resolving the atomic structure of the surface of ice particles within clouds, over the temperature range encountered in the atmosphere and relevant to understanding heterogeneous catalysis on ice, remains an experimental challenge. By using first-principles calculations, we show that the surface of crystalline ice exhibits a remarkable variance in vacancy formation energies, akin to an amorphous material. We find vacancy formation energies as low as ∼0.1-0.2 eV, which leads to a higher than expected vacancy concentration. Because a vacancy's reactivity correlates with its formation energy, ice particles may be more reactive than previously thought. We also show that vacancies significantly reduce the formation energy of neighbouring vacancies, thus facilitating pitting and contributing to pre-melting and quasi-liquid layer formation. These surface properties arise from proton disorder and the relaxation of geometric constraints, which suggests that other frustrated materials may possess unusual surface characteristics. © 2011 Macmillan Publishers Limited. All rights reserved.

Wang J.,Peking University | Zhang Q.,French Institute for Research in Computer Science and Automation
Journal of Process Control | Year: 2014

The study in this paper is motivated by the detection of control valves with asymmetric stiction resulting in oscillations in feedback control loops. The joint characterization of the control valve and the controlled process is formulated as the identification of a class of extended Hammerstein systems. The input nonlinearity is described by a point-slope-based hysteretic model with two possibly asymmetric ascent and descent paths. An iterative identification method is proposed, based on the idea of separating the ascent and descent paths subject to the oscillatory input and output. The structure of the formulated extended Hammerstein system is shown to be identifiable, and the oscillatory signals in feedback control loops are proved to be informative by exploiting the cyclo-stationarity of these oscillatory signals. Numerical, experimental and industrial examples are provided to illustrate the effectiveness of the proposed identification method. © 2013 Elsevier Ltd. All rights reserved.

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.

Nilsson H.A.,Lund University | Samuelsson P.,Lund University | Samuelsson P.,CNRS Institute of Electronics, Microelectronics and Nanotechnology | Caroff P.,Peking University | Xu H.Q.,Lund University
Nano Letters | Year: 2012

Epitaxially grown, high quality semiconductor InSb nanowires are emerging material systems for the development of high performance nanoelectronics and quantum information processing and communication devices and for the studies of new physical phenomena in solid state systems. Here, we report on measurements of a superconductor-normal conductor-superconductor junction device fabricated from an InSb nanowire with aluminum-based superconducting contacts. The measurements show a proximity-induced supercurrent flowing through the InSb nanowire segment with a critical current tunable by a gate in the current bias configuration and multiple Andreev reflection characteristics in the voltage bias configuration. The temperature dependence and the magnetic field dependence of the critical current and the multiple Andreev reflection characteristics of the junction are also studied. Furthermore, we extract the excess current from the measurements and study its temperature and magnetic field dependences. The successful observation of the superconductivity in the InSb nanowire-based Josephson junction device indicates that InSb nanowires provide an excellent material system for creating and observing novel physical phenomena such as Majorana fermions in solid-state systems. © 2011 American Chemical Society.

Zhao X.,Beijing University of Technology | Xia D.,Peking University | Zheng K.,Beijing University of Technology
ACS Applied Materials and Interfaces | Year: 2012

A plum pudding-like Fe 3O 4/Fe/carbon composite was synthesized by a sol-gel polymerization followed by a heat-treatment process and characterized by X-ray diffraction, Raman spectroscopic analysis, thermogravimetric analysis, scanning electron microscopy with energy-dispersive spectroscopy, transmission electron microscopy, and electrochemical test. In this composite, uniform spherical Fe 3O 4/Fe nanoparticles of about 100 nm were embedded into carbon matrix with high monodispersion. As-prepared Fe 3O 4/Fe/carbon composite electrode exhibits a stable and reversible capacity of over 600 mA h g -1 at a current of 50 mA g -1 between 0.002 V and 3.0 V, as well as excellent rate capability. The plum pudding-like structure, in which trace Fe promotes conductivity and carbon matrix mediates the volume change, can enhance the cycling performance and rate capability of Fe 3O 4 electrode. This unique structure is valuable for the preparation of other electrode materials. © 2012 American Chemical Society.

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.

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.

A new quasi-3D structure composed of stacked double-layer subwavelength metal gratings is designed for magnetic resonance in the visible region. The coupling of two-layer gratings induces a type of magnetic plasmon propagation mode characterized by extraordinary optical transmission (EOT) with extremely high transmittance of up to 0.94 for transverse magnetic polarization. The results show that magnetic resonance is an effective method to enhance the transmittance and avoid much energy loss, one of the barriers for application in the visible region. The magnetic resonance or EOT is strongly dependent on the wavelength which can simply be tuned by the period of gratings. This work paves a way to designing metallic metamaterials that are magnetically active in the visible spectral ranges. In addition, the proposed structure can be easily constructed using nanofabrication. © Springer Science+Business Media, LLC.2011.

