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Zhou X.,Sichuan University | Wang F.,Sichuan University
Journal of Computational Chemistry | Year: 2017

Hydrogen-transfer reactions are an important class of reactions in many chemical and biological processes. Barrier heights of H-transfer reactions are underestimated significantly by popular exchange–correlation functional with density functional theory (DFT), while coupled-cluster (CC) method is quite expensive and can be applied only to rather small systems. Quantum Monte-Carlo method can usually provide reliable results for large systems. Performance of fixed-node diffusion quantum Monte-Carlo method (FN-DMC) on barrier heights of the 19 H-transfer reactions in the HTBH38/08 database is investigated in this study with the trial wavefunctions of the single-Slater–Jastrow form and orbitals from DFT using local density approximation. Our results show that barrier heights of these reactions can be calculated rather accurately using FN-DMC and the mean absolute error is 1.0 kcal/mol in all-electron calculations. Introduction of pseudopotentials (PP) in FN-DMC calculations improves efficiency pronouncedly. According to our results, error of the employed PPs is smaller than that of the present CCSD(T) and FN-DMC calculations. FN-DMC using PPs can thus be applied to investigate H-transfer reactions involving larger molecules reliably. In addition, bond dissociation energies of the involved molecules using FN-DMC are in excellent agreement with reference values and they are even better than results of the employed CCSD(T) calculations using the aug-cc-pVQZ basis set. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Wu X.,Sichuan University | Li B.,Sichuan University | Wen X.,Sichuan University
Journal of Nanoparticle Research | Year: 2017

In this study, Fe3O4 microspheres were prepared by a hydrothermal method, and then the synthesized Fe3O4 microspheres were used as template to prepare Fe3O4@MgAl-LDH composite microspheres by a coprecipitation process. Morphology, composition, and crystal structure of synthesized nanomaterials were characterized by X-ray powder diffractometry, scanning electron microscopy, and Fourier transform infrared spectroscopy technologies. The composite hierarchical microspheres are composed of inner Fe3O4 core and outer MgAl-LDH-nanoflake layer, and the average thickness of MgAl-LDH-nanoflake is about 70 nm. The adsorption property of the products toward congo red was also measured using UV–vis spectrometer. The result demonstrated that the Fe3O4@MgAl-LDH composite adsorbent could remove 99.8% congo red in 30 min, and the maximum adsorption capacity is about 404.6 mg/g, while congo red removal rate of pure MgAl-LDH and Fe3O4 are only 86.3 and 53.1% in 40 min, respectively, and their adsorption capacity are 345.72 and 220.56 mg/g, respectively. It indicates the composite Fe3O4@ MgAl-LDH nanomaterials have better adsorption performance than pure Fe3O4 and MgAl-LDH nanomaterials. In addition, the magnetic nanocomposites could be separated easily, and it demonstrated good cycle performance. © 2017, Springer Science+Business Media Dordrecht.

Hu Y.,Sichuan University | Li L.,Sichuan University | Zhang L.,Sichuan University | Lv Y.,Sichuan University
Sensors and Actuators, B: Chemical | Year: 2017

A novel and facile dielectric barrier discharge (DBD) plasma-based strategy for fast fabrication of g-C3N4-Mn3O4 composite is developed. The obtained g-C3N4-Mn3O4 can be used as a superior cataluminescence (CTL) catalyst for H2S gas sensing, with excellent selectivity, high sensitivity, rapid and stable response. Sub-ppm level H2S is able to be detected based on the proposed sensor, providing a splendid alternative for monitoring H2S in various fields. SEM, TEM, XPS, XRD, N2 adsorption–desorption measurement were employed to characterize the as-synthesized sensing material. The composite possesses smaller particle size and enlarged specific surface area, which might be attributed to the oxidizing non-equilibrium plasma etching. Besides, using Mn2+-impregnated g-C3N4 as the only precursor and air as working gas, this synthesis is free of solvent, extra oxidant/reductant or high temperature, offering advantages such as simplicity in construction, convenient operation and fast speed, and it could be easily implemented on a large scale and extended to manufacturing diverse metal oxide-modified composites for different purposes. © 2016 Elsevier B.V.

Lian X.,Sichuan University | Lin L.,Sichuan University | Fu K.,Sichuan University | Ma B.,Sichuan University | And 2 more authors.
Chemical Science | Year: 2017

A highly efficient asymmetric Mannich-type reaction between α-tetralone-derived β-keto esters/amides and 1,3,5-triaryl-1,3,5-triazinanes was realized in the presence of chiral N,N′-dioxide-Ni(ii) or Mg(ii) complex. A variety of optically active β-amino compounds with all-carbon quaternary stereocenters were obtained in good yields with excellent enantioselectivities. A possible transition state was proposed based on these experiments and previous reports. © The Royal Society of Chemistry.

Disclosed herein is a copper(II)-mediated chelation-assisted intermolecular amination of inert C(sp3)[sbnd]H bonds using simple alkylamines as the amino source. A straightforward and step-economic alternative to α,α-disubstituted β-amino acid derivatives is provided consequently. This reaction features good functional group tolerance and relatively broad substrate scope. Furthermore, a coupling product between morpholine and radical inhibitor 2,6-di-tert-butyl-p-cresol (BHT) was isolated, indicating that a single electron transfer (SET) process might be involved in this transformation. © 2017 Elsevier Ltd

Li K.,Sichuan University | Guo Q.,Sichuan University | Guo J.,Sichuan University
International Journal of Computer Mathematics | Year: 2017

Bladder volume is an important and useful indicator to accurately diagnosis urinary diseases. Using the mechanical probe with single vibration source to estimate bladder volume is low-priced and portable. It also contains fast computation speed and low requirements to operators. However, the bladder volume estimated by this kind of probe will be influenced by improper scanning positions. To address this problem, we propose two localization approaches. One is based on geometry method, which has fast computation speed and high accuracy. The other one is based on neural network method, which contains high robustness and stable experiment results. After applying these two approaches to the standard phantom environment and human environment, we get a conclusion that the proposed approaches can effectively decrease the bladder volume estimation error caused by improper scanning positions. © 2016 Informa UK Limited, trading as Taylor & Francis Group.

Wu S.-L.,Sichuan University | Wu G.-C.,Neijiang Normal University
Fundamenta Informaticae | Year: 2017

In this paper, we analyze the convergence properties of the Schwarz waveform relaxation (SWR) algorithm with Robin transmission conditions (TCs) for a class of heat equations with Riemann-Liouville fractional derivative. The Robin TCs contain a free parameter, which has a significant effect on the convergence rate of the SWR algorithm, and optimizing this parameter is an important step for the convergence analysis of the SWR algorithm. By studying the monotonic properties of the convergence factor obtained by applying the Fourier transform to the error functions, we provide a realiable choice of the Robin parameter in the nonoverlapping case. Numerical results are provided, which show that the analyzed Robin parameter results in satisfactory convergence rate.

Deng D.,Sichuan University | Xu P.,Insurance Technology
International Journal of Simulation: Systems, Science and Technology | Year: 2016

We study intersected hierarchical models and their improved edition of data transmission in wireless sensor networks. We determine the problems with data positioning selection in data transmission mechanism of intersected hierarchies. We propose a data collection network structure of wireless sensor based on delayed perception. We improve data frame structures based on mini-slot to reduce the probability of data transmission conflict and thus realize synchronous reduction in network throughput and energy consumption. For multi-hop network, the selection of positioning function and mathematical derivation process are given. The delay and energy consumption calculation model for WSN data collection is established, the Top-Down technology is used to design formation algorithm of network structure to optimize energy consumption level of data collection mechanism by minimizing the communication distance. The experimental result shows: compared with network structure of existing WSN data collection, the network structure proposed can efficiently reduce delay in WSN data collection process, and maintain energy consumption in the whole communication at a relatively lower level. Due to limitations of experimental conditions, there is potential for further improvement to get better experimental results. © 2017, UK Simulation Society. All rights reserved.

Lin L.,Sichuan University | Feng X.,Sichuan University
Chemistry - A European Journal | Year: 2017

Chiral molecules with multiple stereocenters are widely distributed in nature and drugs. Asymmeric catalysis has allowed the formation of a chiral molecule's enantiomers with equal ease by applying the enantiomeric pair of a chiral catalyst. However, the diastereodivergent synthesis is a great challenge because the formation of one of the diastereomers is inherently preferred in most reactions. Under the efforts of chemists, elegant strategies have been developed to full control of absolute and relative stereochemical configurations. In this Minireview, we highlight the significant advances achieved in this field, and present the diastereo-control mechanism in the appropriate place on the expectation that new diastereodivergent strategies can be inspired and more types of enantioselective diastereodivergent reactions can be realized. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yang N.,Sichuan University | He L.,Shenzhen University | Li Z.,Sichuan University | Yu P.S.,University of Illinois at Chicago
Data Mining and Knowledge Discovery | Year: 2017

In real world, a heterogeneous information network (HIN) is often dynamic due to the time varying features of the nodes, and uncertain due to missing values and noise. In this paper, we investigate the problem of reducing the uncertainty of a dynamic HIN, which is an important task for HIN analysis. The challenges are three-fold, the heterogeneity of features, the heterogeneity of constraints, and the dynamic uncertainty. We propose a novel approach, called fusing reconstruction (FRec), which reconstructs the uncertain snapshots of a dynamic HIN in a homogeneous feature space combining two fusions, the fusion of heterogeneous features and the fusion of heterogeneous constraints. To address the challenge of the heterogeneity of features, we propose an invertible fusing transformation (IFT) as the first part of FRec. IFT is a bidirectional transformation, which is able to learn unified latent homogeneous feature representations for heterogeneous nodes and transform them back to the raw heterogeneous feature space by its invertibility. To address the challenge of the heterogeneity of constraints and the challenge of dynamic uncertainty, we propose a heterogeneous constraints fusion based tensor reconstruction model (HCF-TRM) as the second part of FRec. HCF-TRM is able to denoise the uncertain snapshots of a dynamic HIN and recovers the missing values by fusing the spatial smoothness constraint and the temporal smoothness constraint into the tensor reconstruction. At last, the extensive experiments conducted on real datasets and synthetic datasets verify the effectiveness and scalability of FRec. © 2017 The Author(s)

Zhao Y.,Sichuan University | Li S.,Sichuan University | Zheng X.,Sichuan University | Tang J.,Sichuan University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2017

An unprecedented Rh-catalyzed ketone-directed vinylic C−H activation/[4+2] O-annulation of α-aryl enones with internal alkynes followed by a Cu-catalyzed ring contraction in air to provide multiaryl-substituted furan derivatives has been developed. The preliminary mechanism study identifies the active pyrylium salt as the key intermediate. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Wang H.,University of Sichuan | Huang J.,University of Sichuan | Li H.,Sichuan University
Advances in Intelligent Systems and Computing | Year: 2017

Government debt has an impact on economic growth, but there is a big difference when the local government’s fiscal expenditure is efficient or not. This paper tries to explicit the impact of local government debt risk on economic growth, in the case of the efficiency of fiscal expenditure. We assess the local government debt risk by the debt ratio and gain the fiscal expenditure efficiency with Data Envelopment Analysis (DEA). The empirical study shows that the relationship between the efficiency of fiscal expenditure and local government debt risk is significantly negative, and the risk of local government debt has a significantly negative impact on the economic growth, with the data of 28 provinces, municipalities and autonomous regions of China for the period 2011-2013. © Springer Science+Business Media Singapore 2017.

Chen J.,Science and Technology on Surface Physics and Chemistry Laboratory | Meng D.,Science and Technology on Surface Physics and Chemistry Laboratory | Du J.,Sichuan University
Molecular Physics | Year: 2017

First-principles method has been employed to investigate the stability and local reactivity of Au-Pd nanoparticles. AucorePdshell nanoclusters are generally more stable than PdcoreAushell counterparts for studied nanoparticles (55, 85, 147-atom). The stability of Au-Pd nanocluster is attributed to the strong charge transfers from Pd to Au atoms. The d-band centre and Fukui function values indicate that the low-coordination atoms possess the higher reactivity relative to other atoms. The two descriptors are generally in good agreement. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Cao L.,Chinese Academy of Sciences | Fang G.,Chinese Academy of Sciences | Wang Y.,Sichuan University
Langmuir | Year: 2017

A majority of the reported electrografting of aryldiazonium salts result in the formation of covalently attached films with a limited surface coverage of below 5 nmol·cm-2. Herein, we report the preparation of higher-thickness redox-active viologen-grafted electrodes from the electroreduction of viologen phenyl diazonium salts, by either cyclic voltammetric (CV) sweeps or electrolysis using a fixed potential. Both of the methodologies were successfully applied for various conductive surfaces, including glassy carbon (GC), gold disc, indium tin oxide glass, mesoporous TiO2 electrodes, and 3D compacted carbon fibers. A robust maximal viologen coverage, Γviologen = 9.5 nmol·cm-2, was achieved on a GC electrode by CV electroreduction. Electroreduction held at a fixed potential at Eappl. = -0.3 V can fabricate viologen-grafted electrodes with Γviologen in the range of 0-37 nmol·cm-2 in a controllable way, by simply adjusting the electrodeposition time tappl.. Time-dependent Γviologen were found to be 10 nmol·cm-2@2 min, 20 nmol·cm-2@4.2 min, and 30 nmol·cm-2@7 min. Furthermore, a TiO2 electrode coupled with Γviologen of 140 nmol·cm-2 exhibited electrochromic performance, with the color changing from pale yellow to blue and red brown. (Graph Presented). © 2017 American Chemical Society.

Zhou Y.,Sichuan University | Deng H.,Sichuan University | Fu Q.,Sichuan University
Composites Part A: Applied Science and Manufacturing | Year: 2017

The morphology of conductive network and their interfacial interaction with polymer matrix is thought as the key influential issues for the pressure/strain sensing behavior of conductive polymer composites (CPCs). The surface characteristics and size of these secondary insulating fillers should significantly influence the pressure/strain sensing behavior due to its influence on the morphology of conductive network and interfacial interaction between filler and polymer matrix. Herein, insulating SiO2 with different size and surface characteristics are incorporated into carbon black (CB)/silicon rubber (SR) composites to modify its piezo-resistive behavior. The conductivity of CB/SiO2/SR composites with nanoscale and hydrophobic SiO2 changes by several orders of magnitude, with more linear proportional to applied pressure and better stability under long term cyclic pressure due to better dispersion and stronger interfacial interaction. Through such simple method, high-performance piezo-resistive sensors could be fabricated with reversible piezo-resistivity, large pressure application (pressure below 2500 kPa) and tunable piezo-resistive sensitivity. © 2017 Elsevier Ltd

Wang C.,Jiangsu University | Wang C.,Sichuan University | Wang Q.,Jiangsu University | Chen D.,Jiangsu University
Analytical and Bioanalytical Chemistry | Year: 2017

In this paper, a resonance light scattering (RLS) method was developed for detecting kanamycin with high sensitivity and selectivity. Here, aptamer specific to kanamycin was utilized for recognizing and competitively binding with kanamycin, and gold nanoparticles (GNPs) were used as probes. After adding kanamycin into solutions containing aptamer and GNPs, the GNPs would aggregate in the presence of NaCl, which resulted in the RLS signal intensities enhanced dramatically. Based on this phenomenon, kanamycin can be detected in the range of 10 to 600 nM with a limit of detection as 1 nM, which is more sensitive than many other instrumental methods, especially the commonly used UV-visible spectroscopic method. Furthermore, we demonstrated that this method can be used for detecting kanamycin in milk samples with satisfactory results, which is meaningful for solving food safety problems. © 2017 Springer-Verlag Berlin Heidelberg

Hou H.,Central South University | Qiu X.,Central South University | Wei W.,Central South University | Zhang Y.,Sichuan University | Ji X.,Central South University
Advanced Energy Materials | Year: 2017

The ever-increasing demand of lithium-ion batteries (LIBs) caused by the rapid development of various electronics and electric vehicles will be hindered by the limited lithium resource. Thus sodium-ion batteries (SIBs) have been considered as a promising potential alternative for LIBs owing to the abundant sodium resource and similar electrochemical performances. In recent years, significant achievements regarding anode materials which restricted the development of SIBs in the past decades have been attained. Significantly, the sodium storage feasibility of carbon materials with abundant resource, low cost, nontoxicity and high safety has been confirmed, and extensive investigation have demonstrated that the carbonaceous materials can become promising electrode candidates for SIBs. In this review, the recent progress of the sodium storage performances of carbonaceous materials, including graphite, amorphous carbon, heteroatom-doped carbon, and biomass derived carbon, are presented and the related sodium storage mechanism is also summarized. Additionally, the critical issues, challenges and perspectives are provided to further understand the carbonaceous anode materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wu Y.,University of Sichuan | Ding W.,Sichuan University | He Q.,University of Sichuan
International Journal of Food Properties | Year: 2017

Tara gum (Mw = 1519 × 103 g/mol) was degraded by hydrogen peroxide in the presence/absence of ascorbic acid, and properties of the products were investigated using gel permeation chromatography, Fourier transform infrared spectroscopy, atomic force microscope, and rheometer methods. Results showed that molecular weight of tara gum decreased with increasing concentration of hydrogen peroxide. The addition of ascorbic acid could sharply increase the degradation rate and degree of tara gum by hydrogen peroxide, which is also confirmed by atomic force microscope. The degradation products kept the structure characteristics of galactomannan. However, they performed different rheological properties. At 1% (w/v) of concentration, DP1 (941 × 103 g/mol) and DP2 (335 × 103 g/mol) prepared by H2O2 exhibited non-Newtonian behavior, while DP3 (35.1 × 103 g/mol) and DP4 (14.2 × 103 g/mol) obtained by hydrogen peroxide plus ascorbic acid displayed Newtonian property. These results may promote the application of tara gum in diverse fields. © 2017 Taylor & Francis Group, LLC

Cao L.,Chinese Academy of Sciences | Wang Y.,Sichuan University
Journal of Photochemistry and Photobiology A: Chemistry | Year: 2017

Hydroxyl radicals ([rad]OH), together with carbon-centered radicals ([rad]R), derived from photoinduced electron transfer (PET) interactions between viologen and carboxylic acid ion pairs ([bipy++⋯RCOOH]), were developed to photoinitiate the polymerization of various acrylate monomers in the presence of oxygen. The mechanism of the radicals’ formation was established using nanosecond laser flash photolysis and electron spin resonance methods. Carboxylate anion (electron donnor, D) gave one electron to viologen (electron acceptor, A) via either intermolecule (D/A) or intramolecular (D-A) PET, to yield carboxylate radicals (RCOO[rad]) that later underwent decarboxylation, yielding [rad]R radicals which can initiate the photopolymerization of many acrylate monomers. Simultaneously, reduced viologen cation radical (bipy+[rad]) was oxidized by dissolved O2 and returned back to bipy++ dications. [rad]OH radicals emerged from the reaction of H+ with the superoxide radicals (O2[rad]−) that formed during the oxidation of bipy+.. In this way, viologens were observed to act as photocatalysts in the radical generation process based on their strong electron acceptor, as well as efficient light absorption nature. Photopolymerization performance with D-A type viologens, for instance, bipy++−(CH2)nCOOH, extra carboxylic acid was not a requirement. © 2016 Elsevier B.V.

Jing H.,Sichuan University | Su X.,University of Sichuan | You Z.,Sichuan University
Optical Engineering | Year: 2017

A uniaxial three-dimensional shape measurement system with multioperation modes for different modulation algorithms is proposed. To provide a general measurement platform that satisfies the specific measurement requirements in different application scenarios, a measuring system with multioperation modes based on modulation measuring profilometry (MMP) is presented. Unlike the previous solutions, vertical scanning by focusing control of an electronic focus (EF) lens is implemented. The projection of a grating pattern is based on a digital micromirror device, which means fast phase-shifting with high precision. A field programmable gate array-based master control center board acts as the coordinator of the MMP system; it harmonizes the workflows, such as grating projection, focusing control of the EF lens, and fringe pattern capture. Fourier transform, phase-shifting technique, and temporary Fourier transform are used for modulation analysis in different operation modes. The proposed system features focusing control, speed, programmability, compactness, and availability. This paper details the principle of MMP for multioperation modes and the design of the proposed system. The performances of different operation modes are analyzed and compared, and a work piece with steep holes is measured to verify this multimode MMP system. © 2017 Society of Photo-Optical Instrumentation Engineers (SPIE).

Chen K.,Sichuan University | Du P.-A.,Sichuan University | Ren D.,Sichuan University
Tien Tzu Hsueh Pao/Acta Electronica Sinica | Year: 2017

An efficient and accurate technique based on the impedance theory of cavity-backed slot antenna is introduced to calculate the resonant frequencies of a rectangular enclosure with a slot on its wall. Expressing electromagnetic fields in terms of cavity Green's function inside the enclosure and the free space Green's function outside the enclosure, an integral equation for equivalent magnetic current is obtained by enforcing the boundary condition across the slot. The Method of Moments is used to solve the integral equation for the input impedance. We can get resonant frequencies from the zero reactance or the minimum resistance on the frequency-impedance curves. Our method is verified successfully by experimental results and CST. The effects of the cavity size, of the slot length, and of the slot offset on the resonant frequency are discussed. © 2017, Chinese Institute of Electronics. All right reserved.

Mei Y.,Mianyang Teachers College | Liu H.-G.,Sichuan University | Zheng W.-C.,Sichuan University
Polyhedron | Year: 2017

The spin-Hamiltonian parameters (g factors gi and hyperfine structure constants Ai 161, Ai 163, where i = || or ⊥) for 161Dy3+ and 163Dy3+ isotopes in the Y3+ site of tetragonal Rb2NaYF6 crystals are calculated by the diagonalization of energy matrix plus perturbation formulas. The calculated results are reasonably coincident with the experimental values. The calculations suggest that the constants Ai 161 and Ai 163 are negative and positive, respectively and the (DyF6)3− octahedral clusters are, similar to (YbF6)3− and (CeF6)3− clusters in Rb2NaYF6, tetragonally-elongated. The results (containing the reasonableness of tetragonal distortion of (DyF6)3− cluster and the causes of the relatively larger disparities between the calculated and observed Ai 163) are discussed. © 2017 Elsevier Ltd

He Y.,Sichuan University | Wang Y.-X.,Sichuan University | Guo H.,Nanjing Southeast University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2017

We present a fully gauge-invariant linear response theory for ultra-cold Fermi gases undergoing BCS-Bose-Einstein Condensation (BEC) crossover with pair fluctuation effects included, especially in the superfluid phase. The gauge invariance is verified by introducing an effective external electromagnetic (EM) field. For pure BCS-type superfluids, the gauge invariance of the linear response theory can be maintained by constructing a full external EM vertex. By consistently including fluctuations of the order parameters as the self-energy effect is included in the quasi-particles, the Ward identity (WI) is satisfied as a consequence of gauge invariance. The construction of a gauge invariant vertex is non-trivial since in the broken symmetry phase the Nambu-Goldstone mode intertwines with the pairing fluctuation. We find that, under a suitable diagrammatic representation, the construction of such a vertex can be greatly simplified and allows us to build a vertex with pseudogap effects and consistent with the WI in the superfluid phase. We focus on a particular approach known as the G0G t-matrix of pairing fluctuations, but our formalism also works for the G0G0 t-matrix theory as well. © 2017 Elsevier B.V.

This paper discusses a novel conceptual formulation of the fractional-order Euler-Lagrange equation for the fractional-order variational method, which is based on the fractional-order extremum method. In particular, the reverse incremental optimal search of the fractional-order variational method is based on the fractional-order steepest descent approach. Fractional calculus has been applied to the solution of a necessary condition for the fractional-order fixed boundary optimization problems in signal processing and image processing mainly because of its inherent strengths in terms of long-term memory, non-locality, and weak singularity. At first, for the convenience of comparison, the first-order Euler-Lagrange equation for the first-order variational method is derived based on the first-order Green formula. Second, the fractional-order Euler-Lagrange equation for the fractional-order variational method is derived based on Wiener-Khintchine theorem. Third, in order to directly and easily achieve the fractional-order variational method in the spatial domain or the time domain, the fractional-order Green formula and the fractional-order Euler-Lagrange equation based on the fractional-order Green formula are derived, respectively. Fourth, the solution procedure of the fractional-order Euler-Lagrange equation is derived. Finally, a fractional-order inpainting algorithm and a fractional-order denoising algorithm based on the fractional-order variational method are illustrated, respectively. The capability of restoring and maintaining the edges and textural details of the fractional-order image restoration algorithm based on the fractional-order variational method is superior to that of the integer-order image restoration algorithm based on the classical first-order variational method, especially for images rich in textural details. The fractional-order Euler-Lagrange equation for the fractional-order variational method proposed by this paper is a necessary condition for the fractional-order fixed boundary optimization problems, which is a basic mathematical method in the fractional-order optimization and can be widely applied to the fractional-order field of signal analysis, signal processing, image processing, machine intelligence, automatic control, biomedical engineering, intelligent transportation, computational finance and so on. © 2017 IEEE.

Li J.,Sichuan University | Liu Q.,Sichuan University | Ji Q.Q.,Sichuan University | Lai B.,Sichuan University
Applied Catalysis B: Environmental | Year: 2017

To develop a technology for the degradation of the toxic and refractory pollutants, the Fe0-PM-PS system and 6 control experiments were setup in this study. First, effects of Fe0 dosage (0–18.3 g/L), PM dosage (0–25.0 mmol/L), PS dosage (0–30.0 mmol/L), initial pH value (3.0-11.0), air flow rate (0–2.0 L/min), and feeding times of PM and PS (1–5) on the degradation of PNP in aqueous solution by the Fe0-PM-PS system were studied through the single-factor experiment. Furthermore, the optimized experimental conditions (i.e., Fe0 dosage of 11.9 g/L, PM dosage of 15.0 mmol/L, PS dosage of 18.1 mmol/L and feeding times of oxidants of 4) were obtained through response surface methodology (RSM). The result shows that the maximum COD removal efficiency (89.0%) was obtained by the Fe0-PM-PS system under the optimal conditions, which was mainly attributed to the strong synergistic effect among Fe0, PM and PS. In addition, PNP degradation pathway was proposed according to the intermediates detected by HPLC. According to the analysis results of SEM-EDS, XRD and XPS, the reaction mechanism of the Fe0-PM-PS system has been clarified thoroughly. In short, these results suggest that the Fe0-PM-PS system should be proposed as an effective pretreatment process for the toxic and refractory PNP wastewater. © 2016 Elsevier B.V.

Chen Z.,Sichuan University | Lin T.,Sichuan University
Behaviour and Information Technology | Year: 2017

The ability of automatically identifying users’ personality is an important part of building adaptive systems and providing personalised services. However, there is still a lack of evaluation methods which can not only unobtrusively gather user data without supplement equipment, but also provide accurate and real-time prediction of users’ personality. This paper presents a new approach to identifying personality by combining writing features and machine learning techniques. We conducted an exploratory study where we collected participants’ handwriting information and personality information via questionnaire. From these data, we extracted writing features and created classifiers for seven personality dimensions. Our top results include a unique set of writing features which could be predictive of personality and binary classifiers for the seven personality dimensions, with accuracies ranging from 62.5% to 83.9%. These results show that writing features are useful for personality identification when suitable classifiers are adopted. © 2017 Informa UK Limited, trading as Taylor & Francis Group

Cao L.,Chinese Academy of Sciences | Wang Y.,Sichuan University
Journal of Applied Polymer Science | Year: 2017

Azido-grafted cellulose has been reported widely applied for further functionalization by click chemistry. As an alternative method, we proposed alkyne-grafted cellulose as a prototype molecule for Huisgen [3 + 2] cycloaddition with azido-terminated target compounds. Alkyne cellulose was synthesized by acylation with prop-2-ynyl 5-chloro-5-oxopentanoate and, subsequently cycloaddition with 4-aminophenylazide, ethyl 2-azidoacetate, and (S)-2-(Azidomethyl)-1-(tert-butoxycarbonyl)pyrrolidine (Boc-pyrrolidine azide) to form triazole cellulose in a click manner. The reactions were confirmed qualitatively by Fourier transform infrared and NMR spectroscopy and analyzed quantitatively with elemental analysis data. The results show that a degree of substitution of up to 1.91 was obtained for esterification and, in most cases, was preferred completely in a selective way for the primary hydroxyl groups at the O-6 position and partially at the O-2 and O-3 positions. Cycloaddition conversions were found as high as 0.95, 0.99, and 0.99 for aniline–triazole cellulose, acetate–triazole cellulose, and Boc-pyrrolidine-triazole cellulose, respectively. Both esterification and cycloaddition were undertaken under mild conditions without additional heating. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44410. © 2016 Wiley Periodicals, Inc.

Chang Q.,Sichuan University | Hou L.,Sichuan University
Jordan Journal of Mechanical and Industrial Engineering | Year: 2016

For the main purpose of studying the tooth surface equation and undercutting conditions of the cylindrical gears with curvilinear shaped teeth processed by parallel translating mechanism, the tooth surface equation and meshing condition of the cylindrical gears with curvilinear shaped teeth processed by parallel translating mechanism were deduced by the method of differential geometry and coordinate transformation, based on considering cutting tool shape and installation position error. The undercutting line of the cylindrical gears with curvilinear shaped teeth processed by parallel translating mechanism was also calculated. The manufacturing process of the parallel translating mechanism was simulated in three-dimensional software and then the three dimensional solid model of cylindrical gears with curvilinear shaped teeth was obtained. The studies referred to in the present paper have a certain reference value for research, development and design of the cylindrical gears with curvilinear shaped teeth processed by parallel translating mechanism. © 2016 Jordan Journal of Mechanical and Industrial Engineering.

Li H.,Tsinghua University | Cheng P.,Chengdu University of Technology | Jiang L.,Tsinghua University | Yang J.-L.,Chengdu University of Technology | Zu L.,Sichuan University
Angewandte Chemie - International Edition | Year: 2017

Inspired by the biogenetic origin of goniomitine, new synthetic bio-inspired fragmentation strategies for the synthesis of functionalized 2-quinolinones and indolones have been developed. Remarkable synthetic efficiency was achieved by telescoping several transformations into one-pot reactions, allowing for the direct coupling of 2-alkynyl-anilines and diazo ketones. The synthetic utility was demonstrated by the 5-step asymmetric total synthesis of (-)-goniomitine from 2-ethyl-cyclopentanone. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Qin Y.,Chongqing University | Qin Y.,Sichuan University | Mao Y.,Chongqing University | Tang B.,Chongqing University
Mechanical Systems and Signal Processing | Year: 2017

There are various signal decomposition methods, but none of them is satisfactory and all have their own drawbacks. It is worth exploring a new signal decomposition approach with better performance for processing the complex vibration signals. By employing the wavelet modulus maxima and synchronous detection, a novel multicomponent signal decomposition method is proposed in this paper. Firstly, the wavelet modulus maxima of a multicomponent signal are calculated by optimized complex wavelet transform, then the highest instantaneous frequency (IF) is extracted by searching the wavelet modulus maxima with the smallest scales at all the time instants. With the obtained IF, the synchronous detection method is used to calculate the phase offset and the instantaneous amplitude. It follows that the corresponding component with highest IF can be reconstructed. Then the used wavelet modulus maxima in this iteration are removed from the wavelet scalogram and the next IF is sequentially computed. By repeating this process, all components are successively separated from high frequency to low frequency. Compared with ensemble empirical mode decomposition and Hilbert vibration decomposition, it has been proved by three typical multicomponent signals with different noise intensity that the proposed signal decomposition method has higher accuracy, frequency resolution and is more robust to noises. Moreover, the application results further show that the proposed method can be more effectively applied to fault diagnosis of gearboxes, especially when the operating condition is varying or the fault feature is weak. © 2017 Elsevier Ltd

Wang S.,Sichuan University | Chen S.-Y.,Sichuan University | Yu X.-Q.,Sichuan University
Chemical Communications | Year: 2017

Significant progress has been accomplished in directed C-H functionalization through the use of earth-abundant and inexpensive first-row transition metals. Among these base metals, Co is especially attractive in view of its versatile applications in C-H functionalization, in both low- and high-valent states. In this vein, catalytic Co(iii) species can be generated from the dissociation of a Cp*Co(iii) catalyst or through the oxidation of a low-valent cobalt catalyst in the presence of an oxidant. In this feature article, we will discuss the breakthroughs in Cp*Co(iii)-promoted C-H functionalization. In this field, C(sp2)-H functionalization has been extensively studied and developed. In contrast, few C(sp3)-H functionalization reactions have been reported. © The Royal Society of Chemistry.

Zhu G.,Sichuan University | Liu B.,Sichuan University | Liu B.,China Pharmaceutical University
Tetrahedron | Year: 2017

Derivatives of podocarpane-type diterpenoids, including cassane-type, abietane-type and totarane-type diterpenoids, are either widely distributed natural products or common intermediates in synthetic and medicinal chemistry. Although unmasked ortho-benzoquinone has been used in [4+2] cycloadditions in sparse cases due to its multiple reactivity as diene, dienophile, heterodiene and heterodienophile, applications of this motif in cycloadditions of complex molecules are very rare. We report herein that this [4+2] process can be successfully extended to various polycyclic substrates, followed by a photo-decarbonylation, to generate versatile derivatives of podocarpane-type diterpenoids. Racemic synthesis of isolophanthins A & B and abietatrien-3. β-ol was accomplished on the basis of this methodology. © 2017 Elsevier Ltd.

Chen J.,Sichuan University | Mao H.,Sichuan University | Sang Y.,Sichuan University | Yi Z.,Sichuan University
Knowledge-Based Systems | Year: 2017

In this paper, we propose a low-rank representation with symmetric constraint (LRRSC) method for robust subspace clustering. Given a collection of data points approximately drawn from multiple subspaces, the proposed technique can simultaneously recover the dimension and members of each subspace. LRRSC extends the original low-rank representation algorithm by integrating a symmetric constraint into the low-rankness property of high-dimensional data representation. The symmetric low-rank representation, which preserves the subspace structures of high-dimensional data, guarantees weight consistency for each pair of data points so that highly correlated data points of subspaces are represented together. Moreover, it can be efficiently calculated by solving a convex optimization problem. We provide a proof for minimizing the nuclear-norm regularized least square problem with a symmetric constraint. The affinity matrix for spectral clustering can be obtained by further exploiting the angular information of the principal directions of the symmetric low-rank representation. This is a critical step towards evaluating the memberships between data points. Besides, we also develop eLRRSC algorithm to improve the scalability of the original LRRSC by considering its closed form solution. Experimental results on benchmark databases demonstrate the effectiveness and robustness of LRRSC and its variant compared with several state-of-the-art subspace clustering algorithms. © 2017.

Gao J.,University of Sichuan | Liu X.,University of Sichuan | He K.,Sichuan University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2017

To improve the performance of the active contour segmentation on real images, a new segmentation method is proposed. In this model, we construct a function about Gaussian variance according to sub-regions intensity. Further, to avoid the curve vanishing, we design the convergence condition based on the confidence level of segmentation sub-regions. Experimental results show that the proposed method is less sensitive to noise and can suppress inhomogeneous intensity regions efficiently. © 2017 SPIE.

Yin B.,Hunan Normal University | Xiong Y.,Sichuan University
Advances in Intelligent Systems and Computing | Year: 2017

Product design process is the information interation process with knowledge-driven. According to the characteristics of design process, a process-oriented design knowledge classify strategy based on cognitive theory, information technology and design theory was established. The three-layer knowledge model was put forward based on knowledge property, knowledge extraction and application with semantic ontology search was discussion, then the immigration, association, synthesis, reasoning of knowledge were realized. Finally, an instance of refrigerator was used to verify the feasibility. © Springer International Publishing Switzerland 2017.

Wang K.,Sichuan University | Bichot C.-E.,French National Center for Scientific Research | Li Y.,Sichuan University | Li B.,Southwest Jiaotong University
Pattern Recognition | Year: 2017

Building discriminative and robust texture representation to deal with the changes of texture appearance is a fundamental issue in texture classification. The Local Binary Pattern (LBP) and its variants gain a lot of attention during the past decade and achieve great success in texture description. However, the current existing LBP-based features which treat LBP as local differential or orientation gradient operator, exploited local orientation pattern or anisotropic structure information separately. In this paper, we investigate the theoretical scheme of local differential approximation on the polar coordinate system in order to build a new LBP-based descriptor which better takes into account both radial plus tangential components and derivative information. First, we present an operator called circumferential derivative (CD) based on the tangential information with different order of derivatives. Then, we present an operator called radial derivative (RD) based on the radial information with different order of derivatives. Both extract complementary information locally around a central pixel. A new descriptor, the local binary circumferential and radial derivative pattern (CRDP) is constructed to fuse both local circumferential and radial derivative features based on different orders as well as a global feature based on global difference (GD) of central pixel's intensity. Extensive experiments on Outex, CUReT, KTH-TIPS and KTH-TIPS2-a texture datasets indicate that the proposed CRDP descriptor is discriminative and robust. The results obtained by the proposed CRDP descriptor outperforms more than twenty recent LBP-based state-of-the-art methods, including the best reported results in the literature for aforementioned texture datasets to the best of our knowledge. © 2017 Elsevier Ltd

Li W.-Q.,Sichuan University | Li Y.,Sichuan University | Chen J.,University of Southampton | Hou C.-Y.,Sichuan University
Information Systems | Year: 2017

In order to effectively extract the hidden information from the patent texts and to further provide this information to support the product innovation design process, this paper proposed an automatic patent classification method based on the functional basis and Naive Bayes theory. The functions of products are regarded as the innovation attributes, and the function co-reference relations of the patents in different areas are established. Patent classification methods are proposed based on the functions of products and the general steps of the patent classification process are proposed. In addition, three training methods are studied in the experiments, including multi-classification fully supervised training, multiple dichotomous supervised training and semi-supervised training. Through comparing and analyzing the experimental results, a patent text classifier is developed. In summary, this paper provides a general idea and the relevant technologies on how to build a patent knowledge space by automatically extracting and expanding the patent texts. © 2017

Feng H.,Sichuan University | Wang H.-Y.,Sichuan University | Zhao H.-Y.,Sichuan University
Methods in Molecular Biology | Year: 2017

Directed evolution is a powerful strategy for gene mutagenesis, and has been used for protein engineering both in scientific research and in the biotechnology industry. The routine method for directed evolution was developed by Stemmer in 1994 (Stemmer, Proc Natl Acad Sci USA 91, 10747–10751, 1994; Stemmer, Nature 370, 389–391, 1994). Since then, various methods have been introduced, each of which has advantages and limitations depending upon the targeted genes and procedure. In this chapter, a novel alternative directed evolution method which combines mutagenesis PCR with dITP and fragmentation by endonuclease V is described. The kanamycin resistance gene is used as a reporter gene to verify the novel method for directed evolution. This method for directed evolution has been demonstrated to be Efficient, reproducible, and easy to manipulate in practice. © Springer Science+Business Media New York 2017.

OBJECTIVES:: Blockade of the renin–angiotensin II (Ang II) system by AT1 blockers (ARBs) and angiotensin-converting enzyme inhibitors retards the progression of chronic kidney disease (CKD) by reducing albuminuria/proteinuria. However, many patients with CKD suffer from residual albuminuria/proteinuria, which is an independent risk factor for CKD progression. The aim of the current study is to investigate the effect of pitavastatin, one of the adjunctive agents to ARBs, on the reduction of albuminuria/proteinuria and further renoprotection mediated by telmisartan in spontaneously hypertensive rats. METHODS AND RESULTS:: Forty-two-week-old spontaneously hypertensive rats were grouped randomly and received 8 weeks of treatments with vehicle, telmisartan, pitavastatin or a combination of telmisartan and pitavastatin. Both albuminuria and proteinuria were inhibited significantly in the telmisartan-treated group, but an obviously residual albuminuria was maintained. The combination treatment with telmisartan and pitavastatin displayed a more effective decrease in albuminuria and proteinuria, even to the normal level. Enhanced nephroprotection was also observed in this combination group, which was independent of the cholesterol-lowering effects. Further mechanistic studies revealed that the combination therapy greatly attenuated the expression of intrarenal Ang II and AT1, thereby decreasing the activation of TGF-β-Smad and NF-κB and inhibiting fibrosis and inflammation. CONCLUSION:: Adjunctive therapy with pitavastatin dramatically reduced residual albuminuria/proteinuria and enhanced nephroprotection, likely by downregulating the expression of intrarenal Ang II and AT1. It could be concluded that statins might be a promising adjunctive therapeutic agent to conventional ARB treatment in hypertensive renal damage. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.

BACKGROUND: The top-cited systematic reviews/meta-analyses in tuberculosis research have not been identified. The objective of this study was to identify the 100 top-cited systematic reviews/meta-analyses in tuberculosis research, and to understand factors resulting in highly cited works, and establish trends in systematic reviews/meta-analyses in tuberculosis research.METHODS: The Web of Science Core Collection was searched for systematic reviews/meta-analyses on tuberculosis up to January 31, 2016. Articles were ranked by citation count and screened by 2 authors. The following information was collected and analyzed from each included study: citation of Web of Science Core Collection, author, country, year, journal, institution, page number, and reference number.RESULTS: The 100 top-cited studies were cited from 54 to 662 times and were published between 1997 and 2014. Ten authors have more than 1 study as the first author and 10 authors have more than 1 study as corresponding author. The country with the most top-cited studies was USA (n = 26). The institutions with the largest number of the studies were McGill University in Canada (n = 18). The studies were published in 32 journals, whereas 12 were published in PloS Medicine, followed by Lancet Infectious Diseases (n = 11).CONCLUSIONS: Developed countries and high-impact journals may publish more top-cited systematic review/meta-analysis in tuberculosis research.

