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ABSTRACT: Porous hybrid Cu2 O/polypyrrole nanoflakes have been synthesized from solid CuO nanoplate templates through the pyrrole-induced reductive transformation reaction at elevated temperature. The conversion mechanism involves the reductive transformation of CuO to Cu2 O and the in situ oxidative polymerization of pyrrole to polypyrrole. In addition, the morphology of the as-converted nanohybrids depends on the shape of the CuO precursors. The strategy enables us to transform single-crystalline CuO nanosheets into hollow hybrid Cu2 O/polypyrrole nanoframes. The ability to transform CuO and an organic monomer into porous hybrid materials of conducting polymer and Cu2 O with macrosized morphological retention opens up interesting possibilities to create novel nanostructures. Electrochemical examinations show that these porous hybrid Cu2 O/polypyrrole nanostructures exhibit efficient catalytic activity towards oxygen reduction reaction (ORR), excellent methanol tolerance ability, and catalytic stability in alkaline solution, thus making them promising nonprecious-metal-based catalysts for ORR in alkaline fuel cells and metal-air batteries.
Chemistry - An Asian Journal 04/2013; · 4.50 Impact Factor
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ABSTRACT: Pt-Co alloy nanoparticle networks (NNs) with adjustable composition are synthesized by co-reduction of H(2) PtCl(6) and CoCl(2) with NaBH(4) in an ethylene glycol assisted cetyltrimethylammonium bromide/water/chloroform system at room temperature. Electrochemical measurements indicate that the as-prepared spongelike Pt-Co NNs exhibit composition-dependent electrocatalytic activities and CO tolerance with better durability toward methanol and formic acid oxidation than commercially available Pt/C catalyst. In particular, Pt(3) Co NNs show the highest specific activity, while Pt(2) Co NNs exhibit optimal mass activity among Pt-Co alloy NNs with different composition. These Pt-Co alloy NNs may be promising supportless anode catalysts for the direct methanol and direct formic acid fuel cells.
ChemPhysChem 04/2012; 13(10):2601-9. · 3.41 Impact Factor
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ABSTRACT: Three-dimensional Pd polyhedron networks (Pd PNs) have been fabricated for the first time through a one-step, Cu(2+)-assisted, solution-chemical approach. These as-prepared 3D Pd PNs exhibit high stability and remarkably improved electrocatalytic activity toward formic acid oxidation over commercially available Pd black.
Chemical Communications 03/2012; 48(32):3881-3. · 6.17 Impact Factor
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ABSTRACT: Tiny frames: The selective cation-exchange of unpurified ZnSe-diethylenetriamine (DETA) hybrid nanosheets with cadmium ions, followed by the dissolution of DETA and subsequent Ostwald ripening, leads to hollow Cd(x) Zn(1-x) Se nanoframes with tunable compositions. These nanoframes are highly active in the photocatalytic hydrogen evolution from water-splitting.
Angewandte Chemie International Edition 02/2012; 51(13):3211-5. · 13.45 Impact Factor
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Angewandte Chemie International Edition 02/2012; 51(6):1459-63. · 13.45 Impact Factor
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ABSTRACT: Human microsomal cytochrome P450 2E1 (CYP2E1) can oxidize not only low molecular weight xenobiotic compounds such as ethanol, but also many endogenous fatty acids. The crystal structure of CYP2E1 in complex with indazole reveals that the active site is deeply buried into the protein center. Thus, the unbinding pathways and associated unbinding mechanisms remain elusive. In this study, random acceleration molecular dynamics simulations combined with steered molecular dynamics and potential of mean force calculations were performed to identify the possible unbinding pathways in CYP2E1. The results show that channel 2c and 2a are most likely the unbinding channels of CYP2E1. The former channel is located between helices G and I and the B-C loop, and the latter resides between the region formed by the F-G loop, the B-C loop and the β1 sheet. Phe298 and Phe478 act as the gate keeper during indazole unbinding along channel 2c and 2a, respectively. Previous site-directed mutagenesis experiments also supported these findings.
PLoS ONE 01/2012; 7(3):e33500. · 4.09 Impact Factor
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ABSTRACT: Pt(3)Ni alloy nanoparticle networks (Pt(3)Ni NN) were prepared through a simple one-step room-temperature synthetic method. The as-prepared Pt(3)Ni NN exhibited markedly improved activity for both oxygen reduction reaction and electrocatalytic oxidation of small organic molecules over the Pt nanoparticle networks (Pt NN) and commercially available Pt/C.
Chemical Communications 12/2011; 48(21):2665-7. · 6.17 Impact Factor
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ABSTRACT: A facile room-temperature surfactant-free solution–chemical route has been developed to fabricate Cu2O nanocubes, octahedrons, spheres, plates, and polyhedrons by varying the reaction atmosphere (air or Ar) and reducing agent. It is believed that the oxygen adsorption and reaction on the surface of Cu2O may be able to slow down the reduction of Cu(OH)2 and the nucleation of Cu2O and further exert a noticeable influence on the following growth. We find that reducing agents are also important in determining the samples’ final morphology, structure, and composition. It has been demonstrated that the size of Cu2O nanocrystals can be modulated by changing the pH value of the reacting solution or the initial concentration of reacting agents or by adding solvents with high viscosity. In addition, the organic catalytic activity has been demonstrated to be susceptible to the shapes of the synthesized Cu2O materials. {111} planes of Cu2O are found to show higher catalytic activity (two times at 30 °C) than that of {100} facets on the N-arylation reaction of iodobenzene with imidazole. The difference among various crystal planes in catalytic activity may be related to crystal facets’ densities of surface Cu atoms, surface energies, turnover frequency, and electronic surface properties. Furthermore, O2-assisted selective etching is proposed to improve the activity of {100} facets by increasing the active sites. This fundamental understanding shows that morphological control of transition-metal oxides allows selective exposure of catalytically active planes and will most probably be applicable in the development of the next generation of highly efficient heterogeneous catalysts. The selective etching of crystallographic planes may be developed to a general technique to improve catalytic activity of noble metal, oxide nanocrystals, as well as porous catalysts.