Ji X.,Shanghai JiaoTong University | Ji X.,Peking University | Ji X.,University of Maryland University College | Zhang J.-H.,Shanghai JiaoTong University | Zhao Y.,University of Maryland University College
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

We provide a theoretical basis for understanding the spin structure of the proton in terms of the spin and orbital angular momenta of free quarks and gluons in Feynman's parton picture. We show that each term in the Jaffe-Manohar spin sum rule can be related to the matrix element of a gauge-invariant, but frame-dependent operator through a matching formula in large-momentum effective field theory. We present all the matching conditions for the spin content at one-loop order in perturbation theory, which provide a basis to calculate parton orbital angular momentum in lattice QCD at leading logarithmic accuracy. © 2015 The Authors.

Zeng H.M.,Peking University
Zhonghua yu fang yi xue za zhi [Chinese journal of preventive medicine] | Year: 2011

To explore the relationship between the polymorphisms of Toll-like receptor 2 (TLR2) and TLR9 and the susceptibility to gastric cancer. A population-based case-control study was conducted at Linqu county, Shandong province, China, including a total of 248 cases of gastric cancer. Another total of 496 age and sex-matched controls were randomly selected from the same cohorts. TLR2 rs3804099 and TLR9 rs187084 were detected by polymerase chain reaction-restriction fragment length polymorphism method. Odds ratios (ORs) and 95% confidence interval (CI) were computed from logistic regression models after adjusting for age, sex, Helicobacter pylori (H. pylori) infection and smoking status. The frequencies of TT, TC and CC genotype on TLR2 rs3804099 in control group were 43.5% (216/496), 46.6% (231/496) and 9.9% (49/496), respectively; whereas those in case group were 53.2% (132/248), 39.9% (99/248) and 6.9% (17/248), respectively. Significant differences in the frequencies of TLR2 rs3804099 were found between case and control groups (χ(2) = 6.665, P = 0.036). It was found that compared with the TT genotype, TC + CC genotype carriers obviously less susceptible to gastric cancer (OR = 0.68, 95%CI: 0.50 - 0.93). Joint effects analysis indicated that the TLR2 rs3804099 TT genotype carriers and H.pylori infectors had higher susceptibility to gastric cancer(OR = 3.42, 95%CI: 2.16 - 5.42), compared with TC + CC genotype carriers and non-H.pylori infection group. The frequencies of TT, TC and CC genotype on TLR9 rs187084 in control group were 33.3% (165/496), 49.0% (243/496) and 17.7% (88/496), respectively; whereas those in case group were 35.9% (89/248), 50.0% (124/248) and 14.1% (35/248), respectively. No significant association with gastric cancer was observed for TLR9 rs187084 polymorphism (χ(2) = 1.684, P = 0.431). Our findings indicate that TLR2 rs3804099 is closely associated with susceptibility to gastric cancer.

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.

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.

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.

Zhou J.,Peking University | Zhou J.,University of California at San Diego | Li Y.-S.,University of California at San Diego | Chien S.,University of California at San Diego
Arteriosclerosis, Thrombosis, and Vascular Biology | Year: 2014

Atherosclerosis develops preferentially at branches and curvatures of the arterial tree, where blood flow pattern is disturbed rather than being laminar, and wall shear stress has an irregular distribution without defined directions. The endothelium in the atherosusceptible regions, in comparison to that in atheroresistant regions, shows activation of proproliferative and proinflammatory gene expressions, reduced production of nitric oxide (NO), increased leukocyte adhesion, and permeability, as well as other atheroprone phenotypes. Differences in gene expressions and cell phenotypes have been detected in endothelia residing in native atherosusceptible and atheroresistant regions of the arteries, or in arteries from animal models with artificial creation of disturbed flow. Similar results have also been shown in in vitro systems that apply controlled shear stresses with or without clear directions to cultured endothelial cells in fluid-dynamically designed flow-loading devices. The available evidence indicates that the coordination of multiple signaling networks, rather than individual separate pathways, links the mechanical signals to specific genetic circuitries in orchestrating the mechanoresponsive networks to evoke comprehensive genetic and functional responses. © 2014 American Heart Association, Inc.

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.

Yang S.D.,Peking University
Nuclear and Particle Physics Proceedings | Year: 2016

Using the data samples of 102×106Υ(1S) and 158×106Υ(2S) events collected at Belle, several studies on Υ(1S/2S) decays have been performed recently. Charge-parity-even charmonium(-like) states, such as χc0,1,2, ηc, X(3872), X(3915), Y(4140), and X(4350) (only in Υ(2S) data), are first searched in Υ(1S/2S) radiative decays, though there are no significant signals observed. Among double-charmonium final states from Υ(1S/2S) exclusive decays, the evidence for Υ(1S)→J/ψχc1 was found first with a signal significance of 4.6σ, and the branching fraction was measured to be (3.90 ± 1.21(stat.) ± 0.23(syst.)) × 10-6. Some exclusive light hadronic decays are also searched for the first time, including the intermediate vector-tensor, axial-vector-pseudoscaler, and vector-pseudoscaler processes. Signals are observed in the Υ(1S)→φK+K-, ωπ+π-, K*(892)0K-π+, KS0K+π-+c.c., π+π-π0π0, K*(892)0K[U+203E]2*(1430)0 and Υ(2S)→φK+K-, K*(892)0K-π+, π+π-π0π0 decay modes, and evidence is found for the modes of Υ(1S)→π+π-π0, K1(1400)+K-, K*(892)0K[U+203E]0+c.c. and Υ(2S)→KS0K+π-+c.c., K*(892)0K[U+203E]2*(1430)0. In addition, the study of the hadronic transitions, Υ(2S)→(η, π0)Υ(1S), is performed, and B(Υ(2S)→ηΥ(1S))=(3.57±0.25(stat.)±0.21(syst.))×106-4 and B(Υ(2S)→π0Υ(1S))<4.1×10-5 (90%C.L.) are obtained. © 2016 Elsevier B.V.