Liu L.-X.,West China Hospital | Song M.-Y.,Sichuan University | Xie X.-D.,West China Hospital
Medicine (United States) | Year: 2017

In-stent stenosis after treated by Willis covered stent-case reports. Background: Advancements in minimally invasive technology have allowed endovascular reconstruction of internal carotid aneurysm. However, in-stent stenosis is an important and well-characterized complication of stenting after the treatment of internal carotid aneurysm. Case description: We would present 2 patients who were diagnosed with in-stent stenosis after the treatment of Willis covered stent. Case 1: A 57-year-old female with 2-week history of headache and vomiting before admission, whose digital subtraction angiography (DSA) demonstrated left internal carotid C6 aneurysm and showed about 20% stenosis 3 months later since operation in the position where Willis covered stent was deployed. Case 2: A 23-year-old male with skull base fracture, subarachnoid hemorrhage, right femoral fracture for 14 days and epistaxis for 9hours caused by a car accident, whose DSA demonstrated left internal carotid paracliniod pseudoaneurysm. One year later, the patient went to our center again because he had headache and dizziness for 6 months after the interventional operation. His DSA demonstrated about 80% stenosis in the position where Willis covered stent was deployed. The clinical and radiologic characteristics and the experience in dealing with the stenosis are presented. Conclusions: In-stent stenosis after treated with Willis covered is uncommon, but not rare. Operators should pay more attention to the in-stent stenosis during the period of follow-up observation and monitor P2Y12 Reaction Unit (PRU) in the antiplatelet period, especially for the Willis covered stent. What is more, the treatment for stenosis ought to be carefully considered. © 2017 the Author(s).

Guo H.,Nanjing Southeast University | Cai W.,Nanjing Southeast University | He Y.,Sichuan University | Chien C.-C.,University of California at Merced
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2017

The shear viscosity has been shown to be equal to the product of the pressure and relaxation time in normal scale-invariant fluids, but the presence of superfluidity at low temperatures can alter the relation. Using the mean-field BCS-Leggett theory with a gauge-invariant linear response theory for unitary Fermi superfluids, we present an explicit relation between thermodynamic quantities, including the pressure and chemical potential, and transport coefficients, including the shear viscosity, superfluid density, and anomalous shear viscosity from momentum transfer via Cooper pairs. The relation is modified when pairing fluctuations associated with noncondensed Cooper pairs are considered. Within a pairing fluctuation theory consistent with the BCS-Leggett ground state, we found an approximate relation for unitary Fermi superfluids. The exact mean-field relation and the approximate one with pairing fluctuations advance our understanding of relations between equilibrium and transport quantities in superfluids, and they help determine or constrain quantities which otherwise can be difficult to measure. © 2017 American Physical Society.

Jiang N.,University of Electronic Science and Technology of China | Xue C.,University of Electronic Science and Technology of China | Liu D.,Sichuan University | Lv Y.,University of Electronic Science and Technology of China | Qiu K.,University of Electronic Science and Technology of China
Optics Letters | Year: 2017

We propose and numerically demonstrate a secure key distribution scheme based on the dynamic chaos synchronization of two external cavity vertical-cavity surface-emitting lasers (VCSELs) subject to symmetric random-polarization injections. By exchanging the random parameters that control the polarization angles of the driving injection, Alice and Bob can identify the time slots in which high-quality private chaos synchronization is achieved and independently generate a shared key from the synchronized polarization difference signals of their local VCSELs. The results show that Gb/s key distribution with a low bit error ratio can be achieved, and the shared key can pass all NIST tests, which guarantee the randomness of the key. In the proposed scheme, the exchange messages do not contain any information about the key generation, which affords a high-level of security for key distribution. © 2017 Optical Society of America.

Chen D.,China West Normal University | qingyu G.,Sichuan University | Tao J.,Sichuan University
Nuclear Physics B | Year: 2017

We modify the first laws of thermodynamics of a Reissner–Nordstrom anti-de Sitter black hole and a pure de Sitter space–time by the surface tensions. The corresponding Smarr relations are obeyed. The cosmological constants are first treated as fixed constants, and then as variables associated to the pressures. For the black hole, the law is written as δE=TδS−σδA when the cosmological constant is fixed, where E is the Misner–Sharp mass and σ is the surface tension. Adopting the varied constant, we modify the law as δE0=TδS−σeffδA+VδP, where E0=M−Q22,r+ is the enthalpy. The thermodynamical properties are investigated. For the de Sitter space–time, the expressions of the modified laws are different from these of the black hole. The differential way to derive the law is discussed. © 2017 The Author(s)

News Article | April 23, 2017

China, the world’s rising superpower, is experiencing an explosion of faith. The decades of anti-religious campaigns that followed the 1949 communist takeover are giving way to a spiritual transformation—and among the fastest-growing drivers of that transformation are unregistered churches. Once called “house” or “underground” churches because they were small clandestine affairs, these groups have become surprisingly well-organized, meeting very openly and often counting hundreds of congregants. They’ve helped the number of Protestants soar from about 1 million when the communists took power to at least 60 million today. Of these believers, about two-thirds are not affiliated with government churches. In other words, Protestants in non-government churches outnumber worshippers in government churches two to one. This fascinated me, and I wondered how it happened. Why were these independent churches so effective in appealing to China’s burgeoning middle class? And how do they survive despite government efforts to rein in religious groups not part of government-run places of worship? To find out, I knew it would be important to report from the ground up. If you rely solely on newspaper headlines and human rights reports, you’ll only understand one aspect of a society: its problems. For instance, after reading the recent Freedom House report about intensifying religious persecution under Chinese President Xi Jinping, you may come away with the impression that in China the main story of religion is repression. But any casual visitor to the country can tell you that the number of churches, mosques, and temples has soared in recent years, and that many of them are full. While problems abound, the space for religious expression has grown rapidly, and Chinese believers eagerly grab it as they search for new ideas and values to underpin a society that long ago discarded traditional morality. That’s why I made the southwestern city of Chengdu my second home. Living there for weeks at a time, I followed the progress of Early Rain Reformed Church over the course of a year. This unregistered church has had numerous setbacks and always seems on the verge of being closed down. But it keeps bouncing back, thanks in part to one of the most inspiring preachers I’ve met in any country. When Wang Yi addressed his congregation, he looked like an explorer surveying new horizons. He would grasp his pulpit with both hands, leaning forward on the balls of his feet, his eyes squinting through thick glasses as if focusing on a speck in the distance. He had rosy cheeks and a winning smile, and when he spoke, it was in a strong and forceful voice, his words as clear as his arguments. He had been one of China’s most prominent civil rights lawyers before the government detained or drove most of those people out of their profession. By the time that happened early in the second decade of the 21st century, Wang Yi had already found a new calling. He had converted to Christianity in 2005 and founded Early Rain Reformed Church, quickly establishing himself as one of China’s best-known preachers. His church was independent of government control, but that made it all the more dynamic. Videos of his sermons circulated on social media. His plans, ideas, and ambitions seemed boundless. Protestant Christianity was China’s fastest-growing religion, and Wang Yi was one of its stars. But at times he had been accused of arrogance and talking over people’s heads, of giving theoretical sermons about theological issues that no one could understand. Like most Chinese pastors, he was mostly self-taught in the Bible and tended to bring his lawyer’s argumentative nature to church matters. Tonight, though, was a chance to shine. Behind him on a screen was a picture of a dead woman whom people had come to mourn. Wei Suying, a popular member of the church, known to everyone as Auntie Wei, had died of cancer at age 62. Her daughters testified about how she had persuaded them to convert to Christianity. Both said how it had changed their lives, helping them see through the materialism of contemporary society. They had become better people, less obsessed with money, and more concerned about helping others. A few people began sobbing. Now it was Wang Yi’s turn. A few hours earlier, he had been thinking about how the communists exalt famous people by saying wansui, or long live, like “Long Live Chairman Mao.” Wansui (wan-sway) was a term everyone in China knew. It was almost a prefix before the Communist Party’s name, a formulaic chant meant to guarantee that its rule would never end. Auntie Wei’s death made him realize how much he hated that term. It was an offense to God and to ordinary people like Auntie Wei, whose lives truly deserved exaltation. Talking about this was a bit abstract, but he thought it might work. He stood up to speak, as usual without notes. He started softly, forcing everyone to listen carefully. “Auntie Wei was someone I think it would be fair to call a simple woman. She was a mother and had a hard life. She raised two daughters mostly on her own. Her husband had died young.” One of the daughters began sobbing. People in the church began nodding but caught themselves as Wang Yi continued. “She was not someone who heard the word wansui too often. If she heard it, she would have thought it applied to China, or the Communist Party, or Chairman Mao. Wansui: that’s almost always reserved for them. This is wrong. Wansui, this word, if it belongs to anyone, it belongs to Auntie Wei.” A couple of people looked up startled. “I tell you that she can hear wansui now because she is wansui; she is immortal because of Jesus. It’s not the government that can confer this word. It’s God, and it’s us by how we live our daily lives. It’s the choices we make despite the immoral society we live in. This is what real wansui is. It’s nothing that the Communist Party can provide. It’s something we can make ourselves.” Suddenly people were smiling; this was why they came to Early Rain Reformed Church. It was different from the anodyne churches sponsored by the state. It was warm and direct, but most of all it was relevant. It was for people who didn’t want the status quo, who were searching for alternatives to the life around them. Wang Yi was dressed in a suit, with short cropped hair and an earnest expression—a nice, modern young man, a perfect son-in-law. And yet here he was standing in front of them, telling them directly how to challenge the official way of looking at their country. “Auntie Wei was one of our sisters,” Wang Yi said, winding up his eulogy. “We loved her. But it’s she who possesses eternal life, not the government. She created it for herself by living a good life, by being our sister in the church, and resisting the immorality around her.” Now I could see why Wang Yi had made the choice to become a pastor. When he was a public intellectual, most of his words were censored. But here, speaking to one hundred people in a room, he was contributing to a sense that it was ordinary people who possessed real power in a country where all authority seemed to belong to the state. After the service, a son-in-law of Auntie Wei’s walked up to Wang Yi and did something Chinese almost never do: he hugged him. And Wang Yi, blinking back his own tears, looked bewildered but then happy. This was truly his flock, and he was their pastor. On Ash Wednesday—the beginning of Lent, the solemn 40-day period of fasting and prayer marking the lead-up up to Jesus’s crucifixion and resurrection during Easter—I visited Wang Yi’s church again. Like many religious groups in China, Early Rain operated in a grey area. The church wasn’t banned but also wasn’t permitted by the government. It operated openly but couldn’t buy a plot of land to build a proper church. That forced Early Rain (like hundreds of other unregistered churches across China) to find space in buildings like the River Trust Mansion, a seedy office tower in which it occupied half of the 19th floor. “The police officer comes every week. We don’t want to be stuck in the old underground-church mentality. It’s not healthy.” I saw that Wang Yi was in his office. He looked up and waved me in. As always, he was disarmingly frank. I asked him about his plans to set up a seminary. The idea made me nervous. Had the government approved it? “Well, no, they won’t approve it, but the question is if they’ll shut it down. We don’t think so. They asked us if it’s internal, and we said yes, so they seemed okay with that.” “So the idea is that it’s only to train Early Rain church members,” I said. “But will they go out to preach?” “Definitely; the idea is people from here will become missionaries. They’ll learn here.” “But isn’t this a sensitive year? You know…” I trailed off, wondering if his office was bugged. “You mean the big leadership issue?” Wang asked. “Every year is something special. Last year was some anniversary, and a few years ago were the Olympics. Next year will be something else. Right now the Communist Party is not so stable. We can’t know what is going on inside. They may feel they need quiet at all costs, and we’ll have trouble. Or they could also say that they need quiet so will ignore us; after all, we’re not challenging them. We just trust in God and let Him decide.” As we were talking, a policeman walked in. I thought at first it was just one of the many workers or deliverymen in China who sometimes wear blue uniforms. Then I noticed the insignia. Wang Yi stood up, greeting the officer warmly by name, and quickly led him out. Ten minutes later, Wang Yi returned. “The local police officer. He comes every week to get the list of those who attended church. We give them this information; we have nothing to hide, and the congregants are okay with that too. In fact, it’s a precondition for joining our church. You have to give your name, address, and contact information and be willing for us to share it with the authorities. We don’t want to be stuck in the old underground-church mentality. It’s not healthy.” He pointed to a whiteboard on the wall, which was covered with notes and numbers. “There’s the figure for the Sunday morning service: 222. And the afternoon: 92. So the total was 314. We can only seat around 220, so that’s why we have the second service.” “It’s hardly celebrated here at all,” he said. “We had this break in our history—you know, the missionaries being expelled in 1949 and then the anti-religious campaigns—so a lot has been lost. A lot of people don’t really know too much about Lent. We had a service trying to reintroduce the idea and explain it.” Like Early Rain, many Chinese churches are looking abroad for inspiration. They want all the traditions and import them as a package, assembling them like a model airplane. Wang Yi’s church reminded me of The Missionary’s Curse, a book by the British scholar Henrietta Harrison. She traces the history of Cave Gully, a village in northern China that converted to Catholicism in the late 17th century, when local businesspeople heard of the faith in Beijing and brought it back home. They acquired prayer books and some fragmentary knowledge but no systematic understanding of the faith. The result was something highly indigenized. God was seen as another version of the Chinese concept of heaven, or tian. Worship of Mary was conflated with worship of popular female deities in northern China, such as the Buddhist goddess of mercy, Guanyin. The Ten Commandments were a kind of moral formula, familiar to local people through Confucian texts. Western missionaries who tried to correct these practices were rebuffed. But by the 19th century, China was opening up. Rail, telegraph, steamships, and other technological innovations created the first era of globalization. Catholics in Cave Gully realized that they were part of something bigger—a global Catholic Church with rules and standard theological interpretations. Soon, people looked to Rome for benchmarks of how to be a good Catholic. In other words, the opposite of indigenization took place. The religion started with the familiar—respect for a supreme deity, a popular female goddess, moral rules—but moved beyond these easily digested universal manifestations of religion to uniquely Catholic ideas, such as the supremacy of the pope. This history is reflected in Wang Yi and the congregation of Early Rain. They also long to be part of a global movement—something orthodox, standard, and authentic, and not “indigenous.” Harrison sees this as applying not only to Christians but to Chinese society as a whole: As contact increases, international norms and standards seep in. Just as people want to be “real” Christians, they also yearn for a country that is truly committed to human rights, rule of law, and justice. They long for authenticity. Early Rain’s annual meeting was held on a Saturday, on the last full moon before the Spring Festival. Over the past year, the congregation had supported the families of political prisoners and Chengdu’s homeless while trying to balance the needs of its own poor members. It had founded a seminary that was helping its own members deepen their understanding of Christianity and also training dozens of pastors from across China. It had held an inspiring Christmas service despite government harassment. And the church had formed an alliance with two other Reformed churches in Chengdu. Quietly, Wang Yi had traveled farther afield, too, making preliminary contacts across China in hopes of forming a loose coalition of like-minded, urban-based churches. I had been wondering how long he could continue preaching before he would get in trouble. It wasn’t really his sermons that made me wonder. Instead, it was that his church was a parallel realm outside the party’s control. It had its own nursery school, day care, seminary, and elementary school—all located on this floor in the River Trust Mansion that it owned. It handled its own finances, rejecting all foreign money. It held its own elections and annual meetings—just like the government’s, but more transparent. The meeting was efficient and informative, with half a dozen people giving presentations on different aspects of the church. We heard from subcommittees that handled youth work, education, legal affairs, and finances. All of them had PowerPoint presentations and spoke quickly, confidently, and firmly—not unlike the lists, plans, and goals presented by the government during its springtime meetings of parliament. But what they also wanted was passion, and this could only be offered by Wang Yi. They had heard the nuts and bolts, but they needed a vision. “If we’re thrown out of Chengdu, we’re going to get back on the bus and reenter the city.” Wang Yi’s speech ended the meeting. The key for the coming year, he said, was growth. This would only be possible by splitting the church and moving some of the congregants to a new home. Right now, Early Rain had to turn away about 70 for lack of space. Those people would found a new church in the city’s center, near Sichuan University. This was a classic church-planting technique that was outlined in books that the seminary had studied last summer. The books had been published in the United States and translated into Chinese and were now being used as a template. Wang Yi and his deputies had discussed this for many months and decided it was a way also to protect Early Rain. If the mother church were to be closed, then the southern branch could keep going. The church, Wang Yi said, had to grow because Chengdu was growing too. Rural China was emptying out. So growth had to take place here, in big cities that were becoming regional and even international hubs. As always, his lecture had a pedagogical flare: He loved to explain, and the audience loved to learn. Wang Yi described how cities have always played a big role in Christian history—the city on the hill referred to by Jesus and founders of new Christian communities through the ages. “Ever since I was little, I thought that the city was my dream. But why do we want to live in cities?” In the Bible, Wang Yi continued, cities are sometimes shown to be bad; Babylon, for example, was the epitome of worldly sin. But cities are also places for people to better themselves and develop their potential. “I’ll use one word: ‘opportunities.’ What sorts of opportunities? Hope is one. When I was growing up, we used to say, ‘Hong Kong, Hong Kong, why are you so fragrant?’ “It represented capitalism, reform, and opening. It was the goal of every Chinese city to be like Hong Kong. Especially people like me who are from small towns and come to a big city, they want to stay. They also come for culture, for justice, and for generosity. People don’t go to a village to get an education. They go to the city—to the schools or the bookstores. Petitioners don’t go to a village to appeal for help; they go to the city. Beggars come to the city. They don’t go to the countryside. “Entering the city is what Jesus did in Jerusalem. Entering the city is entering a place of justice, of generosity, and of spreading the Gospel. It’s a place of hope. And it’s why we’re in the city here, and growing here. “In the Acts of the Apostles, when Paul was in Lystra spreading the Gospel, what happened? Some people wanted to worship him, thinking he was Zeus. But some stoned him almost to death, and when they thought he wasn’t breathing, they threw him out of the city. But he got up and went back into the city. This line really shocked me. It’s from chapter 14, verse 20: ‘He got up and went back into the city.’ He was thrown out of the city, but he reentered it. “So if we’re thrown out of Chengdu, we’re going to get back on the bus and reenter the city. And the goal isn’t because of opportunities, or culture, but it’s because it is the city that has the chance for peace, for generosity, and for the Gospel. God wants us to be in this city.” I looked around the room. About half the congregation had closed their eyes but had light smiles on their faces, listening to a vision. It was a prophecy of struggle—of perhaps being closed by the government, but also of determination, hope, and victory. Wang Yi stood before them, looking out on his congregation, confident and firm. Then he made his pitch, his claim for them to think of their hometown as more than just another city, but that it and their lives were the center of a great movement. “Earlier today, some disciples asked me what was the main theme of today? I said it’s ‘Entering the city.’ And they said, ‘Well, aren’t we already in Chengdu? Why do we need to enter the city?’ The answer is we need to keep entering the city. The city is the history of humanity’s hope for the future. There’s the city of God and the city of man. In the past it was Babylon, or New York, or Hong Kong, or Chengdu. “When we talk to brothers and sisters, we should ask them, why are you in Chengdu? What sorts of dreams have brought you here? And what are our dreams? We are creating a Jerusalem. This is the city on the hill. For us, Chengdu is this city.” This article has been adapted from Ian Johnson’s book, The Souls of China: The Return of Religion After Mao. Read more from The Atlantic: This article was originally published on The Atlantic.

Last April, for example, Sichuan University scientists announced that they had used CRISPR to program T cells from the immune system of a person with lung cancer to kill tumor cells (Nature 2016, DOI: 10.1038/nature.2016.20988). And late last year, a UC Berkeley team reported harnessing the technology to correct the genetic mutation responsible for sickle cell anemia in stem cells from patients with the disease (Sci. Transl. Med. 2016, DOI: 10.1126/scitranslmed.aaf9336). Eventually, Doudna; Emmanuelle Charpentier, now the director of the Max Planck Institute for Infection Biology; and coworkers discovered that CRISPRs help bacteria fight viral infection. Bacteria snag bits of an invading virus’s RNA and tuck them into CRISPRs, the team found. If the virus strikes again, these modified CRISPRs bind to the pathogen’s DNA, signaling to the enzyme Cas9 to come and dice up the foreign genetic material. The researchers realized they could harness this machinery to cut and paste target DNA fragments at will, as long as they introduced the appropriate designer RNA sequences. What started as a small project “aimed at something seemingly unrelated … led to a very different direction,” Doudna said during the Kavli keynote address on April 3 at the ACS national meeting in San Francisco. C&EN caught up with Doudna at the meeting to discuss the importance of curiosity-driven basic research and her outlook for CRISPR. The convergence of chemistry with other disciplines to tackle interesting problems in science is exciting. More and more, I see chemists using gene editing to make precise changes to molecules, such as proteins. That allows them to connect discoveries made using purified biomolecules outside cells—enzymes reacting in lab vessels, for instance—to what you would find in a living organism. That’s really amazing. With better chemical understanding of the way these enzymes operate, it will be possible to use them in ways that they don’t seem to be deploying in nature. The ability to make changes to the DNA of plant cells also opens up opportunities both in research and in solving problems in agriculture. That includes helping plants defend themselves against infection, drought, and other climate-change-related issues from a chemical perspective. With CRISPR, you understand the precise changes that you’re making to DNA—at the level of individual base pairs—rather than randomly introducing changes by exposing plant seeds to chemicals that cause DNA mutations. In drug discovery, one of the big challenges for chemists is determining the targets of small molecules. Now, you can potentially very rapidly figure out the targets by using CRISPR to query cells on a genomewide scale. You can disrupt certain genes and then ask if cells are still susceptible to the small molecules. I’m excited about that as an important research application but also as a practical way of doing drug discovery. We can do gene editing on cells ex vivo—meaning outside the organism—and the edited cells can then be reintroduced to the body, which gets around the challenge of drug delivery. For clinical use, we’ll probably see treatments like this that involve immune cells in the blood first, since they can be collected outside the body. In agriculture, we’ve already begun seeing products that have been created using precision gene editing. That brings up a bunch of regulatory challenges. The U.S. Department of Agriculture has decided that plant products created using CRISPR that don’t introduce foreign DNA are not considered genetically modified, which has led to lots of discussion. In other countries, the regulation of GMO plants is different, so I think people are being pushed to reevaluate how these are defined based on the opportunities we now have with CRISPR. Where we’ll likely see advancements being made is in deploying CRISPR to do more specific kinds of things. One is using it not to cleave DNA directly but to make a direct chemical modification to DNA, whether it’s changing one nucleotide base into another one or adding a methyl group. CRISPR has made possible genetic changes in individual organisms and even made it possible to pass along changes to offspring. This raises ethical concerns, particularly regarding human embryo or germ-line editing that might lead to permanent changes in the DNA that can be passed on to future generations. I’ve been actively involved in discussing these issues. As scientists, we need to explain what we’re doing and why we’re doing it, not dictating how these discoveries and technologies should be used. We need to participate in those conversations with the public. This is important, especially now, when there’s a lot of questioning about scientific knowledge, the value of facts, and how scientific data are used to help governments make decisions about regulations and funding. In February, the U.S. Patent & Trademark Office upheld patents awarded to the Broad Institute of Massachusetts Institute of Technology and Harvard University for the use of CRISPR in eukaryotic cells. About a month later, the European Patent Office announced plans to award a patent to the University of California that covers a wide range of CRISPR uses. How do you see the patent battle playing out in the years ahead? Patents around important technologies typically are complicated. It takes a while to sort them out, and CRISPR is no different. Honestly, I think it will take a while before the patent situation is resolved in different countries. The exciting thing for me is that we’re seeing rapid deployment of the CRISPR technology both in academic settings and in companies. That’s leading to real advances for various diseases. There are exciting uses in agriculture and in fundamental research. None of that is being hampered by the current patent situation. CORRECTION: This Q&A was updated on April 21, 2017, to correct the affiliation of the team that used CRISPR to fix the genetic mutation responsible for sickle cell anemia in patients’ stem cells. It is UC Berkeley, not Stanford.

Since its inception, MMAAP foundation has awarded over 40 Fellowship and Project grants to support the work of exceptional physician scientists and investigators with the vision, drive and dedication to find new and innovative ways towards advancements in the targeted medical fields. These outstanding award recipients represent more than 20 prestigious Chinese medical institutions including Peking Union Medical College Hospital, Xijing Hospital, the Fourth Military Medical University, Peking University Institute of Hematology, West China Hospital, Sichuan University, Ruijin Hospital, Shanghai Jiaotong University School of Medicine, and others. "The visionary leadership of MMAAP Foundation Chairman and Founder, Howard P. Milstein, has brought together and funded exchanges between outstanding researchers, medical talent, and institutions in these regions," said Sean X. Leng, MD, PhD, President of MMAAP Foundation. "The 2017 recipients are among the most talented investigators in their fields and our support of their work is vital to both furthering medical research and strengthening relations between the U.S. and China." Grant applications were evaluated through a two-step peer review process according to the National Institute of Health standard. Panels of Chinese and U.S. experts in their respective fields jointly reviewed all proposals, and finalists were submitted for approval by MMAAP Foundation. The U.S. panels in Geriatrics, Skin Disease, Hematology, Reproductive Medicine, and Translational Medicine include members of the American Geriatrics Society, Medical Advisory Committee of American Skin Association, New York Blood Center, Jones Foundation for Reproductive Medicine, as well as members of other leading U.S. institutions in each field. The mission of Milstein Medical Asian American Partnership Foundation (MMAAP Foundation) is to improve world health by developing mutually beneficial partnerships between the U.S. and China, as well as greater Asia. Working with some of the premier health organizations in the world, MMAAP Foundation brings together and funds exchanges among the best research, medical talent, and institutions in the regions. This strategy is a high priority for MMAAP Foundation's founder Howard P. Milstein. MMAAP Foundation is a 501(c) (3) non-profit organization. For more than 50 years, the Milstein family has been actively involved in health-related and medical philanthropy. MMAAP Foundation builds upon this distinguished history in five areas: Senior Healthcare, Skin Disease and Melanoma, Reproductive Biology, Blood Research, and Translational Medicine. MMAAP Foundation works in close collaboration with other medical organizations supported by the Milstein family, including American Skin Association, Milstein Melanoma Research Program at The Rockefeller University, Howard and Georgeanna Jones Foundation for Reproductive Medicine, New York Blood Center, and the Program for Translational Chemical Biology at New York-Presbyterian Hospital/Weill Cornell Medical Center. For more information, please visit MMAAP Foundation's website at To view the original version on PR Newswire, visit:

Ping Y.,Beijing University of Chemical Technology | Ping Y.,National University of Singapore | Liu C.-D.,National University of Singapore | Tang G.-P.,Zhejiang University | And 4 more authors.
Advanced Functional Materials | Year: 2010

It is of crucial importance to modify chitosan-based polysaccharides in the designing of biomedical materials. In this work, atom transfer radical polymerization (ATRP) was employed to functionalize chitosan in a well-controlled manner. A series of new degradable cationic polymers (termed as PDCS) composed of biocompatible chitosan backbones and poly((2-dimethyl amino)ethyl methacrylate) (P(DMAEMA)) side chains of different length were designed as highly efficient gene vectors via ATRP. These vectors, termed as PDCS, exhibited good ability to condense plasmid DNA (pDNA) into nanoparticles with positive charge at nitrogen/phosphorus (N/P) ratios of 4 or higher. All PDCS vectors could well protect the condensed DNA from enzymatic degradation by DNase I and they displayed high level oftransfectivity in both COS7, HEK293 and HepG2 cell lines. Most importantly, in comparison with high-molecular-weight P(DMAEMA) and 'gold-standard' PEI (25 kDa), the PDCS vectors showed considerable buffering capacity in the pH range of 7.4 to 5, and were capable of mediating much more efficient gene transfection at low N/P ratios. At their own optimal N/P ratios for trasnsfection, the PDCS/pDNA complexes showed much lower cytotoxicity. All the PDCS vectors were readily to be degradable in the presence of lysozyme at physiological conditions in vitro. These well-defined PDCS polymers have great potentials as efficient gene vectors in future gene therapy. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.

Jin T.-X.,Sichuan University | Liu C.,Sichuan University | Zhou M.,Sichuan University | Chen F.,Sichuan University | Fu Q.,Sichuan University
Composites Part A: Applied Science and Manufacturing | Year: 2015

Poly(butylene succinate) (PBS)/graphene oxide (GO) nanocomposites were fabricated via in situ polymerization with very low GO content (from 0.03 to 0.5 wt%). The microstructures of the nanocomposites were characterized with Raman spectroscopy, fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), sedimentation experiments and atomic force microscopy (AFM). The results showed that PBS chains have been successfully grafted onto GO sheets during in-situ polymerization, accompanied by the thermo-reduction from GO to graphene. The grafted GO displayed a great nucleating effect on PBS crystallization, resulting in largely improved crystallization temperature and decreased spherules size. A simultaneous enhancement in tensile strength and elongation was achieved for PBS/GO nanocomposites fiber. Meanwhile, increase in hydrolytic degradation rate was also observed for these nanohybrids. Our result indicates that using very low content GO is a simple way to achieve good dispersion yet with remarkable property enhancement for polymer/GO nanocomposites. © 2014 Elsevier Ltd.

Retallack G.J.,University of Oregon | Huang C.,Sichuan University
Geology | Year: 2010

Pedogenic accumulations of crystals and nodules of gypsum are common in desert soils, especially extreme deserts such as the Atacama Desert, Chile. Some soils with both pedogenic gypsum and calcite have the gypsic (By) horizon below the calcic (Bk) horizon. Here we present a compilation of 88 gypsic soils from around the world to derive a relationship (R2 = 0.63, standard error = ±129 mm) between depth to the By horizon (D, in centimeters) and mean annual precipitation (P, in millimeters) as follows: P = 87.593e0.0209D. This relationship can be used to derive paleoprecipitation estimates from paleosols, once depth to the gypsic horizon is corrected for compaction due to overburden. Application of this technique to Early Permian paleosols near Gilliland, Texas, confirms paleoprecipitation estimates in the same sequence derived from depth to the calcic horizon. Barite is another sulfate mineral that forms nodular horizons in paleosols, but not in modern soils. Miocene paleosols in Panama with both calcareous and barite nodules suggest that this weakly soluble salt forms at levels in paleosols unlike those of either pedogenic carbonate or gypsum. © 2010 Geological Society of America.

Zhang C.,National University of Ireland | Tang Y.,Sichuan University | Xu X.,University College Cork | Kiely G.,University College Cork
Applied Geochemistry | Year: 2011

It is challenging to perform spatial geochemical modelling due to the spatial heterogeneity features of geochemical variables. Meanwhile, high quality geochemical maps are needed for better environmental management. Soil organic C (SOC) distribution maps are required for improvements in soil management and for the estimation of C stocks at regional scales. This study investigates the use of a geographically weighted regression (GWR) method for the spatial modelling of SOC in Ireland. A total of 1310 samples of SOC data were extracted from the National Soil Database of Ireland. Environmental factors of rainfall, land cover and soil type were investigated and included as the independent variables to establish the GWR model. The GWR provided comparable and reasonable results with the other chosen methods of ordinary kriging (OK), inverse distance weighted (IDW) and multiple linear regression (MLR). The SOC map produced using the GWR model showed clear spatial patterns influenced by environmental factors and the smoothing effect of spatial interpolation was reduced. This study has demonstrated that GWR provides a promising method for spatial geochemical modelling of SOC and potentially other geochemical parameters. © 2011 Elsevier Ltd.

Zhu L.,Sichuan University | Hwa R.C.,University of Oregon
Physical Review C - Nuclear Physics | Year: 2013

In the study of hadron production in Au-Au collisions at the BNL Relativistic Heavy-Ion Collider (RHIC), minijets play an important role in generating shower partons in the intermediate pT region. Momentum degradation of the hard and semihard partons as they traverse the inhomogeneous medium at various azimuthal angles results in a complicated convolution of geometrical, nuclear, and dynamical factors that cannot usually be described in a transparent way. In this work a compact formula is found that represents the inclusive distributions of minijets of any parton type at the surface of the medium for any collision centrality. They take into account the contributions from all initiating partons created at any point in the medium. By comparing with the case of no energy loss, a ratio has been determined that is analogous to the nuclear modification factor for minijets. Phenomenological reality of such distributions is examined by calculating the hadronization of the minijets in the recombination model. Good fits of the data on pion, kaon and proton production throughout the intermediate pT region have been obtained by adjusting the parameters controlling the magnitude of the thermal partons and the degradation rates of the semihard partons. The result gives support to the minijet spectra at any centrality on the one hand, and the hadronization procedure used on the other. An important property made manifest in this study is that quarks and gluons must not lose energy in the same way because the partons form mesons and baryons differently by recombination and the momenta of quarks and gluons must be degraded at different rates in order to reproduce the experimental pion and proton spectra. This is a feature that renders invalid the notion of parton-hadron duality or other hadronization schemes based on similar ideas. © 2013 American Physical Society.

Xia Y.,Sichuan University | Lin L.,Sichuan University | Chang F.,Sichuan University | Fu X.,Sichuan University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2015

A highly efficient asymmetric ring-opening reaction of cyclopropyl ketones with a broad range of thiols, alcohols and carboxylic acids has been first realized by using a chiral N,N′-dioxide-scandium(III) complex as catalyst. The corresponding sulfides, ethers, and esters were obtained in up to 99 % yield and 95 % ee. This is also the first example of one catalytic system working for the ring-opening reaction of donor-acceptor cyclopropanes with three different nucleophiles, let alone in an asymmetric version. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhu W.,University of Sichuan | Liu D.,Sichuan University | Ai H.,University of Sichuan
ACS Applied Materials and Interfaces | Year: 2014

A dual-channel naphthalimide-based chemosensor for rapid and sensitive detection of fluoride ion has been developed. Upon addition of F-, it undergoes deprotonation reaction through H-bonding interactions, and its maximum absorption wavelength is red-shifted for 214 nm to the far-red region, together with drastically quenched fluorescence. In addition, it shows high selectivity toward F- anion, thus could be used for practical applications to detecting F- in both solution and solid state. Furthermore, the fluorescence of NIM could be enhanced in protein-containing acidic environments, hence NIM could act as lysosome marker to differentiate cancer cells from normal ones in cell imaging. © 2014 American Chemical Society.

Soh W.T.,National University of Singapore | Zhong X.,National University of Singapore | Zhong X.,Sichuan University | Ong C.K.,National University of Singapore
Applied Physics Letters | Year: 2014

FeAlSi (Sendust) is known to possess excellent soft magnetic properties comparable to traditional soft magnetic alloys such as NiFe (Permalloy), while having a relatively higher resistance for lower eddy current losses. However, their dynamic magnetic and magneto-transport properties are not well-studied. Via the spin rectification effect, we electrically characterize a series of obliquely sputtered FeAlSi films at ferromagnetic resonance. The variations of the anisotropy fields and damping with oblique angle are extracted and discussed. In particular, two-magnon scattering is found to dominate the damping behavior at high oblique angles. An analysis of the results shows large anomalous Hall effect and anisotropic magneto-resistance across all samples, which decreases sharply with increasing oblique incidence. © 2014 AIP Publishing LLC.

He Y.,Sichuan University | Lee P.A.,Massachusetts Institute of Technology | Varma C.M.,University of California at Riverside
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We show that a finite Hall effect in zero applied magnetic field occurs for partially filled bands in certain time-reversal violating states with zero net flux per unit cell. These states are the Magneto-chiral states with parameters in the effective one-particle Hamiltonian such that they do not satisfy the Haldane-type constraints for topological electronic states. The results extend an earlier discussion of the Kerr effect observed in the cuprates but may be applicable to other experimental situations. © 2014 American Physical Society.

Retallack G.J.,University of Oregon | Huang C.,Sichuan University
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011

The first trees in New York were Middle Devonian (earliest Givetian) cladoxyls (?Duisbergia and Wattieza), with shallow-rooted manoxylic trunks. Cladoxyl trees in New York thus postdate their latest Emsian evolution in Spitzbergen. Progymnosperm trees (?Svalbardia and Callixylon-Archaeopteris) appeared in New York later (mid-Givetian) than progymnosperm trees from Spitzbergen (early Givetian). Associated paleosols are evidence that Wattieza formed intertidal to estuarine mangal and Callixylon formed dry riparian woodland. Also from paleosols comes evidence that Wattieza and Callixylon required about 350mm more mean annual precipitation than plants of equivalent stature today, that Wattieza tolerated mean annual temperature 7°C less than current limits of mangal (20°C), and Callixylon could tolerate temperatures 14°C less than modern mangal. Devonian mangal and riparian woodland spread into New York from wetter regions elsewhere during transient paleoclimatic spikes of very high CO2 (3923±238 ppmv), and subhumid (mean annual precipitation 730±147mm) conditions, which were more likely extrinsic atmospheric perturbations rather than consequences of tree evolution. For most of the Middle Devonian CO2 was lower (2263±238 ppmv), and paleoclimate in New York was semiarid (mean annual precipitation 484±147mm). Such transient perturbations and immigration events may explain the 40million year gap between the late Emsian (400Ma) evolution of trees and Famennian (360Ma) CO2 drawdown and expansion of ice caps. © 2010 Elsevier B.V.

Huang C.M.,Sichuan University | Retallack G.J.,University of Oregon | Wang C.S.,China University of Geosciences
Cretaceous Research | Year: 2012

Pedogenic carbonates were collected from Early Cretaceous strata in Sichuan and Liaoning, China. These paleosol carbonates and calcareous paleosols were evaluated in order to reconstruct atmospheric CO 2 concentrations during the Early Cretaceous using a paleosol barometer. Using the isotopic ratios of pedogenic carbonates from Early Cretaceous (early-middle Berriasian, early Valanginian) strata in Sichuan Basin, averaged atmospheric pCO 2 is estimated to have been 360 ppmv in the early-middle Berriasian and a mean value of 241 ppmv in the early Valanginian. In the late Barremian in western Liaoning, however the average was 530 ppmv, with a range of 365 ppmv and 644 ppmv, lower than previous estimates of pCO 2 for these time periods, consistent with the suggestion of overall climate cooling and paleotemperature fluctuation during the Early Cretaceous. This indicates that not all of the Cretaceous was a high or continuous CO 2 greenhouse, especially during Early Cretaceous. © 2011 Elsevier Ltd.

Polyakov D.,Sichuan University | Polyakov D.,Institute for Information Transmission Problems IITP
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

We investigate the special case of quintic interactions for massless higher spin gauge fields using the string-theoretic vertex operator construction for higher spin gauge fields in Vasiliev's framelike formalism. We compute explicitly the related five-point interaction vertex in the low energy limit of string theory and find that the structure of the quintic s1-s2-s3-s4-s5 higher spin interaction gets drastically simplified and localized if (a) the spin values satisfy the constraint s1+s2+s3=s4+s5+2 (and, more generally, if the sum of three spin values roughly equals the sum of the remaining two) and (b) one of the spin values s4 or s5 is sufficiently small. In this paper, the explicit computation is done for the case s4=4. © 2016 American Physical Society.

Wu J.,Sichuan University | Xiao D.,Sichuan University | Wu W.,Sichuan University | Chen Q.,Sichuan University | And 3 more authors.
Journal of the European Ceramic Society | Year: 2012

Lead-free (Ba 0.85Ca 0.15)(Ti 1-xZr x)O 3 (BCTZ) piezoelectric ceramics were fabricated by normal sintering in air atmosphere. BCTZ ceramics with x=0.10 possess a coexistence of tetragonal and rhombohedral phases at ∼40°C. The Curie temperature of BCTZ ceramics decreases with increasing the Zr content. Piezoelectric properties of BCTZ ceramics are dependent on the poling conditions (i.e., the poling temperature and the poling electric field), and the underlying physical mechanism is illuminated by the phase angle. The BCTZ (x=0.10) ceramic, which locates at the existence of two phases and is poled at E∼4.0kV/mm and T p∼40°C, exhibits an optimum electrical behavior at a room temperature of ∼20°C: d 33∼423pC/N, k p∼51.2%, 2P r∼18.86μC/cm 2, 2E c∼0.47kV/mm, e{open} r∼2892, and tanδ∼1.53%. © 2011 Elsevier Ltd.

Polyakov D.,Sichuan University | Polyakov D.,Institute for Information Transmission Problems IITP
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

We find a class of analytic solutions in open bosonic string field theory, parametrized by the chiral copy of higher spin algebra in AdS3. The solutions are expressed in terms of the generating function for the products of Bell polynomials in derivatives of bosonic space-time coordinates Xm(z) of the open string, the form of which is determined in this work. The products of these polynomials form a natural operator algebra realizations of w∞ (area-preserving diffeomorphisms), enveloping algebra of SU(2) and higher spin algebra in AdS3. The class of string field theory solutions found can, in turn, be interpreted as the "enveloping of enveloping," or the enveloping of AdS3 higher spin algebra. We also discuss the extensions of this class of solutions to superstring theory and their relations to higher spin algebras in higher space-time dimensions. © 2015 American Physical Society.

Huang C.,Sichuan University | Retallack G.J.,University of Oregon | Wang C.,China University of Geosciences | Huang Q.,Petrochina
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2013

A dramatic change in atmospheric composition has been postulated because of global carbon cycle disruption during the Cretaceous (K)-Tertiary (T) transition following the Chicxulub impact and Deccan Trap eruptions. Here, pedogenic carbonates were collected from drill core of a borehole (SK-1 (N)) straddling the Late Cretaceous and early Paleocene strata in the Songliao Basin, northeast China, to reconstruct atmospheric CO2 concentrations using a paleosol paleobarometer. Our estimates for atmospheric pCO2 from paleosol carbonates range between 277±115ppmv and 837±164ppmv between 67.8Ma and 63.1Ma. One large (~66-65.5Ma) and several small CO2 spikes (~64.7-~64.2Ma) during the latest Maastrichtian to earliest Danian are reported here and incorporated with previously published pCO2 estimates also estimated from paleosol carbonates. These CO2 spikes are attributed to one-million-year-long emplacement of the large Deccan flood basalts along with the extraterrestrial impact at the K-T boundary. © 2013 Elsevier B.V.

