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81.
A self-assembly hybrid of gold nanoparticles on graphene modified electrodes for low-potential NADH detection has been achieved. We used the natural polymer chitosan (Chit) to assist the stabilization of graphene in aqueous solution, and immobilize the electronegative Au nanoparticles (NPs) through electrostatic attraction. The synergy of Au NPs with graphene for catalytic oxidation of NADH made the overpotential ca. 220 mV less positive than that on the bare electrode, and remarkably increased the oxidation current. The amperometric sensors based on such modified electrodes for detection of NADH exhibited a good linearity from 1.5 to 320 μM, and showed high sensitivity with a low detection limit of 1.2 μM (S/N = 3). It could also exclude common interfering electroactive compounds like ascorbic acid and possessed good reproducibility and operational stability. Such eminent performance of the Au-RGO/Chit film together with the ability of graphene to significantly enhance the electron transfer between enzymes and the electrode suggested its promise for constructing novel graphene based dehydrogenase biosensors. 相似文献
82.
Xianhu Liu Changyan Zhang Kun Dai Guoqiang Zheng Chuntai Liu Changyu Shen 《先进技术聚合物》2013,24(2):270-272
As a part of continuous efforts to systematically understand the morphological development in water‐assisted injection molding, high density polyethylene with different molecular weights was molded in this study. Unexpectedly, it was found that shish kebab with high lamellar and molecular orientations was formed in the sample with a lower molecular weight (LMW) rather than in the higher one, especially in the water channel layer. Present finding is obviously inconsistent with the general consensus, that is, higher molecular weight (HMW) polymer is much easier to form preferential orientation in flow field than LMW one. Such anomalous phenomenon is explained by the fact that even though melts experienced the same processing, lower shear rate is practically achieved in HMW sample due to its high viscosity. The result indicates that the flow history in industrial processing method is far from that in laboratory one. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
83.
Fabrication of a superhydrophobic surface on a wood substrate 总被引:2,自引:0,他引:2
Shuliang WangJunyou Shi Changyu LiuCheng Xie Chengyu Wang 《Applied Surface Science》2011,257(22):9362-9365
A layer of lamellar superhydrophobic coating was fabricated on a wood surface through a wet chemical process. The superhydrophobic property of the wood surface was measured by contact angle (CA) measurements. The microstructure and chemical composition of the superhydrophobic coating were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). An analytical characterization revealed that the microscale roughness of the lamellar particles was uniformly distributed on the wood surface and that a zinc stearate monolayer (with the hydrophobic groups oriented outward) formed on the ZnO surface as the result of the reaction between stearic acid and ZnO. This process transformed the wood surface from hydrophilic to superhydrophobic: the water contact angle of the surface was 151°, and the sliding angle was less than 5°. 相似文献
84.
Changyu Xia 《manuscripta mathematica》1994,85(1):79-87
LetM be a complete Riemannian manifold with Ricci curvature having a positive lower bound. In this paper, we prove some rigidity
theorems forM by the existence of a nice minimal hypersurface and a sphere theorem aboutM. We also generalize a Myers theorem stating that there is no closed immersed minimal submanifolds in an open hemisphere to
the case that the ambient space is a complete Riemannian manifold withk-th Ricci curvature having a positive lower bound.
Supported by the JSPS postdoctoral fellowship and NSF of China 相似文献
85.
方差分量的非负二次同时估计的可容许性 总被引:3,自引:0,他引:3
设方差分量模型,其中β∈为未知参数,X已知,V1≥0,V2≥0为已知的非负定矩阵.文[1]在一定的条件下给出了非负二次估计可容许的一个充分必要条件.但必要条件是在x=In(单位矩阵),V1=V2>0的条件下给出的,由于这些限制使必要条件不理想.本文去掉了这些限制,对一般的方差分量模型,给出了与文[1]中一样的必要条件,同时也研究了非齐次二次估计的可容许性. 相似文献
86.
Changyu Xia 《Monatshefte für Mathematik》2005,146(2):159-168
Let Sn(c) denote the n-dimensional Euclidean sphere of constant sectional curvature c and denote by CPn(c) the complex projective space of complex dimension n and of holomorphic sectional curvature c. In this paper, we obtain some characterizations of the manifolds S2(c) × S2(c′), S4(c) × S4(c′), CP2(c) × CP2(c′) by their spectrum. 相似文献
87.
88.
Dr. Ming Chen Dr. Ping Xiao Ke Yang Boxu Dong Dong Xu Changyu Yan Xuejiao Liu Jiantao Zai Prof. CheeTong John Low Prof. Xuefeng Qian 《Angewandte Chemie (International ed. in English)》2023,62(16):e202219177
With a theoretical capacity of 847 mAh g−1, Sn has emerged as promising anode material for sodium-ion batteries (SIBs). However, enormous volume expansion and agglomeration of nano Sn lead to low Coulombic efficiency and poor cycling stability. Herein, an intermetallic FeSn2 layer is designed via thermal reduction of polymer-Fe2O3 coated hollow SnO2 spheres to construct a yolk-shell structured Sn/FeSn2@C. The FeSn2 layer can relieve internal stress, avoid the agglomeration of Sn to accelerate the Na+ transport, and enable fast electronic conduction, which endows quick electrochemical dynamics and long-term stability. As a result, the Sn/FeSn2@C anode exhibits high initial Coulombic efficiency (ICE=93.8 %) and a high reversible capacity of 409 mAh g−1 at 1 A g−1 after 1500 cycles, corresponding to an 80 % capacity retention. In addition, NVP//Sn/FeSn2@C sodium-ion full cell shows outstanding cycle stability (capacity retaining rate of 89.7 % after 200 cycles at 1 C). 相似文献
89.
分别采用普通熔融共混法和水辅助加工法,制备了具有不同共混形态的聚丙撑碳酸酯(PPC)/淀粉共混物,并研究了淀粉分散形态对共混物的玻璃化转变温度(Tg)、流变以及力学性能的影响。研究结果表明,采用普通熔融共混法时,淀粉未发生糊化,并以原颗粒状分散于基体中;而采用水辅助加工法时,淀粉发生糊化,并在挤出过程中原位形成纤维结构。当淀粉以纤维形式分散于PPC基体中时,其与PPC间的界面接触面积显著增加,二者的相互作用增强,PPC/淀粉共混物的Tg、储能模量以及复合黏度显著提高。力学性能测试结果表明,当淀粉质量分数为30%,采用水辅助加工法制备的PPC/淀粉共混物的拉伸模量相比于纯PPC提高了67.7%。 相似文献
90.
In this article, we give sufficient conditions for a complete non-compact submanifold in a simply connected manifold of negative
sectional curvature to have only one end. We also prove some Liouville theorems for harmonic maps from the same kind of submanifolds
to manifolds of non-positive curvature. 相似文献