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.

Cheng R.,University of Texas at Austin | Xiao J.,Fudan University | Niu Q.,University of Texas at Austin | Niu Q.,Peking University | Brataas A.,Norwegian University of Science and Technology
Physical Review Letters | Year: 2014

Spin pumping and spin-transfer torques are two reciprocal phenomena widely studied in ferromagnetic materials. However, pumping from antiferromagnets and its relation to current-induced torques have not been explored. By calculating how electrons scatter off a normal metal-antiferromagnetic interface, we derive pumped spin and staggered spin currents in terms of the staggered field, the magnetization, and their rates of change. For both compensated and uncompensated interfaces, spin pumping is of a similar magnitude as in ferromagnets with a direction controlled by the polarization of the driving microwave. The pumped currents are connected to current-induced torques via Onsager reciprocity relations. © 2014 American Physical Society.

Yan M.,Peking University | Korshin G.V.,University of Washington | Chang H.-S.,Savannah River Ecology Laboratory
Water Research | Year: 2014

Formation of disinfection by-products (DBPs) in ten drinking source waters located in the United States was examined in this study. DBP generation was interpreted in the context of halogenation-induced changes of log-transformed absorbance spectra of dissolved organic matter (DOM) present in the waters. This approach allows probing the behavior of relatively minor structures that can be highly sensitive towards any process of interest, notably DOM halogenation. This concept was applied to examine effects of chlorination time on the kinetics of chlorine consumption and release of several DBP groups such as total trihalomethanes (THM4, including CHCl3, CHCl2Br, CHClBr2 and CHBr3), haloacetic acids (HAA9, including MCAA, MBAA, DCAA, TCAA, BCAA, DBAA, BDCAA, DBCAA and TBAA), haloacetonitriles (THAN4, including TCAN, DCAN, BCAN and DBAN), haloketones (HK2, including DCP and TCP), chloral hydrate (CH) and chloropicrin (CPN). Two alternative parameters, namely the differential logarithm of DOM absorbance at 350nm (DLnA350) and change of the spectral slope in the range of wavelengths 325-375nm (DSlope325-375) were introduced to quantify individual DBP species formed and Cl2 consumption. DLnA350 and DSlope325-375, especially DLnA350 were determined to be more reliable than differential absorbance at 272nm that was utilized in prior applications of differential spectroscopy to characterize DBP formation. Strong linear relationships between DLnA350 values and concentrations of major groups of and individual DBP species (e.g. THM4, HAA9, HAN4 and CPN were found to exist (mostly, R2>0.95) and the intercept of these correlations with the y-axis was near zero for the examined water sources. Correlations between DLnA350 values and concentrations of CH and HK2 were also strong but they were nonlinear. The slope of the correlations between the concentrations of major groups of DBP species vs -DLnA350 were also well correlated with SUVA254 and LnA350 for all the examined source waters. It indicates that log-transformations of the absorbance spectra of surface water and parameters based on such transformations (e.g., DLnA350 and DSlope325-375) have a potential to provide an alternative reliable approach to monitor the halogenation of DOM and attendant formation of individual DBP species. © 2013 Elsevier Ltd.

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.

Ali S.S.,University of Toronto | Xia B.,Peking University | Liu J.,University of Toronto | Navarre W.W.,University of Toronto
Current Opinion in Microbiology | Year: 2012

Xenogeneic silencing proteins facilitate horizontal gene transfer by silencing expression of AT-rich sequences. By virtue of their activity these proteins serve as master regulators of a variety of important functions including motility, drug resistance, and virulence. Three families of silencers have been identified to date: the H-NS like proteins of Gram-negative bacteria, the MvaT like proteins of Pseudomonacae, and the Lsr2 proteins of Actinobacteria. Structural and biochemical characterization of these proteins have revealed that they share surprising commonalities in mechanism and function despite extensive divergence in both sequence and structure. Here we discuss the mechanisms that underlie the ability of these proteins to selectively target AT-rich DNA and the contradictory data regarding the mode by which H-NS forms nucleoprotein complexes. © 2012 Elsevier Ltd.