Zhao X.,Sichuan University | Liu X.,Sichuan University | Mei H.,Sichuan University | Guo J.,Sichuan University | And 2 more authors.
Angewandte Chemie - International Edition | Year: 2015

A highly efficient asymmetric dearomatization of indoles was realized through a cascade reaction between 2-isocyanoethylindole and alkylidene malonates catalyzed by a chiral N,N-dioxide/MgII catalyst. Fused polycyclic indolines containing three stereocenters were afforded in good yields with excellent diastereo- and enantioselectivities through a Michael/Friedel-Crafts/Mannich cascade. When 2-substituted 2-isocyanoethylindoles were used, spiroindoline derivatives were obtained through a Michael/Friedel-Crafts reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lv J.C.,Sichuan University | Tan K.K.,National University of Singapore | Yi Z.,Sichuan University | Huang S.,National University of Singapore
IEEE Transactions on Fuzzy Systems | Year: 2010

In this paper, we analyze Xu and Yuilles robust principal component analysis (RPCA) learning algorithms by means of the distance measurement in space. Based on the analysis, a family of fuzzy RPCA learning algorithms is proposed, which is robust against outliers. These algorithms can explicitly be understood from the viewpoint of fuzzy set theory, though Xu and Yuilles algorithms were proposed based on a statistical physics approach. In the proposed algorithms, an adaptive learning procedure overcomes the difficulty of selection of learning parameters in Xu and Yuilles algorithms. Furthermore, the robustness of proposed algorithms is investigated by using the theory of influence functions. Simulations are carried out to illustrate the robustness of these algorithms. © 2006 IEEE.

Polyakov D.,Sichuan University | Polyakov D.,Sogang University | Polyakov D.,Institute for Information Transmission Problems IITP
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We construct analytic solutions in cubic open superstring field theory at higher superconformal ghost numbers. The solutions are the pure ghost ones, given by combinations of Bell polynomials of bosonized superconformal ghost fields multiplied by exponents of the bosonized ghosts. Based on the structure of the solutions, we conjecture them to describe the ghost part of collective vacuum for higher spin modes in open string theory. © 2014 American Physical Society.

Huang Z.,Sichuan University | Liu Y.,Sichuan University | Li C.,Zhejiang University | Yang M.,Sichuan University | And 2 more authors.
Pattern Recognition | Year: 2013

If fusion rules cannot adapt to the changes of environment and individual users, multimodal systems may perform worse than unimodal systems when one or more modalities encounter data degeneration. This paper develops a robust face and ear based multimodal biometric system using Sparse Representation (SR), which integrates the face and ear at feature level, and can effectively adjust the fusion rule based on reliability difference between the modalities. We first propose a novel index called Sparse Coding Error Ratio (SCER) to measure the reliability difference between face and ear query samples. Then, SCER is utilized to develop an adaptive feature weighting scheme for dynamically reducing the negative effect of the less reliable modality. In multimodal classification phase, SR-based classification techniques are employed, i.e., Sparse Representation based Classification (SRC) and Robust Sparse Coding (RSC). Finally, we derive a category of SR-based multimodal recognition methods, including Multimodal SRC with feature Weighting (MSRCW) and Multimodal RSC with feature Weighting (MRSCW). Experimental results demonstrate that: (a) MSRCW and MRSCW perform significantly better than the unimodal recognition using either face or ear alone, as well as the known multimodal methods; (b) The effectiveness of adaptive feature weighting is verified. MSRCW and MRSCW are very robust to the image degeneration occurring to one of the modalities. Even when face (ear) query sample suffers from 100% random pixel corruption, they can still get the performance close to the ear (face) unimodal recognition; (c) By integrating the advantages of adaptive feature weighting and sparsity-constrained regression, MRSCW seems excellent in tackling the face and ear based multimodal recognition problem. © 2013 Elsevier Ltd.

Huang J.,Shenyang Pharmaceutical University | Zhang S.-Y.,Sichuan University | Gao Y.-M.,The First Attached Hospital of Hebei Northern Institute | Liu Y.-F.,The First Attached Hospital of Hebei Northern Institute | Liu Y.-B.,General Hospital of Armed Police Forces
Cell Proliferation | Year: 2014

MicroRNAs are a class of small, non-coding RNAs that can negatively regulate protein-coding genes, and are associated with almost all known physiological and pathological processes, especially cancer. The number of studies documenting miRNA expression patterns in malignancy continues to expand rapidly, with continuously gained critical information regarding how aberrantly expressed miRNAs may contribute to carcinogenesis. miRNAs can influence cancer pathogenesis, playing a potential role as either oncogenes or tumour suppressors. Recently, several miRNAs have been reported to exert different regulatory functions in oesophageal cancer - the carcinoma typically arising from the epithelial lining of the oesophagus. These miRNAs also have potential clinical applications towards developing biomarkers or targets for possible use in diagnosis or therapy in oesophageal cancer. In this review, we have summarized the two (oncogenic or tumour suppressive) roles of miRNAs here, and their applications as potential biomarkers or therapeutic targets, which may illuminate future treatment for oesophageal cancer. © 2014 John Wiley & Sons Ltd.

Chen H.,Sichuan University | Shana Z.-H.,Sichuan University
International Journal of Biological Macromolecules | Year: 2010

Cross-linking agents play an important part in the physical properties of collagen based biomaterials. This paper describes the stabilization of type I collagen using an oxazolidine E-resorcinol compound. It is shown by NMR and elemental analysis techniques that oxazolidine E undergoes ring opening to form an N-methylol intermediate form and then reacts with the hydrogen bonds of resorcinol. Oxazolidine E-resorcinol compound treated collagen fibers are shown by DSC analysis to be more thermally stable than simple oxazolidine E-resorcinol treated collagen. Treated collagen fibers showed shrinkage temperature around 98°C implying that the oxazolidine E-resorcinol compounds impart thermal stability. Circular dichroism revealed that there is no major alteration in the structure of collagen after treatment with the compound. The study demonstrates that the involvement of hydrogen bonding and hydrophobic interaction as the principal mechanisms for stabilization of collagen by oxazolidine E-resorcinol compounds. © 2010 Elsevier B.V.

Miyamoto Y.,NEC Corp | Miyamoto Y.,Japan Science and Technology Agency | Zhang H.,Sichuan University | Tomanek D.,Michigan State University
Physical Review Letters | Year: 2010

We propose to use ultrashort laser pulses to detach intact graphene monolayers from a graphite surface, one at a time. As suggested by a combination of real-time ab initio time-dependent density functional calculations for electrons with molecular dynamics simulations for ions, this athermal exfoliation process follows exposure to femtosecond laser pulses with a wavelength of 800 nm and the full width at half maximum (FWHM) of 45 fs. Shorter pulses (FWHM=10fs) with the same wavelength and intensity speed up the exfoliation and cause transient contraction in subsurface layers. Photoexfoliation should be capable of producing intact graphene monolayers free of contaminants and defects at a high rate. © 2010 The American Physical Society.

Wu J.,Sichuan University | Wang J.,National University of Singapore | Xiao D.,Sichuan University | Zhu J.,Sichuan University
ACS Applied Materials and Interfaces | Year: 2012

A method is used to improve the electrical properties of BiFeO 3 thin films by modifying the Bi content in ceramic targets, where all thin films were prepared on SrRuO 3/Pt/TiO 2/SiO 2/Si(100) substrates by radio frequency sputtering. The Bi content in the ceramic target strongly affects the electrical properties of BiFeO 3 thin films. BiFeO 3 thin films prepared by using the ceramic target of Bi/Fe ≈ 1.15 with a molar ratio demonstrate a low leakage current density and a low dielectric loss. Moreover, a larger remanent polarization of 2P r ≈ 167.6 μC/cm 2 is also demonstrated for the BiFeO 3 thin films prepared by using the ceramic target of Bi/Fe ≈ 1.15, together with an improved fatigue behavior. Therefore, it is an effective way to improve the electrical properties of bismuth ferrite thin films by modifying the Bi content in ceramic targets. © 2012 American Chemical Society.

Miyamoto Y.,NEC Corp | Zhang H.,Sichuan University | Rubio A.,University of the Basque Country
Physical Review Letters | Year: 2010

We show by first-principles simulations that ultrafast laser pulses induce different chemical reactions in a molecule trapped inside a nanotube. A strong laser pulse polarized perpendicular to the tube axis induces a giant bond stretch of an encapsulated HCl molecule in semiconducting carbon nanotube or in a BN nanotube. Depending on the initial orientation of the HCl molecule, the subsequent laser-induced dynamics is different: either complete disintegration or rebonding of the HCl molecule. Radial motion of the nanotube is always observed and a vacancy appears on the tube wall when the HCl is perpendicular to the tube axis. Those results are important to analyze confined nanochemistry and to manipulate molecules and nanostructures encapsulated in organic and inorganic nanotubes. © 2010 The American Physical Society.

Wu J.,Sichuan University | Wu J.,National University of Singapore | Wang J.,National University of Singapore | Xiao D.,Sichuan University | Zhu J.,Sichuan University
Journal of Materials Chemistry | Year: 2011

Sandwich structured (Bi0.92La0.08)(Fe 0.87Zn0.13)O3/(Bi0.92La 0.08)(Fe0.93Zn0.07)O3/(Bi 0.92La0.08)(Fe0.87Zn0.13)O 3 thin films were prepared on Pt/TiO2/SiO 2/Si(100) substrates by radio frequency sputtering. High (110) orientation is induced in these sandwiched structures due to the introduction of the bottom (Bi0.92La0.08)(Fe0.87Zn 0.13)O3 layer with a (110) orientation. The space-charge-limited current mechanism is identified to dominate the leakage behavior of these sandwiched structures, and the lowest leakage current density is well established in such a sandwiched structure with a thickness ratio of 1:1:1 owing to its denser microstructure. All sandwiched structures demonstrate good fatigue behavior at a switching cycle of ∼2.96 × 109 and similar saturated M-H loops with 2M ∼ 15.5 emu cm-3 due to the interface coupling among these constituent layers. The sandwiched structure with a thickness ratio of 1:1:1 possesses a better P-E loop with a high remanent polarization of 2Pr ∼ 142.6 μC cm-2 and a low coercive field of 2Ec ∼ 695.0 kV cm-1. As a result, the sandwiched structure is an effective way to improve the multiferroic and fatigue behavior of bismuth ferrite materials. © 2011 The Royal Society of Chemistry.

Zhao J.,Sichuan University | Fang B.,Sichuan University | Luo W.,Sichuan University | Hao X.,Sichuan University | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2015

A highly enantioselective Mannich reaction of silyl ketene imines with isatin-derived ketimines has been realized by using a chiral N,N'-dioxide/ZnII catalyst. A variety of β-amino nitriles containing congested vicinal tetrasubstituted stereocenters were obtained with excellent outcomes (up to 98%yield, > 19:1 d.r. and 99%ee). Based on the experimental investigations, a possible transition state has been proposed to explain the origin of the asymmetric induction. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Xia Y.,Sichuan University | Liu X.,Sichuan University | Zheng H.,Sichuan University | Lin L.,Sichuan University | Feng X.,Sichuan University
Angewandte Chemie - International Edition | Year: 2015

The asymmetric ring-opening/cyclization of cyclopropyl ketones with primary amine nucleophiles was catalyzed by a chiral N,N'-dioxide/scandium(III) complex through a kinetic resolution process. A broad range of cyclopropyl ketones and primary amines are suitable substrates of this reaction. The corresponding products were afforded in excellent enantioselectivities and yields (up to 97% ee and 98% yield) under mild reaction conditions. This method provides a promising access to chiral 2,3-dihydropyrroles as well as an effective procedure for the kinetic resolution of 2-substituted cyclopropyl ketones. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Miyamoto Y.,Japan National Institute of Advanced Industrial Science and Technology | Zhang H.,Sichuan University | Miyazaki T.,Japan National Institute of Advanced Industrial Science and Technology | Rubio A.,Max Planck Institute for the Structure and Dynamics of Matter | Rubio A.,University of the Basque Country
Physical Review Letters | Year: 2015

We propose a transient interlayer compression in two-dimensional compound materials by using an intense IR laser resonant with the out-of-plane optical phonon mode (A2u mode). As a test case, we studied bilayer hexagonal boron nitride (h-BN), which is one of the compound layered materials. Excited state molecular dynamics calculations using time-dependent density functional theory show an 11.3% transient interlayer contraction of h-BN due to an interlayer dipole-dipole attraction of the laser-pumped A2u mode. These results are applicable to other layered compound materials. Such layered materials are a good material for nanospace chemistry, e.g., intercalating molecules and acting with them, and IR irradiation to contract the interlayer distance could provide a new route for chemical reactions under pressure. The duration of the contraction is at least 1 ps in the current simulation, which is observable by high-speed electron-beam diffraction measurements. © 2015 American Physical Society.

Peng X.,Sichuan University | Zhang L.,Sichuan University | Yi Z.,Sichuan University | Tan K.K.,National University of Singapore
Pattern Recognition | Year: 2014

The models of low-dimensional manifold and sparse representation are two well-known concise models that suggest that each data can be described by a few characteristics. Manifold learning is usually investigated for dimension reduction by preserving some expected local geometric structures from the original space into a low-dimensional one. The structures are generally determined by using pairwise distance, e.g., Euclidean distance. Alternatively, sparse representation denotes a data point as a linear combination of the points from the same subspace. In practical applications, however, the nearby points in terms of pairwise distance may not belong to the same subspace, and vice versa. Consequently, it is interesting and important to explore how to get a better representation by integrating these two models together. To this end, this paper proposes a novel coding algorithm, called Locality-Constrained Collaborative Representation (LCCR), which introduce a kind of local consistency into coding scheme to improve the discrimination of the representation. The locality term derives from a biologic observation that the similar inputs have similar codes. The objective function of LCCR has an analytical solution, and it does not involve local minima. The empirical studies based on several popular facial databases show that LCCR is promising in recognizing human faces with varying pose, expression and illumination, as well as various corruptions and occlusions. © 2014 Elsevier Ltd.

Wu J.,Sichuan University | Xiao D.,Sichuan University | Wu W.,Sichuan University | Zhu J.,Sichuan University | Wang J.,National University of Singapore
Journal of Alloys and Compounds | Year: 2011

In this letter, the effect of dwell time (1-6 h) during sintering on the piezoelectric properties is investigated for the (Ba0.85Ca 0.15)(Ti0.90Zr0.10)O3 ceramics. All ceramics sintered at different dwell time are of a pure phase, and its structure distortion is induced by too long dwell time. Their dielectric constant and remanent polarization increases and the coercive field decreases with increasing dwell time. An enhanced piezoelectric behavior (d33 ∼ 492 pC/N and kp ∼ 51.5%) is demonstrated for the BCTZ ceramic with an optimum dwell time of 5 h, owing to the structure distortion together with a dense microstructure and a larger grain size. © 2011 Elsevier B.V.

Wu J.,Sichuan University | Wang J.,National University of Singapore | Xiao D.,Sichuan University | Zhu J.,Sichuan University
ACS Applied Materials and Interfaces | Year: 2011

The ferroelectric behavior of BiFeO3 thin films is modified by changing the film thicknesses, where the BiFeO3 thin films with different thicknesses were grown on SrRuO3/Pt/TiO2/ SiO2/Si(100) substrates by radio frequency sputtering. The mixture of (110) and (111) orientations is induced for all BiFeO3 thin films regardless of their thicknesses, together with the columnar structure and the dense microstructure. Their dielectric behavior is almost independent of the film thickness where all thin films have a low dielectric loss. A giant remanent polarization of 2Pr ≈ 156.6-188.8 μC/cm2 is induced for the BiFeO3 thin films in the thickness range of 190-600 nm. As a result, it is an effective way to improve the ferroelectric behavior of the BiFeO3 thin film by tailoring the film thickness. © 2011 American Chemical Society.

Wu J.,Sichuan University | Xiao D.,Sichuan University | Wu W.,Sichuan University | Chen Q.,Sichuan University | And 3 more authors.
Scripta Materialia | Year: 2011

In order to shift the tricritical point to room temperature, Ba 0.85Ca0.15Ti0.90Zr0.10O3 (BCTZ) ceramics were prepared by normal sintering with the addition of ZnO. The sintering behavior of BCTZ ceramics is also improved by using ZnO as a sintering aid. The room-temperature tricritical point results in improved electrical properties of ZnO-modified BCTZ ceramics. BCTZ ceramic with 0.06 mol.% ZnO demonstrates good piezoelectric properties: d33 ∼ 521 pC N -1 and kp ∼ 47.8%. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

News Article | December 21, 2016

In the process, Meinert will study questions such as: How did Buddhism spread in multi-cultural, multi-linguistic and multi-religious Central Asia? Which local cultures were influenced by Buddhist ideas? And how did Buddhist beliefs change following the foray into those vast regions of deserts and steppes? The project bears the title "Dynamics in Buddhist Networks in Eastern Central Asia, 6th-14th Centuries", or "Buddhist Road" for short. It is one of eight German projects in the field of social studies and humanities that were selected by the ERC. In the course of the project, the researchers will for the first time investigate the transregional historical links between the Buddhist traditions in modern China, India and Tibet and the regional Buddhist cultures in Central Asia. Projected activities include source analyses of manuscripts in various European archives, as well as several field research trips in the regions of the medieval Buddhist Kingdom of Khotan, the Uyghur Khaganate and the Tangut Empire - regions that today are part of the territory of the People's Republic of China. The international team from Bochum is mainly interested in the way traders and monks distributed Buddhist ideas along the Silk Roads and to what extent those ideas were adopted by native peoples. So far, Buddhism in Eastern Central Asia has not yet been thoroughly studied from the point of view of interregional contacts. Carmen Meinert's team investigates it from the perspective of comparative religious studies. The academics intend to establish a new research approach that incorporates philology, art history, archaeology and religious studies. Thus, they wish to analyse the exchange of religious beliefs in Eastern Central Asia as a dynamic network. Carmen Meinert studied Sinology, Tibetology and Geography at the University of Bonn, where she was awarded her PhD in 2001. She worked as a researcher at Peking University, at Sichuan University, at the University of Hamburg and at the Institute for Advanced Studies in Humanities in Essen. In 2013, Carmen Meinert was appointed Professor for Central Asian Religions at the Centre for Religious Studies at Ruhr-Universität. Prior to that, she had worked as visiting research fellow at the Käte Hamburger Kolleg "Dynamics in the History of Religions between Asia and Europe". "Buddhist Road" is the second ERC-financed project at the Center for Religious Studies. In its capacity as a central research institution at Ruhr-Universität Bochum, the Center actively supports funding applications for innovative research projects in the fields of the history of religion and sociology of religion. Since 2015, the team of the "Jews East" project has been investigating the diverse historical interactions between Jews and Christians in the Middle East, the Caucasus, the Horn of Africa and Southern India.

AUGUSTA, Ga. (Dec. 19, 2016) - Scientists are using "gene scissors" to cut off the code of a defective gene that results in progressively weaker muscles and death in Duchenne muscular dystrophy and replace it with a synthetic code they hope will one day restore healthy life to these patients. "We want to use genetically corrected stem cells to replace the stem cell pool and make new muscles that function normally," said Dr. Yaoliang Tang, cardiovascular researcher in the Vascular Biology Center at the Medical College of Georgia at Augusta University. Tang is a principal investigator on a new $2.6 million National Institutes of Health grant that is enabling the studies in an animal model of the genetic disorder. Every gene has a code that tells it what protein(s) it will ultimately express. In the case of the dystrophin gene in this disease, the code is telling the DNA to tell the RNA to make a short, dysfunctional form of dystrophin, a protein in the muscle cell membrane that is essential to the structural integrity of muscle cells. "It's a construction piece," Dr. Mark Hamrick, bone biologist in the MCG Department of Cellular Biology and Anatomy, said of dystrophin. Muscle cells are normally strong but constantly under stress as we move, breathe and exercise, often experiencing tears but typically rapid repair as well. But in these patients, muscle cells are weak, more prone to injury and death and end up being replaced with small, even weaker muscle fibers. "You have so much regeneration that you get these weak little fibers; they are almost like a neonatal-type fiber; they are so small and weak," Hamrick said. Healthy, strong muscle tissue is soon replaced by weak, dysfunctional fibrous tissue. So the scientists are using technology called CRISPR-Cas9 to cut the problematic piece of the dystrophin gene out of muscle cells, and replace it with a synthetic code that enables normal dystrophin. They will ultimately return to their mouse model of Duchenne muscular dystrophy a progenitor muscle cell that is now expressing longer dystrophin and making stronger muscle cells that will eventually repopulate the weak muscle mass. They are starting with muscle cells from the mouse model and reverting them to a stem-cell like state, called induced pluripotent stem cells. The pluripotent stem cells, which can make any cell type, can be derived from embryonic tissue, but a decade ago, Japanese scientists developed a method to make induced versions from essentially any cell type - such as a muscle cell - a development that would garner a Nobel Prize. The MCG scientists will coax the induced pluripotent stem cells to become muscle progenitor cells, the precursor for the healthy muscle cells needed. The fact that the cells that will ultimately be returned, started with the individual - or the mouse in the case of this basic science study - also reduces concerns that giving the cells will result in a severe immune system response, Tang said. Gene editing also is more efficient in pluripotent stem cells than mature cells, he added. The additional benefit of starting with a muscle cell is that cells have some genetic memory, so these have a predisposition to become muscle cells again, Tang said. "It's going to home to the muscle and differentiate into a muscle cell. So it's going to go back in and rebuild everything," said Hamrick, a co-investigator on the new grant. One concern with using any type of stem cell is the possibility that these cells will also produce cancer. To diminish that possibility, Tang is adding a small molecule called Plurisin#1 to the mix that selectively targets stem cells for elimination. "After we do the gene editing and make the muscle progenitor cells, we just want to remove any tumor-potential pluripotent cells remaining before returning cells to the animal," Tang said. To further aid efficacy, they will use techniques like brief periods of ischemia and reperfusion in the muscles, a technique that Tang has shown will attract stem cells and enhance their activity. They also are engineering nano-sized compartments containing the stem-cell attracting protein SDF-1α for delivery to the dying muscle tissue. CRISPR-Cas9 enables scientists to edit problematic genes by using the Cas9 enzyme for cutting and an RNA molecule that helps identify the right target. The technology can be used to edit a gene, and, as in the case of Tang's study, to also reinsert a substitute. Duchenne muscular dystrophy is one of nine types of muscular dystrophy, according to the Muscular Dystrophy Association. Symptoms of weakness tend to rise between the ages of 3-5 in the condition that is far more common in males. Early on, patients can have trouble standing, keeping their balance and raising their arms. Death often results from respiratory and/or heart failure, since strong muscles are needed to drive these basic life functions. This fall, scientists at China's Sichuan University became the first to use the technology clinically to disable a gene, which can block the immune response, in the immune cells of a patient with aggressive lung cancer. Cancer typically uses the gene to its advantage to weaken the body's attack against it. The scientists then increased the immune cell number and injected them back into the patient. Additional trials are expected next year. It likely will be several years before the MCG scientists know whether their basic science studies will result in these types of clinical trials for patients with Duchenne muscular dystrophy, Tang and Hamrick said. Current therapies for Duchenne muscular dystrophy include steroids, bracing and physical therapy. Earlier this year, the Food and Drug Administration approved the drug eteplirsen for patients, a controversial decision - despite the welcome news for parents and children - because the clinical trial was only in a dozen patients and because of questions about whether the drug sufficiently increases levels of dystrophin. Dr. Neal L. Weintraub, associate director of MCG's Vascular Biology Center and Georgia Research Alliance Herbert S. Kupperman Eminent Scholar in Cardiovascular Medicine, also is a principal investigator on the multiple principal investigator NIH grant.

The government-backed effort, known as the Grain-for-Green Program, has transformed 28 million hectares (69.2 million acres) of cropland and barren scrubland back to forest in an effort to prevent erosion and alleviate rural poverty. While researchers around the world have studied the program, little attention has been paid to understanding how the program has affected biodiversity until now. New research led by Princeton University and published in the journal Nature Communications finds that China's Grain-for-Green Program overwhelmingly plants monoculture forests and therefore falls dramatically short of restoring the biodiversity of China's native forests, which contain many tree species. In its current form, the program fails to benefit, protect and promote biodiversity. Following a literature review, two years of fieldwork and rigorous economic analyses, the researchers found the vast majority of new forests contain only one tree species. While these monocultures may be a simpler route for China's rural residents—who receive cash and food payments, as well as technical support to reforest land—the single-species approach brings very limited biodiversity benefits, and, in some cases, even harms wildlife. The researchers conclude that restoring the full complement of native trees that once grew on the land would provide the best outcome for biodiversity. If native forests are unachievable within the current scope of the program, the researchers recommend mixed forests—which contain multiple tree species and more closely resemble natural forests—as a second option. Mixed forests better protect wildlife than monoculture forests, and would not financially burden farmers participating in the program. Both native and mixed forests also help to mitigate climate change. "Around the world, people are leaving rural areas and moving into cities, potentially creating new opportunities to restore forests on abandoned farmland," said co-author David Wilcove, professor of ecology and evolutionary biology and public affairs in Princeton's Woodrow Wilson School of Public and International Affairs and the Princeton Environmental Institute. "In many places, we're seeing efforts to reforest areas that have once been cleared, and China is the first country to do it on this large of a scale," he said. "The critical policy question is how to restore forests that provide multiple benefits to society, including preventing soil erosion, providing timber and sustaining wildlife. China has an opportunity to do it right and turn these monocultures into mixed or native forests that will be more valuable for wildlife in future years." "If the Chinese government is willing to expand the scope of the program, restoring native forests is, without doubt, the best approach for biodiversity," said lead author Fangyuan Hua, a postdoctoral research associate in the Program in Science, Technology and Environmental Policy in Princeton's Woodrow Wilson School. "But even within the current scope of the program, our analysis shows there are economically feasible ways to restore forests while also improving biodiversity." During the Great Leap Forward in the late 1950s, China converted millions of hectares of native forest to cropland. The country's unprotected forests continued to be heavily exploited in the decades that followed, but without an effective conservation system in place. After a series of powerful floods in the late 1990s, China's government launched a series of landmark ecological initiatives aimed at controlling soil erosion, including the Grain-for-Green Program. The program is in place in 26 of China's 31 mainland provinces and, while its central goal is to prevent erosion, most of the reestablished forest is now used for the production of timber, fiber, tree fruits and other cash crops. Rural residents are encouraged with cash and food incentives to plant forests, shrubs and grasslands, but there seems to be little consideration for biodiversity in determining what is planted. The research team—which included scholars from the Chinese Academy of Sciences, Sichuan University, the University of East Anglia in the United Kingdom and the University of Vermont—wanted to investigate how these approaches to planting influenced biodiversity. They examined four specific questions. "We asked: What types of forest are being established by the program across China?" Hua said. "Then, focusing on a particular region, we asked: How does the biodiversity of the new forests compare to the biodiversity of the croplands they are replacing? How do the new forests compare to native forests? And, would planting more diverse forests result in any biodiversity benefits while also being economically feasible?" The team examined 258 publications, most of which were written in Mandarin, to determine the current tree composition within forests planted by the program. Although the program included a large number of species across China as a whole, they found that the majority of individual forests were planted with only one tree species, such as bamboo, eucalyptus or Japanese cedar. Only three locations actually planted forest native to the area. "To our knowledge, this is the first nationwide synthesis of the tree-species composition of forests reestablished under the program," Hua said. "This is essential to understanding the program's biodiversity implications." Next, the team zeroed in on Sichuan Province in south-central China and conducted fieldwork on bird and bee diversity across all seasons. Birds and bees are good indicators of the overall biodiversity of a particular area, the researchers noted. "Birds are sensitive to the types of trees, the overall age of the forest and the insects within the forest, and bees depend more on resources like pollen or nectar from the understory. Together, these two taxa provide a well-rounded picture of biodiversity within a forest," Hua said. Birds were surveyed using point counts. This measurement entails counting the birds seen and heard from a grid of points placed in the forests and cropland that are separated by certain distances. The bee species were collected and identified using DNA barcoding. All fieldwork was conducted across different types of land including monocultures, mixed forests, cropland and native forest. The researchers found that reforesting land with monocultures resulted in more harm than good for birds. In regions with monocultures, there were fewer bird species, and birds tended to be less abundant. Mixed forests, however, harbored more bird species and similar overall numbers of birds compared with cropland. The bees suffered from reforestation regardless, which was likely caused by the lack of floral resources in replanted forests. Overall, the best environment for birds and bees is native forest, the researchers found, as opposed to the forests reestablished under the Green-for-Grain Program. "Together, our findings point to the enormous potential of biodiversity benefits that China's Green-for-Green Program has yet to realize," Hua said. In the final part of the study, the researchers conducted economic analyses in order to understand the economic impacts of reforestation. They interviewed 166 households and asked what percentage of household income came from forest production. The researchers also calculated the average annual cost of—and income from—forest production per hectare across different types of forests. The median and mean percentages of annual household income contributed by forest production were 5 percent and 12.8 percent, respectively. The net annual profits were not that high, hovering around $400 per hectare (roughly $160 per acre). In terms of profit, mixed forests yielded gains similar to those derived from monocultures. Therefore, switching to a mixed forest, which would improve biodiversity, is unlikely to pose economic risks to households, the researchers concluded. "The work done by Fangyuan and her team is an enormous task," Wilcove said. "These data are crucial. Restoring forests is a tremendously positive thing to do for the world, but you can get a lot more bang for the buck in terms of benefits to society if you know how to do it right based on sound biological and economic data. Fangyuan's work provides this type of keen analysis." More information: Fangyuan Hua et al, Opportunities for biodiversity gains under the world's largest reforestation programme, Nature Communications (2016). DOI: 10.1038/ncomms12717

News Article | November 23, 2016

A Chinese group has become the first to inject a person with cells that contain genes edited using the revolutionary CRISPR–Cas9 technique. On 28 October, a team led by oncologist Lu You at Sichuan University in Chengdu delivered the modified cells into a patient with aggressive lung cancer as part of a clinical trial at the West China Hospital, also in Chengdu. Earlier clinical trials using cells edited with a different technique have excited clinicians. The introduction of CRISPR, which is simpler and more efficient than other techniques, will probably accelerate the race to get gene-edited cells into the clinic across the world, says Carl June, who specializes in immunotherapy at the University of Pennsylvania in Philadelphia and led one of the earlier studies. "I think this is going to trigger ‘Sputnik 2.0’, a biomedical duel on progress between China and the United States, which is important since competition usually improves the end product,” he says. June is the scientific adviser for a planned US trial that will use CRISPR to target three genes in participants’ cells, with the goal of treating various cancers. He expects the trial to start in early 2017. And in March 2017, a group at Peking University in Beijing hopes to start three clinical trials using CRISPR against bladder, prostate and renal-cell cancers. Those trials do not yet have approval or funding. Lu’s trial received ethical approval from a hospital review board in July. Injections into participants were supposed to begin in August but the date was pushed back, Lu says, because culturing and amplifying the cells took longer than expected and then the team ran into China’s October holidays. The researchers removed immune cells from the recipient’s blood and then disabled a gene in them using CRISPR–Cas9, which combines a DNA-cutting enzyme with a molecular guide that can be programmed to tell the enzyme precisely where to cut. The disabled gene codes for the protein PD-1, which normally puts the brakes on a cell’s immune response: cancers take advantage of that function to proliferate. Lu’s team then cultured the edited cells, increasing their number, and injected them back into the patient, who has metastatic non-small-cell lung cancer. The hope is that, without PD-1, the edited cells will attack and defeat the cancer. Lu says that the treatment went smoothly, and that the participant will get a second injection, but declined to give details because of patient confidentiality. The team plans to treat a total of ten people, who will each receive either two, three or four injections. It is primarily a safety trial, and participants will be monitored for six months to determine whether the injections are causing serious adverse effects. Lu’s team will also watch them beyond that time to see if they seem to be benefiting from the treatment. Other oncologists are excited about CRISPR’s entry onto the cancer scene. “The technology to be able to do this is incredible,” says Naiyer Rizvi of Columbia University Medical Center in New York City. Antonio Russo of Palermo University in Italy notes that antibodies that neutralize PD-1 have successfully put lung cancer in check, boding well for a CRISPR-enabled attack on the protein. “It’s an exciting strategy,” he says. “The rationale is strong.” But Rizvi questions whether this particular trial will succeed. The process of extracting, genetically modifying and multiplying cells is “a huge undertaking and not very scalable”, he says. “Unless it shows a large gain in efficacy, it will be hard to justify moving forward.” He doubts it will be superior to the use of antibodies, which can be expanded to unlimited quantities in the clinic. Lu says that this question is being evaluated in the trial, but that it’s too early to say which approach is better.

News Article | December 14, 2016

Scientists at Sichuan Revotek and the Regenerative Medicine Research Center of West China Hospital at Sichuan University have successfully embedded 3D-printed blood vessels into simian test subjects. The vessels, which are made of stem cell-based organic material, were a major breakthrough in vascular regeneration. According to 3Ders the system uses “stem cell bioink, which was prepared from the autologous adipose mesenchymal stem cells (ADSCs) of the monkeys.” Essentially the material came from the monkeys themselves and were not subject to organ rejection. The process involves creating a 3D-printed scaffold of biological material that grafts to natural blood vessels and are virtually indistinguishable from the monkey’s natural organs. This means that real, usable organs and be printed and implanted in a few hours with minimum invasiveness. “The tissues we implanted will have mingled with the original ones and grown into a regular vessel,” said researcher Kang Yujian. “This is unprecedented.” You can check out another fairly gory video here or watch a short animation below.

News Article | January 13, 2016

In the northern reaches of the Tibetan Plateau, dozens of yaks graze on grasslands that look like a threadbare carpet. The pasture has been munched down to bare soil in places, and deep cracks run across the snow-dusted landscape. The animals' owner, a herder named Dodra, emerges from his home wearing a black robe, a cowboy hat and a gentle smile tinged with worry. “The pastures are in a bad state and lack the kind of plants that make livestock strong and grow fat,” says Dodra. “The yaks are skinny and produce little milk.” His family of eight relies on the yaks for most of its livelihood — milk, butter, meat and fuel. Dodra was forced to give up half of his animals a decade ago, when the Chinese government imposed strict limits on livestock numbers. Although his family receives financial compensation, nobody knows how long it will last. “We barely survive these days,” he says. “It's a hand-to-mouth existence.” If the grasslands continue to deteriorate, he says, “we will lose our only lifeline”. The challenges that face Dodra and other Tibetan herders are at odds with glowing reports from Chinese state media about the health of Tibetan grasslands — an area of 1.5 million square kilometres — and the experiences of the millions of nomads there. Since the 1990s, the government has carried out a series of policies that moved once-mobile herders into settlements and sharply limited livestock grazing. According to the official account, these policies have helped to restore the grasslands and to improve standards of living for the nomads. But many researchers argue that available evidence shows the opposite: that the policies are harming the environment and the herders. “Tibetan grasslands are far from safe,” says Wang Shiping, an ecologist at the Chinese Academy of Sciences' (CAS) Institute of Tibetan Plateau Research (ITPR) in Beijing. “A big part of the problem is that the policies are not guided by science, and fail to take account of climate change and regional variations.” The implications of that argument stretch far beyond the Tibetan Plateau, which spans 2.5 million square kilometres — an area bigger than Greenland — and is mostly controlled by China. The grasslands, which make up nearly two-thirds of the plateau, store water that feeds into Asia's largest rivers. Those same pastures also serve as a gigantic reservoir of carbon, some of which could escape into the atmosphere if current trends continue. Degradation of the grasslands “will exacerbate global warming, threaten water resources for over 1.4 billion people and affect Asian monsoons”, says David Molden, director general of the International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu, Nepal. Such concerns propelled me to make a 4,700-kilometre journey last year from Xining, on the northeastern fringe of the plateau, to Lhasa in the Tibetan heartland (see 'Trek across Tibet'). Meeting with herders and scientists along the way, I traversed diverse landscapes and traced the Yellow and Yangtze Rivers to their sources. The trip revealed that Tibetan grasslands are far less healthy than official government reports suggest, and scientists are struggling to understand how and why the pastures are changing. It began to drizzle soon after we set off from the city of Xining on a stretch of newly built highway along the Yellow River. As our Land Cruiser climbed onto a 3,800-metre-high part of the plateau, the vista opened to reveal rolling hills blanketed by a thick layer of alpine meadow, resembling a gigantic golf course. We passed herds of sheep and yaks, white tents and nomads in colourful robes — along with barbed-wired fences that cut the rangeland into small blocks. This part of the Tibetan Plateau, in a region known as Henan county, is blessed with abundant monsoonal rains every summer. The herders who live here are able to maintain healthy livestock and can make a decent living. “We have plenty to go around, and the livestock are well taken care of,” says herder Gongbu Dondrup. But life has been different since the government began to fence up grasslands around a decade ago, says Dondrup. Before that, he took his herd to the best pastures at high elevations in the summer, and then came back down in the winter. Now, he must keep the yaks in an 80-hectare plot that the government assigned to his family. The pasture looks worn, and he is being pressed by the government to further downsize his herd. “I don't know how long it can keep us going,” he says. The fencing initiative is the latest of a string of Chinese grassland policies. After annexing Tibet in 1950, the young revolutionary Chinese republic turned all livestock and land into state properties. Large state farms competed with each other to maximize production, and livestock numbers on the plateau doubled over two decades, reaching nearly 100 million by the late 1970s. But in the 1980s, as China moved towards a market-based economy, Beijing swung to the other extreme: it privatized the pastures and gave yaks back to individual households, hoping that the move would push Tibetans to better manage their land and so boost its productivity. Despite the privatization, nomads continued to use the rangeland communally — often in groups led by village elders. Then the government began to limit herds, and it built fences to separate households and villages. “This has totally changed the way livestock are traditionally raised on the plateau, turning a mobile lifestyle into a sedentary existence,” says Yang Xiaosheng, director of Henan county's rangeland-management office. The fencing policy does have merits when applied in moderation, says Yönten Nyima, a Tibetan policy researcher at Sichuan University in Chengdu. Because an increasing number of nomads now lead a settled life — at least for parts of the year — it helps to control the level of grazing in heavily populated areas, he says. “Fencing is an effective way to keep animals out of a patch of meadow.” Many herders also say that it makes life much easier: they do not have to spend all day walking the hills to herd their yaks and sheep, and if they go away for a few days, they don't worry about the animals running off. But the convenience comes at a cost, says Cao Jianjun, an ecologist at Northwest Normal University in Lanzhou. Fenced pastures often show signs of wear after a few years. In a 2013 study, Cao and his colleagues measured growth of the sedge species preferred by livestock in two scenarios: enclosed pastures and much larger patches of land jointly managed by up to 30 households. Despite similar livestock densities in both cases, the sedge grew twice as fast in the larger pastures, where animals could roam and plants had more opportunity to recover1. That matches the experience of Henan county herders, who say that their land sustains fewer animals than it has in the past. The future of the grasslands looked even bleaker as we left relatively well-to-do Henan county and ventured into the much higher, arid territory to the west. After 700 kilometres, we reached Madoi county, also known as qianhu xian ('county of a thousand lakes'), where the Yellow River begins. Although this region gets only 328 millimetres of rain on average each year, about half of what Henan receives, Madoi was once one of the richest counties on the plateau — famous for its fish, high-quality livestock and gold mines. Now, the wetlands are drying up and sand dunes are replacing the prairies, which means that less water flows into the Yellow River. Such changes on the plateau have contributed to recurring water shortages downstream: the Yellow River often dries up well before it reaches the sea, an event not recorded before 1970. In 2000, China sought to protect this region, along with adjacent areas that give rise to the Yangtze and Mekong Rivers, by establishing the Sanjiangyuan (or Three-Rivers' Headwaters) National Nature Reserve, an area nearly two-thirds the size of the United Kingdom. Nearly one-tenth of the reserve area falls into core zones in which all activities, including herding, are prohibited. The government spends hundreds of millions of US dollars each year on moving nomads out of those core areas, constructing steel meshes to stabilize the slopes and planting artificially bred grass species to restore the eroded land. Outside the core regions, officials have banned grazing on 'severely degraded grasslands', where vegetation typically covers less than 25% of the ground. Land that is 'moderately degraded', where vegetation coverage measures 25–50%, can be grazed for half of the year. Such policies — and related initiatives to limit livestock numbers and fence off areas of pasture — have not been easy on the herders, says Guo Hongbao, director of the livestock-husbandry bureau in Nagchu county in the southern Tibetan Plateau. “The nomads have made sacrifices for protecting the grasslands,” he says. But he also says that the strategies have paid off. Guo and other officials point to satellite studies showing that the plateau has grown greener in the past three decades2. This increase in vegetation growth, possibly the result of a combination of grazing restrictions and climate change, “has had a surprisingly beneficial effect on climate by dampening surface warming”, says Piao Shilong, a climate modeller at Peking University. But ecologists say that such measurements look only at surface biomass and thus are not a good indicator of grassland health. “Not all vegetation species are equal,” says Wang. “And satellites can't see what's going on underground.” This is particularly important in the case of the sedge species that dominate much of the Tibetan Plateau, and that are the preferred food of livestock. These species, part of the Kobresia genus, grow only 2 centimetres above the surface and have a dense, extensive root mat that contains 80% of the total biomass. Studies of pollen in lake sediments show that Kobresia and other dominant sedges emerged about 8,000 years ago, when early Tibetans began burning forests to convert them to grasslands for livestock3. The prehistoric grazing helped to create the thick root mat that blankets the vast plateau and that has stored 18.1 billion tonnes of organic carbon. But Kobresia plants are being driven out by other types of vegetation, and there is a risk that the locked-up carbon could be released and contribute to global warming. Every now and then on the trip to Lhasa, we passed fields blooming with the beautiful red and white flowers of Stellera chamaejasme, also known as wolf poison. “It's one of a dozen poisonous species that have increasingly plagued China's grasslands,” says Zhao Baoyu, an ecologist at the Northwest Agriculture and Forestry University in Yangling. Zhao and his colleagues estimated that poisonous weeds have infested more than 160,000 square kilometres of the Tibetan grasslands, killing tens of thousands of animals a year4. Herders also report seeing new grass species and weeds emerge in recent years. Although most are not toxic, they are much less nutritious than Kobresia pastures, says Karma Phuntsho, a specialist on natural-resource management at ICIMOD. “Some parts of the plateau may seem lush to an untrained eye,” he says. “But it's a kind of 'green desertification' that has little value.” In one unpublished study of the northeastern Tibetan Plateau, researchers found that Kobresia pastures that had gone ungrazed for more than a decade had been taken over by toxic weeds and much taller, non-palatable grasses: the abundance of the sedge species had dropped from 40% to as low as 1%. “Kobresia simply doesn't stand a chance when ungrazed,” says Elke Seeber, a PhD student at the Senckenberg Natural History Museum in Görlitz, Germany, who conducted the field experiment for a project supported by the German Research Foundation (DFG). The changes in vegetation composition have important implications for long-term carbon storage, says project member Georg Guggenberger, a soil scientist at Leibniz University of Hanover in Germany. In moderately grazed Kobresia pastures, up to 60% of the carbon that is fixed by photosynthesis went into the roots and soil instead of the above-ground vegetation — three times the amount seen in ungrazed plots5. This underground organic carbon is much more stable than surface biomass, which normally decomposes within a couple of years and releases its stored carbon into the air. So a shift from Kobresia sedge to taller grasses on the plateau will ultimately release a carbon sink that has remained buried for thousands of years, says Guggenberger. Critics of the grazing restrictions in Tibet say that the government has applied them in a blanket way, without proper study and without taking on board scientific findings. In some cases, they make sense, says Tsechoe Dorji, an ecologist at the ITPR's Lhasa branch, who grew up in a herder family in western Tibet. “A total grazing ban can be justified in regions that are severely degraded”, he says, but he objects to the simple system used by the government to classify the health of the grasslands. It only considers the percentage of land covered by vegetation and uses the same threshold for all areas, without adjusting for elevation or natural moisture levels. “Pastures with 20% vegetation cover, for instance, could be severely degraded at one place but totally normal at another,” says Dorji. This means that some of the grasslands that are classified as severely degraded are actually doing fine — and the grazing ban is actually hurting the ecosystem. “Having a sweeping grazing policy regardless of geographical variations is a recipe for disasters,” he says. China's grazing policy is only one of several factors responsible for such damaging changes, say the researchers. Pollution, global warming and a rash of road-building and other infrastructure-construction projects have all taken a toll on the grasslands. Ten days after leaving Xining, we caught a glimpse of Tibet's future when we arrived at Nam Tso, a massive glacial lake in the southern part of the plateau. Here Dorji and Kelly Hopping, a graduate student at Colorado State University in Fort Collins, have been turning the clock forward by surrounding small patches of grassland with open-topped plastic chambers that artificially raise the temperature. These experiments are important because Tibet is a hotspot in terms of climate change; the average temperature on the plateau has soared by 0.3–0.4 °C per decade since 1960 — about twice the global average. In trials over the past six years, they found that Kobresia pygmaea, the dominant sedge species, develops fewer flowers and blooms much later under warming conditions6. Such changes, says Dorji, “may compromise its reproductive success and long-term competitiveness”. At the experimental site, the artificially warmed pastures have been taken over by shrubs, lichens, toxic weeds and non-palatable grass species, says Hopping. But when the researchers added snow to some heated plots, Kobresia did not lose out to the other plants, which suggests that the loss of soil moisture might be driving the shift in species. Higher temperatures increase evaporation, which can be especially potent at high elevations. “This is not good news for species with shallow roots”, such as the Kobresia favoured by livestock, she says. Piao says that “this interplay between temperature and precipitation illustrates the complexity of ecosystem responses to climate change”. But researchers have too little information at this point to build models that can reliably predict how global warming will affect the grasslands, he says. To fill that gap, Wang and his colleagues started a decade-long experiment in 2013 at Nagchu, where they are using heat lamps to warm patches of grassland by precise amounts, ranging from 0.5 °C to 4 °C. They are also varying the amount of rainfall on the plots, and they are measuring a host of factors, such as plant growth, vegetation composition, nutrient cycling and soil carbon content. They hope to improve projections for how the grasslands will change — and also to determine whether there is a tipping point that would lead to an irreversible collapse of the ecosystem, says Piao. A fortnight into the trip, we finally arrived at the outskirts of Lhasa. At the end of the day, herders were rounding up their sheep and yaks in the shadows cast by snow-capped peaks. They and the other pastoralists across the plateau will have a difficult time in coming decades, says Nyima. Climate change was not a consideration when grassland polices were conceived over a decade ago, and so “many pastoralists are ill prepared for a changing environment”, he says. “There is a pressing need to take this into account and identify sound adaptation strategies.” As a start, researchers would like to conduct a comprehensive survey of plant cover and vegetation composition at key locations across different climate regimes. “The information would form the baseline against which future changes can be measured,” says Wang. Many scientists would also support changes to the grazing ban and fencing policies that have harmed the grasslands. Dorji says that the government should drop the simplistic practice of 'one policy fits all' across the plateau and re-evaluate whether individual regions are degraded enough to merit a ban on grazing. “Unless the pastures are severely degraded, moderate grazing will help to restore the ecosystems,” he says. But scientists are not banking on such reforms happening soon. Policies in Tibet are driven less by scientific evidence than by bureaucrats' quest for power and funds, says a Lhasa-based researcher who requests anonymity for fear of political repercussions. Local officials often lobby Beijing for big investments and expensive projects in the name of weiwen (meaning 'maintaining stability'). Because resistance to Chinese control over Tibet continues to flare up, the government is mostly concerned with maintaining political stability, and it does not require local officials to back up plans with scientific support, says the researcher. “As long as it's for weiwen, anything goes.” But officials such as Guo say that their policies are intended to help Tibet. “Although there is certainly room for improvement in some of the policies, our primary goals are to promote economic development and protect the environment,” he says. Far away from Lhasa, herders such as Dodra say that they are not seeing the benefits of government policies. After we finish our visit at his home, Dodra's entire family walks us into the courtyard — his mother in-law spinning a prayer wheel and his children trailing behind. It has stopped snowing, and the sky has turned a crystal-clear, cobalt blue. “The land has served us well for generations,” says Dodra as he looks uneasily over his pasture. “Now things are falling apart — but we don't get a say about how best to safeguard our land and future.”

