Establishment of an LC-Based Assay to Determine Caffeic Acid Tetramer in Rat Plasma and Its Application to a Pharmacokinetic Study

A facile, sensitive, and accurate liquid chromatographic method with ultraviolet detection was developed for the determination of caffeic acid tetramer in rat plasma. Chromatographic separation was performed on an YMC C18 10 μm column (250 × 4.6 mm) using acetonitrile and phosphate buffer (19:81, v/v) as mobile phase at a flow rate of 1 mL min^?1. The UV detection wavelength was set at 252 nm. The method showed good linearity in the range of 1–150 μg mL^?1 with a satisfactory correlation coefficient (r) of 0.997. The limit of detection was 20 ng mL^?1 while inter- and intra-day precisions were less than 5.39 and 5.48%, respectively. Furthermore, the accuracy ranged from 98.27 to 103.76% with high extraction recoveries of caffeic acid tetramer from plasma greater than 88.0%. This practical methodology opens a facile and effective pathway for a pharmacokinetic study.     

Comparative studies on interactions of bovine serum albumin with cationic gemini and single-chain surfactants

The interactions of bovine serum albumin (BSA) with cationic gemini surfactants alkanediyl-alpha,omega-bis(dodecyldimethylammonium bromide) [C12H25(CH3)2N(CH2)(S)N(CH3)2C12H25]Br2 (designated as C12C(S)C12Br2, S = 3, 6, and 12) and single-chain surfactant dodecyltrimethylammonium bromide (DTAB) have been studied with isothermal titration microcalorimetry, turbidity, fluorescence spectroscopy, and circular dichroism at pH 7.0. Comparing with DTAB, C12C(S)C12Br2 have much stronger binding ability with BSA to induce the denaturation of BSA at very low molar ratio of C12C(S)C12Br2/BSA, and C12C(S)C12Br2 have a much stronger tendency to form insoluble complexes with BSA. The binding of C12C(S)C12Br2 to BSA generates larger endothermic peaks. The first endothermic peak is much stronger than that of the second endothermic peak. The double charges and strong hydrophobicity of the gemini surfactants are the main reasons for these observations. In addition, the spectra results show that the binding of DTAB to BSA only promotes BSA unfolding and aggregation, whereas the secondary structure of BSA is possibly stabilized by a small amount of C12C(S)C12Br2 , even if the small amount of binding C12C(S)C12Br2 could induce the loss of the tertiary structure of BSA. This result may be related to the double tails of gemini surfactants, which may generate the hydrophobic linkages between the nonpolar residues of BSA.     

Subsolidus Binary Phase Diagrams of C10ZnCl‐C16ZnCl and C12ZnCl‐C16ZnCl

Decylammonium tetrachlorozincate (n‐C₁₀H₂₁NH₃)₂ZnCl₄(C₁₀ZnCl), dodecylammonium tetrachlorozincate (n‐C₁₂H₂₅NH₃)₂ZnCl₄(C₁₂ZnCl) and hexadecylammonium tetrachlorozincate (n‐C₁₆H₃₃NH₃)₂ZnCl₄‐(C₁₆ZnCl) were synthesized and a series of their mixtures C₁₀ZnCl‐C₁₆ZnCl and C₁₂ZnCl‐C₁₆ZnCl were prepared. The experimental binary phase diagrams of C₁₀ZnCl‐C₁₆ZnCl and C₁₂ZnCl‐C₁₆ZnCl were established by means of differential scanning calorimetry (DSC), IR and X‐ray diffraction. In the phase diagram a stable solid compound and two eutectoid invariants were observed. It is noticeable that the phase diagram contains solid solution ranges.     

Comparative studies on the micellization of sodium bis(4-phenylbutyl) sulfosuccinate and sodium bis(2-ethylhexyl) sulfosuccinate and their interaction with hydrophobically modified poly(acrylamide)

The micellization process of sodium bis(4-phenylbutyl) sulfosuccinate (SBPBS) has been studied compared to that of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) by surface tension, steady-state fluorescence, microcalorimetry, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements. Meanwhile, the interaction of these two surfactants with hydrophobically modified poly(acrylamide) (HMPAM) was investigated. The results show that the surface tension at the critical micelle concentration (cmc) of SBPBS and the micropolarity probed by pyrene in SBPBS aggregates are both larger than those of AOT. The enthalpy change of micellization (DeltaH(mic)) of AOT is endothermic, while it is exothermic for SBPBS. Strong pi-pi interaction among the adjacent phenyl groups of SBPBS molecules is likely the cause for the above properties of SBPBS. Moreover, vesicles are observed for AOT and SBPBS by DLS and TEM, especially for AOT, whose micelle-vesicle transition has been first confirmed by its calorimetric curve. In the surfactant-HMPAM systems, the critical aggregation concentration (cac), the saturation concentration of aggregation (C(2)), and the thermodynamic parameters of binding have also been determined. The conclusion may be drawn that the binding strength of SBPBS onto HMPAM is stronger than that of AOT.     

