Study on the anodic reaction of Ni in an alkaline solution by transient pH detection based on scanning electrochemical microscopy (SECM)

The anodic reaction of Ni in an alkaline solution was studied by the tip–substrate voltammetry mode of scanning electrochemical microscopy (SECM) and cyclic voltammetry (CV). A platinum microdisc electrode was selected as the tip electrode, which functioned as a pH sensor with transient response capability. The pH value of the solution near the Ni electrode surface varied while the Ni substrate oxidation reaction occurred, and the pH variation could be detected by the tip faradic current. The cyclic voltammogram results showed that two types of hydroxides: i.e. α‐Ni(OH)₂ and β‐Ni(OH)₂ were formed during Ni oxidation in the lower potential region. In the proceedings of α‐Ni(OH)₂ → γ‐NiOOH and β‐Ni(OH)₂ → β‐NiOOH, the process of OH^? concentration decrease in the solution was ahead and behind of electron transfer in the solid phase, respectively. These results indicate that the OH^? adsorption process occurs as an elementary step in the former reaction and the H⁺ diffusion process from the inner to the outer layer of the solid phase occurs as a subsequent step in the latter reaction. The results also revealed that the oxide film on the Ni surface has a two‐layer structure. The real potential of the oxygen evolution reaction (OER) on the Ni surface with different cycles is also analyzed in the paper. Copyright © 2007 John Wiley & Sons, Ltd.     

Modeling and optimization of laser transmission joining process between PET and 316L stainless steel using response surface methodology

Laser joining parameters play a very significant role in determining the quality of laser transmission joining between PET films and 316L stainless steel plates. In the present work, Laser power, joining speed and stand-off-distance were considered as joining parameters. The parameters that influence the quality of laser transmission joining were optimized using response methodology for achieving good joint strength and minimal joint width. The central composite second-order Rotational Design (CCRD) has been utilized to plan the experiments and response surface methodology (RSM) is employed to develop mathematical relationships between joining parameters and desired responses. Based on the developed mathematical models, the interaction effects of the process parameters on laser transmission joining were investigated and optimum joining parameters were achieved. The experimental values nearly agree with the predicted values from mathematical models, indicates that the models can predict the responses adequately and optimize the key process parameters quickly.     

带变量核的广义高阶Marcinkiewicz积分交换子在Herz型Hardy空间的有界性

设A是R~n上的一个m阶可导函数,且D~λA∈Λ_β(0β1,|λ|=m),Ω(x,z)∈L~∞(R~n)×L~s(S~(n-1))(sn/(n-β))是零阶齐次函数且关于变量z满足消失条件.该文证明了广义高阶Marcinkiewicz积分交换子μ_Ω~A及其变形μ_Ω~A在Herz型Hardy空间的有界性.     

高效液相色谱-四极杆-飞行时间质谱快速筛查鉴别食品中非法添加的62种中药材北大核心CSCD

建立了高效液相色谱-四极杆-飞行时间质谱快速筛查鉴别食品中非法添加的62种中药材的方法。依据卫生部关于进一步规范保健食品原料管理的通知(卫法监发[2002]51号)中可用于保健食品的物品名单,确定食品中可能非法添加的62种中药材原料清单,再从62种中药材中筛选其特征组分,获得不同中药材对应的特征组分清单。62种对照药材经甲醇超声提取后,于Thermo Accucore aQ色谱柱(150 mm×2.1 mm,2.6μm)上分离,在电喷雾正负离子扫描模式下,分别以0.1%(v/v)甲酸水溶液-乙腈和水-乙腈为流动相梯度洗脱,进行一级质谱和二级质谱全扫描检测,采用Library View软件建立不同中药材对应的特征组分的一级精确质量数据库和二级碎片质谱库。样品同法处理后上样分析,采用Peak View软件将样品高分辨数据与自建数据库中的质谱图、精确分子离子质量数、碎片离子质量数、保留时间等相关参数进行快速筛查鉴别分析。该工作通过建立“中药材-特征组分”对应清单,构建了食品中易非法添加的62种中药材中共388种特征组分的高分辨质谱库,每种中药材包括5~10种特征组分,通过对实际食品样品配制酒、代用茶及饮料进行筛查分析,1批次配制酒样品与淫羊藿中药材的7种特征组分匹配一致,推断该配制酒样品中加入了淫羊藿中药材。该法可实现无标准品情况下中药材的定性筛查,具有高通量、准确、简便、快捷的特点,解决了食品中非法添加中药材难以识别和确证的难题,可以实现食品中非法添加中药材的快速筛查鉴别分析。     

原位合成H2O2在水处理技术中的应用研究进展

从过氧化氢(H₂O₂)的原位生成技术角度总结了近年来利用原位合成H₂O₂处理水中污染物的研究,分析了当前可充当氢源材料的种类及不同的氢源材料对于提高H₂O₂产率的影响,以及不同的催化剂材料和催化反应环境提高H₂O₂利用率对污染处理效果的影响因素,并对原位合成H₂O₂在水处理领域中面临的挑战和发展前景做了展望,从而为该技术的大规模应用提供指导和借鉴。     

On Eigenmaps Between Spheres

This paper presents the rigidity of ₂-eigenmaps from S⁴ to itself,and the nonexistence of some ₂-eigenmaps, as well as new examplesof eigenmaps between spheres. 2000 Mathematics Subject Classification58E20.     