News Article | November 16, 2016

The powerful gene-editing CRISPR-Cas9 technique is a promising tool in the fight against conditions like retinal degradation, muscular dystrophy and HIV, but so far trials have been restricted to cultured cells and laboratory mice. Now the tool is being used in human trials for the first time, with a team of Chinese scientists injecting CRISPR-edited cells into a patient suffering from lung cancer. CRISPR works like a pair of genetic scissors, allowing scientists to cut very specific sections of DNA out of an organism, such as inherited genes that may lead to disease, and replace them with something more beneficial. Along with its potential to fight cancer and other illnesses in humans, the technique can be used in other living organisms for a variety of purposes, like pest control or improving the yield, hardiness and nutritional value of crops. The current study, led by oncologist Lu You at Sichuan University, is using the technique to modify immune cells of patients with metastatic non-small-cell lung cancer, in the hope that it might boost the body's defenses. In basic terms, the immune system uses a type of white blood cell called a T cell to detect and kill abnormal cells that may turn cancerous. T cells have a built-in mechanism called Programmed cell death protein 1 (PD-1) that shuts them down when they're done, and one of cancer's crafty little tricks is to trigger that process early, weakening the body's immune response and allowing the tumor to grow. To combat this, the Sichuan study is collecting samples of a patient's immune cells and using CRISPR-Cas9 to remove the gene in which PD-1 is encoded. These engineered PD-1 Knockout T cells, as the team calls them, are then cultured in the lab to grow their numbers before being injected back into the patients. Without the PD-1 protein for the cancer to turn against the immune system, the team hopes that the engineered T cells will be able to keep up the fight and kill the tumor. The trial was greenlit in July after receiving ethical approval from a hospital review board, and after collecting and cultivating the T cells, the first patient was injected with edited cells on October 28. While the researchers haven't given details regarding the patient's progress, the treatment apparently went well, and a second injection is planned. The aim of the trial is mostly to determine the safety of the procedure, and to that end, 10 patients will be treated with either two, three or four injections. The study is expected to conclude in April 2018. Several other human trials using CRISPR-Cas9 are currently in the pipeline, including a University of Pennsylvania study expected to start early next year, and a series of others at Peking University in Beijing.

News Article | December 5, 2016

The recipient of the 2017 Acta Biomaterialia Gold Medal is Professor Allan S. Hoffman,             Emeritus Professor of Bioengineering at the University of Washington in Seattle. The Award will be presented at the 2017 Meeting of the Society for Biomaterials to be held in Minneapolis in April 2017. Professor Hoffman studied at M.I.T., where he received his B.S., M.S., and Sc.D. degrees in Chemical Engineering between 1953 and 1957. He taught on the faculty of the Chemical Engineering Department at M.I.T. for a total of ten years. He then spent 46 years as Professor of Bioengineering and Chemical Engineering at the University of Washington in Seattle, Washington. Prof. Hoffman’s major research interests are in drug delivery; diagnostic assays; “smart”, stimuli-responsive polymers; hydrogels; and chemical and biological modification of biomaterial surfaces. He has published over 400 peer-reviewed articles and is co-inventor on over 35 issued patents.  He is co-Editor (along with Buddy D. Ratner, Fred J. Schoen and Jack E. Lemons) of “Biomaterials Science”, Elsevier Publishers, now in its 3rd Edition. His early work in 1984 on the use of “smart” polymers in a temperature-driven phase separation immunoassay sparked a huge worldwide interest in such stimuli-responsive polymers as biomaterials.  Biomedical applications of “smart” polymers continue to grow rapidly around the world at the present time. He has been an Honorary Professor at: Sichuan University, Chengdu, China; South China University of Technology, Guangzhou, China; Wuhan University, Wuhan, China; Shanghai University, Shanghai, China; and Aarhus University, Aarhus, Denmark. In 2013 he completed a four-year appointment (2009-2013) as WCU (“World Class University”) Distinguished Professor at the Kyungpook National University Medical School in Daegu, South Korea. Professor Hoffman was elected to the US National Academy of Engineering in 2005.  His other recognitions and awards include Presidency of the US Society for Biomaterials (1983); the “Biomaterials Science Prize” of the Japanese Society for Biomaterials (1990); the Founders’ Award of the US Society for Biomaterials (in 2000); the Chandra Sharma Award of the Society for Biomaterials and Artificial Organs of India (2003); the “International Polymer Research Award” of the Japanese Society of Polymer Science (2006), and the Founder’s Award of the US Controlled Release Society (2007); Special symposia have been organized in Maui, Hawaii by his colleagues to celebrate his 60th, 70th and 80th birthdays. Former students, along with many academic colleagues, have also organized symposia which they have called “Hoffman Family Symposia” (HFS) and since 2010 there have been four, the first two were in Tokyo, Japan in 2012 and 2014, the third was in Gwangju, Korea in 2015, and a fourth was in Taipei, Taiwan September, 2016.  A fifth HFS will be held in Shanghai, China this coming October, 2017.

News Article | November 4, 2016

The Third Summit on University Social Responsibility (USR), a key initiative of the University Social Responsibility Network (USR Network), kicked-off today (4 November) in Beijing. Co-hosted by The Hong Kong Polytechnic University (PolyU) and Peking University (Peking U), the Summit has attracted over 100 academia from around the world to gather together for a fruitful exchange on an important agenda: "Nurturing a Culture for University Social Responsibility". The Opening Ceremony was held at the Diaoyutai State Guesthouse. Addressing the Opening ceremony, Peking University President Professor Lin Jianhua said, "For universities in the Chinese mainland, we have a commitment to take on the responsibility for the society, the nation and the world. Peking University has inherited and has been diligently following this tradition. On the one hand, we teach students to bear social responsibility during their studies and after graduation. On the other hand, the Universities have to bear their responsibility for the community, the region, and the nation, during their course of development and advancement." Professor Lin added, "This is a difficult mission, and it calls for concerted efforts of higher education leaders." Speaking at the Opening Ceremony, PolyU President Professor Timothy W. Tong said, "Over the last few decades, global challenges such as economic development, environmental protection and technological innovation have driven universities worldwide to redefine their roles and responsibilities beyond traditional education and research in order to bolster their impact on society. Consequently, social responsibility has become a subject high on the agenda." Professor Tong added, "The USR Network member universities sharing the same vision of making our world increasingly just, inclusive, peaceful and sustainable. With an emphasis on collaboration among members and with other networks and alliances, the Network has vigorously promoted USR by organizing a number of projects including this University Social Responsibility Summit." This year, the Summit has brought together more than 50 speakers who are higher education leaders and scholars from over 10 countries and regions. They exchanged views at three Presidents' Roundtable sessions respectively themed "Social Responsibility: A Core Mission of Universities in 21st Century?", "USR: Translating Vision into Action and Impact", and "USR in Asia: Challenges and Opportunities". Plenary sessions held tomorrow (5 November) will include "Community Engagement in Higher Education: Policy and Practice", "Nurturing Future Leaders through Service-Learning: Strategies and Learning Outcomes" and "Building Disaster Response Capacity - University Students as Community First Responders". This is the first time that the Summit has a separate Student Forum on 4 November at Peking University campus. The Forum attracted more than 100 students, many of them are delegates from the USR Network member universities. In addition, there will be a student presentation tomorrow. Four teams of students from PolyU, PekingU, Sichuan University and Beijing Normal University conducted presentations to share the views and practical experience of USR from the students' perspective. Their presence and contribution at the Summit are evidence of the USR Network's commitment to engaging the university community to address world challenges and shape a better future. The second Executive Committee meeting of the USR Network was held yesterday (3 November) to discuss the strategies and work for the coming year. With two new members, University of Sao Paulo, Brazil and University of Pretoria, South Africa, the USR Network now include the following 14 universities (in alphabetical order of their country): For details of the USR Network, please visit

News Article | November 4, 2016

The Opening Ceremony was held at the Diaoyutai State Guesthouse. Addressing the Opening ceremony, Peking University President Professor Lin Jianhua said, “For universities in the Chinese mainland, we have a commitment to take on the responsibility for the society, the nation and the world. Peking University has inherited and has been diligently following this tradition. On the one hand, we teach students to bear social responsibility during their studies and after graduation. On the other hand, the Universities have to bear their responsibility for the community, the region, and the nation, during their course of development and advancement.” Professor Lin added, “This is a difficult mission, and it calls for concerted efforts of higher education leaders.” Speaking at the Opening Ceremony, PolyU President Professor Timothy W. Tong said, “Over the last few decades, global challenges such as economic development, environmental protection and technological innovation have driven universities worldwide to redefine their roles and responsibilities beyond traditional education and research in order to bolster their impact on society. Consequently, social responsibility has become a subject high on the agenda.” Professor Tong added, “The USR Network member universities sharing the same vision of making our world increasingly just, inclusive, peaceful and sustainable. With an emphasis on collaboration among members and with other networks and alliances, the Network has vigorously promoted USR by organizing a number of projects including this University Social Responsibility Summit.” This year, the Summit has brought together more than 50 speakers who are higher education leaders and scholars from over 10 countries and regions. They exchanged views at three Presidents’ Roundtable sessions respectively themed “Social Responsibility: A Core Mission of Universities in 21st Century?”, “USR: Translating Vision into Action and Impact”, and “USR in Asia: Challenges and Opportunities”. Plenary sessions held tomorrow (5 November) will include “Community Engagement in Higher Education: Policy and Practice”, “Nurturing Future Leaders through Service-Learning: Strategies and Learning Outcomes” and “Building Disaster Response Capacity – University Students as Community First Responders”. This is the first time that the Summit has a separate Student Forum on 4 November at Peking University campus. The Forum attracted more than 100 students, many of them are delegates from the USR Network member universities. In addition, there will be a student presentation tomorrow. Four teams of students from PolyU, PekingU, Sichuan University and Beijing Normal University conducted presentations to share the views and practical experience of USR from the students’ perspective. Their presence and contribution at the Summit are evidence of the USR Network’s commitment to engaging the university community to address world challenges and shape a better future. The second Executive Committee meeting of the USR Network was held yesterday (3 November) to discuss the strategies and work for the coming year. With two new members, University of Sao Paulo, Brazil and University of Pretoria, South Africa, the USR Network now include the following 14 universities (in alphabetical order of their country): Australia | University of New South Wales Brazil | University of Sao Paulo Hong Kong, P.R.C. | The Hong Kong Polytechnic University Israel | University of Haifa Japan | Kyoto University Korea | Yonsei University P.R.C. | Peking University P.R.C. | Beijing Normal University P.R.C. | Sichuan University P.R.C. | South Africa University of Pretoria U.K. | Clare Hall, University of Cambridge U.K. | The University of Manchester U.S.A. | Tufts University U.S.A. | Washington University in St. Louis For details of the USR Network, please visit

Huang H.,Ewha Womans University | Huang H.,Shandong University of Technology | Nandhakumar R.,Karunya University | Choi M.,Ewha Womans University | And 2 more authors.
Journal of the American Chemical Society | Year: 2013

The chiral ketone (S)-3 shows high kinetic enantioselectivities toward the l form for general underivatized amino acids with hydrophobic side chains and a high thermodynamic enantioselectivity toward the d form for cysteine with its -SH polar side chain when used as an extractant in enantioselective liquid-liquid extractions in the presence of Aliquat 336. Consecutive extractions by imine formation and hydrolysis increase the enantiopurity of the amino acid, as both of these reactions are l-form-selective. © 2013 American Chemical Society.

Wang K.,Sichuan University | Zhang T.,Chengdu Medical College | Dong Q.,University of Sichuan | Nice E.C.,Monash University | And 2 more authors.
Cell Death and Disease | Year: 2013

Stem cells are characterized by their unique ability of self-renewal to maintain the so-called stem cell pool. Over the past decades, reactive oxygen species (ROS) have been recognized as toxic aerobic metabolism byproducts that are harmful to stem cells, leading to DNA damage, senescence or cell death. Recently, a growing body of literature has shown that stem cells reside in redox niches with low ROS levels. The balance of Redox homeostasis facilitates stem cell self-renewal by an intricate network. Thus, to fully decipher the underlying molecular mechanisms involved in the maintenance of stem cell self-renewal, it is critical to address the important role of redox homeostasis in the regulation of self-renewal and differentiation of stem cells. In this regard, we will discuss the regulatory mechanisms involved in the subtly orchestrated balance of redox status in stem cells by scavenger antioxidant enzyme systems that are well monitored by the hypoxia niches and crucial redox regulators including forkhead homeobox type O family (FoxOs), apurinic/apyrimidinic (AP) endonuclease1/redox factor-1 (APE1/Ref-1), nuclear factor erythroid-2-related factor 2 (Nrf2) and ataxia telangiectasia mutated (ATM). We will also introduce several pivotal ROS-sensitive molecules, such as hypoxia-inducible factors, p38 mitogen-activated protein kinase (p38) and p53, involved in the redoxregulated stem cell self-renewal. Specifically, all the aforementioned molecules can act as 'redox sensors' by virtue of redox modifications of their cysteine residues, which are critically important in the control of protein function. Given the importance of redox homeostasis in the regulation of stem cell self-renewal, understanding the underlying molecular mechanisms involved will provide important new insights into stem cell biology. © 2013 Macmillan Publishers Limited.

Xu H.-Y.,Harbin University of Science and Technology | Zheng Z.,Sichuan University | Mao G.-J.,Heilongjiang University
Journal of Hazardous Materials | Year: 2010

The existence of 'electrostatic poles' on the schorl surface encouraged us to apply schorl for a TiO2 support. TiO2/schorl composite photocatalyst was prepared and characterized by XRD, SEM and UV/DRS, and their photocatalytic activity was evaluated by discoloration of acid fuchsine (AF). The results indicated that TiO2 existed in the form of anatase and was well deposited and enwrapped on the schorl surface. The absorption edge of TiO2/schorl exhibited a slight red shift in the UV/DRS spectra, compared with that of pure TiO2. The photocatalytic activity of TiO2/schorl for AF discoloration was higher than that of pure TiO2. The AF discoloration ratio approached 100% after irradiation time of 12 h. The optimum photocatalyst was found to be that containing 4.76 wt.% of schorl and sintered at 550 °C. The reaction followed pseudo-first-order kinetics, discussed by the Langmuir-Hinshelwood model. Hypotheses were proposed to interpret the mechanism for the enhanced photocatalytic activity of TiO2/schorl. © 2009 Elsevier B.V. All rights reserved.

Luo H.,Sichuan University | Song F.,Sichuan University | Zhang L.,Chengdu Medical College | Hou Y.,Sichuan University
International Journal of Legal Medicine | Year: 2015

In the present study, 23 Y-STR loci (DYS576, DYS389I, DYS389 II, DYS448, DYS19, DYS391, DYS481, DYS549, DYS533, DYS438, DYS437, DYS570, DYS635, DYS390, DYS439, DYS392, DYS393, DYS458 DYS456, DYS643, YGATAH4, and DYS385ab) were investigated in 266 unrelated, healthy autochthonous individuals from the Zhuang minority population residing in the Guangxi Zhuang Autonomous Region, China. One hundred and eighty-nine alleles and 245 haplotypes were found in the Zhuang group. Two hundred and twenty-four haplotypes among them were unique, and the remaining 21 haplotypes were found in two individuals. Discrimination capacity was 0.9211. Haplotype diversity was 0.9993 and gene diversity ranged from 0.4173 (DYS437) to 0.9678 (DYS385ab). Populations’ differentia was calculated and compared with Tibetan, Bai, Dai, Minnan Han, Beijing Han, Chengdu Han, Xuanwei Han, and Southern Han ethnic groups in China, the Singapore Han population, and the Kinh group from Ho Chi Minh City, Vietnam, in the same 23 Y-STR loci. Our results showed that these 23 Y-STRs are highly genetically polymorphic in the Zhuang group and can also enrich Chinese ethnic genetic information. © 2015, Springer-Verlag Berlin Heidelberg.

Chang J.,Shanghai JiaoTong University | Chang J.,Sichuan University | Lian P.,Shanghai JiaoTong University | Wei D.-Q.,Shanghai JiaoTong University | And 5 more authors.
Physical Review Letters | Year: 2010

The Car-Parrinello molecular dynamics simulations were employed to investigate thermal decomposition of the solid nitromethane. It is found that it undergoes chemical decomposition at about 2200 K under ambient pressure. The initiation of reactions involves both proton transfer and commonly known C-N bond cleavage. About 75 species and 100 elementary reactions were observed with the final products being H2O, CO2, N2, and CNCNC. It represents the first complete simulation of solid-phase explosive reactions reported to date, which is of far-reaching implication for design and development of new energetic materials. © 2010 The American Physical Society.

Cheng C.,Sichuan University | Nie S.,Sichuan University | Li S.,Sichuan University | Li S.,Shanghai JiaoTong University | And 5 more authors.
Journal of Materials Chemistry B | Year: 2013

A green and facile method for preparing biopolymer functionalized reduced graphene oxide (RGO) by using mussel inspired dopamine (DA) as the reducing reagent and the functionalized molecule is proposed. In the study, GO is reduced by DA and DA is adhered to RGO by one-step pH-induced polymerization of DA (polydopamine, PDA), and then heparin or protein is grafted onto the PDA adhered RGO (pRGO) through catechol chemistry. The obtained pRGO, heparin grafted pRGO (Hep-g-pRGO), and BSA grafted pRGO (BSA-g-pRGO) exhibit fine 2D morphology and excellent stability in water and PBS solution. Furthermore, the biocompatibility of the biopolymer functionalized RGO are investigated using human blood cells and human umbilical vein endothelial cells (HUVECs). The biopolymer functionalized RGO exhibits an ultralow hemolysis ratio (lower than 1.8%), and the cellular toxicity assay suggests that the biopolymer functionalized RGO has good cytocompatibility for HUVEC cells, even at a high concentration of 100 μg mL-1. Moreover, the high anticoagulant ability of Hep-g-pRGO indicates that the grafted biopolymer could maintain its biological activity after immobilization onto the surface of pRGO. Therefore, the proposed safe and green biomimetic method confers the biopolymer functionalized RGO with great potential for various biological and biomedical applications. © 2013 The Royal Society of Chemistry.

Liu H.,University of Auckland | Chen Y.,Sichuan University | Zhao H.,Nanjing University of Information Science and Technology | Wei S.,Sichuan University | Gao W.,University of Auckland
Journal of Alloys and Compounds | Year: 2010

The strontium (Sr) addition to the Mg-5 wt.%Sn alloy results in grain refinement and the formation of a rod-shaped and a bone-shaped MgSnSr intermetallic phase which are mainly straddle on the grain boundaries. The yield strength is improved, while the tensile strength and elongation first increased, and then decreased with a large addition of Sr. Optimum mechanical properties at ambient temperature are obtained at a content of 2.14 wt.%Sr. Tensile properties of the alloys at elevated temperatures are also improved, and the decrease of strength at elevated temperature slowed down with increasing Sr addition, indicating that Sr can improve the thermal stability of Mg-Sn alloys. © 2010 Elsevier B.V. All rights reserved.

Zhang H.,Sichuan University | Miyamoto Y.,Japan National Institute of Advanced Industrial Science and Technology | Rubio A.,University of the Basque Country
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We have used first-principles simulations based on time-dependent density functional theory to show that short laser pulses can trigger preferential hydrogen desorption from the upper or lower side of suspended graphane (H-terminated graphene). This control is achieved by using intense ultrashort p-polarized laser pulses (∼2 fs) with an asymmetric time envelope. The dynamical Stark effect induced by the pulse creates an asymmetric charge distribution and force field on the H ions, even at low laser fluence. At finite temperatures the carbon-hydrogen stretching softens, favoring H desorption from one side. This transient geometry can be modified by halogen functionalization, which results in a two-dimensional dipolar structure. © 2012 American Physical Society.

Zhao W.,KTH Royal Institute of Technology | Zhao W.,Sichuan University | Glavas L.,KTH Royal Institute of Technology | Odelius K.,KTH Royal Institute of Technology | And 2 more authors.
Chemistry of Materials | Year: 2014

A one-pot reaction to synthesize electrically conductive hemicellulose hydrogels (ECHHs) is developed via a facile and green approach in water and at ambient temperature. ECHHs were achieved by cross-linking O-acetyl- galactoglucomannan (AcGGM) with epichlorohydrin in the presence of conductive aniline pentamer (AP) and were confirmed by infrared spectroscopy (IR) and elemental analysis. All hydrogels had macro-porous structures, and the thermal stability of ECHHs was improved by the addition of AP. Hydrogel equilibrium swelling ratios (ESRs) varied from 13.7 to 11.4 and were regulated by cross-linker concentration. The ESRs can also be tuned from 9.6 to 6.0 by changing the AP content level from 10 to 40% (w/w) while simultaneously altering conductivity from 9.05 × 10-9 to 1.58 × 10-6 S/cm. ECHHs with controllable conductivity, tunable swelling behavior, and acceptable mechanical properties have great potential for biomedical applications, such as biosensors, electronic devices, and tissue engineering. © 2014 American Chemical Society.

Zhang J.,University for Business Studies | Zhang D.,Sichuan University
IEEE Signal Processing Letters | Year: 2010

Studies show that no detectors for LSB matching have yet proven universally reliable and it is hard to predict which types of image are suitable for a specific steganalyzer. For the kind of decompressed images, this paper presents an efficient steganalyzer that exploits the fact that the noise residuals in the DCT domain are rather concentrated on zero and very sensitive to LSB matching. Experimental results show that it is almost perfect at embedding rate 0.5 bpp and that it is the accuracy of 90.9% at 0.1 bpp against the accuracy of 44.6% with the WAM steganalyzer. However, the proposed detector works only as long as the exact JPEG decompressor is known. © 2009 IEEE.

Zhang H.,Sichuan University | Miyamoto Y.,Nanosystem Research Institute | Rubio A.,University of the Basque Country
Physical Review Letters | Year: 2012

Helium ion microscopy (HIM), which was released in 2006 by Ward et al., provides nondestructive imaging of nanoscale objects with higher contrast than scanning electron microscopy. HIM measurement of suspended graphene under typical conditions is simulated by first-principles time-dependent density functional theory and the 30 keV He+ collision is found to induce the emission of electrons dependent on the impact point. This finding suggests the possibility of obtaining a highly accurate image of the honeycomb pattern of suspended graphene by HIM. Comparison with a simulation of He0 under the same kinetic energy shows that electron emission is governed by the impact ionization instead of Auger process initiated by neutralization of He+. © 2012 American Physical Society.

Fujinaga K.,University of California at San Francisco | Barboric M.,University of Helsinki | Li Q.,Sichuan University | Luo Z.,University of California at San Francisco | And 3 more authors.
Nucleic Acids Research | Year: 2012

The positive transcription elongation factor b (P-TEFb) regulates RNA polymerase II elongation. In cells, P-TEFb partitions between small active and larger inactive states. In the latter, HEXIM1 binds to 7SK snRNA and recruits as well as inactivates P-TEFb in the 7SK snRNP. Several stimuli can affect this P-TEFb equilibrium. In this study, we demonstrate that protein kinase C (PKC) phosphorylates the serine at position158 (S158) in HEXIM1. This phosphorylated HEXIM1 protein neither binds to 7SK snRNA nor inhibits P-TEFb. Phorbol esters or the engagement of the T cell antigen receptor, which activate PKC and the expression of the constitutively active (CA) PKCθ protein, which is found in T cells, inhibit the formation of the 7SK snRNP. All these stimuli increase P-TEFb-dependent transcription. In contrast, the kinase-negative PKCθ and the mutant HEXIM1 (S158A) proteins block effects of these PKC-activating stimuli. These results indicate that the phosphorylation of HEXIM1 by PKC represents a major regulatory step of P-TEFb activity in cells. © 2012 The Author(s).

Liu M.,Shanghai JiaoTong University | Liu S.,Zhangzhou Normal University | Zhao Q.,Sichuan University
Information Sciences | Year: 2014

Orientation field represents the topological structure of the interleaved ridge and valley flows in fingerprint images. Although a number of methods have been proposed for orientation estimation, reliable computation of orientation field is still a challenging problem due to the poor quality of some fingerprints. This paper proposes a method to reconstruct fingerprint orientation field by weighted discrete cosine transform (DCT). First, the DCT functions are used to build the basis atoms for linear representation of orientation field. Then, the DCT basis atoms of low and high orders are combined with the weights determined by singularity measurements for orientation reconstruction. The weighted DCT model is further extended for partial fingerprints to gradually and iteratively reconstruct the orientations in noisy or missing parts of fingerprints. The proposed method can perform well in smoothing out the noise while maintaining the orientation details in singular regions. Extensive experiments have been done to compare the proposed method with some existing methods on NIST and FVC fingerprint databases in terms of the reconstruction accuracy of orientation field, fingerprint indexing performance, and fingerprint recognition accuracy. Experimental results illustrate the effectiveness of the proposed method in reconstructing orientation fields, especially for poor quality and partial fingerprints. © 2013 Elsevier Inc. All rights reserved.

Xie Z.-B.,Sichuan University | Xie Z.-B.,East China Institute of Technology | Wang N.,Sichuan University | Jiang G.-F.,East China Institute of Technology | Yu X.-Q.,Sichuan University
Tetrahedron Letters | Year: 2013

A green and convenient protocol has been developed for asymmetric cross-aldol reaction. In this Letter, bovine pancreatic lipase (BPL) was first reported to catalyze the aldol reaction and acidic buffer was first used for promiscuous enzymatic aldol reaction. © 2012 Elsevier Ltd. All rights reserved.

Ma Z.,Sichuan University | Xu Z.,Nanjing University of Information Science and Technology
International Journal of Intelligent Systems | Year: 2016

Pythagorean fuzzy sets (PFSs), originally proposed by Yager, are a new tool to deal with vagueness with the square sum of the membership degree and the nonmembership degree equal to or less than 1, which have much stronger ability than Atanassov's intuitionistic fuzzy sets to model such uncertainty. In this paper, we modify the existing score function and accuracy function for Pythagorean fuzzy number to make it conform to PFSs. Associated with the given operational laws, we define some novel Pythagorean fuzzy weighted geometric/averaging operators for Pythagorean fuzzy information, which can neutrally treat the membership degree and the nonmembership degree, and investigate the relationships among these operators and those existing ones. At length, a practical example is provided to illustrate the developed operators and to make a comparative analysis. © 2016 Wiley Periodicals, Inc.

Shao Z.,Institutions of Higher Education of Sichuan Province | Shao Z.,Sichuan University | Vesel A.,University of Maribor
IET Communications | Year: 2013

Let u and v be vertices of a graph G = (V, E) and d(u, v) be the distance between u and v in G. For positive integers k1, k2,.., kn with k1>k2 > .. > kn an L(k1, k2,.., kn)-labelling of G is a function f : V(G)→{0, 1,..} such that for every u, v∈ V (G) and for all 1≤i≤n, f(u) - f(v)≤ki if d(u, v) = i. The span of f is the difference between the largest and the smallest numbers in f (V(G)). Theλk1,k2,..,kn -number of G is the minimum span over all L(k1, k2, .., kn)-labellings of G. In this study, an integer linear programming model and a satisfiability test reduction for an L(k1, k2, .., kn)-labelling are proposed. Both approaches are used for studying the Λ3,2,1-numbers of strong, Cartesian and direct products of paths and cycles. © The Institution of Engineering and Technology 2013.

Faustman C.,University of Connecticut | Sun Q.,Sichuan University | Mancini R.,University of Connecticut | Suman S.P.,University of Kentucky
Meat Science | Year: 2010

Lipid oxidation and myoglobin oxidation in meat lead to off-flavor development and discoloration, respectively. These processes often appear to be linked and the oxidation of one of these leads to the formation of chemical species that can exacerbate oxidation of the other. Several investigators have reported preservation of fresh meat color following the inclusion of antioxidant ingredients. An understanding of the complementary oxidation interaction provides a basis for explaining quality deterioration in meat and also for developing strategies to maintain optimal sensory qualities. © 2010 Elsevier Ltd.

News Article | March 2, 2017

Nanoengineers at the University of California San Diego have 3D printed a lifelike, functional blood vessel network that could pave the way toward artificial organs and regenerative therapies. The new research, led by nanoengineering professor Shaochen Chen, addresses one of the biggest challenges in tissue engineering: creating lifelike tissues and organs with functioning vasculature -- networks of blood vessels that can transport blood, nutrients, waste and other biological materials -- and do so safely when implanted inside the body. Researchers from other labs have used different 3D printing technologies to create artificial blood vessels. But existing technologies are slow, costly and mainly produce simple structures, such as a single blood vessel -- a tube, basically. These blood vessels also are not capable of integrating with the body's own vascular system. "Almost all tissues and organs need blood vessels to survive and work properly. This is a big bottleneck in making organ transplants, which are in high demand but in short supply," said Chen, who leads the Nanobiomaterials, Bioprinting, and Tissue Engineering Lab at UC San Diego. "3D bioprinting organs can help bridge this gap, and our lab has taken a big step toward that goal." Chen's lab has 3D printed a vasculature network that can safely integrate with the body's own network to circulate blood. These blood vessels branch out into many series of smaller vessels, similar to the blood vessel structures found in the body. The work was published in Biomaterials. Chen's team developed an innovative bioprinting technology, using their own homemade 3D printers, to rapidly produce intricate 3D microstructures that mimic the sophisticated designs and functions of biological tissues. Chen's lab has used this technology in the past to create liver tissue and microscopic fish that can swim in the body to detect and remove toxins. Researchers first create a 3D model of the biological structure on a computer. The computer then transfers 2D snapshots of the model to millions of microscopic-sized mirrors, which are each digitally controlled to project patterns of UV light in the form of these snapshots. The UV patterns are shined onto a solution containing live cells and light-sensitive polymers that solidify upon exposure to UV light. The structure is rapidly printed one layer at a time, in a continuous fashion, creating a 3D solid polymer scaffold encapsulating live cells that will grow and become biological tissue. "We can directly print detailed microvasculature structures in extremely high resolution. Other 3D printing technologies produce the equivalent of 'pixelated' structures in comparison and usually require sacrificial materials and additional steps to create the vessels," said Wei Zhu, a postdoctoral scholar in Chen's lab and a lead researcher on the project. And this entire process takes just a few seconds -- a vast improvement over competing bioprinting methods, which normally take hours just to print simple structures. The process also uses materials that are inexpensive and biocompatible. Chen's team used medical imaging to create a digital pattern of a blood vessel network found in the body. Using their technology, they printed a structure containing endothelial cells, which are cells that form the inner lining of blood vessels. The entire structure fits onto a small area measuring 4 millimeters × 5 millimeters, 600 micrometers thick (as thick as a stack containing 12 strands of human hair). Researchers cultured several structures in vitro for one day, then grafted the resulting tissues into skin wounds of mice. After two weeks, the researchers examined the implants and found that they had successfully grown into and merged with the host blood vessel network, allowing blood to circulate normally. Chen noted that the implanted blood vessels are not yet capable of other functions, such as transporting nutrients and waste. "We still have a lot of work to do to improve these materials. This is a promising step toward the future of tissue regeneration and repair," he said. Moving forward, Chen and his team are working on building patient-specific tissues using human induced pluripotent stem cells, which would prevent transplants from being attacked by a patient's immune system. And since these cells are derived from a patient's skin cells, researchers won't need to extract any cells from inside the body to build new tissue. The team's ultimate goal is to move their work to clinical trials. "It will take at least several years before we reach that goal," Chen said. Full paper: "Direct 3D bioprinting of prevascularized tissue constructs with complex microarchitecture." Authors of the study are Wei Zhu*, Xin Qu*, Jie Zhu, Xuanyi Ma, Sherrina Patel, Justin Liu, Pengrui Wang, Cheuk Sun Edwin Lai, Yang Xu, Kang Zhang and Shaochen Chen of UC San Diego; and Maling Gou of Sichuan University. *These authors contributed equally to this work. This work was supported in part by grants from the California Institute for Regenerative Medicine (RT3-07899), the National Institutes of Health (R01EB021857) and the National Science Foundation (CMMI-1332681 and CMMI-1644967).

