Electrocatalytic Oxidation of Formic Acid on Pd/Ni Heterostructured Catalyst

通过两步还原法制备了Pd/Ni双金属催化剂.由于金属Pd原子在先行还原的Ni纳米粒子表面的外延生长以及其在Ni表面及Pd表面生长表现出的吉布斯自由能差异，最终导致了异结构Pd/Ni纳米粒子的形成.高分辨电子透射显微镜结果证实了异结构的存在，然而X射线衍射测量表明Pd/Ni纳米粒子具有类似于Pd的面心立方结构.制备的Pd/Ni纳米粒子与同等条件下合成的Pd纳米粒子相比对甲酸氧化呈现了更高的电催化活性，而且电催化稳定性也要明显优于纯Pd纳米粒子，证明Pd/Ni双金属催化剂是可选的直接甲酸燃料电池阳极催化剂.双金属催化剂对甲酸氧化电催化活性和稳定性增强可能是Ni原子的修饰改变了Pd粒子表面配位不饱和原子的电子结构所致.A Pd/Ni bimetallic nanostructured electrocatalyst was fabricated via a two-step reduction route. Owing to an epitaxial growth of Pd atoms on the surface of Ni nanoparticles, heterostructured Pd/Ni nanocomposites were formed and verified by high resolution transmission electron microscopy combined with energy-dispersion X-ray spectroscopy. X-ray diffraction confirmed that the as-prepared Pd/Ni nanocomposites possessed a single face-centered-cubic (fcc) Pd structure, probably due to a weaker diffraction intensity of metallic Ni and/or overlapping by that of Pd. The intrinsic catalytic activity on the Pd/Ni is higher than that on the Pd. Moreover, the durability of formic acid oxidation on the Pd/Ni was much enhanced over the Pd nanoparticles. The change in electronic structure of the surface coordination unsaturated Pd atoms and the possible dissolution of Ni species from the Pd/Ni heterostructure may account for such an improved durability for formic acid oxidation.This work was supported by the National Basic Research Program of China (973 Program) (No. 2012CB932800), the Natural Science Foundation of China (No. 21073219), Shanghai Science and Technology Committee (No. 11DZ1200400) and the Knowledge Innovation Engineering of the CAS (No. 12406, 124091231).This work was supported by the National Basic Research Program of China (973 Program) (No. 2012CB932800), the Natural Science Foundation of China (No. 21073219), Shanghai Science and Technology Committee (No. 11DZ1200400) and the Knowledge Innovation Engineering of the CAS (No. 12406, 124091231).作者联系地址：1. 中国科学院上海高等研究院，上海 201210；2. 中国科学院研究生院，北京 100039Author's Address: 1. Shanghai Advanced Research Institute, Chinese Academy of Sciences CAS, Shanghai 201210, China; 2. Graduate School of the CAS, Beijing 100039, China通讯作者E-mail：[email protected] & [email protected]

An improved maximal entropy based bracketing transduction grammar translation model with ensemble learning

With an important characteristic that using discriminative lexicalized reordering model to capture the phrase movement during translation, the maximum entropy based bracketing translation grammar (MEBTG) has become one of the research hotspots of statistical machine translation in recent years. However, the research of this model is far from mature. Specifically, MEBTG system tends to suffer from the problems related to over-fitting of the reordering examples. To solve this problem, we propose to apply ensemble learning framework to improve discriminative reordering model of MEBTG system. In the specific implementation, we first respectively try bagging and cross-validation to construct multiple basic classifiers, and then investigate two integration methods to combine the results of these classifiers. The experimental results on large-scale data set demonstrate the effectiveness of our method. ? 2014 Binary Information Press

Analysis and reduction of phase errors caused by nonuniform surface reflectivity in a phase-shifting measurement system

The measurement accuracy of a phase-shifting measurement system is adversely affected by phase errors. This paper presents a theoretical analysis of phase errors caused by nonuniform surface reflectivity, such as varying reflectivity and a sharp change in reflectivity. Based on the analysis, a method to adaptively adjust the maximum input gray level of each pixel in projected fringe patterns to the local reflectivity was proposed to reduce phase errors. Experimental results for a planar checkerboard show that the measurement error can be reduced by 56.6% by using the proposed method

Prediction of the liquid film reversal of annular flow in vertical and inclined pipes