Qing L.,Peking University | Aoyama T.,Kyoto University
Journal of Integrative Plant Biology | Year: 2012

Recent plant development studies have identified regulatory pathways for epidermal cell differentiation in Arabidopsis thaliana. Interestingly, some of such pathways contain transcriptional networks with a common structure in which the homeobox gene GLABLA2 (GL2) is downstream of the transactivation complex consisting of MYB, bHLH, and WD40 proteins. Here, we review the role of GL2 as an output device of the conserved network, and update the knowledge of epidermal cell differentiation pathways downstream of GL2. Despite the consistent position of GL2 within the network, its role in epidermal tissues varies; in the root epidermis, GL2 promotes non-hair cell differentiation after cell pattern formation, whereas in the leaf epidermis, it is likely to be involved in both pattern formation and differentiation of trichomes. GL2 expression levels act as quantitative factors for initiation of cell differentiation in the root and leaf epidermis; the quantity of hairless cells in non-root hair cell files is reduced by gl2 mutations in a semi-dominant manner, and entopically additive expression of GL2 and a heterozygous gl2 mutation increase and decrease the number of trichomes, respectively. Although few direct target genes have been identified, evidence from genetic and expression analyses suggests that GL2 directly regulates genes with various hierarchies in epidermal cell differentiation pathways. © 2012 Institute of Botany, Chinese Academy of Sciences.

Chang Y.-J.,Peking University | Huang X.-J.,Peking Tsinghua Center for Life science
Bone Marrow Transplantation | Year: 2014

Research on the different mechanisms for crossing HLA barriers has progressed over the past 10 years. General outlines have come into view for a solution to this issue and are often presented as 'haploidentical SCT' immunology. In this review, we discuss several mechanisms that have recently been described in ex vivo and in vivo settings that can either avoid GVHD or promote hematopoietic reconstitution in haploidentical settings. The host and donor T-cell responses to allogeneic HLA molecules are a fundamental obstacle to the successful application of haploidentical transplantation, which results in unacceptably high incidences of GVHD and graft rejection. Thus, the T-cell response is a central factor in the establishment of a novel haploidentical transplant protocol with superior outcomes. © 2014 Macmillan Publishers Limited.

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.

Chen Y.,Peking University | Wang R.,Lakehead University
Respiratory Physiology and Neurobiology | Year: 2012

Hydrogen sulfide (H2S) is an important gasotransmitter in the mammalian respiratory system. The enzymes that produce H2S - mainly cystathionine-β-synthase and cystathionine-γ-lyase - are expressed in pulmonary and airway tissues. Endogenous H2S participates in the regulation of the respiratory system's physiological functions and pathophysiological alterations, such as chronic obstructive pulmonary disease, asthma, pulmonary fibrosis and hypoxia-induced pulmonary hypertension, to name a few. The cellular targets of H2S in the respiratory system are diverse, including airway smooth muscle cells, epithelial cells, fibroblasts, and pulmonary artery smooth muscle cells. H2S also regulates respiratory functions such as airway constriction, pulmonary circulation, cell proliferation or apoptosis, fibrosis, oxidative stress, and neurogenic inflammation. Cross-talk between H2S and other gasotransmitters also affects the net outcome of lung function. The metabolism of H2S in the lungs and airway may serve as a biomarker for specific respiratory diseases. It is expected that strategies targeted at the metabolism and function of H2S will prove useful for the prevention and treatment of selective chronic respiratory diseases. © 2012 Elsevier B.V.

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.

He Y.,Osaka University | Tsutsui M.,Osaka University | Fan C.,Peking University | Taniguchi M.,Osaka University | Kawai T.,Osaka University
ACS Nano | Year: 2011

One major challenge of nanopore-based DNA sequencing technology is to find an efficient way to reduce DNA translocation speed so that each nucleotide can reside long enough in the pore for interrogation. Here we report the electrical tuning of DNA translocation speed by gate modulation of nanopore wall surface charges. We find that native surface-charge-induced counterions in the electroosmotic layer substantially enhance advection flow of fluid, which exerts stronger dragging forces on the translocating DNA, and thereby lowering the DNA translocation speed. We propose a feedback device architecture to regulate DNA translocation by modulating the effective wall surface charge density σw*via lateral gate voltages-at the beginning, a positive gate bias is applied to weaken σw* in order to enhance the capture rate of DNA molecule; upon detection of ionic current variance indicating DNA has been driven into the nanopore, gate bias is turned to be negative so that σw* is reinforced and DNA translocation is retarded. We show that a gate electric field can dramatically decrease the DNA translocation speed at a rate about 55 μm/s per 1 mV/nm. © 2011 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).

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.

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.

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.

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.

Scuteri A.,Hospital San Raffaele Pisana | Wang H.,Peking University
Journal of Alzheimer's Disease | Year: 2014

Carotid-femoral pulse wave velocity (PWV), an index of large artery stiffness, is a good proxy of arterial aging and also an independent marker of cardiovascular disease. A consistently growing number of studies has shown a significant inverse association of arterial aging and cognitive function: the greater the PWV, the lower the cognitive performance (and the greater its decline over time)-regardless of heterogeneity in study populations, sample size, and measure of cognitive functions adopted in each study. Therefore the epidemiological evidence and the biological plausibility require adoption of strategies to foster the routine measurement of PWV and cognitive function measurements in each and every older subject, particularly those at higher cardiovascular risk. Consistently, limited available healthcare resources should be progressively shifted from a sterile differential diagnosis between Alzheimer-type and vascular dementia to interventions aimed to reduce PWV and, thus, to prevent dementia before its onset or to decrease its rate of progression. © 2014 - IOS Press and the authors. All rights reserved.