News Article | January 6, 2016

Formidable capacity in genome sequencing, access to millions of patients and the promise of solid governmental support: those are the assets that China hopes to bring to the nascent field of precision medicine, which uses genomic, physiological and other data to tailor treatments to individuals. Almost exactly one year after US President Barack Obama announced the Precision Medicine Initiative, China is finalizing plans for its own, much larger project. But as universities and sequencing companies line up to gather and analyse the data, some observers worry that problems with the nation’s health-care infrastructure — in particular a dearth of doctors — threaten the effort’s ultimate goal of improving patient care. Precision medicine harnesses huge amounts of clinical data, from genome sequences to health records, to determine how drugs affect people in different ways. By enabling physicians to target drugs only to those who will benefit, such knowledge can cut waste, improve health outcomes using existing treatments, and inform drug development. For example, it is now clear that individuals with a certain mutation (which is mostly found in Asian people) respond better to the lung-cancer drug Tarceva (erlotinib; W. Pao et al. Proc. Natl Acad. Sci. USA 101, 13306–13311; 2004), and the discovery of a mutation that causes 4% of US cystic fibrosis cases led to the development of the drug Kalydeco (ivacaftor). The Chinese government is expected to officially announce the initiative after it approves its next five-year plan in March. Just how much the effort will cost is unclear — but it will almost certainly be larger and more expensive than the US$215-million US initiative. Since last spring, Chinese media has been abuzz with estimates of a 60-billion yuan (US$9.2-billion) budget, spread over 15 years. But this figure is not finalized, cautions Zhan Qimin, director of the State Key Laboratory of Molecular Oncology at Peking Union Medical College in Beijing, who is involved in the initiative. He says that the effort will consist of hundreds of separate projects to sequence genomes and gather clinical data, with support for each ranging from tens of millions of yuan to more than 100 million yuan. Anticipating the initiative, leading institutes — including Tsinghua University, Fudan University and the Chinese Academy of Medical Sciences — are scrambling to set up precision-medicine centres. Sichuan University’s West China Hospital, for instance, plans to sequence 1 million human genomes itself — the same goal as the entire US initiative. The hospital will focus on ten diseases, starting with lung cancer. Both the US and the Chinese efforts will focus on genetic links to diseases that are particularly deadly, such as cancer and heart disease. But China will target specific cancers, such as stomach and liver cancer, which are common there. The Chinese initiative is part of a series of research-funding efforts that will replace two major grant programmes, known as 863 and 973, that are due to be phased out by 2017. The new programmes will be “more organized, more efficient”, says Zhan. Genome-sequencing companies are already vying to provide services to deal with the anticipated demand. For several years, China has boasted high genome-sequencing capacity. In 2010, the genomics institute BGI in Shenzhen was estimated to host more sequencing capacity than the entire United States. This was thanks to its equipment, purchased from Illumina of San Diego, California, which at the time represented state-of-the-art technology. But Illumina has since sold upgraded machines to at least three other genomics firms — WuXi PharmaTech and Cloud Health, both in Shanghai, and the Beijing-based firm Novogene. Jason Gang Jin, co-founder and chief executive of Cloud Health, says that this trio, rather than BGI, will be the main sequencing support for China’s precision-medicine initiative — although BGI’s director of research, Xu Xun, disagrees. Xu says that precision medicine is a priority for BGI and that the organization has a diverse portfolio of sequencers that still gives it an edge. “If you are talking about real data output, BGI is still leading in China, maybe even globally,” he says. BGI has already established a collaboration with the Zhongshan Hospital’s Center for Clinical Precision Medicine in Shanghai, which opened in May 2015 with a budget of 100 million yuan and is run by Fudan University. Regardless of the details, Jin thinks that China will be faster than the United States at sequencing genomes and identifying mutations that are relevant to personalized medicine because China’s larger populations of patients for each disease will make it easier to find sufficient numbers to study. Still, it remains to be seen whether China has the resources to apply these insights to the individualized care of patients. “China wants to do it, and everybody is very excited,” says Ta Jen Liu, project director at the MD Anderson Cancer Center in Houston, Texas, who helps to establish collaborations in China and is familiar with the precision-medicine scene there. But there are hurdles. He notes that Chinese researchers and pharmaceutical companies have not had much success in developing drugs so far; that the pathologists needed to diagnose specific diseases are scarce in China; and that physicians there are notoriously overworked. “Doctors are always overwhelmed with patients, seeing 60 or 70 a day,” he says. “They don’t have time to sit down and think about what is best for specific patients.” David Weitz, a physicist at Harvard University who is starting a company in Beijing to develop diagnostic instruments for use in precision medicine, agrees that there will be obstacles, but notes the initiative’s assets. “We need lots of data to validate ideas, to validate tests,” he says. “There’s lots of data here.” He thinks that this, combined with the Chinese government’s determination to succeed, will mean that the effort will ultimately win out. “They really seem devoted to meeting the needs of the society,” he says. “It’s an exciting thing, to try to help that many people.”

Estimates for 2015 suggest that 5.9 million children worldwide died before reaching the age of five, including 2.7 million newborns. Globally, four million (4.02 million) fewer child deaths occurred in 2015 than in 2000, mainly thanks to reductions in deaths from pneumonia, diarrhoea, death during birth, malaria and measles. However, progress on reducing newborn deaths (in the first 28 days) has been slower meaning that as a whole the world failed to reach the Millennium Development Goal (MDG) target of reducing child deaths by two-thirds between 1990 and 2015. The study, published in The Lancet, provides the most up-to-date figures for deaths of children under five years old and includes data for all 194 countries that are World Health Organisation states (see appendix 6 for country-level data). The 2015 figures highlight the inequality in child deaths around the world with the national rates of child death ranging from 1.9 to 155.1 deaths per 1000 births, and 60.4% (3.6 million) of all deaths occurring in 10 countries. Progress since 2000 has largely been due to reductions in the rates of deaths from pneumonia, diarrhoea, malaria, measles and deaths during birth - each reduced by more than 30% worldwide between 2000 and 2015 (see figure 2). However, some of these still remain leading causes of deaths. Globally in 2015, the leading causes of death for children under five years old were complications due to premature birth (17.8%, 1.1 million deaths), pneumonia (15.5%, 0.9 million deaths) and death during birth (11.6%, 0.7 million deaths). Countries with the highest rates of child death (100 or more deaths per 1000 births) include Angola, Central African Republic, Chad, Mali, Nigeria, Sierra Leone and Somalia. In these countries pneumonia, malaria and diarrhoea were the leading causes of death (see figure 3), so to improve survival in these regions the researchers recommended improving the uptake of breastfeeding, providing vaccines for pneumonia, malaria and diarrhoea, and improving water and sanitation. In comparison, for countries with the lowest rate of child death (less than 10 deaths per 1000 births) which include the Russian Federation and the United States of America, the leading causes of death include congenital abnormalities, complications due to premature birth and injuries (see figure 3). Improved detection and surgery for congenital abnormalities, better medical care during pregnancy and childbirth, and more research on effectiveness of injury interventions could help improve survival in these countries. Although the number of newborn deaths was reduced from 3.9 million in 2000 to 2.7 million in 2015 (see appendix 6), progress has been slower than the improvements in survival for one month to five year olds. This resulted in the proportion of newborn deaths increasing from 39.3% in 2000 to 45.1% in 2015. If newborn deaths had reduced at the same rate as that of children aged between one month and five years old the MDG target to reduce child deaths by two-thirds between 1990 to 2015 might have been reached. "Child survival has improved substantially since the Millennium Development Goals were set even though the target to reduce child deaths by two-thirds was not achieved" says Dr Li Liu, lead author, Johns Hopkins Bloomberg School of Public Health, USA. "The problem is that this progress is uneven across all countries, meaning a high child death rate persists in many countries. Substantial progress is needed for countries in sub-Saharan Africa and Southern Asia to achieve the child survival target of the Sustainable Development Goals." [1] The model used in the study provides estimates based on vital registration data and from high quality literature on causes of child deaths. It used statistical analysis to estimate figures for countries with poor data collection due to there being fewer birth and death registries. Writing in a linked Comment, Professor Peter Byass, Umeå Centre for Global Health Research says "Undoubtedly child mortality is falling, and the world should be proud of this progress" but he adds "... Of the estimated six million under-5 child deaths in 2015, only a small proportion were adequately documented at the individual level, with particularly low proportions evident in low-income and middle-income countries, where most childhood deaths occur... That six million under-5 children continue to die every year in our 21st century world is unacceptable, but even worse is that we seem collectively unable to count, and hence be accountable for, most of those individual deaths." The study was funded by the Bill & Melinda Gates Foundation and the World Health Organization. It was conducted by the Johns Hopkins Bloomberg School of Public Health, The London School of Hygiene and Tropical Medicine, the World Health Organisation, The China National Office of Maternal and Child Health Surveillance and Sichuan University. [1] Quote direct from author and cannot be found in the text of the Article.

Cai S.,Sichuan University | Zhang Y.,Sichuan University | Zhang H.,Sichuan University | Yan H.,China Academy of Engineering Physics | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2014

Hydrophobic antireflective coatings with a low refractive index were prepared via a base/acid-catalyzed two-step sol-gel process using tetraethylorthosilicate (TEOS) and methyltriethoxysilane (MTES) as precursors, respectively. The base-catalyzed hydrolysis of TEOS leads to the formation of a sol with spherical silica particles in the first step. In the second step, the acid-catalyzed MTES hydrolysis and condensation occur at the surface of the initial base-catalyzed spherical silica particles, which enlarge the silica particle size from 12.9 to 35.0 nm. By a dip-coating process, this hybrid sol gives an antireflective coating with a refractive index of about 1.15. Moreover, the water contact angles of the resulted coatings increase from 22.4 to 108.7° with the increases of MTES content, which affords the coatings an excellent hydrophobicity. A core-shell particle growth mechanism of the hybrid sol was proposed and the relationship between the microstructure of silica sols and the properties of AR coatings was investigated. © 2014 American Chemical Society.

Yang P.,Sichuan University | Gu Y.,Sichuan University
Journal of Polymer Research | Year: 2011

A pure benzoxazine synthesized from phenolphthalein through Mannich reaction, 3,3-bis(3,4-dihydro-3-phenyl-2H-1,3-benzoxazinyl)-1(3H)- isobenzofuranone (Boz-BP), was characterized by FTIR and 1H NMR. Its curing behavior was different with that of 2,2-bis(4-phenyl-3,4-dihydro-2H-1,3- benzoxazinyl)isopropane (Boz-BA) because Boz-BP possesses highly steric and inactivated phenol rings. During curing period, the reactivity of ortho position of phenolic hydroxyl group was retarded and the addition of -CH 2- group generated in ring-opening reaction preferred to taking place on para position of aniline ring, which is beneficial for better thermal properties. Furthermore, additional hydrogen bonding would be formed between carbonyl groups on phthalide structure and hydroxyl groups in Boz-BP based polymer (P(Boz-BP)). Compared with the analogous polymer from Boz-BA (P(Boz-BA)), P(Boz-BP) displayed higher glass transition temperature, better thermal stability, better dimensional stability and flame-retardant properties. © 2011 Springer Science+Business Media B.V.

Chen Y.,Sichuan University | Wang R.,Chengdu Product Quality Supervision Inspection Institute | Zhou J.,Sichuan University | Fan H.,Sichuan University | Shi B.,Sichuan University
Polymer | Year: 2011

Thermo-sensitive polyurethane (TSPU) solution containing varying concentration of in situ-generated TiO2 nanoparticles was successfully prepared via an organic-inorganic hybrid technique, and the final nanocomposite membranes were formed via solution casting. Depending on the membrane formation temperature (Tmf) during casting, completely-opposite gas transport behaviors of the TSPU nanocomposite membranes were observed. When Tmf was lower than the melting point (T m) of soft segment (PCL10000) in the TSPU, gas permeability coefficients of the nanocomposite membranes were found to increase significantly with increasing nano-TiO2 concentration. Conventional composite theory failed to explain such observation because filler particles are generally considered to create more tortuous diffusion path in the polymer for penetrants, and should thereby lead to a systematic reduction in gas permeability. This counter-intuitive phenomenon was then rationalized by postulating that rigid TSPU chain could not pack efficiently around the TiO 2 nanoparticles during solvent evaporation, which resulted in polymer layer with higher free volume at the interface than the bulk polymer regions. Evidences supporting such presumption were provided by (1) density measurement that found negative deviation of actual densities of TSPU nanocomposite membranes from theoretical prediction; (2) positron annihilation lifetime spectroscopy that demonstrated increased free-volume size and concentration within TSPU upon the in situ generation of TiO2 nanoparticles. However, when Tmf was elevated above the Tm of the soft segment, flexible TSPU chain seemed able to pack around the TiO2 nanoparticles as efficiently as in the bulk polymer. In this case, gas transport behavior of the TSPU nanocomposite membranes followed the prediction of conventional composite theory. © 2011 Elsevier Ltd. All rights reserved.

Ran Q.-C.,Sichuan University | Ran Q.-C.,University of Sichuan | Gu Y.,Sichuan University
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2011

Polymerization reactions of a new aldehyde-functional benzoxazine (4HBA-a) were investigated in detail. The curing behavior of 4HBA-a was studied by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) methods. The results indicate that the disappearance of the aldehyde group from 4HBA-a and the ring-opening reaction of 4HBA-a occur simultaneously. Gases evolved during the curing process of 4HBA-a were analyzed by thermogravimetric analyzer interfaced with FTIR spectra. The elimination of CO 2 is attributed to the oxidation and decarboxylation of the aldehyde groups. In addition, the crosslink sites of the aldehyde groups in the polymer structure are confirmed by model reactions. A possible reactive position should be sited in ortho position of phenol rather than ortho and/or para positions of N-phenyl ring. Finally, the crosslinked structures of polymerized 4HBA-a have been proposed. © 2011 Wiley Periodicals, Inc.

Wei J.,University of Sichuan | Ju X.-J.,University of Sichuan | Zou X.-Y.,University of Sichuan | Xie R.,University of Sichuan | And 4 more authors.
Advanced Functional Materials | Year: 2014

Novel multi-stimuli-responsive microcapsules with adjustable controlled-release characteristics are prepared by a microfluidic technique. The proposed microcapsules are composed of crosslinked chitosan acting as pH-responsive capsule membrane, embedded magnetic nanoparticles to realize "site-specific targeting", and embedded temperature-responsive sub-microspheres serving as "micro-valves". By applying an external magnetic field, the prepared smart microcapsules can achieve targeting aggregation at specific sites. Due to acid-induced swelling of the capsule membranes, the microcapsules exhibit higher release rate at specific acidic sites compared to that at normal sites with physiological pH. More importantly, through controlling the hydrodynamic size of sub-microsphere "micro-valves" by regulating the environment temperature, the release rate of drug molecules from the microcapsules can be flexibly adjusted. This kind of multi-stimuli-responsive microcapsules with site-specific targeting and adjustable controlled-release characteristics provides a new mode for designing "intelligent" controlled-release systems and is expected to realize more rational drug administration. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Li Y.,Sichuan University
Sheng wu yi xue gong cheng xue za zhi = Journal of biomedical engineering = Shengwu yixue gongchengxue zazhi | Year: 2010

TNF-related apoptosis-inducing ligand (TRAIL) is a member of factor TNF family, which could be potentially developed as novel antitumor agent due to its selective and efficient induction of apoptosis in tumor cells. Gene recombinant expression is an important tool for production of pharmaceutical protein. In this paper, the gene encoding human soluble TRAIL (114-281aa fragment) was cloned by PCR and then inserted into the Pichia Pastoris expression vector pPIC9K. The transformants were double-screened on plates containing neomycin G418 and many clones with high levels of G418-resistance were selected for further studies on protein expression. The recombinant human soluble TRAIL was secreted into the BMMY media under the condition of 3% methanol. And the recombinant protein was purified to homogeneity (-80% purity) by using Ni-agarose affinity chromatography. The yield of this protein is about 1-2 mg per liter culture. Cell viability assays demonstrated that human soluble TRAIL was cytotoxic in both leukemia cells Jurkat and lung cancer cells A549. After treatment with 0.05 microg/ml TRAIL, the survival rate of Jurkat cells was about 10%. The expressed TRAIL showed dose-dependent cytotoxicity in A549 cells within the range of 0.1-1 microg/ml. When the protein concentration reached 1 microg/ml, the survival rates of A549 cells were about 30%. However, the recombinant human soluble TRAIL did not show obvious cytotoxicity in human skin fibroblast cells (HSF) at concentrations tested. There results demonstrate that human soluble TRAIL is selectively cytotoxic in tumor cells. The expression system constructed in this experiment might contribute to further production of soluble TRAIL and TRAIL-based novel fusion proteins in large quantities.

Wei X.-F.,Sichuan University | Bao R.-Y.,Sichuan University | Cao Z.-Q.,Sichuan University | Yang W.,Sichuan University | And 2 more authors.
Macromolecules | Year: 2014

Stereocomplex (SC) crystallites, formed between enantiomeric poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA), show a melting point 50 C higher than that of PLLA or PDLA homocrystallites, which makes it possible for SC crystallites to be reserved in the melt of PLLA in asymmetric PLLA/PDLA blends and to act as a rheological modifier and a nucleation agent for PLLA. Herein, by a rheological approach, a transition from the liquid-like to solid-like viscoelastic behavior was observed for the SC crystallites reserved melt, and a frequency-independent loss tangent at low frequencies appeared at a PDLA concentration of 2.0 wt %, revealing the formation of SC crystallite network. By a delicately designed dissolution experiment, the structure of the formed network was explored. The results indicate that the network are not formed by SC crystallites connected directly with each other or by bridging molecules, but by the interparticle polymer chains which are significantly restrained by the cross-linking effect of SC crystallites. Nonisothermal and isothermal crystallization show that the reserved SC crystallites can accelerate remarkably the crystallization rate of PLLA due to heterogeneous nucleation effect. Besides, a special PDLA concentration dependence, e.g., the overall crystallization rate is almost independent of PDLA content for the blends with PDLA content higher than PDLA percolation concentration (2.0 wt %), was also observed. The increase of nuclei density for the blends containing PDLA from 2 to 5 wt % was estimated from POM observations. The result of an enhanced nucleation but an unchanged overall crystallization rate reveals the confining effect of the SC crystallite network on PLLA crystallization. This confining effect can be ascribed to the restrained diffusion ability of PLLA chains owing to the SC crystallite network. © 2014 American Chemical Society.

Gao X.,Sichuan University | Zhang S.,Sichuan University | Mai F.,Sichuan University | Lin L.,Sichuan University | And 3 more authors.
Journal of Materials Chemistry | Year: 2011

In our work, efforts have been made to build conductive networks with carbon nanotubes in highly oriented polymer fibres/tapes. It is often reported as a complicated or expensive procedure. Herein, a simple but efficient method is demonstrated for the fabrication of high performance conductive polymer fibres/tapes. To achieve this, carbon nanotubes were selectively dispersed in the polyethylene (PE) phase of a PE/polypropylene (PP) blend to construct conductive networks from a double percolated structure. It was demonstrated that the conductive network could be preserved even at high draw ratio by tailoring the double percolated structure (the blend composition and amount of carbon nanotubes), and a maximum conductivity of 2 S m-1 and strength of 174 MPa has been achieved. Furthermore, subsequent thermal annealing was shown to recover the conductive network and cracks after annealing. It is interesting to note that such a double percolated conductive fibre/tape could be used for self-healing purposes. Therefore, this study provides a guideline for the fabrication of multi-functional high performance conductive polymer fibres/tapes. Finally, a kinetic model was used to study the relaxation process of highly oriented conductive networks during annealing. © 2011 The Royal Society of Chemistry.

Li G.,Sichuan University | Song F.,Sichuan University | Wu D.,Sichuan University | Lan J.,Sichuan University | And 5 more authors.
Advanced Functional Materials | Year: 2014

Mechanofluorochromic materials have great potential for a wide variety of applications such as sensors, memory devices, motion systems, security systems, and so forth. However, only few design principles have been disclosed, which greatly impedes the growth of mechanofluorochromic dyes. Here, a strategy of molecular design for mechanochromic luminescence is reported, based on the cation-anion interaction-directed switching of molecular stacking. On the basis of this strategy, a series of common N-heteroaromatic onium fluorophores such as imidazolium, 1,2,4-triazolium, triazolopyridinium, benzoimidazolium, γ-carbolinium, and pyridinium salts have been designed and proved to have striking reversible mechanofluorochromic behaviors. The simple attachment of a non-fluorescent imidazolium unit to the pyrene scaffold through a flexible carbon chain can even trigger the mechanofluorochromic phenomenon, which gives a consummate interpretation that the cation-anion interaction can be considered as an important general tool to design organic mechanochromic luminescent materials. Molecular Design: A cation-anion interaction-directed molecular design strategy for mechanochromic luminescence is proposed. On the basis of this strategy, a series of common N-heteroaromatic onium fluorophores such as imidazolium, 1,2,4-triazolium, triazolopyridinium, benzoimidazolium, γ-carbolinium, and pyridinium salts are designed and prove to have striking reversible mechanofluorochromic behaviors. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gu Y.,University of East Anglia | Li H.,University of East Anglia | Dong H.,University of East Anglia | Zeng Y.,University of East Anglia | And 9 more authors.
Nature | Year: 2016

All Gram-negative bacteria, mitochondria and chloroplasts have outer membrane proteins (OMPs) that perform many fundamental biological processes. The OMPs in Gram-negative bacteria are inserted and folded into the outer membrane by the β-barrel assembly machinery (BAM). The mechanism involved is poorly understood, owing to the absence of a structure of the entire BAM complex. Here we report two crystal structures of the Escherichia coli BAM complex in two distinct states: an inward-open state and a lateral-open state. Our structures reveal that the five polypeptide transport-associated domains of BamA form a ring architecture with four associated lipoproteins, BamB-BamE, in the periplasm. Our structural, functional studies and molecular dynamics simulations indicate that these subunits rotate with respect to the integral membrane β-barrel of BamA to induce movement of the β-strands of the barrel and promote insertion of the nascent OMP. © 2016 Macmillan Publishers Limited. All rights reserved.

Cui S.,Sichuan University
Sheng wu yi xue gong cheng xue za zhi = Journal of biomedical engineering = Shengwu yixue gongchengxue zazhi | Year: 2011

This paper proposes a technique to denoise the worm artifacts of elastogram using 2-D wavelet shrinkage denoising method. Firstly, strain estimate matrix including worm artifacts was decomposed to 3 levels by 2-D discrete wavelet transform with Sym8 wavelet function, and the thresholds were obtained using Birg6-Massart algorithm. Secondly, all the high frequency coefficients on different levels were quantized by using hard threshold and soft threshold function. Finally, the strain estimate matrix was reconstructed by using the 3rd layer low frequency coefficients and other layer quantized high frequency coefficients. The simulation results illustrated that the present technique could efficiently denoise the worm artifacts, enhance the elastogram performance indices, such as elastographic signal-to-noise ratio (SNRe) and elastographic contrast-to-noise ratio (CNRe), and could increase the correlation coefficient between the denoised elastogram and the ideal elastogram. In comparison with 2-D low-pass filtering, it could also obtain the higher elastographic SNRe and CNRe, and have clearer hard lesion edge. In addition, the results demonstrated that the proposed technique could suppress worm artifacts of elastograms for various applied strains. This work showed that the 2-D wavelet shrinkage denoising could efficiently denoise the worm artifacts of elastogram and enhance the performance of elastogram.

Xu J.,Sichuan University | Zhao Q.,Sichuan University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

Although 2D facial landmark detection methods built on the cascaded regression framework have been widely researched, their performance was still limited by face shape deformations and poor light conditions. With the assist of extra shape information provided by 3D facial model, these difficulties can be eased to some degree. In this paper, we propose 3D Cascaded Regression for detecting facial landmarks on 3D faces. Our algorithm makes full use of both texture and depth information to overcome the difficulties caused by expression variations, and generates shape increments based on a weighted mixture of two separated shape updates regressed from texture and depth, respectively. Finally, the shape estimation is mapped into the original 3D facial data to obtain three-dimensional landmark coordinates. Experimental results on the BU-4DFE database demonstrate that our proposed approach achieves satisfactory performance in terms of detection accuracy and robustness, significantly superior to state-of-the-art method. © Springer International Publishing AG 2016.

Cao X.L.,Sichuan University | Cheng C.,Sichuan University | Ma Y.L.,Sichuan University | Zhao C.S.,Sichuan University
Journal of Materials Science: Materials in Medicine | Year: 2010

Silver nanoparticles were prepared by chemical reduction method using chitosan as stabilizer and ascorbic acid as reducing agent in this work. The silver/chitosan nanocomposites were characterized in terms of their particle sizes and morphology by using UV spectrophotometer, nano-grainsize analyzer, and transmission electron microscopy. Antibacterial activities of these nanocomposites were carried out for Staphylococcus aureus and Escherichia coli. The silver nanoparticles exhibited significantly inhibition capacity towards these bacteria. Detailed studies on the biocompatibility of the silver/chitosan nanocomposites were investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromide assay and cell adhesion test. The results indicated that these silver/chitosan nanocomposites were benefit for the proliferation and adhesion of L-929 cells, and the biocompatibilities between the nanocomposites and the cells would become better with the culturing days. We anticipated that these silver/chitosan nanocomposites could be a promising candidate as coating material in biomedical engineering and food packing fields wherein antibacterial properties and biocompatibilities are crucial. © 2010 Springer Science+Business Media, LLC.

Zhang Y.,Sichuan University | Liu X.,Sichuan University | Zhao X.,Sichuan University | Zhang J.,Sichuan University | And 3 more authors.
Chemical Communications | Year: 2013

An efficient catalytic asymmetric intermolecular C2 Friedel-Crafts alkylation reaction between N-methyl skatole and β,γ-unsaturated α-ketoesters has been realized by a chiral N,N′-dioxide-Ni(ii) complex. The corresponding indole derivatives were obtained in good yield (up to 96%) with excellent enantioselectivities (up to 99% ee) under mild reaction conditions. © 2013 The Royal Society of Chemistry.

Bai H.,Sichuan University | Zhang W.,Sichuan University | Deng H.,Sichuan University | Zhang Q.,Sichuan University | Fu Q.,Sichuan University
Macromolecules | Year: 2011

Derivative N,N',N''-tricyclohexyl-1,3,5-benzenetricarboxylamide (TMC-328) was considered as a model to tailor the crystal superstructure of poly(L-lactide) (PLLA), and three crystal morphologies including cone-like, shish-kebab, and needle-like structures were obtained using melt crystallization. Morphological observations of PLLA crystallites were conducted on a polarized optical microscopy equipped with a hot stage under crossed polarizers. PLLA shows a spherulitic crystal morphology and the crystal morphology for nucleated PLLA is clearly different from that of PLLA-0 and dependent on the loading levels of TMC-328 in PLLA. The results also show that only a fraction of TMC-328 molecules self-organize into some fine fibrils, and no stable physical network is formed upon cooling. The morphology of TMC-328 in PLLA melt varies with the increase of its concentrations, inducing three characteristic crystal morphologies.

Jiang Q.,Sichuan University | Wong A.O.L.,University of Hong Kong
American Journal of Physiology - Regulatory Integrative and Comparative Physiology | Year: 2014

Somatostain (SS) is known to inhibit growth hormone (GH) and prolactin (PRL) secretion. Somatolactin (SL) is a member of the GH/PRL family, but its regulation by goldfish brain somatostatin-28 (gbSS-28) has not been examined. To this end, the structural identity of goldfish SLα was established by 5'/3'-rapid amplification of cDNA ends. As revealed by in situ hybridization and immunohistochemical staining, the expression of SL isoforms was detected in pituitary cells located in the neurointermediate lobe (NIL). The transcripts of goldfish SS receptor 5a (Sst5a) but not Sst1b, Sst2, or Sst3a were detected in the goldfish NIL cells by RT-PCR. In goldfish pituitary cells, gbSS-28 not only had an inhibitory effect on basal SLα and SLβ mRNA levels but also could abolish insulin-like growth factor-stimulated SL gene expression. In primary cultures of goldfish NIL cells, gbSS-28 reduced forskolin-stimulated total cAMP production. With the use of a pharmacological approach, the adenylate cyclase (AC)/cAMP and phos-pholipase C (PLC)/inositol trisphosphate (IP3)/protein kinase C (PKC) cascades were shown to be involved in gbSS-28-inhibited SLα mRNA expression. Similar postreceptor signaling cascades were also observed for gbSS-28-reduced SLβ mRNA expression, except that PKC coupling to PLC was not involved. These results provide evidence that gbSS-28 can inhibit SLα and SLβ gene expression at the goldfish pituitary level via Sst5 through differential coupling of AC/cAMP and PLC/IP3/PKC cascades. © 2014 the American Physiological Society.

Chu Y.,Sichuan University | Liu X.,Sichuan University | Li W.,Sichuan University | Hu X.,Sichuan University | And 2 more authors.
Chemical Science | Year: 2012

A simple and H 2O 2-efficient asymmetric epoxidation of α,β-unsaturated carbonyl compounds was accomplished using a chiral N,N′-dioxide-Sc(iii) complex catalyst. A number of optically active epoxides were obtained from the corresponding α,β-unsaturated ketones and α,β-unsaturated amides under additive-free conditions. The catalytic system is convenient with good water- and air-tolerance, as well as excellent yields and enantioselectivities. © 2012 The Royal Society of Chemistry.

Wei S.,Sichuan University | Li X.,Sichuan University | Yang Z.,Sichuan University | Lan J.,Sichuan University | And 3 more authors.
Chemical Science | Year: 2012

The self-assembly of the rigid, bent, chiral bis(triazol-ylidene) ligands with the linear coordinated group 11 metal centers brought about dramatic architectural variation of metallosupramolecular assemblies from the familiar dinuclear M 2L 2 to the trinuclear cylindrical foldamers M 3L 3 through a small variation of the R group of ligand. The foldamers [(S)-2·Ag] 3(X) 3 further underwent counteranion-triggered hierarchical self-assembly into well-grown nanofibers capable of gelating solvents. © 2012 The Royal Society of Chemistry.

Wu J.,Sichuan University | Huang G.,Sichuan University | Wang X.,Sichuan University | He X.,Sichuan University | Zheng J.,Sichuan University
Soft Matter | Year: 2011

To explore the complex molecular dynamics of glass-forming substances in the softening dispersion region from the glassy state to the rubbery state, polyisobutylene (PIB) and chlorinated butyl rubber (CIIR), representives of an amorphous polymer with effective chain packing and low intermolecular cooperativity, were doped with low molecular weight brominated para-tert-octyl phenolic resin (PR) and then tested using dielectric spectroscopy. The results show that the PR molecules, having little effect on the overall molecular dynamics of PIB and CIIR, can be used as the dielectric probes to successfully monitor local segmental motion, sub-Rouse modes and Rouse modes in the dielectric spectra simultaneously. The relaxation times of the local segmental motion and the Rouse modes can be directly obtained from the dielectric spectra. It is found that the Rouse modes have weaker temperature-dependence than the local segmental motion, indicating the thermorheological complexity of PIB and CIIR. Consequently, the local segmental motion superposes the Rouse modes at a temperature near T g. This study suggests that the dielectric probes have the capability to detect and study different modes of molecular motion around the softening dispersion region. © 2011 The Royal Society of Chemistry.

Guo J.-H.,Sichuan University | Zhang H.,Sichuan University
Structural Chemistry | Year: 2011

Using first-principles calculations, we investigate the adsorption behaviors of H2 in B/C/N sheets (including BCN, BC2N, and BC3N) and discuss the effect of external electric fields on H 2 adsorbed for BCN and BC2N sheets. For a single H 2 adsorbed on BCN and BC2N sheets, the adsorption energy increases dramatically with the electric field intensity increasing, and the maximum adsorption energy can reach 0.55 eV in the electric field of F = 0.050 a.u. and one layer H2 can adsorb on BCN and BC2N sheets, corresponding to the maximum hydrogen storage capacity of 5.1 wt%. The average adsorption energy calculated larger than that of in the field-free case. © Springer Science+Business Media, LLC 2011.

Yi Z.,Sichuan University
IEEE Transactions on Neural Networks | Year: 2010

The competitive layer model (CLM) can be described by an optimization problem. The problem can be further formulated by an energy function, called the CLM energy function, in the subspace of nonnegative orthant. The set of minimum points of the CLM energy function forms the set of solutions of the CLM problem. Solving the CLM problem means to find out such solutions. Recurrent neural networks (RNNs) can be used to implement the CLM to solve the CLM problem. The key point is to make the set of minimum points of the CLM energy function just correspond to the set of stable attractors of the recurrent neural networks. This paper proposes to use LotkaVolterra RNNs (LV RNNs) to implement the CLM. The contribution of this paper is to establish foundations of implementing the CLM by LV RNNs. The contribution mainly contains three parts. The first part is on the CLM energy function. Necessary and sufficient conditions for minimum points of the CLM energy function are established by detailed study. The second part is on the convergence of the proposed model of the LV RNNs. It is proven that interesting trajectories are convergent. The third part is the most important. It proves that the set of stable attractors of the proposed LV RNN just equals the set of minimum points of the CLM energy function in the nonnegative orthant. Thus, the LV RNNs can be used to solve the problem of the CLM. It is believed that by establishing such basic rigorous theories, more and interesting applications of the CLM can be found. © 2010 IEEE.

Chen Y.-H.,Sichuan University | Mao Y.-M.,State University of New York at Stony Brook | Li Z.-M.,Sichuan University | Hsiao B.S.,State University of New York at Stony Brook
Macromolecules | Year: 2010

It has been well established that, although both shear flow and β-nucleating agent could separately induce β-crystals in isotactic polypropylene (iPP) in an efficient manner, their combination in fact depressed the content of β-crystals when compared with quiescently crystallized β-nucleated iPP. In the current study, in-situ synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) measurements were performed to investigate this behavior. The WAXD data obtained were quantitatively analyzed to determine the independent contributions of applied shear flow and added β-nucleating agent in terms of nucleation stage and subsequent α-and β-crystal growth stage. In the nucleation stage, the addition of β-nucleating agent increased the amount of β-nuclei, while the application of shear flow and the interactions between shear and β-nucleating agent enhanced the amount of α-nuclei (the amounts of α-and β-nuclei were in the same order of magnitude). As a result, in the initial crystallization, α-and β-crystals grew competitively, causing simultaneously increments of α-and β-crystals. However, in the growth stage, the growth rate of β-crystals was faster than that of α-crystals where the epitaxial growth of β-crystals on α-crystals also occurred (due to more favorable isothermal crystallization temperature for β-crystal growth). Consequently, the content of β-crystals became dominant in the limited growth space; however, it was still less than that formed from the quiescent isothermal crystallization of β-nucleated iPP. As the shear rate increased, more shear-induced α-nuclei were formed, further decreasing the amount of β-crystals. Nevertheless, when shear and β-nucleating agent coexisted, β-crystals emerged earlier than α-crystals. The SAXS results indicated that the combination of shear and β-nucleating agent changed the stacking manner of molecular chains, so that the long period of sheared, β-nucleated iPP was comparable to that of quiescently crystallized iPP. © 2010 American Chemical Society.

Jia J.,University of Sichuan | Xu F.,Sichuan University | Long Z.,University of Sichuan | Hou X.,University of Sichuan | And 2 more authors.
Chemical Communications | Year: 2013

A simple and rapid fluorescence sensing platform based on the MIL-53(Fe) MOF was developed for fast, highly selective and ultrasensitive direct determination of MeHg+. © The Royal Society of Chemistry 2013.

Chen Y.-H.,Sichuan University | Zhong G.-J.,Sichuan University | Lei J.,Sichuan University | Li Z.-M.,Sichuan University | Hsiao B.S.,State University of New York at Stony Brook
Macromolecules | Year: 2011

The crystallization of isotactic polypropylene (iPP) under the coexistence of shear flow and carbon nanotubes (CNTs) was investigated by means of in situ synchrotron X-ray scattering techniques, i.e. wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). Compared to sheared pure iPP, the combined effect of shear flow and CNTs endowed iPP crystals with weak degree of orientation at the early stage of crystallization but high degree of orientation in the later period. This was because the initial orientation of molecular chains induced by shear was suppressed as a result of the increased viscoelasticity of iPP melt in the presence of CNTs, but subsequently oriented molecular chains were stabilized by CNT surface absorption. The crystallization kinetics of sheared CNTs/iPP nanocomposites was synergistically promoted, where the crystallization rate was increased about 40 times in comparison to that of quiescently crystallized pure iPP. The Avrami exponent of CNTs/iPP nanocomposites and sheared iPP was around 2, indicating two-dimensional lamellar growth. The Avrami exponent of sheared CNTs/iPP nanocomposites surprisingly appeared to be 2.52, suggestive of mixed two-dimensional lamellar growth and three-dimensional sphrulitic growth geometries. Moreover, β-crystals were absent in sheared CNTs/iPP nanocomposites in contrast to the normal observation that α-row nuclei induced by shear generated β-crystals. The synergistic crystallization rate, the mixed crystal growth geometry as well as the absence of β-crystals in sheared CNTs/iPP nanocomposites were in close relation with intense interaction between shear flow and CNTs, which gave rise to extra nuclei in sheared CNTs/iPP melt. Apart from heterogeneous nucleating sites originated from CNTs and homogeneous nucleating sites (row-nuclei) initiated by shear, extra nuclei were taken into account to contribute to the further accelerated crystallization kinetics. The extra nuclei became active growth points of branching sites on the two-dimensional lamellae to generate three-dimensional spherulitic growth, thus leading to mixed crystal growth geometry of sheared CNTs/iPP nanocomposites. Besides, extra nuclei as well as α-nuclei derived from CNTs remarkably encouraged the formation of α-crystals, responsible for inexistence of β-crystals in sheared CNTs/iPP nanocomposites. © 2011 American Chemical Society.

Liu H.,Sichuan University | Wang R.,Beijing Institute of Fashion Technology | Xu X.,Sichuan University
Journal of Applied Polymer Science | Year: 2011

Novel phosphorus-containing copolyester nanocomposites were synthesized by in situ polymerization with 2-carboxyethyl(phenylphosphinic) acid (CEPPA) and nano-ZnCO 3. The flame retardancy and static and dynamic mechanical properties of poly(ethylene terephthalate) (PET)/nano-ZnCO 3 composites and phosphorus-containing copolyester/nano-ZnCO 3 composites were evaluated with limiting oxygen index measurements, vertical burning testing (UL-94), a universal tensile machine, and a dynamic mechanical analysis thermal analyzer. The phosphorus-containing copolyester nanocomposites had higher limiting oxygen indices (ca. 32%) and a V0 rating according to the UL-94 test; this indicated that nano-ZnCO 3 and CEPPA greatly improved the flame retardancy of PET. The static mechanical test results showed that the breaking strength, modulus, and yield stress of the composites tended to increase with increasing nano-ZnCO 3 content; when 3 wt % nano-ZnCO 3 was added to PET and the phosphorus-containing copolyester, the breaking strength of the composites was higher than that of pure PET. Dynamic mechanical analysis indicated that the dynamic storage modulus and loss modulus of the PET composites increased markedly in comparison with those of pure PET. However, the glass-transition temperatures associated with the peaks of the storage modulus, mechanical loss factor, and loss modulus significantly decreased with the addition of ZnCO 3 and CEPPA. The morphologies of the composites were also investigated with scanning electron microscopy, which revealed that nano-ZnCO 3 was dispersed homogeneously in the PET and copolyester matrix without the formation of large aggregates. In addition, the interfacial adhesion of nano-ZnCO 3 and the matrix was perfect, and this might have significantly affected the mechanical properties of the composites. © 2011 Wiley Periodicals, Inc.

Jun W.,Sichuan University | Yi J.,Sichuan University | Cai X.-F.,Sichuan University
Journal of Applied Polymer Science | Year: 2011

A novel charring agent, poly(p-propane terephthalamide) (PPTA), was synthesized with terephthaloyl chloride and 1,2-propanediamine through solution polycondensation at a low temperature. PPTA was used together with ammonium polyphosphate (APP) to prepare a novel intumescent flame retardant (IFR) for an acrylonitrile butadiene styrene (ABS) resin. The flammability and thermal stability of the IFR-ABS composites were investigated with limiting oxygen index, UL 94 vertical burning, and thermogravimetric analysis tests. The results showed that the IFR system had excellent flame retardancy and antidripping properties for ABS. The thermogravimetric curves suggested that there was a distinct synergistic effect of PPTA and APP, and this effect greatly promoted the char formation of the IFR-ABS composites and hence improved the flame retardancy. Additionally, the structure and morphology of char residues were studied with Fourier transform infrared and scanning electron microscopy. © 2010 Wiley Periodicals, Inc.

Bai H.,Sichuan University | Luo F.,Sichuan University | Zhou T.,Sichuan University | Deng H.,Sichuan University | And 2 more authors.
Polymer | Year: 2011

Large amount of work has been reported on the annealing of polypropylene (PP) and the related changes in mechanical properties. However, the structure-property correlations and the physical origin of annealing induced microstructural evolution are still not very clear. In this work, taking β-form PP (β-PP) as example, the microstructural changes induced by annealing were investigated from macromolecular to crystalline lamellae level with Fourier transform infrared (FTIR) spectroscopy, conventional differential scanning calorimetry (DSC), temperature-modulated DSC (TMDSC), wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and dynamic mechanical analysis (DMA). Besides mobile amorphous fraction (MAF), the role of rigid amorphous fraction (RAF) in toughening PP is particularly taken into consideration. It is shown that annealing increases the chain mobility in MAF and decreases it in RAF. Such an effect is believed to be mainly associated with the formation of looser MAF and more RAF by the microstructural re-arrangement involving conformational ordering of partial amorphous chain segments and a significant interlamellae thickening. A thorough analysis of structure-property relationship through observing plastic deformation behaviors by scanning electron microscope (SEM) and estimating stress transmission between crystalline and amorphous phases, suggests that both MAF and RAF play important role on toughening β-PP. They can promote the initiation of microvoids effectively upon deformation by reducing the stress transmission. As a result, large-scale plastic deformation is triggered. This work is important and provides a new insight into the mechanisms of microstructural evolution and subsequent improvement in impact toughness during annealing. © 2011 Elsevier Ltd. All rights reserved.

Wang M.,Sichuan University | Liu X.,Sichuan University | He P.,Sichuan University | Lin L.,Sichuan University | Feng X.,Sichuan University
Chemical Communications | Year: 2013

Enantioselective cyclization of α-isocyano esters with azodicarboxylates catalyzed by FeII-N,N′-dioxide complexes has been developed. Under mild conditions, a variety of 1,2,4-triazoline derivatives was obtained in high yields and enantioselectivities. © 2013 The Royal Society of Chemistry.

Gao C.,Sichuan University | Zhou H.,Sichuan University | Wei S.,Sichuan University | Zhao Y.,Sichuan University | And 2 more authors.
Chemical Communications | Year: 2013

A series of novel triazinonide-bridged bisimidazolium pincers were easily synthesized by quaternization of functionalized N-phenylimidazoles with highly reactive cyanuric chloride under mild conditions. The pincer 3c was proven to be a very efficient ligand for in situ Pd-catalyzed Suzuki-Miyaura reaction with ppm-level catalyst loading. © 2013 The Royal Society of Chemistry.

