Classical Keggin Intercalated into Layered Double Hydroxides: Facile Preparation and Catalytic Efficiency in Knoevenagel Condensation Reactions

The family of polyoxometalate (POM) intercalated layered double hydroxide (LDH) composite materials has shown great promise for the design of functional materials with numerous applications. It is known that intercalation of the classical Keggin polyoxometalate (POM) of [PW₁₂O₄₀]^3? (PW₁₂) into layered double hydroxides (LDHs) is very unlikely to take place by conventional ion exchange methods due to spatial and geometrical restrictions. In this paper, such an intercalated compound of Mg_0.73Al_0.22(OH)₂ [PW₁₂O₄₀]_0.04?0.98 H₂O (Mg₃Al‐PW₁₂) has been successfully obtained by applying a spontaneous flocculation method. The Mg₃Al‐PW₁₂ has been fully characterized by using a wide range of methods (XRD, SEM, TEM, XPS, EDX, XPS, FT‐IR, NMR, BET). XRD patterns of Mg₃Al‐PW₁₂ exhibit no impurity phase usually observed next to the (003) diffraction peak. Subsequent application of the Mg₃Al‐PW₁₂ as catalyst in Knoevenagel condensation reactions of various aldehydes and ketones with Z‐CH₂‐Z′ type substrates (ethyl cyanoacetate and malononitrile) at 60 °C in mixed solvents (V_2‐propanol:V_water=2:1) demonstrated highly efficient catalytic activity. The synergistic effect between the acidic and basic sites of the Mg₃Al‐PW₁₂ composite proved to be crucial for the efficiency of the condensation reactions. Additionally, the Mg₃Al‐PW₁₂‐catalyzed Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate demonstrated the highest turnover number (TON) of 47 980 reported so far for this reaction.     

Simultaneous determination of pharmacologically active ingredients in Rhodiola by capillary chromatography with electrochemical detection

Rhodiola, in which there are abundant pharmacologically active ingredients, is one of the functional adaptogenic agent that aid specific bodily functions to adapt to the changes and stress of life in addition to being tonic. In an attempt to qualitatively and quantitatively determine the pharmacologically active ingredients in Rhodiola, a new method based on capillary electrophoresis with electrochemical detection (CE-ED) has been developed. The effects of working electrode potential, pH and concentration of running buffer, separation voltage, applied potential and injection time on CE-ED were investigated. Under the optimum conditions, the analytes could be well separated within 24 min at the separation voltage of 18 kV in a 80 mmol L(-1) borax running buffer (pH 9.0). Good linear relationship was established between peak current and concentration of analytes over two orders of magnitude with detection limits (S/N=3) ranged from 3.16 x 10(-7) to 1.11 x 10(-7)g mL(-1) for all target ingredients. This proposed method has been successfully applied for the analysis of real samples, with satisfactory results.     

Fast determination of sugars in Coke and Diet Coke by miniaturized capillary electrophoresis with amperometric detection

The fast separation capability of a novel miniaturized capillary electrophoresis with amperometric detection (CE-AD) system was demonstrated by determining sugar contents in Coke and diet Coke with an estimated separation efficiency of 60,000 TP/m. Factors influencing the separation and detection processes were examined and optimized. The end-capillary 300 microm Cu wire amperometric detector offers favorable signal-to-noise characteristics at a relatively low potential (+0.50 V vs. Ag/AgCl) for detecting sugars. Three sugars (sucrose, glucose, and fructose) have been separated within 330 s in a 8.5 cm length capillary at a separation voltage of 1000 V using a 50 mM NaOH running buffer (pH 12.7). Highly linear response is obtained for the above compounds over the range of 5.0 to 2.0 x 10(2) microg/mL with low detection limit, down to 0.8 microg/mL for glucose (S/N = 3). The injection-to-injection repeatability for analytes in peak current (RSD < 3.6%) and for migration times (RSD < 1.4%) was excellent. The new miniaturized CE-AD system should find a wide range of analytical applications involving assays of carbohydrates as an alternative to conventional CE and micro-CE.     

