Large‐time behavior of a two‐scale semilinear reaction–diffusion system for concrete sulfatation

We study the large‐time behavior of (weak) solutions to a two‐scale reaction–diffusion system coupled with a nonlinear ordinary differential equations modeling the partly dissipative corrosion of concrete (or cement)‐based materials with sulfates. We prove that as t → ∞ , the solution to the original two‐scale system converges to the corresponding two‐scale stationary system. To obtain the main result, we make use essentially of the theory of evolution equations governed by subdifferential operators of time‐dependent convex functions developed combined with a series of two‐scale energy‐like time‐independent estimates. Copyright © 2014 John Wiley & Sons, Ltd.     

A multiscale Galerkin approach for a class of nonlinear coupled reaction-diffusion systems in complex media

A Galerkin approach for a class of multiscale reaction-diffusion systems with nonlinear coupling between the microscopic and macroscopic variables is presented. This type of models are obtained e.g. by upscaling of processes in chemical engineering (particularly in catalysis), biochemistry, or geochemistry. Exploiting the special structure of the models, the functions spaces used for the approximation of the solution are chosen as tensor products of spaces on the macroscopic domain and on the standard cell associated to the microstructure. Uniform estimates for the finite dimensional approximations are proven. Based on these estimates, the convergence of the approximating sequence is shown. This approach can be used as a basis for the numerical computation of the solution.     

催化光度法测定痕量钒——钒(Ⅴ)-溴甲酚紫-过氧化氢体系

催化光度法测定钒已有报道[1～3],在0.45 mol·L-1磷酸介质及加热条件下,过氧化氢氧化溴甲酚紫褪色反应非常缓慢,而痕量钒对此反应具有较高的催化活性,且在一定浓度范围内,钒量与褪色反应程度呈线性关系,据此可建立测定痕量钒的方法.方法的检出限为1.9×10-6g·L-1,测定范围为0.003～1.8 mg·L-1.方法操作简便,重现性好,用于钢样中痕量钒的测定,结果满意.     

酶促开环聚合合成双亲性H型嵌段共聚物及其自组装

通过固定化酶Novozyme435（NV435）催化聚乙二醇（PEG）开环聚合己内酯（CL）得到端基带有羟基的ABA型三嵌段聚合物,用2,2-二氯代乙酰氯将聚合物的端羟基功能化形成H型大分子引发剂,在CuCl／HMTETA体系中引发4-乙烯基吡啶（4VP）进行原子转移自由基聚合反应（ATRP）,得到了具有两亲性的H型五嵌段聚合物（PVP）2-b—PCL-b．PEG-PCL-（PVP）2,用红外光谱（FT IR）,核磁共振（^1H NMR）,凝胶渗透色谱（GPC）对其结构与分子量及其分子量分布进行了表征,结果表明：H型五嵌段聚合物分子量46121g／mol,分子量分布1．30．并利用动态光散射（DLS）和原子力显微镜（AFM）对聚合物在水溶液中的自组装行为进行了研究,H型嵌段聚合物的胶束呈球形结构,平均直径为70nm左右．     

TDDFT Study on the Electronic Excitations and First Hyperpolarizabilities of Mixed-metal Carbonyl Clusters W2Ir2（μ-L）（CO）8（η^5-C5H4Me）2（L = dppe/dppf）

Mixed-metal carbonyl clusters of W2Ir2（CO）10（η^5-C5H4Me）2 1 and W2Ir2（μ-L）（CO）8（η^5-C5H4Me）2 （L = dppe 2, dppf 3） have been studied by TDDFT method focusing on their electronic and nonlinear optical properties. These three clusters exhibit the first static hyperpolarizabilities of medium magnitude （βtot-10×10^-30 esu）. The origin of β is discussed by the new proposed orbital-pair decomposition scheme by Barandes et al. The result suggests that the β values of the two clusters are mainly originated from d-d electron transition within the metal skeleton, and d-p （π＊） electron transition from metals to carbonyls and phenyl. The additional coordination by the electron donor group, ferrocene, makes cluster 3 own much larger β values, and the relatively longer range charge transfer from d orbitals of ferrocene to d orbirals of Ir and W is responsible for the enhanced β values.     