Li K.,Sichuan University | Li Z.,Sichuan University | Feng K.,Sichuan University | Xu X.,Sichuan University | And 2 more authors.
Journal of the American Chemical Society | Year: 2013

We demonstrated the synthesis and characterization of two conjugated copolymers, PBDTFBZO and PBDTFBZS, consisting of dialkylthiol substituted benzo[1,2-b:4,5-b′]dithiophene donor and monofluorinated benzotriazole acceptor blocks. The resulting copolymers show large band gaps, deep HOMO and LUMO energy levels. Improved Voc, Jsc, and FF were obtained at the same time to increase overall efficiencies of their single and tandem polymer solar cells. The enhanced Voc can be ascribed to a low-lying HOMO energy level by incorporating dialkylthiol and fluorine substituents on the polymer backbone. The improvement in Jsc and FF are likely due to high carrier mobility, suppressed charge recombination, and fine nanostructure morphology. A 7.74% PCE was achieved from the regular single device based on PBDTFBZS:PC71BM blend film with 3% 1,8-diiodooctane (DIO) additive. In combination with low band gap diketopyrrolopyrrole (DPP)-based copolymer, tandem devices based on PBDTFBZS exhibited high PCE up to 9.40%. The results indicate that PBDTFBZO and PBDTFBZS are promising polymer donor materials for future application of large-area polymer solar cells. © 2013 American Chemical Society.

Yue W.-W.,Sichuan University | Li H.-J.,Sichuan University | Xiang T.,Sichuan University | Qin H.,Sichuan University | And 3 more authors.
Journal of Membrane Science | Year: 2013

Zwitterionic polymer of poly(sulfobetaine methacrylate) (PSBMA) was grafted from polysulfone (PSf) membrane via surface-initiated atom transfer radical polymerization (SI-ATRP). The polysulfone-. graft-poly(sulfobetaine methacrylate) (PSf-. g-PSBMA) membrane was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared spectra (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and static water contact angle (WCA) measurement. The membrane showed excellent protein antifouling property though the water flux decreased to some content; nevertheless, the protein rejection ratio of the modified membrane was not change. The biocompatibility of the membrane was characterized by protein adsorption, hemolysis assay, platelet adhesion, plasma recalcification time, activated partial thromboplastin time (APTT), thrombin time (TT) and cytotoxicity experiments, and the results indicated that the modified PSf membrane had good blood compatibility and cytocompatibility. © 2013 Elsevier B.V.

Long C.,Sichuan University | Zhao L.,Tsinghua University | You J.-S.,Sichuan University | Wang M.-X.,Tsinghua University
Organometallics | Year: 2014

Catalyzed by CuOTf under very mild conditions, aryl triflates which are embedded in the azacalix[1]arene[3]pyridine macrocycle underwent coupling reactions with metal halides and acetates to afford respectively halogenated and acyloxylated arene products in moderate to excellent yields. The unprecedented CuOTf-catalyzed transformations of aryl triflates proceeded through an oxidative addition of intramolecularly chelated Cu(I) into the C-O bond of aryl triflates to form arylcopper(III) intermediates which underwent anion exchange and reductive elimination reactions with nucleophiles to yield functionalized macrocyclic products. © 2014 American Chemical Society.

Zhang R.,Southwest Petroleum University | He X.,Southwest Petroleum University | Huang G.,Sichuan University
Journal of Polymer Research | Year: 2014

In this paper, the changes in dynamics of Poly (butyl acrylate) (PBA) and Poly (ethyl acrylate) (PEA) after introducing internal double bonds (through copolymerizing with isoprene (IP)) were studied through sight of fragility theory. The dynamic fragility was determined. And the result shows that dynamic fragility indexes of PBA-co-IP and PEA-co-IP are smaller than PBA and PEA. Furthermore, the scaled dynamic mechanical spectra show that PBA-co-IP and PEA-co-IP have longer length of glass-rubber transition region. In one side, our work is well fitted to the universal theory that smaller fragility leads to longer soft dispersing in glass-rubber transition region. In the other side, adding internal double bonds is an effective way to weak fragility of polymers, which results in a broader transition region. © 2014 Springer Science+Business Media Dordrecht.

Wang W.,University of Sichuan | Zhang M.-J.,University of Sichuan | Chu L.-Y.,University of Sichuan | Chu L.-Y.,Sichuan University
Accounts of Chemical Research | Year: 2014

Functional polymeric microparticles with typical sizes of 1-1000 μm have received considerable attention for many applications. Especially in biomedical fields, polymeric microparticles with advanced functions such as targeted delivery, controlled encapsulation, or "capture and release" show great importance as delivery systems for active molecules and drugs, as imaging agents for analytics and diagnostics, as microreactors for confined bioreactions, and more. Generally, the functions of these microparticles rely on both their structures and the properties of their component materials. Thus, creating unique structures from functional materials provides an important strategy for developing advanced functional polymeric microparticles.Several methods, such as dispersion polymerization, precipitation polymerization, copolymer self-assembly, and phase-separated polymer precipitation can be used to make functional microparticles, but each has limitations, for example, their limited control over the particle size and structure. Using emulsions as templates, however, allows precise control over the size, shape, composition, and structure of the resulting microparticles by tuning those of the emulsions via specific emulsification techniques. Microfluidic methods offer excellent control of emulsion droplets, thereby providing a powerful platform for continuous, reproducible, scalable production of polymeric microparticles with unprecedented control over their monodispersity, structures, and compositions. This approach provides broad opportunities for producing polymeric microparticles with novel structure-property combinations and elaborately designed functions.In this Account, we highlight recent efforts in microfluidic fabrication of advanced polymeric microparticles with well-designed functions for potential biomedical applications, and we describe the development of microfluidic techniques for producing monodisperse and versatile emulsion templates. We begin by describing microparticles made from single emulsions and then describe those from complex multiple emulsions, showing how the resulting microparticles combine novel structures and material properties to achieve their advanced functions. Monodisperse emulsions enable production of highly uniform microparticles of desired sizes to achieve programmed release rates and passive targeting for drug delivery and diagnostic imaging. Phase-separated multiple emulsions allow combination of a variety of functional materials to generate compartmental microparticles including hollow, core-shell, multicore-shell, and hole-shell structures for controlled encapsulation and release, selective capture, and confined bioreaction. We envision that the versatility of microfluidics for microparticle synthesis could open new frontiers and provide promising and exciting opportunities for fabricating new functional microparticles with broad implications for myriad fields. © 2013 American Chemical Society.

Guan X.,Sichuan University | Zhang J.,Sichuan University | Wang Y.,Sichuan University
Chemistry Letters | Year: 2014

Photochemical processes provide a temporal and spatial control of the reaction, which offers an efficient way for chemical synthesis and affords extensive applications in materials science. In this study, a new photocatalyst system based on a Cu(II)/carboxylate complex was developed for photoinduced CuAAC reaction. The results show that the conversion was over 90% after irradiation for 30min. © 2014 The Chemical Society of Japan.

Liu X.,Sichuan University | Lin L.,Sichuan University | Feng X.,Sichuan University
Organic Chemistry Frontiers | Year: 2014

A class of conformationally flexible ligands composed of a tertiary amino oxide-amide backbone and a straight-chain alkyl spacer was developed. These C2-symmetric chiral N,N′-dioxide ligands could be straightforwardly synthesized from readily available amino acids and amines. They act as neutral tetradentate ligands to bind a wide variety of metal ions. Non-planar cis-α M(N,N′-dioxide) complexes enable an intriguing and easily fine-tuned chiral platform for a number of asymmetric reactions. Privileged N,N′-dioxide ligands frequently show wide substrate generality and exceptional levels of stereocontrol for a specific catalytic reaction. We describe approaches to the ligand design and synthesis, structure and bonding in coordination complexes, and the recent developments in asymmetric catalysis. © 2014 the Partner Organisations.

Xia S.,Sichuan University | Sun Z.,Sichuan University | Yi L.,Sichuan University | Wang Y.,Sichuan University
RSC Advances | Year: 2013

Novel functional diamine, 6-hexyloxy-naphthalen-3′,5′- diaminobenzoate (N6) containing a rigid naphthalene unit, was molecularly designed and successfully synthesized. PIs (polyimides) were obtained by copolymerization of N6, 3,3′-dimethyl-4,4′-methylenediamine (DMMDA) and 4,4′-oxydiphthalic anhydride (ODPA). The structures of the intermediates, diamines and PIs were confirmed by FT-IR and 1H NMR spectra. All PIs obtained could be dissolved in polar aprotic solvents and low-boiling-point solvents. PI (polyimide) films attained using a casting method showed favorably high transmittance above 95% in the wave length range of 400-700 nm and could align LCs vertically before and after rubbing treatment. PI-N6 derived from N6, DMMDA and ODPA exhibited a much higher temperature at a 5% weight loss (T5) compared with the corresponding PI-C6 from 4-hexyloxy-biphenyl-3′,5′-diaminobenzoate (C6). For PI-N6, the weight ratio of the side chains was smaller than that of PI-C6, but a much higher T5 was attained. The results demonstrated that the introduction of a naphthalene unit into the side chain could effectively improve the thermal stability of PI without sacrificing its solubility. Moreover, the outstanding thermal stability of the PIs was explained in a preliminary manner by the imidization reaction mechanism. This journal is © The Royal Society of Chemistry 2013.

Zhao K.,University of North Dakota | Zhao K.,Sichuan University | Deng X.,University of Chicago | He C.,University of Chicago | And 2 more authors.
Infection and Immunity | Year: 2013

Bacteria can naturally secrete outer membrane vesicles (OMVs) as pathogenic factors, while these vesicles may also serve as immunologic regulators if appropriately prepared. However, it is largely unknown whether Pseudomonas aeruginosa OMVs can activate inflammatory responses and whether immunization with OMVs can provide immune protection against subsequent infection. We purified and identified OMVs, which were then used to infect lung epithelial cells in vitro as well as C57BL/6J mice to investigate the immune response and the underlying signaling pathway. The results showed that OMVs generated from P. aeruginosa wild-type strain PAO1 were more cytotoxic to alveolar epithelial cells than those from quorum-sensing (QS)-deficient strain PAO1-ΔlasR. The levels of Toll-like receptor 4 (TLR4) and proinflammatory cytokines, including interleukin-1ß (IL-1ß) and IL-6, increased following OMV infection. Compared with lipopolysaccharide (LPS), lysed OMVs in which the membrane structures were broken induced a weak immune response. Furthermore, expression levels of TLR4-mediated responders (i.e., cytokines) were markedly downregulated by the TLR4 inhibitor E5564. Active immunization with OMVs or passive transfer of sera with a high cytokine quantity acquired from OMV-immunized mice could protect healthy mice against subsequent lethal PAO1 challenges (1.5×1011 CFU). Collectively, these findings indicate that naturally secreted P. aeruginosa OMVs may trigger significant inflammatory responses via the TLR4 signaling pathway and protect mice against pseudomonal lung infection. © 2013, American Society for Microbiology.

Yuan L.,Sichuan University | Zhang P.,Sichuan University | Feng W.,Sichuan University | Gong B.,State University of New York at Buffalo
Current Organic Chemistry | Year: 2011

Association units with high strength and specificity are getting increasing attention in the construction of well-defined selfassembling systems, which are making controlled non-covalent synthesis a reality. A class of hydrogen-bonded duplexes consisting of oligoamide strands carrying various combinations (sequences) of hydrogen-bond donors and acceptors has exhibited superb ability as intermolecular association units. These duplexes are featured by programmable sequence-specificity, predictable binding strength, ready synthetic availability and modifiability. With association constants ranging from ~104 to 109M-1, these hydrogen-bonded duplexes offer a diverse set of association units capable of specifying intermolecular association in a controlled and directed manner. The efficacy of these molecules as molecular assembler has already been demonstrated by a number of examples such as the construction of supramolecular block copolymers, the templation of β-sheets, directed chemical reactions such as olefin metathesis and disulfide exchange. By integrating hydrogen bonding with dynamic covalent interactions, covalently linked duplexes are formed sequence-specifically in a selfassembling fashion in highly competitive media, which represents a major progress in creating association units combining the strength of covalent bonds and the specificity of multiple hydrogen bonds. Recently, hydrogen-bonded and/or covalent crosslinked duplexes have been found to serve as gelators for organic solvents, which may open a new avenue for developing novel materials. © 2011 Bentham Science Publishers Ltd.

To further understand the kinetics of the thermal denaturation of type I collagen, the 16 and 8 mg/mL bovine hide collagen solutions were studied by differential scanning calorimetry at different heating rates. The activation energy of the denaturation process was examined utilizing the differential (Friedman) and the integral (Ozawa-Flynn-Wall) isoconversional methods, and several kinetic models were evaluated using the method of multivariate non-linear regression. Besides, the denaturation behavior was simulated under different temperature conditions. Results showed that the activation energy decreased in a different way at lower and higher degrees of conversion, respectively. A three-state model, in which a reversible step was followed by an irreversible one, was the best of the estimated models to describe the denaturation process, which could be approximated by single-step or two-consecutive-step in terms of temperature conditions.© 2010 Elsevier Ltd. All rights reserved.

Wang X.,Sichuan University | Huang G.,Sichuan University | Wu J.,Sichuan University | Nie Y.,Sichuan University | He X.,Sichuan University
Journal of Physical Chemistry B | Year: 2011

In this Article, we report the first study of the molecular dynamics in the glass-rubber transition region in polyisobutylene by 2D correlation dynamic mechanical spectroscopy (2DC-DMS). With the help of the high resolution and high sensitivity of the technique, the sub-Rouse modes are independently separated from the Rouse modes and local segmental motion (LSM). According to the positions and widths of autopeaks of three modes of molecular motions, the loss tangent peak is resolved into three peaks by nonlinear fitting method. Moreover, the glass-rubber transition region is divided into three regions. 2DC-DMS has been demonstrated to be a powerful tool for studying the molecular motions with different time/length scales. © 2011 American Chemical Society.

Zeng Y.,Sichuan University | Zhao B.,Sichuan University | Zhu L.,Sichuan University | Tong D.,Sichuan University | Hu C.,Sichuan University
RSC Advances | Year: 2013

A large abundance of environmentally harmful biomass waste is generated by water blooms. In order to provide an applicable solution for the relief of the environmental pressure, natural algae of Taihu Lake water blooms (CTL), mainly cyanobacteria, were catalytically pyrolyzed over silica-supported nickel phosphide to produce bio-oil. The properties of the bio-oil, such as chemical composition, elemental composition, and higher heating value (HHV), were examined. The composition of the gas product was also detected. The results suggest that catalytic pyrolysis could effectively convert the algae to a high quality bio-oil, in which the oxygen content was considerably reduced from 41.7 wt% in the algae to 8.0 wt% in the bio-oil. Long-chained alkanes became the primary component (59.4%). The HHV of the bio-oil obtained from catalytic pyrolysis was 37.2 MJ kg-1. The results indicate that it is possible to achieve high-grade renewable transportation fuels via catalytic pyrolysis of environmentally harmful CTL, and nickel phosphide is an applicable and effective catalyst. © The Royal Society of Chemistry 2013.

RADA16-I peptide hydrogel, a type of nanofiber scaffold derived from self-assembling peptide RADA16-I, has been extensively applied to regenerative medicine and tissue repair in order to develop novel nanomedicine systems. In this study, using RADA16-I peptide hydrogel, a three-dimensional (3D) cell culture model was fabricated for in vitro culture of three ovarian cancer cell lines. Firstly, the peptide nanofiber scaffold was evaluated by transmission electron microscopy and atom force microscopy. Using phase contrast microscopy, the appearance of the representative ovarian cancer cells encapsulated in RADA16-I peptide hydrogel on days 1, 3, and 7 in 24-well Petri dishes was illustrated. The cancer cell-nanofiber scaffold construct was cultured for 5 days, and the ovarian cancer cells had actively proliferative potential. The precultured ovarian cancer cells exhibited nearly similar adhesion properties and invasion potentials in vitro between RADA16-I peptide nanofiber and type I collagen, which suggested that RADA16-I peptide hydrogel had some similar characteristics to type I collagen. The precultured ovarian cancer cells had two-fold to five-fold higher anticancer drug resistance than the conventional two-dimensional Petri dish culture. So the 3D cell model on peptide nanofiber scaffold is an optimal type of cell pattern for anticancer drug screening and tumor biology.

Zhou R.,Sichuan University | Li B.,Sichuan University | Wu N.,Sichuan University | Gao G.,Sichuan University | And 2 more authors.
Chemical Communications | Year: 2011

Cyclen-functionalized perylenediimides PBI-1 and PBI-2 were first synthesized as highly sensitive and selective fluorescent chemosensors for Pb 2+ in aqueous solution. PBI-2 shows a better selectivity for Pb 2+ in the presence of other metal ions and, importantly, it can successfully enter the cell and be applied in imaging of living cells. © 2011 The Royal Society of Chemistry.

Li Y.,Sichuan University | Lian S.,Sichuan University | Tong D.,Sichuan University | Song R.,Sichuan University | And 4 more authors.
Applied Energy | Year: 2011

Nannochloropsis sp., one kind of green microalgae cultivated autotrophically and axenically in laboratory, is used as raw material to produce biodiesel by one-step method in an amended reactor. The effects of several reaction parameters on transesterification over Mg-Zr solid base catalyst were investigated through both conventional method and one-step method. One-step method could give a higher yield of methyl ester than conventional two-step method, which demonstrates that the present one-step method is suitable for biodiesel production from the microalgae Nannochloropsis sp. Moreover, the present one-step method realizes the convenient in situ separation of catalyst from microalgae residue which can be easily used consequently, reducing the procedure units as well as the overall costs. © 2011 Elsevier Ltd.

Du J.,Sichuan University | Huang Z.,Sichuan University | Yu X.-Q.,Sichuan University | Pu L.,Sichuan University | Pu L.,University of Virginia
Chemical Communications | Year: 2013

A Zn(ii) complex was found to exhibit greatly enhanced fluorescence in the presence of histidine but not in the presence of any other amino acids including cysteine. This sensor could also distinguish histidine from other imidazole derivatives. © 2013 The Royal Society of Chemistry.

Cao W.,Sichuan University | Liu X.,Sichuan University | Peng R.,Sichuan University | He P.,Sichuan University | And 2 more authors.
Chemical Communications | Year: 2013

A cooperative bimetallic catalyst system was applied in the catalytic asymmetric cross-dehydrogenative coupling of β-ketoesters and xanthene. Various optically active xanthene derivatives bearing a quaternary stereogenic carbon center were obtained in moderate to good yields (up to 90%) with excellent enantioselectivities (up to 99% ee). Meanwhile, a transition-state model was proposed to explain the origin of the asymmetric induction. © 2013 The Royal Society of Chemistry.

Zhang S.,Sichuan University | Zhang S.,University of Sichuan | Song F.,Sichuan University | Song F.,University of Sichuan | And 4 more authors.
Chemical Communications | Year: 2013

A concise and efficient approach to arylquinones from widely available hydroquinones has been developed through a tandem reaction involving the oxidation of hydroquinones and subsequent oxidative C-H/C-H cross-coupling of the resulting quinones with arenes. © 2013 The Royal Society of Chemistry.

Zhang W.,Sichuan University | Li W.,Sichuan University | Qin S.,Sichuan University
Organic and Biomolecular Chemistry | Year: 2012

Computational investigations on the asymmetric hydrosilylation of acetophenone over ligated CuH catalysts were performed with the DFT method. The calculations predict that the catalytic reaction involves two steps: (1) CuH addition to the carbonyl group via a four-membered transition state (TS) with the formation of copper-alkoxide intermediates; (2) regeneration of the ligated CuH catalyst by an external SiH4 through a metathesis process to yield the corresponding silyl ether. The calculations in the chiral diphosphine-ligated CuH systems suggest that the metathesis process is the rate-determining step (RDS). The CuH addition step is vital for the distribution of the racemic products and therefore represents the stereo-controlling step (SCT). In this step, the greater steric hindrance between the aromatic rings of the ligands and the substrate is identified as the major factor for enantioselectivity. The corresponding TS in the face-to-face mode, suffering less steric hindrance, is more stable than its analogue in the edge-to-face mode. The enantioselectivities are calculated to be related not only to the P-Cu-P bite angles in the stereo-controlling TSs, but also to the substituents at the P-aryl rings of the chiral ligands. In short, a larger P-Cu-P bite angle and suitably modified P-aryl rings together are necessary to achieve excellent ee values.

Cai Y.,Sichuan University | Li J.,Sichuan University | Chen W.,Sichuan University | Xie M.,Sichuan University | And 3 more authors.
Organic Letters | Year: 2012

Catalytic asymmetric sulfenylation of unprotected 3-substituted oxindoles has been developed via cooperative catalysis of a chiral N,N′-dioxide- Sc(OTf) 3 complex and a Brønsted base. Utilizing readily available N-(phenylthio)phthalimide as the sulfur source, a wide range of optically active 3-phenylthiooxindoles were obtained in excellent yields with excellent enantioselectivities under mild reaction conditions. © 2012 American Chemical Society.

Cai Y.,Sichuan University | Liu X.,Sichuan University | Zhou P.,Sichuan University | Kuang Y.,Sichuan University | And 2 more authors.
Chemical Communications | Year: 2013

The first iron(iii)/N,N′-dioxide-catalyzed asymmetric haloamination of 3-alkylidene- and 3-arylidene-indolin-2-ones was developed, affording the corresponding chiral oxindole derivatives bearing vicinal haloamine substituents with excellent results (up to 99% yield, 99% ee, >19:1 dr). This iron catalyst also exhibits perfect enantioselectivity for chalcone derivatives. The cooperative activation of the substrate and the reagent in concert guarantees the high stereoselectivity. © 2013 The Royal Society of Chemistry.

Yang D.,Sichuan University | Yang Q.,Beijing Jiaotong University | Yang L.,Sichuan University | Luo Q.,Sichuan University | And 3 more authors.
Chemical Communications | Year: 2013

An asymmetrically substituted squaraine ASQC bearing a 9-carbazyl substituent exhibits an extremely deep HOMO energy level of -5.46 eV and a relatively low bandgap of 1.65 eV, hence renders solution-processed organic solar cells with an impressive Voc of up to 1.12 V and a PCE of 2.82%. © 2013 The Royal Society of Chemistry.

Zhang L.-Q.,Sichuan University | Yang S.,Sichuan University | Huang X.,Sichuan University | You J.,Sichuan University | Song F.,Sichuan University
Chemical Communications | Year: 2013

A highly efficient and selective Ru-catalyzed direct C2-olefination of indoles, pyrroles, and carbazoles assisted by a removable N-dimethylcarbamoyl group has been developed by using O2 as the terminal oxidant. Both electron-deficient and unactivated alkenes are applicable to the protocol. © The Royal Society of Chemistry 2013.

Luo Y.B.,Sichuan University
Applied Mechanics and Materials | Year: 2014

Organic/inorganic nanocomposites have been widely focused because of their special properties. By modifying nano TiO2 and polylactic acid (PLA) with lactic acid, PLA/TiO2 nanocomposites was prepared, and the test on the dynamic mechanical property, thermal property, and thermal deformation temperature showed that adding nano TiO2 helped improve PLA's mechanics property, thermal decomposition temperature, and thermal deformation temperature to certain extent. © (2014) Trans Tech Publications, Switzerland.

Cong X.,Sichuan University | You J.,Sichuan University | Gao G.,Sichuan University | Lan J.,Sichuan University
Chemical Communications | Year: 2013

2-Pyridylmethyl ether-directed ortho-C-H olefination of phenols via a seven-membered cyclopalladated intermediate has been disclosed to construct a variety of ortho-alkenyl phenols and ortho-alkyl phenols. © 2013 The Royal Society of Chemistry.

Zhu D.,Sichuan University | Zhang L.,Sichuan University | Song M.,Sichuan University | Wang X.,Sichuan University | Chen Y.,Sichuan University
Chemical Communications | Year: 2013

We demonstrate for the first time that a Pd nanolayer, which is in situ formed on the Ni foam via the galvanic exchange method, greatly improves the energy output, the round-trip efficiency and the cyclability of the aprotic Li-air battery in ambient or simulated air. © The Royal Society of Chemistry 2013.

Yang F.,Sichuan University | Wang Z.,Sichuan University | Song F.,Sichuan University | Liu X.,Sichuan University | And 2 more authors.
Chemical Communications | Year: 2013

A new family of imidazoline-arylene macrocycles have been constructed through the simultaneous formation of four imidazoline rings in one step. These macrocycles can efficiently complex with fullerenes C60 and C 70 through the formation of ground-state complexes. © 2013 The Royal Society of Chemistry.

Chen C.,Sichuan University | Liu G.B.,Sichuan University | Wang Y.,Southwest University for Nationalities | Li J.L.,Sichuan University | Liu H.,Sichuan University
Electrochimica Acta | Year: 2013

A LiFePO4/C composite was synthesized by a simple solid-state reaction method using stearic acid as reductive agent and carbon source and nano-sized FePO4·2H2O as precursor which was prepared from intermediate Fe3(PO4)2· 8H2O using industrial FeSO4·7H2O and industrial NH4H2PO4 at a low cost. The structure, morphology and electrochemical performance of LiFePO4/C were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge tests, cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that the LiFePO4/C has an olivine-type structure with nano-size and exhibits excellent electrochemical properties. The discharge capacities are 159 mAh g-1, 148 mAh g-1 and 113 mAh g-1 at 0.1 C, 1 C and 10 C, respectively. Furthermore, the capacity retention rate is higher than 99% after 100 cycles at 1 C and 10 C. The excellent electrochemical performances of LiFePO4/C composite should be attributed to spherical nanoparticles as well as less impurity in FePO4·2H 2O precursor. © 2013 Elsevier Ltd.

Li C.Y.,Beijing University of Chemical Technology | Yuan W.,Chinese Academy of Sciences | Jiang H.,Beijing University of Chemical Technology | Li J.S.,Sichuan University | And 3 more authors.
Bioconjugate Chemistry | Year: 2011

Successful gene transfection on a tissue scaffold is of crucial importance in facilitating tissue repair and regeneration by enabling the localized production of therapeutic drugs. Polycaprolactone (PCL) has been widely adopted as a scaffold biomaterial, but its unfavorable cell-adhesion property needs to be improved. In this work, the PCL film surface was conjugated with poly((2-dimethyl amino)ethyl methacrylate) (P(DMAEMA))/gelatin complexes via surface-initiated atom transfer radical polymerization (ATRP) for improving cell immobilization and subsequent gene transfection. A simple aminolysis-based method was first used for the covalent immobilization of ATRP initiators on the PCL film. Well-defined P(DMAEMA) brushes were subsequently prepared via surface-initiated ATRP from the initiator-functionalized PCL surfaces. The P(DMAEMA) chains with a pK a of 7.0-7.3 were used for conjugating gelatin with a pI of 4.7 via electrostatic interaction. The amount of complexed gelatin increased as that of the grafted P(DMAEMA) layer. The cell-adhesion property on the functionalized PCL surface could be controlled by adjusting the ratio of P(DMAEMA)/gelatin. It was found that the gene transfection property on the immobilized cells was dependent on the density of the immobilized cells on the functionalized PCL film. With the good cell-adhesive nature of gelatin and the efficient gene transfection on the dense immobilized cells, the incorporating the suitable of P(DMAEMA)/gelatin complexes onto PCL surfaces could endow the PCL substrates new and interesting properties for potential tissue engineering applications. © 2011 American Chemical Society.

Han B.,University of Sichuan | Han B.,Chinese Academy of Sciences | Jiang X.,University of Sichuan | Hou X.,University of Sichuan | And 2 more authors.
Analytical Chemistry | Year: 2014

It was found that carbon atomic emission can be excited in low temperature dielectric barrier discharge (DBD), and an atmospheric pressure, low power consumption, and compact microplasma carbon atomic emission spectrometer (AES) was constructed and used as a universal and sensitive gas chromatographic (GC) detector for detection of volatile carbon-containing compounds. A concentric DBD device was housed in a heating box to increase the plasma operation temperature to 300 C to intensify carbon atomic emission at 193.0 nm. Carbon-containing compounds directly injected or eluted from GC can be decomposed, atomized, and excited in this heated DBD for carbon atomic emission. The performance of this new optical detector was first evaluated by determination of a series of volatile carbon-containing compounds including formaldehyde, ethyl acetate, methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol, and absolute limits of detection (LODs) were found at a range of 0.12-0.28 ng under the optimized conditions. Preliminary experimental results showed that it provided slightly higher LODs than those obtained by GC with a flame ionization detector (FID). Furthermore, it is a new universal GC detector for volatile carbon-containing compounds that even includes those compounds which are difficult to detect by FID, such as HCHO, CO, and CO2. Meanwhile, hydrogen gas used in conventional techniques was eliminated; and molecular optical emission detection can also be performed with this GC detector for multichannel analysis to improve resolution of overlapped chromatographic peaks of complex mixtures. © 2013 American Chemical Society.

Deng D.,Sichuan University | Jiang X.,University of Sichuan | Yang L.,National Research Council Canada | Hou X.,Sichuan University | And 2 more authors.
Analytical Chemistry | Year: 2014

Because of its unique properties and capability of formation of well-dispersed aqueous colloids in aqueous phase, graphene oxide can be used for the efficient preconcentration of heavy metal ions prior to their determination. The complete collection of graphene oxide colloids from water has generally been considered to be insurmountable. Here, graphene oxide aggregation triggered by introducing NaCl was used to develop a novel organic solvent-free cloud point extraction-like method for the determination of trace toxic metals. The graphene oxide sheets were uniformly dispersed in aqueous samples or standard solutions for a fast and efficient adsorption of Pb(II), Cd(II), Bi(III), and Sb(III) owing to its hydrophilic character and the electrostatic repulsion among the graphene oxide sheets, and its aggregation immediately occurred when the electrostatic repulsion was eliminated via adding NaCl to neutralize the excessive negative charges on the surface of graphene oxide sheets. The aggregates of graphene oxide and analytes ions were separated and treated with hydrochloric acid to form a slurry solution. The slurry solution was pumped to mix with KBH4 solution to generate hydrides, which were subsequently separated from the liquid phase and directed to an atomic fluorescence spectrometer or directly introduced to an inductively coupled plasma optical emission spectrometer for detection. On the basis of a 50 mL sample volume, the limits of detection of 0.01, 0.002, 0.01, and 0.006 ng mL-1 were obtained for Pb, Cd, Bi, and Sb, respectively, when using atomic fluorescence spectrometry, providing 35-, 8-, 36-, and 37-fold improvements over the conventional method. Detection limits of 0.6, 0.15, 0.1, and 1.0 ng mL-1 were obtained with the use of slurry sampling inductively coupled plasma optical emission spectrometry. The method was applied for analysis of two Certified Reference Materials and three water samples for these elements. © 2013 American Chemical Society.

This study produced nano-porous titanium dioxide (TiO2) using two-step method, and on the basis of experimental materials, the study also made a resistance-type formaldehyde sensor whose base was made of aluminium oxide (Al2O3) ceramic. Besides, the study analyzed responding sensitivity, selectivity, stability and response recovery time of formaldehyde gas sensor as well as response mechanism of the sensor on formaldehyde (HCHO); meanwhile, the influence of humidity on gas sensitive response was also explored. In addition, equipment that had functions of Zigbee wireless transmission and detecting surrounding environment was installed in the building, and on the basis of application of ZigBee communication protocol in build environment monitoring and developed formaldehyde gas sensor, the study further explored wireless sensor nodes which could detect HCHO concentration in real time. Subordinate nodes were responsible for acquisition and transmission of data of HCHO concentration, temperature and humidity, while principle nodes were mainly responsible for controlling operating status of subordinate nodes and receiving and dis-playing data. Received data could be displayed on liquid crystal display (LCD) of principle nodes or be sent to upper computer for systematical analysis through universal serial bus (USB). Therefore, wireless sensor nodes could not only be used in gas sensitive tests, but also be used as a kind of portable indoor HCHO detector. Copyright © 2016 American Scientific Publishers All rights reserved.

Wang Z.,Sichuan University | Ran Q.,Sichuan University | Zhu R.,Sichuan University | Gu Y.,Sichuan University
RSC Advances | Year: 2013

A novel modified polybenzoxazine with bi-continuous phase separated morphology was successfully prepared from the blend of bisphenol A-aniline benzoxazine (BA-a), N,N′-(2,2,4-trimethylhexane-1,6-diyl)bismaleimide (TBMI) and catalyst imidazole. The thermal and toughness properties of the phase-separated blend cast were improved compared with polybenzoxazine. © 2013 The Royal Society of Chemistry.

Liu J.,Sichuan University
International journal of nanomedicine | Year: 2011

A nanoscale injectable in situ-forming hydrogel drug delivery system was developed in this study. The system was based on a self-assembling peptide RADA16 solution, which can spontaneously form a hydrogel rapidly under physiological conditions. We used the RADA16 hydrogel for the controlled release of paclitaxel (PTX), a hydrophobic antitumor drug. The RADA16-PTX suspension was prepared simply by magnetic stirring, followed by atomic force microscopy, circular dichroism analysis, dynamic light scattering, rheological analysis, an in vitro release assay, and a cell viability test. The results indicated that RADA16 and PTX can interact with each other and that the amphiphilic peptide was able to stabilize hydrophobic drugs in aqueous solution. The particle size of PTX was markedly decreased in the RADA16 solution compared with its size in water. The RADA16-PTX suspension could form a hydrogel in culture medium, and the elasticity of the hydrogel showed a positive correlation with peptide concentration. In vitro release measurements indicated that hydrogels with a higher peptide concentration had a longer half-release time. The RADA16-PTX hydrogel could effectively inhibit the growth of the breast cancer cell line, MDA-MB-435S, in vitro, and hydrogels with higher peptide concentrations were more effective at inhibiting tumor cell proliferation. The RADA16-PTX hydrogel was effective at controlling the release of PTX and inhibiting tumor cell growth in vitro. Self-assembling peptide hydrogels may work well as a system for drug delivery.

Liu H.,Sichuan University | Wang R.,Beijing Institute of Fashion Technology | Xu X.,Sichuan University
Polymer Degradation and Stability | Year: 2010

Nano-Mg(OH) 2 (nanometre magnesium hydroxide, nano-MH) was successfully introduced into the esterification and polycondensation system by in situ polymerization to obtain PET/magnesium salt composites (PETMS). The thermal properties and flame retardancy of PETMS were investigated by differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), UL-94 vertical burning and limited oxygen index (LOI) test. The DSC and TGA results show that magnesium salts in the PET matrix have little effect on the thermal properties of PET, but a significant effect on the thermal stabilities of the composites. The results of LOI and UL-94 test show PETMS have higher LOI values (≥25%) and V-0 rating without melt dripping in the UL-94 test, indicating that PETMS have good flame retardancy and anti-dripping property. Moreover, the residues of magnesium salts and composites after TGA test were also studied by Fourier transform infrared spectroscopy (FTIR) to better understand the mechanism of flame retardancy, which reveals that magnesium salts accelerate the degradation of PET and catalyze the formation of char. The SEM results show the morphological structures of the char effectively protect the composites' internal structures and inhibit the heat, smoke transmission and reduce the fuel gases when the fire contacts them. © 2010 Elsevier Ltd. All rights reserved.

Yang F.,Sichuan University | Song F.,Sichuan University | Li W.,Sichuan University | Lan J.,Sichuan University | You J.,Sichuan University
RSC Advances | Year: 2013

Room-temperature ortho-arylation and acetoxylation of anilides have been achieved using cationic palladium (Pd[TFA]+) as catalyst and (NH 4)2S2O8 as oxidant. Preliminary investigation of the mechanism suggests that palladium may have different oxidation states in the catalytic cycles of these two transformations. © 2013 The Royal Society of Chemistry.

Yang J.,Sichuan University | Wang K.,Sichuan University | Deng H.,Sichuan University | Chen F.,Sichuan University | Fu Q.,Sichuan University
Polymer | Year: 2010

Injection-molded products usually show hierarchical structure from skin to core due to the existence of shear gradient and temperature gradient. Investigating the hierarchical structure is helpful to better understand the structure-property relationship of injection-molded sample, which is important for design and preparation of polymer products with high performance. In this work, the hierarchical structures of injection-molded bars of high-density polyethylene (HDPE)/multi-walled carbon nanotubes (MWCNTs) composite were explored by examining the microstructure and crystal morphology, layer by layer, along the sample thickness, using SEM, DSC and 2D-WAXS. To enhance the shear effect, a so-called dynamic packing injection molding (DPIM) technique was used to prepare the molded bar with high orientation level. Interestingly, SEM revealed that in the skin and core zones, the lamellae of PE anchored randomly on the surface of MWCNTs, while well-defined nanohybrid shish-kebab (NHSK) entities, in which fibrillous carbon nanotubes (CNTs) act as shish while HDPE lamellae act as kebab, exist in the oriented zone. The changed NHSK crystal structure along the thickness direction of molded bar is considered as due to the shear gradient and thermal gradient in injection molding. And the underlying origin of in situ formation of NHSK under shear effects is discussed based on experimental observations. © 2009 Elsevier Ltd. All rights reserved.

Xia T.,Sichuan University | Huang Y.,Sichuan University | Peng X.,Sichuan University | Li G.,University of Sichuan
Macromolecular Chemistry and Physics | Year: 2010

The influence of hydrophilic SiO2 nanoparticles on the morphology of polystyrene (PS)/ poly(vinyl methyl ether) (PVME) (10/90) blends in an unstable region has been investigated using optical microscopy and dynamic rheology techniques. For PS/PVME (10/90) blends annealed at 120 °C, the formation of a transient network structure and subsequent phase inversion indicates that a typical viscoelastic phase separation has occurred. However, for PS/ PVME (10/90) blends filled with 4 wt.-% SiO2 nanoparticles, a droplet-like structure was formed immediately without the appearance of a network-like structure. The rheological relaxation time of the blends suggested that the morphology transition observed in the PS/PVME/SiO2 (10/90/4) blend was related to the change in the dynamic asymmetry between the PS-rich phase and the PVME-rich phase, which was induced by the selective affinity of the SiO2 nanoparticles for PVME. After the incorporation of SiO 2 nanoparticles, the PVME-rich majority phase, which is originally the dynamically fast phase, became the slow phase, and led to a dynamic inversion compared with those unfilled blends. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Xu J.-Z.,Sichuan University | Chen C.,University of Sichuan | Wang Y.,Sichuan University | Tang H.,Sichuan University | And 2 more authors.
Macromolecules | Year: 2011

Combined effects of graphene nanosheets (GNSs) and shear flow on the crystallization behavior of isotactic polypropylene (iPP) were investigated by in-situ synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) techniques. For crystallization under quiescent condition (at 145 °C), the half-crystallization time (t1/2) of nanocomposites containing 0.05 and 0.1 wt % GNSs was reduced to at least 50% compared to that of neat iPP, indicating the high nucleation ability of GNSs. The crystallization rate of iPP was directly proportional to the GNS content. Under a relatively weak shear flow (at a rate of 20 s-1 for 5 s duration) and a low degree of supercooling, the neat iPP exhibited an isotropic structure due to the relaxation of row nuclei. However, visible antisotropic crystals appeared in sheared iPP/GNSs nanocomposites, indicating that GNSs induced a network structure hindering the mobility of iPP chains and allowing the survival of oriented row nuclei for a long period of time. The presence of GNSs clearly enhanced the effects of shear-induced nucleation as well as orientation of iPP crystals. Two kinds of nucleating origins coexisted in the sheared nanocomposite melt: heterogeneous nucleating sites initiated by GNSs and homogeneous nucleating sites (row nuclei) induced by shear. The difference of t 1/2 of nanocomposites with and without shear was significantly larger than that of neat iPP. The presence of GNSs and shear flow exhibited a synergistic interaction on promoting crystallization kinetics of iPP, although the effect of GNS concentration was not apparent. From WAXD results of isothermal and nonisothermal crystallization of sheared iPP, it was found that the appearance of β-crystals depended on the preservation of row nuclei, where the α-crystals were predominant in the iPP/GNSs nanocomposites, indicating that GNSs could directly induce α-crystals of iPP. © 2011 American Chemical Society.

Sun X.,Sichuan University | Cao Y.,Sichuan University | Xu H.,Sichuan University | Liu Y.,Sichuan University | And 2 more authors.
Bioresource Technology | Year: 2014

Triacylglyceride (TAG) and carbohydrate are potential feedstock for biofuels production. In this study, a two-stage process was applied for enhancing TAG/carbohydrate production in the selected microalgae - Neochloris oleoabundans HK-129. In stage I, effects of nitrogen, light intensity and iron on cell growth were investigated, and the highest biomass productivity of 292.83±5.83mg/L/d was achieved. In stage II, different nitrogen-starvation periods, light intensities and iron concentrations were employed to trigger accumulation of TAG and carbohydrate. The culture under 2-day N-starvation, 200μmol/m2/s light intensity and 0.037mM Fe3+ concentration produced the maximum TAG and carbohydrate productivity of 51.58mg/L/d and 90.70mg/L/d, respectively. Nitrogen starvation period and light intensity had marked effects on TAG/carbohydrate accumulation and fatty acids profile, compared to iron concentration. The microalgal lipid was mainly composed of C16/C18 fatty acids (90.02%), saturated fatty acids (29.82%), and monounsaturated fatty acids (32.67%), which is suitable for biodiesel synthesis. © 2014 Elsevier Ltd.