替代元素铝和钕对La-Mg-Ni系AB3.5型贮氢合金性能的影响

用冷坩埚磁悬浮熔炼方法制备La0.7Mg0.3（Ni0.85-xCo0.15Alx）3.4（x=0.00,0.04）和La0.7-yNdyMg0.3（Ni0.81Co0.15Al0.04）3.4（y=0.10）贮氢合金,采用XRD,FESEM,EDS,P-C-T测试及三电极电化学性能测试研究合金的相结构、相成分、P-C-T曲线、电化学性能及相应电极的表面状态。Rietveld法全谱拟合表明,La0.7Mg0.3（Ni0.85Co0.15）3.4合金为多相结构,主相为Ce2Ni7型六方相,主相成分为（La,Mg）（Ni0.85Co0.15）2.9-3.3。P-C-T曲线显示随着Al和Nd的依次替代,平台压力从0.0118 MPa降低到0.0057 MPa再升高到0.0073 MPa。电化学性能测试表明,最大放电容量先从392.9 mAh.g^-1降低到363.4 mAh.g^-1再降低到343.7 mAh.g^-1,循环稳定性则从59.6%增加到73.1%再增加到79.7%。     

Aqua­tris­(1,10‐phenan­throline)­(trans‐2,3‐di­methyl­acrylato)­ytterbium(III)

The title mononuclear complex, [Yb(C₅H₇O₂)₃(C₁₂H₈N₂)(H₂O)], is a most uncommon carboxylate complex of a rare earth metal. Each Yb^III ion is eightfold coordinated, being bonded to five O atoms of three dimethylacrylate groups, both N atoms of a phenanthroline and one O atom of a water molecule, giving a distorted square antiprismatic coordination polyhedron.     

中药菟丝子中生物活性成分的毛细管电泳-电化学检测

采用毛细管电泳-电化学检测法(CE-ECD)同时测定了菟丝子中芦丁、金丝桃甙、山柰酚、对香豆酸和槲皮素等5种主要生物活性成分的含量,考察了运行缓冲液酸度和浓度、分离电压、氧化电位和进样时间等实验参数对分离检测的影响。在最佳实验条件下,以直径300 μm的碳圆盘电极为工作电极,检测电位为+950 mV(vs. 参比电极),以50 mmol/L的硼砂缓冲溶液(pH 9.0)为运行缓冲液,上述各组分在19 min内能完全分离。芦丁、金丝桃甙、山柰酚、对香豆酸和槲皮素在两个数量级的范围内呈良好线性关系,检测下限(按S/N=3计) 分别为1.93×10-5,3.55×10-4,3.65×10-5,1.73×10-5和1.46×10-4 g/L。该法已成功地应用于菟丝子中活性成分的分离检测,结果令人满意。     

微循环系统动力学综合数学模型研究(Ⅰ)——理论基础

根据微循环系统的生理情况,建立了微循环系统动力学非定常、非线性分布参数模型,包括血液动力学、间质动力学、淋巴动力学、蛋白质传输动力学、氧动力学、热量传输动力学和肌原性与代谢性调控过程,综合反映了它们之间的相互作用,并考虑了微动脉自律运动和血液非线性粘弹性的影响.几何模型是一个包括微动脉、开放与储备毛细血管、微静脉、初始淋巴管和微动静脉吻合支的简单网络.这种综合模型有助于临床数据的分析研究和“数值实验手段”的建立.     

金刚石与金属(或合金)的结合界面分析

本文从晶体结构方面说明了金刚石化学性质稳定的原因,介绍了提高金刚石工具性能所采用的三种常用方法:金刚石表面金属化、金属基体改性和工艺改变方法.这三种方法起作用的机理可解释为由于强碳化物元素的加入,使得内界面张力系数的降低和发生晶界反应.从而改善了界面结合.另外,本文还介绍了当前金刚石工具的研究主要集中于微量合金元素特别是稀土元素的加入,这可改善金刚石工具综合性能.     

高气液比垂直管流连续携液实验

在可视化管流实验架上, 采用压缩空气和雾化液体作为实验介质, 模拟连续携液过程并测试 实验参数; 采用高速摄像仪捕捉到气流中液滴实际形状------椭球体. 实验发现: 圆球体模型、 椭球体模型计算结果与实验值分别偏差10{\%}, 58.3{\%}. 分析椭球体受力状态并结合实验数据导出了新的椭球体数学模型, 按照新模型计算的结 果与7口产水气井生产情况一致.     

Folate Conjugated CdHgTe Quantum Dots with High Targeting Affinity and Sensitivity for In vivo Early Tumor Diagnosis

CdHgTe-folate conjugates, acting as novel active-targeting fluorescence probes, were prepared by covalent conjugation of CdHgTe QDs and folic acid. Their characteristics, such as optical spectra, stability and cancer cell targeting were investigated in detail. The fluorescence wavelength of CdHgTe-folate conjugates was 790 nm and a full width at half-maximum (FWHM) of them was 50–70 nm. Their fluorescence stability could satisfy the need of long and continuous fluorescence imaging. The in vivo dynamic bio-distribution of CdHgTe-folate conjugates in S180 tumor beard mouse model was monitored by a NIR imaging system. The resultes indicated that CdHgTe-folate conjugates targeted to tumor effectively. The high fluorescence intensity together with targeting effect makes CdHgTe-folate conjugates promising candidates for imaging, monitoring and early diagnosis of cancer at molecular and cell level.