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.

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.

Han F.,Peking University
Sleep and Breathing | Year: 2012

Introduction: Narcolepsy is a debilitating sleep disorder characterized by excessive daytime sleepiness, cataplexy and intrusive REM sleep. Deficits in endogenous orexins are a major pathogenic component of the disease. This disorder is also associated with the gene marker, HLADQB1*0602. An increased prevalence of sleep apnea in narcolepsy suggested interactions among ventilatory chemosensitivity, narcolepsy-cataplexy, and sleep apnea. Results Evidence from animal studies using orexin knockout mice and focal microdialysis of an orexin receptor antagonist demostrated that orexins are also contributed to respiratory regulation in a vigilance state-dependent manner, as animals with orexins dysregulation have attenuated hypercapnic ventilatory responses predominately in wakefulness, which is consistent with the notion that the activity of orexinergic neurons is higher during wake than sleep periods. Human model of hypocretin deficiency is patients with narcolepsy-cataplexy. In contrast to findings suggested by animal studies, we found significant decrease in hypoxic responsiveness but not in hypercapnic responsiveness in narcoleptics, and further analysis indicated that decreased ventilatory responses to hypoxia in human narcolepsy-cataplexy is in relation to HLA-DQB1*0602 status, not hypocretin deficiency. Conclusion Unlike in mouse, hypocretin-1 is not a major factor contributing to chemoresponsiveness in human. Species differences may exist. © Springer-Verlag 2011.

Dou Y.,Peking University
Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association | Year: 2011

The accurate assessment of body fluid volume is important in many clinical situations. Hannan et al. proposed a single-frequency bioimpedance equation (HE) to calculate extracellular water (ECW) and total body water (TBW). There are two equations based on the bioimpedance spectroscopy (BIS) method for the evaluation of body fluid volume: Xitron equations (XE) and body composition spectroscopy equations (BCSE). The aim of the study was to compare the accuracy of these three equations in body fluid volume point estimation in maintenance hemodialysis (MHD) patients. The BIS method was performed in MHD patients before and after a hemodialysis (HD) session. TBW, ECW and intracellular water (ICW) were calculated by XE, BCSE and HE, respectively. Hydration status (HS) was calculated using inputs of XE, BCSE and HE. ICW before dialysis was compared to ICW after dialysis. The change of TBW and HS using different equations was compared to actual ultrafiltration volume (AUV) that was calculated as weight difference of pre- to postdialysis. Fifty MHD patients (27 females) were included in the study. Significant changes in ICW were observed using the XE and HE method with ultrafiltration (XE: 15.51 ± 5.07 versus 16.17 ± 5.34 L, P < 0.01; HE: 17.40 ± 5.13 versus 16.55 ± 4.71 L, P < 0.01). However, no significant ICW change was observed using BCSE (17.47 ± 4.35 versus 17.54 ± 4.36 L, P > 0.05). ΔTBW_XE and ΔTBW_HE were significantly different from AUV (XE 1.76 ± 0.89 versus 2.46 ± 0.89 L, P < 0.01; HE 4.16 ± 1.36 versus 2.46 ± 0.89 L, P < 0.01); however, ΔTBW_BCSE was much closer to AUV (2.27 ± 0.90 versus 2.46 ± 0.89 L, P = 0.129). The change of HS using inputs of BCSE was also closer to AUV (2.41 ± 0.86 versus 2.46 ± 0.89 L, P = 1.0). Our study indicated that BCSE provided a better point estimation of ICW and TBW.

Wang Y.,Peking University | Blelloch R.,University of California at San Francisco
Results and Problems in Cell Differentiation | Year: 2011

The ability to self-renew and to differentiate into at least one-cell lineage defines a stem cell. Self-renewal is a process by which stem cells proliferate without differentiation. Proliferation is achieved through a series of highly regulated events of the cell cycle. MicroRNAs (miRNAs) are a class of short noncoding RNAs whose importance in these events is becoming increasingly appreciated. In this chapter, we discuss the role of miRNAs in regulating the cell cycle in various stem cells with a focus on embryonic stem cells. We also present the evidence indicating that cell cycle-regulating miRNAs are incorporated into a large regulatory network to control the self-renewal of stem cells by inducing or inhibiting differentiation. In addition, we discuss the function of cell cycle-regulating miRNAs in cancer. © 2011 Springer-Verlag Berlin Heidelberg.

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.

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.

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.

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.

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.