Investigation on LCST behavior of a new amorphous/crystalline polymer blend: Poly(n‐methyl methacrylimide)/poly(vinylidene fluoride)

The liquid–liquid phase‐separation (LLPS) behavior of poly(n‐methyl methacrylimide)/poly(vinylidene fluoride) (PMMI/PVDF) blend was studied by using small‐angle laser light scattering (SALLS) and phase contrast microscopy (PCM). The cloud point (T_c) of PMMI/PVDF blend was obtained using SALLS at the heating rate of 1 °C min^?1 and it was found that PMMI/PVDF exhibited a low critical solution temperature (LCST) behavior similar to that of PMMA/PVDF. Moreover, T_c of PMMI/PVDF is higher than its melting temperature (T_m) and a large temperature gap between T_c and T_m exists. At the early phase‐separation stage, the apparent diffusion coefficient (D_app) and the product (2Mk) of the molecules mobility coefficient (M) and the energy gradient coefficient (k) arising from contributions of composition gradient to the energy for PMMI/PVDF (50/50 wt) blend were calculated on the basis of linearized Cahn‐Hilliard‐Cook theory. The kinetic results showed that LLPS of PMMI/PVDF blends followed the spinodal decomposition (SD) mechanism. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1923–1931, 2008     

Layer‐by‐layer Assembled Multilayers of Graphene/Mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin for Detection of Dopamine

Graphene/mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin multilayer films composed of graphene sheet (GS) and mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin (NH₂‐β‐CD) were fabricated easily by two steps. First, negatively charged graphene oxide (GO) and positively charged mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin (NH₂‐β‐CD) were layer‐by‐layer (LBL) self‐assembled on glassy carbon electrode (GCE) modified with a layer of poly(diallyldimethylammonium chloride) (PDDA). Then graphene/mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin (GS/NH₂‐β‐CD) multilayer films were built up by electrochemical reduction of graphene oxide/mono‐(6‐amino‐6‐deoxy)‐β‐cyclodextrin (GO/NH₂‐β‐CD). Combining the high surface area of GS and the active recognition sites on β‐cyclodextrin (β‐CD), the GS/NH₂‐β‐CD multilayer films show excellent electrochemical sensing performance for the detection of DA with an extraordinary broad linear range from 2.53 to 980.05 µmol·L^?1. This study offers a simple route to the controllable formation of graphene‐based electrochemical sensor for the detection of DA.     

非保守圆薄板的轴对称振动和稳定性

建立了受切向均布随从力作用的圆薄板在面内周边可移、不可移两种情况下的轴对称控制方程，用打靶法直接导出求解变系数常微分方程特征值问题数值解的计算式．通过数值计算，给出了周边可移、不可移的简支、固支圆板自振频率和临界载荷的特征曲线以及相应的临界发散载荷，并分析了泊松比对圆板自振频率和临界载荷的影响．     

A novel method for the sensitive detection of mutant proteins using a covalent-bonding tube-based proximity ligation assay

Tumorigenesis is the cumulative result of multiple gene mutations. The mutant proteins that are expressed by mutant genes in cancer cells are secreted into the blood and are useful biomarkers for the early diagnosis of cancer. However, some difficulties exist; for example, the same gene will express different protein mutants in different patients, and early tumors secrete only small amounts of mutant protein. Thus, the presence of mutant proteins in plasma has not previously been exploited for the early diagnosis of cancer. Proximity ligation assay is a protein-detection method that has been developed in recent years and has been widely used because of its high sensitivity. However, this approach still suffers from some shortcomings that should be addressed. In this paper, we develop a covalent-bonding tube-based proximity ligation assay (TB-PLA). The limit of detection of TB-PLA for 0.001 pM, and the method exhibited a broad dynamic range of up to seven orders of magnitude. Furthermore, we coupled the conformation-specific antibody PAb240 of p53 mutants to PCR tubes for TB-PLA. The assay was capable of detecting an approximately 500-fold lower concentration of mutant p53 in serum compared with sandwich ELISA. Thus, we demonstrate TB-PLA to be a highly sensitive and effective approach that is suitable for the early clinical diagnosis of cancer using the conformation-specific antibodies of protein mutants.