燃烧法制备纳米CdFe2O4及表征

以Fe（NO3）3.9H2O和Cd（NO3）2.4H2O为原料,以柠檬酸为还原剂,采用燃烧法制备了CdFe2O4纳米粉体,用X射线粉末衍射仪（XRD）、透射电子显微镜（TEM）、红外光谱（IR）和振动样品磁强计（VSM）等手段对样品进行了表征,结果表明,样品为尖晶石型铁酸镉纳米粉体,其粒径大约为20—50nm,且具有超顺磁性。     

Charge fluctuations in Au+Au collisions at RHIC energy

A hadron and string cascade model, JPCIAE, together with the corresponding Monte Carlo event generator, has been employed in this paper to investigate further the charge fluctuations in Au+Au collisions at Snn = 130 GeV. The default JPCIAE calculations are in good agreement with PHENIX and STAR data. We found that the thermal predictions for the π gas, the resonance π gas and quark matter deviate, respectively, from the corresponding dynamical simulations from the JPCIAE model. The discrepancies were also found between the π charge fluctuations and the charge fluctuations of all species of hadrons. However the charge fluctuations for "π from ρ and ω decay" and for all the hadrons from resonance decay are close to each other, indicating the correlation between positively and negatively charged hadrons is not sensitive to the species of hadrons. This work shows further that it is questionable to use the charge fluctuations as a signature of QGP.     

Investigation of aggregation behavior using computational methods and absorption spectra for trisazo direct dyes

Direct dyes are likely to self-associate in aqueous solutions. Here, we present the aggregation characteristics of three trisazo direct dyes investigated using a procedure, which combines computational and experimental approaches. The geometric features of the molecules and their aggregates were elucidated by molecular modeling and optimization. The relative energies specific for the aggregation process yielded the optimum number of molecules forming an aggregate: two for AHDS dye and three for SDH and AIDS dyes. The results were further confirmed by using spectrometric determination and mathematical analysis. Accordingly, molecular aggregation was studied in aqueous solutions as a function of dye concentration (10^?6–10^?3 mol/l) and solution pH (4–10). As the dye concentration increased, shifts in absorption spectra were observed, suggesting the formation of aggregates. The pH variation produced a change in the spectral maximum, confirming the aggregation. The mathematical processing of the absorption spectrum data confirmed the number of chemical species of each aggregate as resulted from computational calculations.     

Liquid chromatography with mass spectrometry enantioseparation of pomalidomide on cyclodextrin‐bonded chiral stationary phases and the elucidation of the chiral recognition mechanisms by NMR spectroscopy and molecular modeling

A sensitive and validated liquid chromatography with mass spectrometry method was developed for the enantioseparation of the racemic mixture of pomalidomide, a novel, second‐generation immunomodulatory drug, using β‐cyclodextrin‐bonded stationary phases. Four cyclodextrin columns (β‐, hydroxypropyl‐β‐, carboxymethyl‐β‐, and sulfobutyl‐β‐cyclodextrin) were screened and the effects of eluent composition, flow rate, temperature, and organic modifier on enantioseparation were studied. Optimized parameters, offering baseline separation (resolution = 2.70 ± 0.02) were the following: β‐cyclodextrin stationary phase, thermostatted at 15°C, and mobile phase consisting of methanol/0.1% acetic acid 10:90 v/v, delivered with 0.8 mL/min flow rate. For the optimized parameter at multiple reaction monitoring mode 274.1–201.0 transition with 20 eV collision energy and 100 V fragmentor voltage the limit of detection and limit of quantitation were 0.75 and 2.00 ng/mL, respectively. Since enantiopure standards were not available, elution order was determined upon comparison of the circular dichroism signals of the separated pomalidomide enantiomers with that of enantiopure thalidomide. The mechanisms underlying the chiral discrimination between the enantiomers were also investigated. Pomalidomide‐β‐cyclodextrin inclusion complex was characterized using nuclear magnetic resonance spectroscopy and molecular modeling. The thermodynamic aspects of chiral separation were also studied.