Zhu J.,Beijing University of Technology | Ma B.-Q.,Beijing University of Technology | Ma B.-Q.,Peking University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

We calculate g1T and h1L ⊥, two of the eight leading twist transverse momentum dependent parton distributions (TMDs), in the light-cone quark-diquark model. The new TMDs can be measured through semi-inclusive deep inelastic scattering (SIDIS). We present predictions of the single and double spin asymmetries related to g1T and h1L ⊥ in SIDIS at HERMES, COMPASS, and JLab kinematics respectively. © 2010 Elsevier B.V.

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.

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 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.

Li H.-N.,Academia Sinica, Taiwan | Li Z.,Michigan State University | Yuan C.-P.,Michigan State University | Yuan C.-P.,Peking University
Physical Review Letters | Year: 2011

We provide a novel development in jet physics by predicting the energy profiles of light-quark and gluon jets in the framework of perturbative QCD. Resumming large logarithmic contributions to all orders in the coupling constant, our predictions are shown to agree well with Tevatron CDF and Large Hadron Collider CMS data. We also extend our resummation formalism to the invariant mass distributions of light-quark and gluon jets produced in hadron collisions. The predicted peak positions and heights in jet mass distributions are consistent with CDF data within uncertainties induced by parton distribution functions. © 2011 American Physical Society.

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.

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..

Huang S.,Washington University in St. Louis | Kang W.,Peking University | Yang L.,Washington University in St. Louis
Applied Physics Letters | Year: 2013

We report first-principles results on the electronic structure of silicene. For planar and simply buckled silicenes, we confirm their zero-gap nature and show a significant renormalization of their Fermi velocity by including many-electron effects. However, the other two recently proposed silicene structures exhibit a finite bandgap, indicating that they are gapped semiconductors instead of expected Dirac-fermion semimetals. This finite bandgap is preserved with the Ag substrate included. Moreover, our GW calculation reveals enhanced many-electron effects in these two-dimensional structures. Finally, the bandgap of the latter two structures can be tuned in a wide range by applying strain. © 2013 AIP Publishing LLC.

Zhang H.S.,Peking University | Zhang H.S.,University of California at Irvine | Lin Z.,University of California at Irvine | Holod I.,University of California at Irvine
Physical Review Letters | Year: 2012

A nonlinear oscillation of frequency and amplitude is found by massively parallel gyrokinetic simulations of Alfvén eigenmodes excited by energetic particles in toroidal plasmas. The fast and repetitive frequency chirping is induced by the evolution of coherent structures in the phase space. The dynamics of the coherent structures is controlled by the competition between the phase-space island formation due to the nonlinear particle trapping and the island destruction due to the free streaming. The chirping dynamics provides a conceptual framework for understanding nonlinear wave-particle interactions underlying the transport process in collisionless plasmas. © 2012 American Physical Society.

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.

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.

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.

Rogers T.M.,University of Arizona | Lin D.N.C.,University of California at Santa Cruz | Lin D.N.C.,Peking University
Astrophysical Journal Letters | Year: 2013

We investigate tidal dissipation of obliquity in hot Jupiters. Assuming an initial random orientation of obliquity and parameters relevant to the observed population, the obliquity of hot Jupiters does not evolve to purely aligned systems. In fact, the obliquity evolves to either prograde, retrograde, or 90°orbits where the torque due to tidal perturbations vanishes. This distribution is incompatible with observations which show that hot Jupiters around cool stars are generally aligned. This calls into question the viability of tidal dissipation as the mechanism for obliquity alignment of hot Jupiters around cool stars. © 2013. The American Astronomical Society. All rights reserved..

Li Z.,Peking University | Li Z.,Chinese Academy of Sciences
Astrophysical Journal Letters | Year: 2013

If gamma-ray bursts (GRBs) produce high-energy cosmic rays, neutrinos are expected to be generated in GRBs via photo-pion productions. However, we stress that the same process also generates electromagnetic (EM) emission induced by the secondary electrons and photons, and that the EM emission is expected to be correlated with neutrino flux. Using Fermi/Large Area Telescope results on gamma-ray flux from GRBs, the GRB neutrino emission is limited to be <20 GeV m-2 per GRB event on average, which is independent of the unknown GRB proton luminosity. This neutrino limit suggests that IceCube, operating at full scale, requires stacking of more than 130 GRBs in order to detect one GRB muon neutrino. © 2013. The American Astronomical Society. All rights reserved..

Wu Z.L.,Peking University
Journal of hematology & oncology | Year: 2011

The purpose of the study was to investigate the expression and prognostic value of STAT3 in diffuse large B-cell lymphoma (DLBCL). Seventy-four DLBCL patients from 2001 to 2007 were reviewed in the study. The STAT3 expression in their tumor tissues was examined using the immunohistochemistry (IHC) method, and evaluated for its association with clinicopathological parameters. Strong nuclear staining of STAT3 and phosphorylated-STAT3tyr705 (P-STAT3) were observed in 19 cases (25.7%) and 24 cases (32.4%), respectively, and the expression levels were highly consistent between them (P = 0.001). The high nuclear expression of STAT3 was more frequent in the non-germinal center B cell-like (non-GCB) DLBCL than that in the GCB subtype, but not reaching significance (P < 0.061). The high nuclear expression of STAT3 was found to be correlated with poor overall survival (OS) (P = 0.005). Multivariate Cox regression analysis showed that the STAT3 expression was an independent prognostic factor for DLBCL patients regardless of CHOP or R-CHOP regimen used as the first-line therapy. STAT3 is more frequently expressed in non-GCB DLBCL than that in GCB subtype, and its strong nuclear expression is correlated with poor OS in DLBCL.