Yu X.-X.,Sichuan University | Liu F.,Sichuan University | Xu Y.-T.,Sichuan University | Wan C.-X.,Sichuan University
Journal of Materials Science: Materials in Medicine | Year: 2010

To overcome the cytotoxicity of the chemical reagents used to fix bioprostheses, genipin, a naturally occurring crosslinking agent, was used to fix biological tissues in present study. We prepared the biological vascular scaffolds through cell extraction and fixing the porcine thoracic arteries with 1% (by w/v) genipin solution for 3 days, and then examined their mechanical properties and microstructures; glutaraldehyde- and epoxy-fixed counterparts were used as controls. HUVECs were seeded on the type I collagen-coated surface of different modified acellular vascular tissues (fixed with different crosslinking agents), and the growths of HUVECs on the specimens were demonstrated by means of MTT test, the secretion of PGI2 and vWF by HUVECs on the various specimens was also measured. Finally, HUVECs were seeded on the luminal surface of acellular biological vascular scaffolds (<6 mm internal diameter) which were, respectively, treated in the same manner described above, and then cultured for 9 days. On the ninth day, the HUVECs on the luminal surface of these vascular scaffolds were examined morphologically and by immunohistochemistry. Genipin-fixation can markedly diminish antigenicity of the vascular tissues through partially getting rid of cell or reducing the level of free amino groups in the vascular tissues. Genipin-fixed acellular vascular tissues mimicked the natural vessels due to the maintenance of the integrity of total structure and the large preservation of the microstructures of collagen fibers and elastic fibers; therefore, it appeared suitable to fabricate vascular scaffolds in mechanical properties. Compared to controls, the genipin-fixed acellular vascular tissues were characterized by low cytotoxicity and good cytocompatibility. The HUVECs can not only proliferate well on the genipin-fixed acellular vascular tissues, but also preserve the activities and function of endothelial cells, and easily make it endothelialized in vitro. The results showed that the genipin-fixed acellular porcine vascular scaffolds should be promising materials for fabricating vascular grafts or the scaffolds of tissue-engineered blood vessels. © 2009 Springer Science+Business Media, LLC.

Wen C.,Sichuan University | Xiaoming D.,Southwest University | Tao L.,Sichuan University | Tao Y.,Sichuan University
Knowledge-Based Systems | Year: 2014

Negative selection algorithm (NSA) is an important algorithm for the generation of artificial immune detectors. However, the randomly generated candidate detectors have to be compared with the whole self set to exclude self reactive detectors. The inefficiency of the comparing process seriously limited the application of immune algorithms. Therefore, a new negative selection algorithm GF-RNSA is proposed in the paper. Firstly, the feature space is divided into a number of grid cells, and then detectors are separately generated in each cell. As candidate detectors just need to compare with the self antigens located in the same cell rather than with the whole self set, the detector training can be more efficient. The theoretical analysis demonstrated that the time complexity of GF-RNSA is effectively reduced that the exponential relationships between self size and time complexity in traditional NSAs is eliminated. The experimental results showed that: not only the time cost of negative selection, but also the time cost of data preprocess and detection are reduced, while the detection accuracy is not much declined. © 2013 Elsevier B.V. All rights reserved.

Zhou L.,Sichuan University | Yu L.,Sichuan University | Ding M.,Sichuan University | Li J.,Sichuan University | And 3 more authors.
Macromolecules | Year: 2011

To obtain a pH-sensitive multifunctional polyurethane micelle drug carrier, a novel pH-sensitive macrodiol containing acid-cleavable hydrazone linkers, poly(ε-caprolactone)-hydrazone-poly(ethylene glycol)-hydrazone-poly(ε- caprolactone) diol (PCL-Hyd-PEG-Hyd-PCL), was synthesized and characterized with proton nuclear magnetic resonance spectra (1H NMR). A series of pH-sensitive biodegradable polyurethanes (pHPUs) were designed and synthesized using pH-sensitive macrodiol, l-lysine ethyl ester diisocyanate (LDI) and l-lysine derivative tripeptide as chain extender, which can provide an active reaction site for the development of positive target polyurethane micelles for drug delivery. The bulk structures of the prepared polyurethanes were carefully characterized with 1H NMR, gel permeation chromatograph (GPC), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). The polyurethanes could be cleaved in acidic media (pH ∼ 4-6) as well as degraded in PBS and enzymatic solution, as demonstrated by 1H NMR and weight loss, respectively. The cytotoxicity of their degradation products was evaluated using methylthiazoletetrazolium (MTT) assay in vitro, resulting in no apparent inhibition effect on the fibroblasts. These polyurethanes could self-assemble into micelles in aqueous solutions, as verified using dynamic light-scattering (DLS). Our present work provides a new method for the preparation of amphiphilic multiblock polyurethanes with pH-sensitivity and biodegradability. It could be a good candidate as biodegradable multifunctional carrier for active intracellular drug delivery. © 2011 American Chemical Society.

Wang Y.,Sichuan University
Zhonghua liu xing bing xue za zhi = Zhonghua liuxingbingxue zazhi | Year: 2010

To study the infection status and the molecular characteristics of Vibrio parahaemolyticus isolated from diarrheal patients in Shenzhen, in 2007 to 2008 and to provide evidence for the prevention and control of diarrheal diseases caused by Vibrio parahaemolyticus. More than 80 fecal specimens from four sentinel surveillance hospitals were collected and cultured each month. A total of 361 isolates of Vibrio parahaemolyticus were sero-typed and examined by real-time PCR for the presence of two major virulence genes, tdh and trh. Of 361 strains, 60 O3: K6 strains isolated from six suspected outbreaks in August, 2007 and in September, 2008 were typed by pulsed-field gel electrophoresis (PFGE). 4384 stool samples were detected in four sentinel surveillance hospitals and with 361 Vibrio parahaemolyticus strains isolated that belonged to 28 serotypes. Serotype O3:K6, O4:K8 and O1:KUT accounted for 67.90%, 7.50% and 6.10%, respectively. Of 361 strains, 337 strains belonged to tdh+trh-, 11 strains were tdh-trh- and 13 strains were tdh+trh+. The most prevalent serotype which caused diarrheal diseases was tdh+trh in Shenzhen. The 60 isolates were discriminated into twenty different PFGE patterns, which belonged to three clones. Among the 60 isolates, most of the PFGE patterns of isolates from the suspected outbreak locations were identical and some strains isolated from different year were different. Vibrio parahaemolyticus isolates in Shenzhen were dominated by O3:K6 strains. Most of these isolates carried tdh gene and few carried trh gene. Meanwhile, the identical patterns of isolates from 6 suspected outbreaks locations demonstrated that Vibrio parahaemolyticus outbreaks occurred in July 2007 and in September 2008 in Shenzhen. However, the dominated strains' PFGE patterns were different each year, indicating that the sources of Vibrio parahaemolyticus had a multiplex nature and the multiplex sources such as water, sea food and pickled products should be integrated monitored. Laboratory based surveillance of diarrheal diseases could contribute in establishing early warning system for the better prevention and control of diarrheal diseases.

Liu J.-Q.,Sichuan University | Duan Y.-W.,CAS Kunming Institute of Botany | Hao G.,South China Agricultural University | Ge X.-J.,CAS South China Botanical Garden | Sun H.,CAS Kunming Institute of Botany
Journal of Systematics and Evolution | Year: 2014

As the highest and largest plateau in the world, the Qinghai-Tibet Plateau, with its numerous endemic species, is one of the important alpine biodiversity hotspots. Only recently have the evolutionary histories and underlying adaptations of these alpine plants become clear, through research mostly based on testable experiments and analyses. In this issue, we collected a total of 13 papers related to such aims. In addition, we selected a few published papers to highlight the major findings in the recent past. We also outlined the outlook and direction of future research. © 2014 Institute of Botany, Chinese Academy of Sciences.

Xu D.,Sichuan University | Cui Q.,University of Wisconsin - Madison | Guo H.,University of New Mexico
International Reviews in Physical Chemistry | Year: 2014

Metallo-enzymes play an indispensible role in many biological functions, and their modes of substrate binding and catalysis differ considerably from those of metal-free enzymes. A thorough understanding of the catalytic mechanisms of these enzymes cannot be achieved with experiments alone. In this review, recent theoretical investigations of the structure, binding, and catalysis of zinc hydrolases, which cleave substrate C-N and C-O bonds with high efficiency, are surveyed. Particular attention is paid to several extensively studied zinc peptidases as well as metallo-β-lactamases, which are responsible for ever-increasing bacterial resistance to penicillin-based antibiotics. These studies, particularly the ones using quantum mechanical/molecular mechanical methods, provide valuable insights into metal/ligand interactions, substrate binding and catalysis of these important metallo-enzymes. © 2014 © 2014 Taylor & Francis.

Hu Y.,Beijing University of Chemical Technology | Zhao N.N.,Beijing University of Chemical Technology | Li J.S.,Sichuan University | Yang W.T.,Beijing University of Chemical Technology | Xu F.J.,Beijing University of Chemical Technology
Journal of Materials Chemistry | Year: 2012

The inherent hydroxyl groups on the porous polycaprolactone (PPCL) films (prepared by using poly(ethylene glycol) as the pore-forming agent) could be reacted with 2-bromoisobutyrate bromide to produce a sufficient concentration of surface-coupled atom transfer radical polymerization (ATRP) initiators for the subsequent surface-initiated ATRP of thermo-responsive N-isopropylacrylamide (NIPAAm) at room temperature. A kinetics study revealed that the chain growth of the grafted NIPAAm polymer (P(NIPAAm)) was very fast and consistent with a 'controlled' process. The graft copolymerization not only occurred on the porous film surface, but also took place into the film bulk. The resultant P(NIPAAm)-grafted PPCL (PPCL-g-P(NIPAAm)) films assumed a uniform and interconnected porous structure and exhibited a temperature-sensitive property with a lower critical solution temperature (LCST) of about 32 °C, not unlike pure P(NIPAAm). The release of bovine serum albumin (BSA as a model protein) from the PPCL-g-P(NIPAAm) films was characterized by an initial burst, followed by a sustained release. These thermo-responsive PPCL-g-P(NIPAAm) porous films are potentially useful in biomedical fields. This journal is © 2012 The Royal Society of Chemistry.

Zhang X.-X.,Sichuan University | Xia B.-B.,Sichuan University | Ye H.-P.,Sichuan University | Zhang Y.-L.,Sichuan University | And 4 more authors.
Journal of Materials Chemistry | Year: 2012

Polydimethylsiloxane (PDMS)-silica ORMOSIL (organically modified silicate) sols were prepared by a one-pot sol-gel process using tetraethyl orthosilicate as an inorganic precursor and hydroxyl-terminated PDMS as an organic modifier, and antireflective (AR) coatings were prepared with these sols by dip coating. It was found that the addition of PDMS to silica sols significantly increased the viscosity and the controllable viscosity range of the silica sols, affording us a simple route to prepare very thick AR coatings with controlled thickness by a single deposition step. The coated fused silica substrates retained very high transmission of up to 99.9% at a determined wavelength. The addition of PDMS to the silica sols improved the hydrophobicity and abrasion-resistance of the coating, and prevented to some extent the coating from cracking which occurred in a pure inorganic thick AR coating. The PDMS-silica ORMOSIL AR coatings are stable after standing for 2 months at room temperature in an environment of 95% relative humidity. The relationship between structure and properties of the coatings is discussed considering the particle growth mechanism. © 2012 The Royal Society of Chemistry.

Gao C.-B.,Sichuan University | Zhou J.-L.,Sichuan University
Zidonghua Xuebao/Acta Automatica Sinica | Year: 2011

In this paper, according to the developed fractional differentiation and its applications in modern signal processing, we extend it to the quaternion body and put forward a novel concept: quaternion fractional directional differentiation, for image enhancement. We first use a quaternion function to color image and give the definition and calculation method of the quaternion fractional directional derivative. Then, we deduce their numerical calculation templates along eight directions. According to the fractional directional differentiation along the eight directions, the maximum of the norm of quaternion fractional directional differentiation for every point in the image plane is found, then this maximum as the pixel value of this point is viewed, and the enhanced image is obtained. Experimental results show that our method can greatly increase high frequency, reinforce medium frequency, and non-linearly preserve low frequency of signals, hence it is superior to those based on the traditional methods of differentiation in visual effects. Copyright © 2011 Acta Automatica Sinica.

Guo J.,University of Sichuan | Guo J.,Sichuan University | Wang X.,University of Sichuan | Miao P.,Sichuan University | And 4 more authors.
Journal of Materials Chemistry | Year: 2012

Controllable magnetic Ag@Ni core-shell nanoparticles (NPs) have been designed and constructed on the bayberry tannin (BT) grafted skin collagen fiber (SCF) though a simple one-step route. Due to the mild and naturally occurring reduction ability of BT, when the SCF-BT made contact with the mixture of Ag +/Ni 2+ solution, BT was able to preferentially reduce Ag + into Ag NPs, and subsequently, the formed Ag NPs served as in situ seeds for the over growth of magnetic Ni shell by the reduction of NaBH 4. The systematic TEM and EDS analysis confirmed that the as-prepared Ag@Ni NPs on SCF-BT were a typical core-shell structure. Magnetic study of core-shell NPs indicated that their magnetic properties could be tuned by modulating their shell thickness with the change of Ag +/Ni 2+ molar ratio. The diameter and size distribution of SCF-supported Ag@Ni core-shell NPs also can be controlled by varying the grafting degree of BT on SCF, as characterized by TEM. A novel and important application of these SCF-supported Ag@Ni core-shell NPs composites is use as high-performance microwave absorption materials in the whole X-band, C-band and some part of S-band with maximum reflection loss (RL) of -51 dB. The further analysis of electromagnetic parameters indicated that the enhancement of dielectric loss properties of SCF-supported Ag@Ni core-shell NPs is introduced by the multiple defective site polarization and interfacial polarization in bimetallic interface. In addition, owing to the combinated magnetic property on the nickel shell, the SCF-supported Ag@Ni core-shell NPs also exhibited a significant eddy current effect and anisotropic energy effect for the microwave absorption. To the best of our knowledge, this is the first time to explore tailoring the magnetic property, electromagnetic property and microwave absorption performance of functional core-shell NPs by tuning their core-shell microstructures. The present work has a significant potential for the development of novel, lightweight, low-cost, flexible and highly efficient microwave absorbing materials. © 2012 The Royal Society of Chemistry.

Fu H.Y.,Sichuan University | Doucet H.,CNRS Chemistry Institute of Rennes
European Journal of Organic Chemistry | Year: 2011

The palladium-catalysed direct arylation of methyl 2-furoate with aryl bromides was studied. The use of KOAc as the base, dimethylacetamide (DMAc) as the solvent and Pd(OAc) 2 as the catalyst was found to give 5-arylfurans regioselectively and without decarboxylation. These methyl 5-aryl-2-furoates gave 2,5-diarylfurans by decarboxylative coupling by using Pd(OAc) 2 as the catalyst. Methyl 2-furoate thus represents a convenient alternative substrate to furan for the synthesis of mono- or poly-arylated furans. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cheng X.,Sichuan University | Wu J.,Sichuan University | Lou X.,Xi'an University of Science and Technology | Wang X.,Xi'an University of Science and Technology | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2014

Both giant d33 and high TC have been obtained in a lead-free piezoelectric ternary system (0.995 - x)K0.48Na 0.52NbO3-0.005BiScO3-xBi0.5(Na 0.7K0.2Li0.1)0.5ZrO3. Thanks to the rhombohedral-tetragonal phase coexistence and the enhanced dielectric and ferroelectric properties, the ceramic with a composition of x = 0.04 shows a giant d33 of ∼366 pC/N together with TC of ∼335 C, thereby paving the way for achieving both high d33 and high TC in KNN-based materials. In addition, such a ceramic has a good thermal stability of d33 (e.g., d33 > 319 pC/N, T ≤ 300 °C) and an enhanced stability of ferroelectric properties against temperature. The domain-wall energy barrier of ∼0.15 eV is derived from the temperature dependence of the back-switching polarization. © 2014 American Chemical Society.

Guo Z.,Sichuan University | Chen X.,Sichuan University | Xin J.,Sichuan University | Wu D.,Sichuan University | And 2 more authors.
Macromolecules | Year: 2010

The influence of molecular weight and arm number of star polymers on the buildup and pH-dependent morphology changes of multilayer films assembled from star poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) and linear poly(styrenesulfonate) (PSS) was systematically investigated. Well-defined star PDMAEMA, consisting of β-cyclodextrin (CD) core and different arm number (21, 14, and 7) were successfully synthesized via atom transfer radical polymerization (ATRP). It is found that star polymers with certain arm number deposit more mass with the increase of molecular weight. As for the star polymers with almost the same arm length but different arm number, film assembled from 14-arm star PDMAEMA exhibits the fastest growth and the most significant morphology changes upon the pH 2.75 treatment. It is assumed that the interdiffusion of PSS controlled by star PDMAEMA with different structures should be responsible for the different buildup and pH-dependent morphology changes of the multilayer films. © 2010 American Chemical Society.

Su Y.,University of Sichuan | Lv Y.,Sichuan University
RSC Advances | Year: 2014

Due to the high surface area, excellent conductivity, high mechanical strength, and good biocompatibility, graphene has become a growing area of interest since it was first discovered in 2004. Despite these important achievements in the design of fluorescent, colorimetric and electrochemical sensors, the merging of graphene and chemiluminescence (CL) or electrochemiluminescence (ECL), especially CL is still in its infancy. In this review, according to the roles that graphene and its derivatives play in various CL or ECL systems, we discuss the new CL and ECL sensors in particular, in the last two years. Furthermore, we discuss some future prospects and critical challenges in this field. Additionally, possible solutions to overcome these challenges are presented. © 2014 The Royal Society of Chemistry.

Huang Z.-B.,Sichuan University | Yin G.-F.,Sichuan University | Liao X.-M.,Sichuan University | Gu J.-W.,PLA General Hospital of Chengdu Military Region
Frontiers of Materials Science | Year: 2014

Polypyrrole (PPy), the earliest prepared conducting polymer, has good biocompatibility, easy synthesis and flexibility in processing. Compared with metal and inorganic materials, doped PPy has better mechanical match with live tissue, resulting in its many applications in biomedical field. This mini-review presents some information on specific PPy properties for tissue engineering applications, including its synthesis, doping, bio-modification. Although some challenges and unanswered problems still remain, PPy as novel biomaterial has promoted the development tissue engineering for its clinical application in the future. © 2014 Higher Education Press and Springer-Verlag Berlin Heidelberg.

Kwang-Hua C.W.,Sichuan University
Canadian Journal of Physics | Year: 2013

Possible onset of the quantum plasticity in soft-solid He-4 was discovered recently in 7 nm diameter (Vycor glass) nanopores. Here, by using the transition-state model together with the specific activation energy and activation volume, we investigated the possible frictionless plastic flows of soft-solid He-4 under high pressure in confined nanodomains and we observed a series of sudden changes in the shearing stresses at corresponding very high shear strain rates of (locally amorphous) soft-solid He-4 for different activation volumes considering the role of He-3 impurities. Our calculated critical velocity for a fixed concentration of He-3 quantitatively agrees with recent reported values. © 2013 Published by NRC Research Press.

Fu Z.,Sichuan University
International Journal of Modern Physics A | Year: 2013

Using the lattice simulations we measure the point-to-point κ correlators in the Asqtad-improved staggered fermion formulation with the sufficiently light u/d quark. We then analyze these correlators using the rooted staggered chiral perturbation theory (rSχPT). After the chiral extrapolation, we obtain the physical κ mass with 835±93 MeV, which is in agreement with the recent BES experimental values. These numerical simulations are carried out with the MILC Nf = 2+1 flavor fine gauge configurations at a lattice spacing of a ≈0.09 fm. © 2013 World Scientific Publishing Company.

Ren C.,Sichuan University | Qiu W.,Sichuan University | Chen Y.,Sichuan University
Separation and Purification Technology | Year: 2013

Low cost, highly active TiO2/SiO2 catalysts have been prepared using TiOSO4·2H2O and SiO2 sol by a precipitation method. Among the catalysts, the TiO2/SiO 2 complex containing 5 wt.% of SiO2 and calcined at 650 °C, presents the highest photocatalytic activity. The conversion of benzene on the TiO2/SiO2 sample is 63% higher than it was presented by the un-doped TiO2. Ti-O-Si bond in the TiO 2/SiO2 samples, containing SiO2 both 7.5 wt.% and 10 wt.%, was observed from FT-IR spectroscopy, even though the TiO 2/SiO2 samples were prepared by an inorganic synthesized route from TiOSO4 and SiO2 sol. XRD, BET, and NH 3-TPD reveal that the crystal size of catalysts decreases, the surface area increases, and the amounts of total acidic sites go up when the silica is doped into the TiO2 photocatalysts. The photocatalytic activity of the TiO2/SiO2 prepared is mostly attributed to their high surface area, large pore volume, large surface acidity, and more surface hydroxyl groups. © 2013 Elsevier B.V. All rights reserved.

Tao X.,Sichuan University | Gu Y.-H.,Sichuan University | Wang H.-Y.,Sichuan University | Zheng W.,Sichuan University | And 3 more authors.
PLoS ONE | Year: 2012

Background: Sweet potato (Ipomoea batatas L. [Lam.]) ranks among the top six most important food crops in the world. It is widely grown throughout the world with high and stable yield, strong adaptability, rich nutrient content, and multiple uses. However, little is known about the molecular biology of this important non-model organism due to lack of genomic resources. Hence, studies based on high-throughput sequencing technologies are needed to get a comprehensive and integrated genomic resource and better understanding of gene expression patterns in different tissues and at various developmental stages. Methodology/Principal Findings: Illumina paired-end (PE) RNA-Sequencing was performed, and generated 48.7 million of 75 bp PE reads. These reads were de novo assembled into 128,052 transcripts (≥100 bp), which correspond to 41.1 million base pairs, by using a combined assembly strategy. Transcripts were annotated by Blast2GO and 51,763 transcripts got BLASTX hits, in which 39,677 transcripts have GO terms and 14,117 have ECs that are associated with 147 KEGG pathways. Furthermore, transcriptome differences of seven tissues were analyzed by using Illumina digital gene expression (DGE) tag profiling and numerous differentially and specifically expressed transcripts were identified. Moreover, the expression characteristics of genes involved in viral genomes, starch metabolism and potential stress tolerance and insect resistance were also identified. Conclusions/Significance: The combined de novo transcriptome assembly strategy can be applied to other organisms whose reference genomes are not available. The data provided here represent the most comprehensive and integrated genomic resources for cloning and identifying genes of interest in sweet potato. Characterization of sweet potato transcriptome provides an effective tool for better understanding the molecular mechanisms of cellular processes including development of leaves and storage roots, tissue-specific gene expression, potential biotic and abiotic stress response in sweet potato. © 2012 Tao et al.

Chen D.,China West Normal University | Wu H.,Sichuan University | Yang H.,Sichuan University
Advances in High Energy Physics | Year: 2013

In this paper, using Hamilton-Jacobi method, we address the tunnelling of fermions in a 4-dimensional Schwarzschild spacetime. Based on the generalized uncertainty principle, we introduce the influence of quantum gravity. After solving the equation of motion of the spin-1/2 field, we derive the corrected Hawking temperature. It turns out that the correction depends not only on the black hole's mass but also on the mass (energy) of emitted fermions. It is of interest that, in our calculation, the quantum gravity correction decelerates the temperature increase during the radiation explicitly. This observation then naturally leads to the remnants in black hole evaporation. Our calculation shows that the residue mass is Mp/β0, where Mp is the Planck mass and β0 is a dimensionless parameter accounting for quantum gravity effects. The evaporation singularity is then avoided. © 2013 Deyou Chen et al.

Liu M.,Sichuan University | Tang J.-H.,Sichuan University | Cui C.,Sichuan University | Li C.,Sichuan University | Chen X.-Z.,Sichuan University
Journal of Chemical and Engineering Data | Year: 2013

In this study, the solubilities and densities of a ternary system (NaH 2PO4 + CO(NH2)2 + H2O) at 298.15 K was investigated using isothermal solution saturation and moist residues. According to the experimental results, the phase diagram and the diagram of densities versus composition were plotted. It turned out that there were one cosaturated point (CO(NH2)2 + NaH 2PO4·2H2O), two univariant curves, and two crystallization regions corresponding to NaH2PO 4·2H2O and CO(NH2)2 in this ternary system. The system belonged to a simple eutectic type, in which no double salt was formed. This research filled the blank of phase diagram in this ternary system and demonstrated the absence of double salt in the system. © 2012 American Chemical Society.

Lourembam J.,Nanyang Technological University | Wu J.,Sichuan University | Ding J.,King Abdullah University of Science and Technology | Lin W.,Nanyang Technological University | Wu T.,King Abdullah University of Science and Technology
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

In this paper, we investigate the electric field effect on epitaxial Pr0.65(Ca0.75Sr0.25)0.35MnO3 thin films in electric double-layer transistors. Different from the conventional transistors with semiconducting channels, the sub(micrometer)-scale phase separation in the manganite channels is expected to result in inhomogeneous distribution of mobile carriers and local enhancement of electric field. The field effect is much larger in the low-temperature phase separation region compared to that in the high-temperature polaron transport region. Further enhancement of electroresistance is achieved by applying a magnetic field, and a 250% modulation of resistance is observed at 80 K, equivalent to an increase of the ferromagnetic metallic phase fraction by 0.51%, as estimated by the general effective medium model. Our results illustrate the complementary nature of electric and magnetic field effects in phase-separated manganites, providing insights on such novel electronic devices based on complex oxides. © 2014 American Physical Society.

Gao Y.-D.,Sichuan University | Gao Y.-D.,CAS Chengdu Institute of Biology | Harris A.J.,Oklahoma State University | Zhou S.-D.,Sichuan University | He X.-J.,Sichuan University
Molecular Phylogenetics and Evolution | Year: 2013

The Hengduan Mountains (H-D Mountains) in China flank the eastern edge of the Qinghai-Tibet Plateau (Q-T Plateau) and are a center of great temperate plant diversity. The geological history and complex topography of these mountains may have prompted the in situ evolution of many diverse and narrowly endemic species. Despite the importance of the H-D Mountains to biodiversity, many uncertainties remain regarding the timing and tempo of their uplift. One hypothesis is that the Q-T Plateau underwent a final, rapid phase of uplift 8-7. million years ago (Mya) and that the H-D Mountains orogeny was a separate event occurring 4-3. Mya. To evaluate this hypothesis, we performed phylogenetic, biogeographic, divergence time dating, and diversification rate analyses of the horticulturally important genus Lilium, including Nomocharis. The Lilium-. Nomocharis complex is distributed throughout the temperate Northern Hemisphere but is most diverse within the H-D Mountains and Q-T Plateau. Our matK and ITS phylogenies support previous studies showing that Nomocharis is nested within Lilium. However, we detected incongruence between the two gene trees which may result from hybridization. Dating analyses performed using the ITS dataset showed that the evolution of major lineages within Lilium-. Nomocharis may be temporally coincident with Q-T Plateau uplift occurring 8-7. Mya and H-D Mountains uplift approximately 4-3. Mya. Our analyses of diversification times and rates among Lilium-. Nomocharis clades are less conclusive. However, these do suggest high extinction rates among H-D Mountains lineages. © 2013 Elsevier Inc.

Lian X.,Sichuan University | Lin L.,Sichuan University | Wang G.,Sichuan University | Liu X.,Sichuan University | Feng X.,Sichuan University
Chemistry - A European Journal | Year: 2015

A catalytic asymmetric dearomatization of 2-naphthols with azodicarboxylates has been accomplished by using a N,N′-dioxide-scandium(III) complex as a chiral catalyst. A number of optically active β-naphthalenone compounds with a nitrogen-containing quaternary carbon stereocenter were obtained in up to 99 % yield and up to 99 % ee under mild reaction conditions. The reaction could be scaled up to a gram-scale with the yield and ee maintained. Based on these experiments and on previous reports, a possible transition state was proposed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Qu W.,Beijing Institute of Radiation Medicine | Zhou Y.,Beijing Institute of Radiation Medicine | Zhou Y.,Sichuan University | Zhang Y.,Beijing Institute of Radiation Medicine | And 5 more authors.
Nucleic Acids Research | Year: 2012

Evaluating the specificity of polymerase chain reaction (PCR) primers is an essential step in PCR primer design. The MFEprimer-2.0 server allows users to check primer specificity against genomic DNA and messenger RNA/complementary DNA sequence databases quickly and easily. MFEprimer-2.0 uses a k-mer index algorithm to accelerate the search process for primer binding sites and uses thermodynamics to evaluate binding stability between each primer and its DNA template. Several important characteristics, such as the sequence, melting temperature and size of each amplicon, either specific or non-specific, are reported on the results page. Based on these characteristics and the user-friendly output, users can readily draw conclusions about the specificity of PCR primers. Analyses for degenerate primers and multiple PCR primers are also supported in MFEprimer-2.0. In addition, the databases supported by MFEprimer-2.0 are comprehensive, and custom databases can also be supported on request. The MFEprimer-2.0 server does not require a login and is freely available at More over, the MFEprimer-2.0 command-line version and local server version are open source and can be downloaded at © 2012 The Author(s).

Zhang D.,Sichuan University | Liu Y.,Sichuan University | Shi Y.,Sichuan University | Huang G.,Sichuan University
RSC Advances | Year: 2014

A series of heptaphenylhydrogensilsesquioxane/polydimethylsiloxane (POSS/PDMS) nanocomposites are prepared through grafting and blending. Subsequently, the melting and isothermal crystallization behaviors of the POSS/PDMS nanocomposites are investigated by differential scanning calorimetery (DSC). There is an evident fluctuation in melting temperature though the melting curves of the nanocomposites show similar crystallinities to PDMS. The results indicate that the crystallization rate of the nanocomposites increases with the addition of POSS before POSS loading reaches 3 wt%, but it decreases with further addition of POSS. The maximum crystallization rate of the nanocomposites even achieves more than 2.5 times that of neat PDMS. According to X-ray diffraction (XRD) and scanning electron microscopy (SEM) results, uniformly dispersed POSS is more efficient in behaving as a nucleating agent, while the large agglomerates of POSS tend to crystallize by themselves, whose crystal regions restrict the PDMS chain segments from forming ordered structures. When POSS crystallites are larger than 31.5 nm, the orientation of PDMS chain segments can be significantly depressed. © 2014 The Royal Society of Chemistry.

He Y.,Sichuan University | Guo H.,Nanjing Southeast University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

We propose a topological defect or instanton solution with nonzero Hopf invariant to the 3+1D non-Abelian gauge theory coupled with scalar fields. This solution, which we call Hopf defect, represents a spacetime event that makes a 2. π rotation of vacuum manifold of the monopole. Although the action of this Hopf defect is logarithmically divergent, it may still give relevant contributions in a finite-sized system. Since the Chern-Simons term for the unbroken U(1) gauge field may appear in the low energy effective theory, the Hopf defect may possibly generate a phase factor change for the monopoles. © 2014 The Authors.

Liu B.,Sichuan University | Liu B.,Lanzhou University | Abbott R.J.,University of St. Andrews | Lu Z.,Lanzhou University | And 2 more authors.
Molecular Ecology | Year: 2014

Despite the well-known effects that Quaternary climate oscillations had on shaping intraspecific diversity, their role in driving homoploid hybrid speciation is less clear. Here, we examine their importance in the putative homoploid hybrid origin and evolution of Ostryopsis intermedia, a diploid species occurring in the Qinghai-Tibet Plateau (QTP), a biodiversity hotspot. We investigated interspecific relationships between this species and its only other congeners, O. davidiana and O. nobilis, based on four sets of nuclear and chloroplast population genetic data and tested alternative speciation hypotheses. All nuclear data distinguished the three species clearly and supported a close relationship between O. intermedia and the disjunctly distributed O. davidiana. Chloroplast DNA sequence variation identified two tentative lineages, which distinguished O. intermedia from O. davidiana; however, both were present in O. nobilis. Admixture analyses of genetic polymorphisms at 20 SSR loci and sequence variation at 11 nuclear loci and approximate Bayesian computation (ABC) tests supported the hypothesis that O. intermedia originated by homoploid hybrid speciation from O. davidiana and O. nobilis. We further estimated that O. davidiana and O. nobilis diverged 6-11 Ma, while O. intermedia originated 0.5-1.2 Ma when O. davidiana is believed to have migrated southward, contacted and hybridized with O. nobilis possibly during the largest Quaternary glaciation that occurred in this region. Our findings highlight the importance of Quaternary climate change in the QTP in causing hybrid speciation in this important biodiversity hotspot. © 2014 John Wiley & Sons Ltd.

Wu S.,Sichuan University | Li H.,Sichuan University | Huang G.,Sichuan University | Wu J.,Sichuan University
RSC Advances | Year: 2014

Crystallization is of primary importance to the properties of olefin block copolymers (OBCs). In the present work, multi-walled carbon nanotubes (MWCNTs) and graphene are used as nucleating agents for the crystallization of OBC. Thus nanocomposites of OBC filled with MWCNTs and graphene were prepared by solution blending. Differential scanning calorimetry (DSC) tests were carried out to study the effect of CNTs and graphene on isothermal crystallization of OBC; polarizing optical microscopy (POM), and wide-angle X-ray diffraction (WAXD) were used to study the morphology and crystal structure of OBC and its nanocomposites. It is found that both MWCNTs and graphene act as effective nucleating agents that significantly shorten the induction period of crystallization and increase the crystallization rate of OBC, exhibiting a remarkable decrease in the Avrami exponent n, surface folding energy σe and crystallization activation energy ΔE. These two carbon-based fillers both act as templates for hard block chains of OBC to form an ordered structure on the surface of nanoparticles during the induction period, bringing about some increase in equilibrium temperature. With the decrease in n, σe and ΔE not as remarkable as those of MWCNTs, graphene exhibited weaker nucleating ability than MWCNTs which might be due to strict lattice matching. The melting process of OBC and its nanocomposites are also studied; the nanocomposites exhibit two melting peaks at higher crystallization temperature which mainly refer to the melting of the crystals with different crystal sizes and perfection during heating, which is not observed for neat OBC. © 2014 the Partner Organisations.

In this study, the microstructures, hierarchical distribution of β-phase crystalline morphology and mechanical properties of neat isotactic polypropylene (iPP) prepared by conventional injection molding (CIM) and gas-assisted injection molding (GAIM) were intensively examined. The obtained samples were characterized via two-dimensional small-angle X-ray scattering (2D SAXS), polarizing light microscopy (PLM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD) and tensile testing. It was found that the strong shear effect introduced during the gas penetration of the GAIM process greatly influences the morphology and the formation of β-crystals in the pure PP specimens. Shish-kebab and β-cylindrite morphologies were observed simultaneously in the sub-skin layer of the GAIM part for the first time, where the flow pattern was complex and the shear strength was believed to be the maximum. Furthermore, an iPP specimen with β-crystals existing in the entire cross section of the molded bar were obtained for the GAIM sample without adding β-nucleating agents or other components. However, the pure iPP sample with a low content of β-crystals were only found in the skin layer of the CIM part. In addition, due the coexistence of shish-kebab and β-cylindrite structures, the mechanical properties of the GAIM specimen were significantly improved when compared with the CIM sample. Based on these experimental observations, a schematic illustration was proposed to interpret the mechanism of the formation of the unusual hierarchical distribution of β-crystals during the GAIM process. © 2014 the Partner Organisations.

Li J.,Sichuan University | Guo Z.,Sichuan University | Xin J.,Sichuan University | Zhao G.,South China University of Technology | Xiao H.,University of New Brunswick
Carbohydrate Polymers | Year: 2010

A series of cationic star polymers with 21 arms (21ACSPs) were synthesized through atom transfer radical polymerization using a β-cyclodextrin initiator with 21 initiation sites. Monomers containing primary, tertiary amino and quaternary ammonium groups were polymerized using 21Br-β-CD, Cu(I)Br and 2,2′-dipyridyl as initiator, catalyst and ligand, respectively. It was found that a co-solvent of 1-methyl-2-pyrrolidione and water (1:1) could facilitate the reaction, resulting in a well-controlled living polymerization. The conversion was up to 95% compared to the previously reported method (60%). AFM and DLS measurement revealed that 21ACSPs have the ability to condense the plasmid DNA (pCMV-Luc) to 80-180 nm. 21ACSPs with primary and tertiary amino groups exhibited higher cell transfection efficiency to CHSE-214 cells than 21ACSPs with quaternary ammonium groups. Meanwhile, all of the reported star polymers have no obvious cytotoxicity. The findings from this work are expected to be helpful for the development of efficient DNA delivery system. © 2009 Elsevier Ltd. All rights reserved.

Li W.,Sichuan University | Huang X.,Sichuan University | You J.,Sichuan University
Organic Letters | Year: 2016

A Ru-catalyzed intermolecular silylation of unreactive, aliphatic C(sp3)-H bonds has been described for the first time. This protocol features low catalyst loading, a relatively broad substrate spectrum, good functional group tolerance, and no sensitivity to air, which provides a convenient and practical pathway for the construction of C-Si bonds. (Chemical Equation). © 2016 American Chemical Society.

A novel charring agent poly(1,3-propylene terephthalamide) (PPTA) was synthesized and characterized by Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance. This novel charring agent combined with ammonium polyphosphate (APP) was adopted as an intumescent flame retardant (IFR) to impart flame retardance and dripping resistance to acrylonitrile-butadiene-styrene copolymer (ABS). Flammability and thermal behaviors of the treated ABS were investigated by limiting oxygen index, vertical burning test and thermogravimetric analysis. The results showed that the IFR with the novel charring agent had both excellent flame retardant and anti-dripping abilities for ABS. The thermogravimetric analysis curves indicated that there was a synergistic effect between PPTA and APP, which greatly promoted the char formation of IFR-ABS composites. Meanwhile, the thermal degradation mechanism of PPTA and APP/PPTA was characterized using thermogravimetric analysis/infrared spectrometry. The results demonstrated that APP changed the thermal degradation behavior of PPTA and reacted with PPTA to form a crosslinked structure. Additionally, the structure and morphology of char residues were studied by Fourier transform infrared spectroscopy and scanning electron microscopy. © 2011 Society of Chemical Industry.

Ye H.Q.,Queen Mary, University of London | Li Z.,Queen Mary, University of London | Peng Y.,Queen Mary, University of London | Wang C.C.,Nanjing University | And 8 more authors.
Nature Materials | Year: 2014

Modern telecommunications rely on the transmission and manipulation of optical signals. Optical amplification plays a vital part in this technology, as all components in a real telecommunications system produce some loss. The two main issues with present amplifiers, which rely on erbium ions in a glass matrix, are the difficulty in integration onto a single substrate and the need of high pump power densities to produce gain. Here we show a potential organic optical amplifier material that demonstrates population inversion when pumped from above using low-power visible light. This system is integrated into an organic light-emitting diode demonstrating that electrical pumping can be achieved. This opens the possibility of direct electrically driven optical amplifiers and optical circuits. Our results provide an alternative approach to producing low-cost integrated optics that is compatible with existing silicon photonics and a different route to an effective integrated optics technology. © 2014 Macmillan Publishers Limited. All rights reserved.

Cai P.,Sichuan University | Song H.,Sichuan University | Zhang L.,Sichuan University | Lv Y.,Sichuan University
Sensors and Actuators, B: Chemical | Year: 2012

In the present work, ZnO hierarchical microspheres were synthesized by hydrothermal methods in the sodium dodecyl sulfate-N,N-dimethyl-formamide- thiourea (SDS-DMF-thiourea) system. XRD, SEM, TEM, and N 2 adsorption measurements were used to characterize the prepared ZnO materials. Compared with ZnO nanoparticles (ZnO NPs), the as-prepared ZnO hierarchical microspheres (ZnO HMs) exhibit a better cataluminescence (CTL) response to ethanol. The response and recovery time of the home-made ethanol gas sensor with zinc oxide hierarchical microspheres as sensing materials were about 5 s and 25 s, respectively. The linear dependence of the sensitivity on the ethanol concentration was observed in the range of 4-400 ppm with excellent selectivity. These results indicated that ZnO hierarchical microspheres would be a good candidate for fabricating practical cataluminescence ethanol sensor. © 2012 Elsevier B.V.

Li L.,University of Sichuan | Liu C.,University of Sichuan | Wang Q.-H.,University of Sichuan | Wang Q.-H.,Sichuan University
Optics Letters | Year: 2012

We propose an optical switch based on the electrowetting effect. A transparent oil and a dye-doped water fill a cell. The two liquids are immiscible and form a curved interface. A transparent pillar-shaped platform with a round dome is fixed on the substrate. The dome of the platform is submerged in the water. As a result, light is highly absorbed by the covered water. When the shape of the water is changed, the oil can touch the dome of the platform due to the electrowetting effect. Then the transparent platform and the oil form a channel which can pass through the incident light. Our results show that the system can obtain a high optical attenuation (̃928:1) and reasonable response time (̃47 ms). The diameter of the aperture can be tuned from 0 to ̃3.0 mm. The proposed optical switch has potential application in light shutters, variable optical attenuators, and adaptive irises. © 2012 Optical Society of America.

Fu Z.,Sichuan University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

The s-wave pion-kaon (πK) scattering lengths at zero momentum are calculated in lattice QCD with sufficiently light u/d quarks and strange quark at its physical value by the finite size formula. The light quark masses correspond to m π=0.330-0.466GeV. In the Asqtad improved staggered fermion formulation, we measure the πK four-point correlators for both the isospin I=1/2 and 3/2 channels, and analyze the lattice simulation data at the next-to-leading order in the continuum three-flavor chiral perturbation theory, which enables a simultaneous extrapolation of πK scattering lengths at the physical point. We adopt a technique with the moving wall sources without gauge fixing to obtain substantiable accuracy; moreover, for the I=1/2 channel, we employ the variational method to isolate the contamination from the excited states. Extrapolating to the physical point yields the scattering lengths as m πa 3/2=-0.0512(18) and m πa 1/2=0.1819(35) for the I=3/2 and 1/2 channels, respectively. Our simulation results for πK scattering lengths are in agreement with the experimental reports and theoretical predictions, and can be comparable with other lattice simulations. These simulations are carried out with MILC N f=2+1 flavor gauge configurations at lattice spacing 0.15fm. © 2012 American Physical Society.