具结构阻尼的拟线性膜方程的吸引子及其上半连续性

本文研究具结构阻尼的拟线性膜方程utt+△2u+(-△)αut+△φ(△u)+f(u)=g的适定性以及解的长时间动力学行为,其中α∈(1,2),旨在研究耗散指标α对方程解的适定性和长时间动力学行为的影响.本文证明非线性项φ(s)存在一个依赖于耗散指标α的临界指数pα=N+4(α-1)/(N-4(α-1))(N=3,4)...     

22种水质监测用标准物质的研制

介绍22种水质监测用标准物质的研制过程。结果表明,该22种标准物质的均匀性、稳定性良好,定值准确、可靠、满足实际工作需求。     

反相高效液相色谱法测定烤烟叶片发育过程中的类胡萝卜素类物质

建立了采用反相高效液相色谱测定烤烟叶片中类胡萝卜素的方法。烤烟叶片先用含0.1%丁基羟基甲苯（BHT）的90%丙酮水溶液萃取,然后加入0.1 g醋酸铅,于4 ℃下以10000 r/min离心5 min以去除蛋白质。色谱柱为 C18反相柱(3.9 mm i.d.×150 mm, 5 μm)。流动相:A,甲醇-异丙醇(体积比为1∶1）;B,超纯水。洗脱程序:0~10 min,70%A+30%B;10~17 min,100%A;17~30 min(90%A+10%B)。流速：0.5 mL/min。进样量:10 μL。检测波长:450 nm。该方法简化了样品的前处理过程,4种类胡萝卜素物质的加标回收率为91.77%~97.42%,相对标准偏差为 3.46%~0.98%。用该方法研究了烤烟发育过程中类胡萝卜素含量的变化规律,获得了与文献较为一致的结果。     

Design and analysis of optically pumped semiconductor VECSEL with ANECz optical control layer

Through the reversible isomerization of trans-cis-trans under the linear polarization light, the molecules of azo materials have the same tropism which is vertical to the polarization of light. This means that azo materials have photo-induced birefringence which is related to optical power and polarization angle of the light. Based on the photo-induced birefringence of azo materials, we design a new type of optically pumped semiconductor vertical external cavity surface emitting laser （OPS-VECSEL） which can control the polarization and frequency of the ejection laser. The functional molecules of azo materials are [3-azo- （4＇nitro）]- （9-ethyl）-carbazole （ANECz）.     

A Multi-Symplectic Scheme for RLW Equation

The Hamiltonian and multi-symplectic formulations for RLW equation are considered in this paper. A new twelve-point difference scheme which is equivalent to multi-symplectic Preissmann integrator is derived based on the multi-symplectic formulation of RLW equation. And the numerical experiments on solitary waves are also given. Comparing the numerical results for RLW equation with those for KdV equation, the inelastic behavior of RLW equation is shown.     

Parameter determination and response analysis of viscoelastic material

The parameter determination of viscoelastic material is a multi-variable, multi-aim nonlinear optimization problem, which made the optimization process very complicated. In this paper a hybrid optimal algorithm was proposed to determine the viscoelastic parameters in the constitutive relation according to the experimentally obtained mechanical properties. This algorithm merges the Broydon–Fletcher–Goldfarb–Shanno search into a genetic algorithm framework as a basic operator in order to enhance the local search capability. The proposed hybrid algorithm not only can reduce the iterative times greatly but can abolish the limitation of initial parameter values. Nonlinear material characteristic curve-fitting was carried out using the proposed algorithm and other existing approaches. And the comparison results show this algorithm is accurate and effective. The numerical simulation and experimental study of viscoelastic cantilever beam also indicates that the finite element formulation and the calculative viscoelastic model parameters are reliable. The proposed optimization method can be extended to further complex parameter estimation researches.