07/2011;
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ABSTRACT: The human cytochrome P450 2A13 (CYP2A13) and P450 2A6 (CYP2A6) are 94% identical in amino acid sequence, but they metabolize many substrates with different efficiencies. Previous experimental results have shown that CYP2A13 exhibited catalytic activity that was more than 300-fold higher than CYP2A6 toward 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a carcinogen present in tobacco products. At present, however, the structural determinants accounting for the differential catalytic activities of these two isozymes toward NNK remain unclear. In the present study, molecular docking combined with molecular dynamics simulation and binding free energy calculation was performed to investigate the above issue. The results demonstrate that NNK was able to form a hydrogen bond with Asn297 in either CYP2A13 or CYP2A6. The hydrogen-bond acceptor was the pyridine nitrogen of NNK in the CYP2A13 complex, but it changed to the carbonyl oxygen in the CYP2A6 complex. NNK interacted with the residues in helix I and the K-β2 loop in CYP2A13, whereas it preferred to contact with the phenylalanine cluster in CYP2A6. The residues in helix I and the K-β2 loop of CYP2A13 played a vital role in keeping NNK in a more stable binding state. The binding free energies calculated by MM-GBSA were in agreement with the experimental results.
Journal of molecular graphics & modelling 05/2011; 30:1-9. · 2.17 Impact Factor
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ABSTRACT: Over the past decade, absorption, distribution, metabolism, and excretion (ADME) property evaluation has become one of the most important issues in the process of drug discovery and development. Since in vivo and in vitro evaluations are costly and laborious, in silico techniques had been widely used to estimate ADME properties of chemical compounds. Traditional prediction methods usually try to build a functional relationship between a set of molecular descriptors and a given ADME property. Although traditional methods have been successfully used in many cases, the accuracy and efficiency of molecular descriptors must be concerned. Herein, we report a new classification method based on substructure pattern recognition, in which each molecule is represented as a substructure pattern fingerprint based on a predefined substructure dictionary, and then a support vector machine (SVM) algorithm is applied to build the prediction model. Therefore, a direct connection between substructures and molecular properties is built. The most important substructure patterns can be identified via the information gain analysis, which could help to interpret the models from a medicinal chemistry perspective. Afterward, this method was verified with two data sets, one for blood-brain barrier (BBB) penetration and the other for human intestinal absorption (HIA). The results demonstrated that the overall predictive accuracies of the best HIA model for the training and test sets were 98.5 and 98.8%, and the overall predictive accuracies of the best BBB model for the training and test sets were 98.8 and 98.4%, which confirmed the reliability of our method. In the additional validations, the predictive accuracies were 94 and 69.5% for the HIA and the BBB models, respectively. Moreover, some of the representative key substructure patterns which significantly correlated with the HIA and BBB penetration properties were also presented.
Journal of Chemical Information and Modeling 06/2010; 50(6):1034-41. · 4.68 Impact Factor
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ABSTRACT: To evaluate the benefit of bilateral cochlear implants (BCIs) in prelingually deafened children on hearing rehabilitation as well as on speech and language development.
Two cases of congenital profound deaf children, who received unilateral cochlear implantation (CI, MEDEL C40+) on the age of 2 and 7.5, respectively, were performed secondary CI in the contralateral ear on their age of 5 and 9.5, respectively. One year after the secondary CI, the cochlear implant aided hearing threshold and speech discrimination rate were tested for both ears separately and together. The pronounce/speech distinct rate of the BCIs users were evaluated by their parents, surgeon and audiologist.
In comparison to unilateral aided ear, the mean hearing threshold at the frequency 250-4,000 Hz of the 2 cases with BCIs decreased by 13 dB and 11 dB, respectively. The speech discrimination rate of the BCIs users increased by 9% and 10%, respectively. The speech recognition in noise was improved. And their pronounce/speech distinct was improved.
BCIs can provide a significant benefit in hearing, speech understanding, language development and pronounce/speech rehabilitation for prelingually deafened children.
Lin chuang er bi yan hou ke za zhi = Journal of clinical otorhinolaryngology 11/2003; 17(10):577-9.
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ABSTRACT: In this paper, a novel optimization method, based on the conjugate gradient technique, is proposed for moving average (MA) system identification. The independent, identically distributed non-Gaussian input and Gaussian measurement noise are assumed. Experiments were performed to compare the proposed methods with some of current linear methods. The simulation results show that the proposed optimization method gives better performance with smaller bias and smaller standard deviation
Signal Processing, 1996., 3rd International Conference on; 11/1996
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ABSTRACT: In this paper, higher order statistic (HOS) based blur
identification methods are proposed to estimate blur coefficients in
image restoration, in which the image is considered as a colored
process. One dimensional (1-D) based blur identification algorithms are
proposed, and their extensions to two dimensional (2-D) cases are
discussed. The experimental results are presented to demonstrate the
performance of the proposed methods in this paper
Image Processing, 1996. Proceedings., International Conference on; 10/1996