Xiao Y.-L.,Sichuan University | Su X.,Sichuan University | Chen W.,Sichuan University
Optics Letters | Year: 2012

System geometrical calibration is a challenging task in fringe-reflection 3D measurement because the fringe displayed on the LCD screen does not lie within the camera's field of view. Commonly, a flat mirror with markers can accomplish system geometrical calibration. However, the position of the markers must be precisely located by photogrammetry in advance. In this Letter, we introduce a calibration method by use of a markerless flat mirror. Experiments in phase measuring deflectometry demonstrate that the proposed method is simple and flexible. © 2012 Optical Society of America.

Fu Z.-W.,Sichuan University
Communications in Theoretical Physics | Year: 2012

We study s-wave pion-pion scattering length in lattice QCD for pion masses ranging from 330 MeV to 466 MeV. In the "Asqtad" improved staggered fermion formulation, we measure full ππ four-point correlators for isospin I = 0 and 2 channels, and use chiral perturbation theory at next-to-leading order to extrapolate our simulation results. Extrapolating to the physical pion mass yields scattering lengths as m πa 0 I=2 = -0.041 6(2) and m πa 0 I=0 = 0.186(2) for isospin I = 2 and 0 channels, respectively. Our lattice simulation for ππ scattering length in I = 0 channel is an exploratory study, where we include the disconnected contribution, and our preliminary result is near to its experimental value. These simulations are carried out with MILC 2 + 1 flavor gauge configurations at lattice spacing a 0.15 fm. © 2012 Chinese Physical Society and IOP Publishing Ltd.

Li G.,Tsinghua University | Xie X.,Tsinghua University | Zu L.,Sichuan University
Angewandte Chemie - International Edition | Year: 2016

Reported herein is the total synthesis of calophylineA, an indoline natural product possessing distinct ring connectivity which has not been synthesized previously. The synthetic route features several key transformations, including an aza-pinacol rearrangement to construct the nitrogen-containing bridged [3.2.2] bicycle, a Heck cyclization to assemble the fused 6/5/6/5 ring system, and a challenging late-stage aldol reaction to generate both a neopentyl quaternary stereogenic center and an oxygen-containing bridged [3.2.1] bicycle. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fu Z.,Sichuan University | Fu K.,Tsinghua University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We deliver an exploratory lattice QCD examination of the K *(892) meson decay width via the p-wave scattering phase shift of a pion-kaon (πK) system in the isospin I=1/2 channel. The modified Rummukainen-Gottlieb formula for a two-particle system with arbitrary mass is employed to extract phase shifts, which clearly reveal the existence of a resonance at a mass around the K *(892) meson mass. The effective range formula is applied to describe the energy dependence of the phase shift and we extract the effective K *→πK coupling constant as g K*πK=6.38(78). The decay width estimated from the phase shift is about 64.9±8.0MeV, which is in reasonable accordance with the experiment. Our lattice investigations are conducted on a 203×48 MILC gauge configuration with the N f=2+1 flavors of the asqtad-improved staggered dynamical sea quarks at (m π+m K)/m K *0.739 and lattice spacing a0.15fm. © 2012 American Physical Society.

Jiang N.,Sichuan University | Zhang C.,Sichuan University | Qiu K.,Sichuan University
Optics Letters | Year: 2012

A physical-enhanced secure passive optical network (PON) based on chaos synchronization is proposed and numerically demonstrated. In this scheme, the chaotic output of an external-cavity semiconductor laser is used as the transmission carrier in both downstream and upstream directions, the chaos modulation technology is used to encrypt the downstream data, and the multiplexed subcarrier-modulation technology is adopted for the upstream transmission. Simulation results demonstrate that both the downstream data and the upstream data encrypted into the chaotic carriers can be successfully decrypted; moreover, the security of downstream can be enhanced by properly increasing the bit rate, and the upstream security can be maintained at a high level. The proposed PON affords secure all-optical access at the physical layer. © 2012 Optical Society of America.

Xiao Y.-L.,Sichuan University | Su X.,Sichuan University | Chen W.,Sichuan University | Liu Y.,Sichuan University
Applied Optics | Year: 2012

Three-dimensional (3D) shape measurement of an aspheric mirror with fringe reflection photogrammetry involves three steps: correspondence matching, triangulation, and bundle adjustment. Correspondence matching is realized by absolute phase tracking and triangulation is computed by the intersection of reflection and incidence rays. The main contribution in this paper is constraint bundle adjustment for carefully dealing with lens distortion in the process of ray intersection, as compared to the well-known grating reflection photogrammetry. Additionally, a free frame is proposed to alleviate troublesome system geometrical calibration, and constraint bundle adjustment is operated in the free frame to refine the 3D shape. Simulation and experiment demonstrate that constraint bundle adjustment can improve absolute measurement accuracy of aspheric mirrors. © 2012 Optical Society of America.

Fu Z.,Sichuan University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

A proposal by Lüscher enables us to extract the elastic scattering phases from two-particle energy spectrum in a cubic box using lattice simulations. Rummukainen and Gottlieb further extend it to the moving frame, which is devoted to the system of two identical particles. In this work, we generalize Rummukainen-Gottlieb's formula to the generic two-particle states where two particles are explicitly distinguishable, namely, the masses of the two particles are different. Their relations with the elastic scattering phases of two-particle energy spectrum in the continuum are obtained for both C 4v and C 2v symmetries. Our analytical results will be very helpful for the study of some resonances, such as kappa, vector kaon, and so on. © 2012 American Physical Society.

Liao G.,Sichuan University
Lecture Notes in Electrical Engineering | Year: 2013

In international business activities, people of different cultures should follow some principles of intercultural communication in engaging in business activities, so as to reduce the friction, avoid communication obstacles, and make a deal done smoothly. © 2013 Springer-Verlag.

Yan D.-X.,Sichuan University | Ren P.-G.,Xi'an University of Technology | Pang H.,Sichuan University | Fu Q.,Sichuan University | And 2 more authors.
Journal of Materials Chemistry | Year: 2012

A combination of high-pressure compression molding plus salt-leaching was first proposed to prepare porous graphene/polystyrene composites. The specific shielding effectiveness of the lightweight composite was as high as 64.4 dB cm 3 g -1, the highest value ever reported for polymer based EMI shielding materials at such a low thickness (2.5 mm). This journal is © The Royal Society of Chemistry.

Pang H.,Sichuan University | Yan D.-X.,Sichuan University | Bao Y.,Sichuan University | Chen J.-B.,Sichuan University | And 2 more authors.
Journal of Materials Chemistry | Year: 2012

Super-tough conducting carbon nanotube (CNT)/ultrahigh-molecular-weight polyethylene (UHMWPE) composites were prepared by a facile method; a very small amount of high-density polyethylene (HDPE) was used as the percolated polymer phase to load the CNTs. A structural examination revealed the formation of unique conductive networks by combination of the typical segregated and double-percolated structure, in which the fully percolated CNT/carrier polymer layers were localized at the interfaces between UHMWPE granules. Owing to the synergistic effect of the segregated and double-percolated structures, only 0.3 wt% of CNTs can make the composite very conductive. More interestingly, after the addition of only 2.7 wt% of HDPE, the ultimate strain, tear strength, and impact strength reached 478%, 35.3 N and 58.1 kJ m-2, respectively; these corresponded to remarkable increases of 265%, 61.9%, and 167% in these properties compared with the conventional segregated materials. These results were ascribed to the intensified interfacial adhesion between UHMWPE granules, which resulted from the strong inter-diffusion and heat-sealing between the HDPE and UHMWPE molecules. A model was proposed to explain the outstanding ductility and toughness properties of the segregated and double-percolated CPC material. © The Royal Society of Chemistry 2012.

Chang H.-W.,Sichuan University | Wang M.-H.,Sichuan University
Signal Processing: Image Communication | Year: 2011

Image quality assessment (IQA) is of fundamental importance to numerous image processing applications. Generally, image quality metrics (IQMs) regard image quality as fidelity or similarity with a reference image in some perceptual space. Such a full-reference IQA method is a kind of comparison that involves measuring the similarity or difference between two signals in a perceptually meaningful way. Modeling of the human visual system (HVS) has been regarded as the most suitable way to achieve perceptual quality predictions. In fact, natural image statistics can be an effective approach to simulate the HVS, since statistical models of natural images reveal some important response properties of the HVS. A useful statistical model of natural images is sparse coding, which is equivalent to independent component analysis (ICA). It provides a very good description of the receptive fields of simple cells in the primary visual cortex. Therefore, such a statistical model can be used to simulate the visual processing at the level of the visual cortex when designing IQMs. In this paper, we propose a fidelity criterion for IQA that relates image quality with the correlation between a reference and a distorted image in the form of sparse code. The proposed visual signal fidelity metric, which is called sparse correlation coefficient (SCC), is motivated by the need to capture the correlation between two sets of outputs from a sparse model of simple cell receptive fields. The SCC represents the correlation between two visual signals of images in a cortical visual space. The experimental results after both polynomial and logistic regression demonstrate that SCC is superior to recent state-of-the-art IQMs both in single-distortion and cross-distortion tests. © 2011 Elsevier B.V. All rights reserved.

Wang Y.,CAS Nanjing Institute of Geology and Palaeontology | Huang C.,Sichuan University | Sun B.,Lanzhou University | Quan C.,Jilin University | And 3 more authors.
Earth-Science Reviews | Year: 2014

The Cretaceous was one of the most remarkable periods in geological history, with a "greenhouse" climate and several important geological events. Reconstructions of atmospheric CO2 using proxies are crucial for understanding the Cretaceous "greenhouse." In this paper we summarize the major approaches for reconstructing CO2 based on paleobotanical or geochemical data, and synthesize the CO2 variations throughout the Cretaceous. The results show that atmospheric CO2 levels remained relatively high throughout the Cretaceous, but were lower in the early Cretaceous, highest in the mid-Cretaceous and gradually declined during the late Cretaceous. However, this overall trend was interrupted by several rapid changes associated with ocean anoxic events (OAEs) and the end-Cretaceous catastrophic event. New data on paleo-CO2 levels from paleobotanical and paleosol evidences support not only the overall trends indicated by geochemical models, but provide more precise records of the short-term fluctuations related to brief episodes of climate change. Temporal resolution within the long quiet magnetic period in the middle Cretaceous is one of the obstacles preventing us from a more comprehensive understanding of the CO2 climate linkage. But new paleo-CO2 determinations and climatic data from stratigraphic sections of sediments intercalated with datable volcanic rocks will allow a better understanding of the relationships between fluctuations of atmospheric CO2, climate change, and geological events. © 2013 Elsevier B.V.

Wang H.,University of Sichuan | Wu J.,Sichuan University
Journal of Alloys and Compounds | Year: 2014

In this work, the (Ba1-xCax)(Ti 0.94Sn0.03Zr0.03)O3 (BCTSZ-x) lead-free ceramics were prepared by the conventional solid-state method, and effects of Ca2+ content on their phase structure, microstructure, and electrical properties were investigated. The phase structure of the ceramics endures a series of the phase transitions from orthorhombic, orthorhombic-tetragonal, to tetragonal phase as the Ca2+ content increases. Their grain size gradually drops as the Ca2+ continues increasing, the dense microstructure is developed, and the Ba2+, Ca2+, Ti4+, Sn4+, and Zr4+ are homogenously distributed in the ceramic matrix. In addition, adding Ca 2+ can not decrease the Curie temperature of the BCTSZ-x ceramics. Enhanced dielectric, ferroelectric, and piezoelectric properties (e.g., εr ∼ 3783, tan δ ∼ 1.3%, Pr ∼ 11.1 μC/cm2, d33 ∼ 359, and kp ∼ 0.45) were observed in the ceramic with x = 0.08 owing to the involved O-T phase boundary. As a result, the addition of Ca2+ can effectively enhance the piezoelectricity of barium titanate-based ceramics without the decrease of TC. © 2014 Elsevier B.V. All rights reserved.

Chen Y.,University of Sichuan | Pen Z.,Sichuan University | Wang Q.,University of Sichuan | Zhu J.,Sichuan University
Journal of Alloys and Compounds | Year: 2014

W/Cr co-doped BIT (BTWC) ceramics {Bi4Ti3-xW xO12+x + 0.25 wt% Cr2O3 (x = 0-0.1)} with a strong ferroelectricity and a high electrical resistivity were prepared by a conventional ceramic process, and effects of W doping content on their crystalline structures, ferroelectric properties and electrical conduction characteristics were also explored. By the co-doping of W/Cr, the crystallographic evolution happened in BTWC ceramics, and then the degree of the lattice distortion of BTWC ceramics decided on their spontaneous polarization and influenced their electrical resistivity. Moreover, both the increased applied field and measurement temperature can improve the Pr. The great improvement in remanent polarization and resistivity of BTWC ceramics were mainly attributed to the decreased concentration of oxygen vacancies by doping W6+. The Bi4Ti2.95W0.05O 12.05 + 0.25 wt% Cr2O3 ceramic possessed a large Pr of 16 μC/cm2 and a high ρdc (600 °C) of 2.94 × 106 Ω cm, respectively, which makes it a promising candidate for high-temperature applications. © 2014 Elsevier B.V. All rights reserved.

Li J.,Sichuan University | Shao L.,Sichuan University | Yuan L.,University of Sichuan | Wang Y.,Sichuan University
Materials and Design | Year: 2014

Poly(vinyl alcohol) (PVA)/reduced graphite oxide (rGO) nanocomposites were synthesized by solvothermal reduction of graphite oxide (GO) in the presence of PVA. The solvent, the mixed dimethyl sulfoxide (DMSO)-dimethylformamide (DMF), could act not only as a reducing agent but also as a good stabilizer, which achieved effectively reduction of GO in the PVA matrix and avoided the agglomeration of rGO during reduction. A 53.0% increase in tensile strength and 52.6% improvement of Young's modulus were achieved by addition of 3. wt% of rGO. Furthermore, a significant improvement of thermal stability was observed for the PVA/rGO nanocomposites. © 2013 Elsevier Ltd.

Jiang H.,Sichuan University | Zhao W.,Sichuan University | Li C.,Sichuan University | Wang Y.,Sichuan University
Polymer | Year: 2011

Increased using of plastic optical elements has generated a need for applying antireflection coatings onto plastic substrates. In this paper we reported a facile method to preparing porous thin films on plastic substrates by spin-casting poly (methyl methacrylate) (PMMA)/polystyrene (PS) mixed latices, followed by selectively removing PS particles. The refractive index of the porous coating is directly related to its porosity which could be controlled by varying mixing fraction of the sacrificial PS particles. The obtained porous thin films exhibited excellent anti-reflective (AR) performance over visible range with minimum reflection of 0.02%. The powerful control on refractive index and the versatility of this method makes it practicable to prepare antireflective coating on various plastic substrates with optimal performance. © 2010 Elsevier Ltd. All rights reserved.

Tang B.,Chongqing University | Song T.,Chongqing University | Li F.,Sichuan University | Deng L.,Chongqing University
Renewable Energy | Year: 2014

Fault diagnosis for wind turbine transmission systems is an important task for reducing their maintenance cost. However, the non-stationary dynamic operating conditions of wind turbines pose a challenge to fault diagnosis for wind turbine transmission systems. In this paper, a novel fault diagnosis method based on manifold learning and Shannon wavelet support vector machine is proposed for wind turbine transmission systems. Firstly, mixed-domain features are extracted to construct a high-dimensional feature set characterizing the properties of non-stationary vibration signals from wind turbine transmission systems. Moreover, an effective manifold learning algorithm with non-linear dimensionality reduction capability, orthogonal neighborhood preserving embedding (ONPE), is applied to compress the high-dimensional feature set into low-dimensional eigenvectors. Finally, the low-dimensional eigenvectors are inputted into a Shannon wavelet support vector machine (SWSVM) to recognize faults. The performance of the proposed method was proved by successful fault diagnosis application in a wind turbine's gearbox. The application results indicated that the proposed method improved the accuracy of fault diagnosis. © 2013 Elsevier Ltd.

Wang X.,Sichuan University | Chen F.,Sichuan University | Gu Y.,Sichuan University
Journal of Polymer Science, Part A: Polymer Chemistry | Year: 2011

Six bis-benzoxazines based on bisphenols with different bridging groups, -C(CH3)2-, -CH2-, -O-, -CO-, -SO2-, and single bond, were synthesized in toluene. The influence of electronic effects from bridging groups on ring-forming reaction and thermal ring-opening polymerization were relatively discussed in detail. Their structures were characterized by high-performance liquid chromatography, Fourier transform infrared, 1H NMR, differential scanning calorimetry, and elementary analysis. The quantum chemistry parameters of the bisphenols and bis-benzoxazines were calculated by molecular simulation. The results indicated that the electron-withdrawing groups inhibited the synthetic reaction by decreasing the charge density of α-Cs of bisphenols and increasing energy barriers of the synthetic reactions. However, the electron-withdrawing groups promoted the thermally activated polymerization, which resulted from their activation energy and curing temperature decrease by increasing the bond length and lowering the bond energy of C-O on oxazine rings. Besides, because of stronger electron-withdrawing sulfone group, there were more arylamine methylene Mannich bridge structure in the polybenzoxazine. © 2011 Wiley Periodicals, Inc.

Li Y.,Michigan State University | Jiang S.,Michigan State University | Jiang S.,Sichuan University | Cintron-Rivera J.G.,Sichuan University | Peng F.Z.,Sichuan University
IEEE Transactions on Industrial Electronics | Year: 2013

The voltage-fed Z-source inverter/quasi-Z-source inverter (qZSI) has been presented suitable for photovoltaic (PV) applications mainly because of its single-stage buck and boost capability and improved reliability. This paper further addresses detailed modeling and control issues of the qZSI used for distributed generation (DG), such as PV or fuel cell power conditioning. The dynamical characteristics of the qZSI network are first investigated by small-signal analysis. Based on the dynamic model, stand-alone operation and grid-connected operation with closed-loop control methods are carried out, which are the two necessary operation modes of DG in distributed power grids. Due to the mutual limitation between the modulation index and shoot-through duty ratio of qZSI, constant capacitor voltage control method is proposed in a two-stage control manner. Minimum switching stress on devices can be achieved by choosing a proper capacitor voltage reference. Experimental results are presented for validation of the theoretical analysis and controller design. © 1982-2012 IEEE.

Yang M.-B.,Sichuan University | Bao R.-Y.,Sichuan University | Cao J.,Sichuan University | Liu Z.-Y.,Sichuan University | And 2 more authors.
Journal of Materials Chemistry A | Year: 2014

Balanced stiffness and toughness is always the goal of high-performance general plastics for engineering purposes and the interfacial crystalline structure control has been proved to be an effective way to approach this goal. In this work, a kind of novel β-nucleating agent (β-NA) for isotactic polypropylene (iPP), one of the most rapidly developing general plastics, was supported onto the surface of octadecylamine functionalized graphene oxide (GO-D), and the effects of functionalized graphene oxide (GO) on the crystallization behavior, crystalline structures and mechanical properties of iPP composites were studied. The presence of the octadecyl chain changes the hydrophilic GO to be hydrophobic, and further supporting of β-NA onto GO-D (GO-N) does not change its solubility in xylene. The hydrophobic nature of octadecyl chains on the GO-D and GO-N surfaces leads to improved interfacial adhesion with the non-polar iPP matrix. At the same time, GO-N exhibits high efficiency in inducing the formation of β-crystals of iPP. The relative content of β-crystals, kβ, reaches a value as high as 73.6% at a loading of 0.1 wt% GO-N, resulting in a maximum increase in impact strength by almost 100% and a simultaneous improvement of the tensile strength by about 30%. This work provides a potential industrializable technique for high-performance iPP nanocomposites. © 2014 The Royal Society of Chemistry.

Wang X.,Sichuan University | Wu J.,Sichuan University | Xiao D.,Sichuan University | Cheng X.,Sichuan University | And 4 more authors.
Journal of Materials Chemistry A | Year: 2014

To protect the environment and human health, it is necessary to develop high-performance lead-free piezoceramics to replace the lead-based ones in some electronic devices. Here we report first a large piezoelectricity in (K,Na)NbO3-based lead-free piezoceramics prepared by the conventional solid-state method. The rhombohedral-tetragonal phase boundary is observed in the ceramics with a composition of 0.04 ≤ x ≤ 0.06. Those ceramics with 0.01 ≤ x ≤ 0.06 possess a good comprehensive performance of d33 (380-460 pC N-1) and TC (170-287 °C). Moreover importantly, a peak d33 of ∼460 pC N-1 is shown in the ceramic with x = 0.04, which is superior to all other reported results of KNN-based ceramics, including the reported results by Saito et al. (Nature, 2004, 432, 84). We believe that such a material system is a very promising candidate for potassium-sodium niobate piezoceramics. © 2014 The Royal Society of Chemistry.

Wang Z.,Sichuan University | Yao Q.,Sichuan University | Kang T.,Sichuan University | Feng J.,Sichuan University | And 3 more authors.
Chemical Communications | Year: 2014

An efficient lanthanide(iii)-catalyzed diastereo- and enantioselective Michael addition of 3-substituted benzofuran-2(3H)-ones to 4-oxo-enoates was developed. The desired adducts with contiguous quaternary-tertiary stereocenters were obtained in up to 99% yield with up to >95/5 dr and 98% ee. © 2014 the Partner Organisations.

Zeng Z.,Sichuan University | Li Y.,Sichuan University | Deng J.,Nanchang Hangkong University | Huang Q.,Nanchang Hangkong University | Peng Q.,Sichuan University
Journal of Materials Chemistry A | Year: 2014

Using tetrathienoacene (TT) and diketopyrrolopyrrole (DPP) units as donor and acceptor blocks, three new low band gap (LBG) conjugated copolymers (PTTDPO, PTTDPS and PTTDPSe) with different heterocycle bridges (furan, thiophene and selenophene) were designed and synthesized by Stille coupling polymerization reactions. Their structures were verified by 1HNMR spectroscopy and elemental analysis. All these copolymers exhibit broad absorption bands with small band gaps. UV-vis absorption spectra and cyclic voltammetry (CV) measurements indicated that the selenophene inclusion resulted in a reduction in the band gap, which could be attributed to a reduction of oxidation potentials and an increase of the electron affinities of the related copolymer. The density functional theory (DFT) calculations showed that PTTDPSe with selenophene bridges favoured a much more planar conformation than PTTDPO and PTTDPS, which afforded a higher hole mobility of 7.9 × 10-4 cm2 V-1 s-1. Photovoltaic properties of the copolymers blended with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as an electron acceptor were investigated. The polymer solar cell (PSC) based on the structure of ITO/PEDOT:PSS/PTTDPSe:PC71BM (1 : 1.5, w/w)/Ca/Al exhibited a high power conversion efficiency (PCE) of 5.68% with an improved short circuit current density (Jsc) of 15.62 mA cm-2. The primary results show that changing heterocycle bridges with different electron-donating ability can easily and finely tune the optical absorptions, band gaps and energy levels of DPP-containing copolymers. The results also demonstrate that the TT unit is a new and promising electron-donating donor block for constructing highly efficient LBG photovoltaic materials. © 2014 The Royal Society of Chemistry.

Qi X.,Sichuan University | Yao X.,Sichuan University | Deng S.,Sichuan University | Zhou T.,Sichuan University | Fu Q.,Sichuan University
Journal of Materials Chemistry A | Year: 2014

A novel water-induced shape memory polymer based on polyvinyl alcohol (PVA) was prepared by introducing graphene oxide (GO). Due to the strong hydrogen bonding interaction between PVA and GO, some additional physically cross-linked points could be formed in PVA, which largely improved shape memory properties of PVA. Solvent-induced shape memory behavior was observed by immersing PVA/GO nanocomposites in water. The water-induced shape recovery was due to the decrease of glass transition temperature and storage modulus. This could be explained by the swelling plasticizing effect of water on PVA, as indicated by the obvious expansion in volume of PVA. On the other hand, the weakened hydrogen bonding between PVA and GO was also observed after immersing the PVA/GO nanocomposites in water. Thus both the plasticizing effect and the competitive hydrogen bonding were the two main reasons for the shape recovery of PVA/GO nanocomposites. This study provides a framework for developing new shape memory polymers (SMPs) and for better understanding the shape recovery mechanism in solvent-induced SMPs. © 2014 The Royal Society of Chemistry.

Wu J.-M.,Sichuan University | Zhang Y.-Z.,Sichuan University
Applied Biochemistry and Biotechnology | Year: 2010

Ligninolytic enzymes are well-known to play the crucial roles in lignin biodegradation and have potential applications in industrial processes. The filamentous white-rot fungus, Phanerochaete chrysosporium, has been widely used as a model organism for studying these ligninolytic enzymes that are able to degrade the lignin during the secondary metabolism. To study the gene expression in secondary metabolism and metabolic switching phase of P. chrysosporium, we constructed a metabolic-switching phase suppression subtractive hybridization (SSH) cDNA library and a secondary metabolic phase SSH cDNA library to compare their mRNA expression profiles. We isolated the genes that are specially expressed and subsequently identified four genes that specially expressed during metabolic-switching phase while 22 genes in secondary metabolic phase. Accordingly, these specially expressed genes might play key roles in different metabolic stages, which would offer more new insights into the shift from nitrogen to lignin metabolism. © 2010 Springer Science+Business Media, LLC.

Shi L.,CAS Chengdu Institute of Optics and Electronics | Zhang Z.,Sichuan University | Cao A.,CAS Chengdu Institute of Optics and Electronics | Luo X.,CAS Chengdu Institute of Optics and Electronics | Deng Q.,CAS Chengdu Institute of Optics and Electronics
Optics Express | Year: 2015

An economical method for fabricating spiral phase plate (SPP) with continuous surface is proposed in this paper. We use an interval to quantize a three dimensional surface of an SPP into two dimensional bars to form a binary mask. The exposure dose can be precisely distributed through this mask in the exposure process. We discuss the select criterion of the quantization interval and the fabricating processes of SPP in detail. In the results, we present the fabrication of four kinds of high quality SPPs with different topological charges. The morphology analysis and the corresponding optical measurements verify the reliability of our fabrication method. © 2015 Optical Society of America.

Chen L.,Sichuan University | He Y.,Sichuan University | Chai S.,Guangdong Shengyi Technology Ltd Corporation | Qiang H.,Sichuan University | And 2 more authors.
Nanoscale | Year: 2013

Two-dimensional graphene and graphene-based materials have attracted tremendous interest, hence much attention has been drawn to exploring and applying their exceptional characteristics and properties. Integration of graphene sheets into macroscopic fibers is a very important way for their application and has received increasing interest. In this study, neat and macroscopic graphene fibers were continuously spun from graphene oxide (GO) suspensions followed by chemical reduction. By varying wet-spinning conditions, a series of graphene fibers were prepared, then, the structural features, mechanical and electrical performances of the fibers were investigated. We found the orientation of graphene sheets, the interaction between inter-fiber graphene sheets and the defects in the fibers have a pronounced effect on the properties of the fibers. Graphene fibers with excellent mechanical and electrical properties will yield great advances in high-tech applications. These findings provide guidance for the future production of high performance graphene fibers. © 2013 The Royal Society of Chemistry.

Lin L.,Sichuan University | Liu S.,Sichuan University | Zhang Q.,Sichuan University | Li X.,Sichuan University | And 3 more authors.
ACS Applied Materials and Interfaces | Year: 2013

The use of conductive polymer composites (CPCs) as strain sensors has been widely investigated and various resistivity-strain sensitivities are desirable for different applications. In this study, the use of mixed carbon fillers and functionalized carbon nanotubes was demonstrated to be vital for preparing thermoplastic polyurethane (TPU)-based strain sensors with tunable sensitivity. To understand the strain sensing behavior, we carried out scanning electron microscopy (SEM), Raman spectroscopy, wide-angle X-ray diffraction (WAXD), mechanical test, and rheology-electrical measurement. Hybrid fillers of multi-walled carbon nanotubes (MWNTs) and carbon black (CB) could reduce the entanglement in conductive network structure, thus increase the resistivity-strain sensitivity. Furthermore, incorporation of additional functionalized MWNTs in the CPCs could enhance the interfacial interaction between nanofillers and TPU, leading to further increase in sensitivity. Through such a simple method, strain sensors could be efficiently fabricated with large strain-sensing capability (strain as large as 200%) and a wide range of strain sensitivity (gauge factor ranging from 5 to 140238). Finally, the exponential revolution of resistive response to strain was fitted with a model based on tunneling theory by Simmons. It was observed that the change in tunneling distance and the number of conductive pathways could be accelerated significantly by adjusting conductive network structure and interfacial interaction. This study provides a guideline for the preparation of high-performance CPC strain sensors with a large range of resistivity-strain sensitivity. © 2013 American Chemical Society.

Wang L.R.,Sichuan University | Qin H.,Sichuan University | Nie S.Q.,University of Sichuan | Sun S.D.,Sichuan University | And 3 more authors.
Acta Biomaterialia | Year: 2013

In this study, heparin-like poly(ethersulfone) (HLPES) was synthesized by a combination of polycondensation and post-carboxylation methods, and was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectrum and gel permeation chromatography. Owing to the similar backbone structure, the synthesized HLPES could be directly blended with pristine PES at any ratios to prepare PES/HLPES membranes. After the introduction of HLPES, the microscopic structure of the modified PES membranes was changed, while the hydrophilicity was significantly enhanced. Bovine serum albumin and bovine serum fibrinogen adsorption, activated partial thromboplastin time, thromb time and platelet adhesion for the modified PES membranes were investigated. The results indicated that the blood compatibility of the PES/HLPES membranes was significantly improved compared with that of pristine PES membrane. For the PES/HLPES membranes, obvious decreases in platelet activation on PF-4 level, in complement activation on C3a and C5a levels, and in leukocytes activation on CD11b levels were observed compared with those for the pristine PES membrane. The improved blood compatibility of the PES/HLPES membrane might due to the existence of the hydrophilic groups (-SO 3Na, -COONa). Furthermore, the modified PES membranes showed good cytocompatibility. Hepatocytes cultured on the PES/HLPES membranes presented improved growth in terms of SEM observation, MTT assay and confocal laser scanning microscope observation compared with those on the pristine PES membrane. These results indicate that the PES/HLPES membranes present great potential in blood-contact fields such as hemodialysis and bio-artificial liver supports. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Liu J.,Sichuan University | Zhang C.,University of Sichuan | Xu D.,Sichuan University
Journal of Molecular Graphics and Modelling | Year: 2012

Xylanase Cex from Cellulomonas fimi is a bifunctional enzyme that catalyzes the degradation of both cellulose and xylan. As a result, it might find valuable applications in production of biofuels. In this work, we presented a detailed theoretical investigation of hydrolysis of the xylopentaose molecule catalyzed by Cex, using a hybrid quantum mechanical and molecular mechanical approach. Our results support the experimental observation that the hydrolysis proceeds via the net retention mechanism. More interestingly, our simulations indicate that the xylose unit at -1 binding site should take a boat (B 2,5) conformation as a possible reactive conformer, while the oxo-carbenium ion-like transition states take the combination of B 2,5/ OS 2 for glycosylation, and OS 2/ O,3B for deglycosylation. Our molecular dynamics simulations of mutants further suggest that two catalytic residues (E127 and E233) play the vital role in this ring distortion. Indeed, this conformational change is necessary to facilitate the first step of nucleophilic attack by E233 at the anomeric carbon center. © 2012 Elsevier Inc.

Liu J.,Sichuan University | Liu J.,University of Sichuan | Zhao X.,Sichuan University | Zhao X.,Massachusetts Institute of Technology
Nanomedicine | Year: 2011

Combining physics, engineering, chemistry and biology, we can now design, synthesize and fabricate biological nanomaterials at the molecular scale using self-assembling peptide systems. These peptides have been used for fabrication of nanomaterials, including nanofibers, nanotubes and vesicles, nanometer-thick surface coating and nanowires. Some of these peptides are used for stabilizing membrane proteins and drug delivery, and others provide a more permissive environment for 3D cell culture, tissue engineering and repair of tissues in regenerative medicine. Self-assembling peptides are also useful for fabricating a wide spectrum of exquisitely fine architectures, nanomaterials and nanodevices for nanomedicine and nanobiotechnology. These peptide systems lie at the interface between molecular biology, chemistry, materials science and engineering. The studies of designed self-assembling peptides and their applications will help us to understand nature's enormous power and how to apply it to benefit other disciplines and society. © 2011 Future Medicine Ltd.

Zhou M.,Sichuan University | Li Y.,Sichuan University | He C.,Sichuan University | Jin T.,Sichuan University | And 2 more authors.
Composites Science and Technology | Year: 2014

In this work, dopamine was introduced as a modifier for the surface treatment of ramie fiber. The interfacial crystallization of Poly (butylene succinate) (PBS) on the surface of treated fiber was investigated using polarized light microscope (PLM). It was found that raw ramie fiber has almost no nucleation ability on the crystallization of PBS. However, a beautiful transcrystalline (TC) structure could be successfully induced at the surface of treated fiber, which indicates a significantly improved nucleation ability of dopamine on PBS crystallization. Even more importantly, it was found that the interfacial shear strength between PBS and the treated fiber was very much improved due to the formation of transcrystalline structure. In order to further investigate the role of dopamine on interfacial enhancement, PBS/treated ramie fiber (10. wt%) composites were prepared by compression molding under the same condition with PLM. The tensile test showed that the tensile strength of composites with TC structure was increased by 30% when crystallized for 4. min than that of composites with an amorphous layer when crystallized for 0. min. This result suggested again that the interfacial enhancement was indeed due to the interfacial crystallization. Our work demonstrates that dopamine could be a green and novel surface modifier for natural fiber, and control of interfacial crystallization could be an efficient way for the interfacial enhancement between matrix and fillers. © 2013 Elsevier Ltd.

Li G.,Sichuan University
CSAE 2012 - Proceedings, 2012 IEEE International Conference on Computer Science and Automation Engineering | Year: 2012

The ocean animation is an important part of the visual simulation system. Using the view concerned projection grid can efficiently realize the rendering of ocean without boundary. But when using it to deal with the rendering of restricted region, it has some limitations. In this article, we introduce the twice clip method to deal with the restricted region rendering of ocean water. The experiment shows that the twice clip method can solve the problem and achieve good rendering effect and meet the real-time requirement of visual simulation system. © 2012 IEEE.

Wang X.,Sichuan University | Wu J.,Sichuan University | Xiao D.,Sichuan University | Zhu J.,Sichuan University | And 5 more authors.
Journal of the American Chemical Society | Year: 2014

Environment protection and human health concern is the driving force to eliminate the lead from commercial piezoelectric materials. In 2004, Saito et al. [ Saito et al., Nature, 2004, 432, 84. ] developed an alkali niobate-based perovskite solid solution with a peak piezoelectric constant d33 of 416 pC/N when prepared in the textured polycrystalline form, intriguing the enthusiasm of developing high-performance lead-free piezoceramics. Although much attention has been paid on the alkali niobate-based system in the past ten years, no significant breakthrough in its d33 has yet been attained. Here, we report an alkali niobate-based lead-free piezoceramic with the largest d33 of ∼490 pC/N ever reported so far using conventional solid-state method. In addition, this material system also exhibits excellent integrated performance with d33∼390-490 pC/N and T C∼217-304 C by optimizing the compositions. This giant d 33 of the alkali niobate-based lead-free piezoceramics is ascribed to not only the construction of a new rhombohedral-tetragonal phase boundary but also enhanced dielectric and ferroelectric properties. Our finding may pave the way for "lead-free at last". © 2014 American Chemical Society.

Xu H.,Sichuan University | Song P.,Sichuan University | Gu W.,Sichuan University | Yang Z.,Sichuan University
Ecotoxicology and Environmental Safety | Year: 2011

In a pre-experiment, Agaricus bisporus mycelia grown in PDL medium were found to have a substantial ability to tolerate and accumulate heavy metals. In the study, we investigated changes in the contents of soluble protein and thiol compounds as well as the activities of antioxidant enzymes caused by copper, zinc, lead, and cadmium (nitrate salts) in mycelia of A. bisporus during short-and long-term exposure. Results showed that high-level metal concentrations significantly decrease the contents of soluble protein after long-term exposure, Cu and Zn concentrations significantly increase the thiol compounds levels after long-term exposure, while high-level Cd significantly decrease thiol compounds after long-term exposure. Additionally, SOD activities were significantly increased after long-term exposure to metals, especially to Cd. The CAT activities were enhanced after long-term exposure to low-level Cu and high-level Zn, and enhanced after short-and long-term exposure to high-level Pb. The POD activities were significantly increased after long-term exposure to metals, and increased after short-term exposure to Cd and high-level Pb. © 2011.

Yao X.,Sichuan University | Qi X.,Sichuan University | He Y.,Sichuan University | Tan D.,Sichuan University | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2014

In the present work, a series of thermoplastic polyurethane (TPU)/microfibrillated cellulose (MFC) nanocomposites were successfully synthesized via in situ polymerization. TPU was covalently grafted onto the MFC by particular association with the hard segments, as evidenced by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The adequate dispersion and network structure of MFC in the TPU matrix and the strong interfacial interaction through covalent grafting and hydrogen bonding between MFC and TPU resulted in significantly improved mechanical properties and thermostability of the prepared nanocomposites. The tensile strength and elongation-at-break of the nanocomposite containing only 1 wt % MFC were increased by 4.5-fold and 1.8-fold compared with that of neat TPU, respectively. It was also very interesting to find that the glass transition temperature (Tg) of TPU was decreased significantly with the introduction of MFC, indicating potential for low-temperature resistance applications. Most importantly, compared with TPU nanocomposites reinforced with other nanofillers, the TPU/MFC nanocomposites prepared in this work exhibited excellent transparency and higher reinforcing efficiency. © 2014 American Chemical Society.

Cheng M.,Beijing University of Chemical Technology | Shi F.,Beijing University of Chemical Technology | Li J.,Sichuan University | Lin Z.,Sichuan University | And 5 more authors.
Advanced Materials | Year: 2014

Macroscopic supramolecular assembly is a promising method for manufacturing macroscopic, ordered structures for tissue-engineering scaffolds. A flexible spacing coating is shown to overcome undesired surface and size effects and to enable assembly of macroscopic cubes with host/guest groups. The assembled pairs disassembled upon introduction of competitive guest molecules, thereby demonstrating a multivalent assembly mechanism. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Xu J.,Beijing Computational Science Research Center | Xu J.,Sichuan University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

Global quantum discord (GQD), proposed by Rulli and Sarandy [C.C. Rulli, M.S. Sarandy, Phys. Rev. A 84 (2011) 042109], is a generalization of quantum discord to multipartite states. In this Letter, we provide an equivalent expression for GQD, and obtain the analytical expressions of GQD for two classes of multi-qubit states. The phenomena of sudden transition and freeze of GQD are also discussed. © 2012 Elsevier B.V. All rights reserved.

Yuan L.,Sichuan University
Lecture Notes in Electrical Engineering | Year: 2014

Processor technology is advancing from bus-based multicores to network- on-chip-based many-cores, posting new challenges for operating system design. In this paper, we present the trends in computer architecture that will affect operating system design, and summarize three concrete challenges for operating system design coming with these trends. In the end, we propose a new operating system architecture, Chameleon, to meet these challenges. © Springer-Verlag Berlin Heidelberg 2014.

Yang L.,Sichuan University | Zhu J.,Sichuan University | Xiao D.,Sichuan University
RSC Advances | Year: 2012

A microemulsion-mediated hydrothermal method has been demonstrated for synthesizing ZnSe and Fe-doped ZnSe quantum dots (QDs). The properties of ZnSe QDs can be controlled by using the surfactants of polyoxyethylene lauryl ether and Triton X-100. The resulting QDs were found to be in a zinc blende crystal structure, with optimal spherical shape, nearly monodispersed and controlled in their Fe/Zn ratio. In terms of the optical spectra, polyoxyethylene lauryl ether attenuates nucleation and growth, yielding smaller ZnSe QDs with a dominant surface-defect luminescence. Conversely, Triton X-100 produces larger ZnSe QDs with a high crystallinity and a lower density of surface defects, resulting in the enhanced band-edge luminescence. A growth mechanism involving the possible formation of nanoparticles based on the effect of surfactant in microemulsions has also been explored in this paper. Using an appropriate surfactant favors the modulation of the strength of the water-in-oil interface and the exchange dynamics of micelles. Highly fluorescent Fe-doped ZnSe QDs were also synthesized. With an increase of Fe2+ concentration, the band-edge emission peak is systematically blue-shifted. This behavior is indicative of a reduction of the reaction rate.© 2012 The Royal Society of Chemistry.

Jiang H.,Sichuan University
Wei sheng wu xue bao = Acta microbiologica Sinica | Year: 2010

We studied the reduction of soluble and highly toxic selenite to elemental red selenium, under aerobic condition by Pseudomonas alcaliphila MBR, with organic carbon as electron donor. The strain could grow under pH 6-11 and resist to high concentration of selenite with the minimal inhibitory concentration of 50 mmol/L. After 5 days, the strain used sodium citrate as electron donor, and reduced 2.0 mmol/L selenite to elemental red selenium from the culture fluid, the elemental red selenium was stored outside the cells. The glutathione and nitrate could increase the number of reduction rate. This study implies the application of Pseudomonas alcaliphila MBR to convert selenite to elemental red selenium.

Xiao Y.,Sichuan University | Xiao Y.,China Three Gorges University | Cao Y.,Sichuan University | Wu Y.,Sichuan University
Applied Optics | Year: 2012

An improved algorithm for phase-to-height mapping in phase-measuring profilometry (PMP) is proposed, in which the phase-to-height mapping relationship is no longer restricted to the condition that the optical axes of the imaging system must be orthogonal to the reference plane in the basic PMP. Only seven coefficients independent of the coordinate system need to be calibrated, and the system