Ida S.,Tokyo Institute of Technology | Lin D.N.C.,University of California at Santa Cruz | Lin D.N.C.,Peking University | Nagasawa M.,Tokyo Institute of Technology
Astrophysical Journal | Year: 2013

The ubiquity of planets and diversity of planetary systems reveal that planet formation encompasses many complex and competing processes. In this series of papers, we develop and upgrade a population synthesis model as a tool to identify the dominant physical effects and to calibrate the range of physical conditions. Recent planet searches have led to the discovery of many multiple-planet systems. Any theoretical models of their origins must take into account dynamical interactions between emerging protoplanets. Here, we introduce a prescription to approximate the close encounters between multiple planets. We apply this method to simulate the growth, migration, and dynamical interaction of planetary systems. Our models show that in relatively massive disks, several gas giants and rocky/icy planets emerge, migrate, and undergo dynamical instability. Secular perturbation between planets leads to orbital crossings, eccentricity excitation, and planetary ejection. In disks with modest masses, two or less gas giants form with multiple super-Earths. Orbital stability in these systems is generally maintained and they retain the kinematic structure after gas in their natal disks is depleted. These results reproduce the observed planetary mass-eccentricity and semimajor axis-eccentricity correlations. They also suggest that emerging gas giants can scatter residual cores to the outer disk regions. Subsequent in situ gas accretion onto these cores can lead to the formation of distant (≳ 30 AU) gas giants with nearly circular orbits. © 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.

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.

Yan Z.,Peking University
Quintessence international (Berlin, Germany : 1985) | Year: 2012

Burning mouth syndrome (BMS) is a common chronic pain condition that lacks a satisfactory treatment approach. This systematic review was designed to examine the effects of acupuncture or acupoint injection on the management of BMS and to evaluate the evidence supporting the use of acupuncture therapy for BMS in clinical practice. The following databases were searched for relevant articles: Cochrane Oral Health Group Trials Register (July 2011), Cochrane Central Register of Controlled Trials (issue 7, 2011), MEDLINE (1966 to June 2011), and electronic medical database from the China-National Knowledge Infrastructure (1979 to June 2011). Articles were screened, and the quality of the included trials was assessed independently by two reviewers. After screening, nine studies with 547 randomized patients were included in this review. All nine articles were published in Chinese and were clinical trial studies with a Jadad score < 3. Their results showed that acupuncture/acupoint injection may benefit patients with BMS. The evidence supported the efficacy of acupuncture/acupoint injection therapy in reducing BMS pain and related symptoms. In light of the positive outcomes reported, the use of acupuncture therapy for BMS patients warrants further research.

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.

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.

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.

Zhou G.-L.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

A scheme is presented to cancel out topologically unfactorized infrared divergences in the inclusive production of heavy quarkonia, which affect the nonrelativistic QCD (NRQCD) factorization of these processes. Heavy quarkonia are defined as resonance states of QCD instead of a color-singlet heavy quark pair. Thus the final heavy quark pair is not necessarily a color singlet. In addition, heavy quarkonia are reconstructed from their decay products. As a result, the transitions between states containing heavy quarks caused by exchanges of soft gluons are also taken into account here. Such cancellation is crucial for the NRQCD factorization of these processes. © 2016 American Physical Society.

Lu Y.,Texas State University | Liu Y.,Peking University
Computers, Environment and Urban Systems | Year: 2012

The rapid development and increasing availability of various location acquisition technologies provide geospatial studies with both opportunities and challenges. These opportunities and challenges are discussed in this paper focusing on the following three aspects: the massive acquisition of location data and data quality, the analysis of massive location data and pattern discovery, and privacy protection for massive location data. This paper examines the current status of and the potential opportunities for geospatial research in these three areas and notes the major challenges. Finally, the development of this special issue is described, and the four articles included in this special issue are presented. © 2012.

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 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.

Yan H.,Peking University | Lazarian A.,University of Wisconsin - Madison | Schlickeiser R.,Ruhr University Bochum
Astrophysical Journal | Year: 2012

High-energy gamma-ray emission has been detected recently from supernova remnants (SNRs) and their surroundings. The existence of molecular clouds near some of the SNRs suggests that the gamma rays originate predominantly from p-p interactions with cosmic rays (CRs) accelerated at a closeby SNR shock wave. Here we investigate the acceleration of CRs and the gamma-ray production in the cloud self-consistently by taking into account the interactions of the streaming instability and the background turbulence both at the shock front and in the ensuing propagation to the clouds. We focus on the later evolution of SNRs, when the conventional treatment of the streaming instability is valid but the magnetic field is enhanced due to Bell's current instability and/or the dynamo generation of magnetic field in the precursor region. We calculate the time dependence of the maximum energy of the accelerated particles. This result is then used to determine the diffusive flux of the runaway particles escaping the shock region, from which we obtain the gamma spectrum consistent with observations. Finally, we check the self-consistency of our results by comparing the required level of diffusion with the level of the streaming instability attainable in the presence of turbulence damping. The energy range of CRs subject to the streaming instability is able to produce the observed energy spectrum of gamma rays. © 2012. The American Astronomical Society. All rights reserved.