This work proposes a simplified model and a unified model to predict the critical gas velocities of film reversal based on the conservative momentum principle. The simplified model is expressed by an analytical solution of dimensionless form, while the unified model is presented by an iterative solution. The measured datasets of different pipe angles and diameters from the present and published works were used for model evaluation. The proposed simplified model is recommended to predict the film reversal because it can accurately predict the critical velocity with the total relative errors of 10.18% in the laboratory and 27.03% in the field, outperforming the unified model and published models. The unified model has a total relative error of 11.56% in the laboratory and 34.26% in the field. The contributions of the proposed two models are discussed by model comparisons. The results show that the simplified model integrates the merits of simple form and high accuracy; but, owing to the simplifications, the simplified model is not rigorous in the mechanism. In contrast, the unified model is more rigorous because it considers the interior liquid film viscosity, the droplet entrainment, and the non-uniform film thickness distribution in inclined pipes. The superiority of the unified model is discussed by comparing it with previous models in vertical and inclined pipes. The unified model contributes to understanding the underlying mechanism of film reversal. In general, the proposed simplified model and unified model complement each other to improve the prediction of the film reversal practically and theoretically.</p

Localization of Nucleophosmin in Nuclear Matrix and Changes in Its Expression During the Differentiation of Human Neuroblastoma Induced by Retinoic Acid

In this study, female and male Thais clavigera whelks were exposed to aqueous and dietary (using oysteis as the prey) tributyltin gm for up to 45 days. followed by a 30-day depuration, in order to examine the gender differences in TBT accumulation and transformation The metabolites of TBT [dibutyltin (DBT) and monobutyltin (MBT)] were also measured in different tissues of the whelks (digestive, reproductive and remaining organs) during the exposure and depuration periods By the end of the exposure period. all of the female whelks developed imposex after TBT exposure, and both the relative penis size index and the vas deferens sequence index were positively correlated with the tissue burden of TBT However, biomagnification of TBT did not occur in the whelks. TBT was rapidly accumulated in their digestive and reproductive organs from both routes of exposure, and both elimination and biotransformation of TBT were also rapid The redistribution of TBT among tissues was obvious during the exposure period but negligible during depuration MBT was generally the major metabolite in each tissue, indicating a significant metabolism of TBT by the whelks Accumulation, transformation, as well as elimination, were more significant following dietary exposure than following aqueous exposure In particular, we observed gender-related differences in the biokinetics of TBT Rapid biotransformation and elimination of TBT were detected in the male whelks, while the female whelks had higher bioaccumulation but lower elimination of TBT in their reproductive organs Internal remobilization of TBT from digestive to reproductive organs was also more obvious in the females, indicating that the reproductive organs of females were the main targets of TBT accumulation (C) 2010 Elsevier B.V All rights reservedNational Natural Science Foundation of China [40476048]; 863 project [2007AA09Z126]; Marine Public Welfare Project of China [200805090

Preparation and Characterization of PLGA Nanospheres Surface Modified with Biotinylated Chitosan

【中文摘要】合成了生物素化壳聚糖（Bio-CS)，并通过核磁共振（1H NMR)及电感耦合等离子体光质谱法（ICP-MS）对其进行结构确证。采用溶剂挥发法（W1/O/W2）制备聚乳酸-羟基乙醇酸（PLGA)纳米粒，并通过共价交联法对纳米粒进行Bio-CS表面修饰。未修饰的PLGA纳米粒在扫描电镜下观察呈规则球状形态，平均粒径为（248.4±21.0）nm，Zeta电势为-（21.21±2.13）mV，Bio-CS修饰后的PLGA纳米粒保持球状形态，平均粒径为（268.3±23.4）nm，Zeta电势为（25.45±2.59）mV。采用X射线光电子能谱（XPS)以及试剂盒对纳米粒表面生物素进行定性及定量研究，结果显示，经过Bio-CS修饰后的纳米粒表面含有N,S元素，生物素取代为31%的Bio-CS修饰的PLGA纳米粒，其表面生物素含量为（1.36±0.34）μmol/100mg纳米粒。 【Abstract】Biotinylated chitosan (Bio-CS conjugates or Bio-CS) were synthesized and characterized. The degree of substitution(DS), as defined as the number of biotin per 100 anhydroglucose units of CS, was determined by (1)H NMR and ICP. Poly (lactic-co-glycolic acid) (PLGA) nanospheres were prepared by a solvent evaporation technique(W(1)/O/W(2)). The surface of PLGA nanosphere was modified with Bio-CS by covalent binding. PLGA nanospheres were almost spherical in shape under the scanning electron microscopy (SEM) observation, and their mean diameter determined by the laser light scattering technique was (248.4 +/- 21.0) urn. Bio-CS modified PLGA nanospheres were also spherical in shape; their mean diameter and Zeta potential value were (268.3 +/- 23.4) nm and (21.21 +/- 2.13) mV, respectively. The surface chemistry of nanospheres was quantitatively studied by X-ray photoelectron spectroscopy(XPS). The results show the N region corresponding to the primary amide of CS and the S region corresponding to the biotin, indicating that PLGA nanospheres were successfully surface-modified with Bio-CS. The content of biotin on the surface of Bio-CS modified PLGA nanospheres with DS of biotin of 31% was determined using a commercially available Quant * Tag (TM) Biotin Kit and its value was (1.36 +/- 0.34) mol/100 mg