Ma Y.-Q.,Beijing University of Technology | Wang K.,Beijing University of Technology | Chao K.-T.,Peking University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

A complete next-to-leading-order calculation in α s for the J/ψ and ψ ′ prompt production at the Tevatron, LHC, and RHIC in nonrelativistic QCD is presented. We argue that the next-to-next-to-leading-order color-singlet contribution may not be so important as to resolve the large discrepancy between theory and experiment in J/ψ large p T production cross sections. Therefore, a complete next-to-leading-order calculation, including both color-singlet and color-octet contribution, is necessary and essential to give a good description for J/ψ and ψ ′ production. We also study the methods to fit the long-distance matrix elements using either two linear combined matrix elements or three matrix elements, and find these two methods can give consistent results. Compared with the measurements at the LHC and RHIC for prompt J/ψ and ψ ′ production, our predictions are found to agree with all data. In particular, the recently released large p T data (up to 60-70 GeV) at the LHC are in good agreement with our predictions. Our results imply that the universality of color-octet matrix elements holds approximately in charmonium hadroproduction, when one uses fixed-order perturbative calculation to describe data (the data in small p T region are not included). Our work may provide a new test for the universality of color-octet matrix elements, and the color-octet mechanism in general. © 2011 American Physical Society.

Bian X.,Peking University | Bian X.,China National Institute of Biological Sciences
Brain Research | Year: 2013

GABAergic neurons in the medial amygdala (MeA) have been indicated in information processing in reproductive behavior and fear/anxiety. However, basic knowledge of their physiological and morphological properties is still very limited, probably due to the technical challenge to selectively record the GABAergic neurons. In this study, I characterized properties of the MeA GABAergic neurons by performing whole-cell patch clamp recordings from brain slices of adult knock-in mice selectively expressing green fluorescence protein (GFP) in GABAergic neurons. The majority (73%) of GABAergic neurons exhibiting low threshold calcium spike were classified as type I neurons, with morphological properties of being bitufted or stellate, and dendrites either aspiny or covered by various shapes of spines. Axonal collaterals of some neurons were observed near somata as well as in other amygdaloid nuclei. Neurons incapable of generate low threshold calcium spikes were divided into two types. Type II neurons (11%) exhibited hyperpolarization-activated sag and higher input resistance (>400 MΩ). Most Type II neurons exhibited asymmetric dendritic trees extending towards the superficial layer covered with long neck dendritic spines. The axons of type II neurons formed large collaterals and projected to other amygdaloid nuclei. Type III neurons (16%) lack prominent hyperpolarization-activated sag and possessed lower input resistance (<400 MΩ). These neurons were local interneurons with smooth multipolar dendritic trees. Since both MeA and nearby amygdaloid nuclei are involved in fear/anxiety processing, two types of MeA GABAergic projection neurons and a third type of interneurons that might participate in anxiety-related behavior were revealed by my present study. © 2013 Elsevier B.V. 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.

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.

Zhang F.,CAS National Astronomical Observatories | Lu Y.,CAS National Astronomical Observatories | Yu Q.,Peking University
Astrophysical Journal | Year: 2013

In this paper, we investigate the link between the hypervelocity stars (HVSs) discovered in the Galactic halo and the Galactic center (GC) S-stars, under the hypothesis that they are both the products of the tidal breakup of the same population of stellar binaries by the central massive black hole (MBH). By adopting several hypothetical models for binaries to be injected into the vicinity of the MBH and doing numerical simulations, we realize the tidal breakup processes of the binaries and their follow-up dynamical evolution. We find that many statistical properties of the detected HVSs and GC S-stars could be reproduced under some binary injecting models, and their number ratio can be reproduced if the stellar initial mass function is top-heavy (e.g., with slope ∼-1.6). The total number of the captured companions is ∼50 that have masses in the range ∼3-7 M⊙ and semimajor axes ≲ 4000 AU and survive to the present within their main-sequence lifetime. The innermost one is expected to have a semimajor axis ∼300-1500 AU and a pericenter distance ∼10-200 AU, with a significant probability of being closer to the MBH than S2. Future detection of such a close star would offer an important test to general relativity. The majority of the surviving ejected companions of the GC S-stars are expected to be located at Galactocentric distances ≲ 20 kpc, and have heliocentric radial velocities ∼-500-1500 km s-1 and proper motions up to ∼5-20 mas yr-1. Future detection of these HVSs may provide evidence for the tidal breakup formation mechanism of the GC S-stars. © 2013. The American Astronomical Society. All rights reserved.

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.

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.

Liew S.-L.,University of Southern California | Han S.,Peking University