Global Regularity of 3D Nonhomogeneous Incompressible Micropolar Fluids

This paper is concerned with the global well-posedness of strong and classical solutions for the 3D nonhomogeneous incompressible micropolar equations with vacuum. We prove that the problem (1.1)–(1.5) has a unique global strong/classical solution \((\rho,u,w)\), provided \(\mu_{1}\) is sufficiently large, or \(\|\rho_{0}\|_{L^{\infty}}\) or \(\|\rho_{0}^{1/2}u_{0}\| ^{2}_{L^{2}}+\|\rho_{0}^{1/2}w_{0}\|^{2}_{L^{2}}\) is small enough.

     

Novel materials for bioanalytical and biomedical applications: Environmental response and binding/release capabilities of amphiphilic hydrogels with shape‐persistent dendritic junctions

The binding and release capabilities of a hydrogel series, constructed of hydrophilic poly(ethylene glycol) segments and hydrophobic dendritic junctions [poly (benzyl ether)s], are evaluated in aqueous media. The environmental response of the amphiphilic networks is also tested in water at three pH values: 1.5, 7.0, and 10.1. The highest swelling ratio is observed under acidic conditions and varies between 3.7 and 6.5, depending on the crosslinking density and dendrimer generation. Gel specimens with embedded indicators react within 3–6 s with a clear color switch to the change in the pH of the surrounding medium. The experiments with model anionic and cationic indicators and stains show that the hydrogels have basic interiors. The gel binding capabilities depend on the water solubility of the substrate and on the size of the incorporated dendritic fragments. Model release studies have been performed at 37 °C and pHs 1.5, 7.0, and 10.1. The observed phenomena are explained by the transformations in the structure and charge that both the networks and the model compounds undergo with the changes in the pH of the aqueous medium. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4017–4029, 2005     

Elucidation of chiral recognition processes of macrocyclic antibiotic vancomycin

A theoretical investigation was carried out on the retention and separation of enantiomeric molecules including nonsteroidal anti-inflammatory drugs, anti-neoplastic compounds and N-derivatized amino acids by capillary electrophoresis using macrocyclic antibiotics, a new class of chiral selectors, as stationary phase. Firstly docking methods were used to study the enantiorecognition in chiral electrophoresis. The molecular dynamics simulations of the two diastereoisomer complexes were then performed in order to understand how these antibiotics recognize the enantiomers. Another approach was applied in this study to establish a quantitative structure-enantioselectivity relationship (QSER) model, able to describe the resolution of a series of chiral compounds in capillary electrophoresis using vancomycin as the resolving agent.     

Electrogenerated Fe(I) Porphyrins: Efficient Electrocatalysts for Reductive Dechlorination of DDT in N,N′‐Dimethylformamide

Two iron(I) porphyrins were electrogenerated and then utilized as catalysts for the reductive dechlorination of 1,1‐bis(4‐chlorophenyl)‐2,2,2‐trichloroethane (DDT) in N,N′‐dimethylformamide. No reaction is observed between DDT and the Fe(III) or Fe(II) forms of the porphyrin, but the electrogenerated Fe(I) porphyrin efficiently catalyzes the electroreduction of DDT to give (1,1‐bis(4‐chlorophenyl)‐2,2‐dichloroethane) DDD, (1,1‐bis(4‐chlorophenyl)‐2,2‐dichloroethylene) DDE and (1,1‐bis(4‐chlorophenyl)‐2‐dichloroethane) DDMU as determined by GC‐MS analysis. The reductive dechlorination was monitored by electrochemistry, controlled potential electrolysis and spectroelectrochemistry and a mechanism for the reaction involving the reduced porphyrins and DDT is proposed. Comparisons are also made between the catalytic properties of metalloporphyrins containing iron, cobalt and manganese central metal ions under the same solution conditions.     

Optimization of mobile phase for the determination of Esomeprazole and related compounds and investigation of stress degradation by LC–MS

In this study, the objective was to investigate the degradation behavior of Esomeprazole under different recommended stress conditions according to International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use [1] by HPLC. Our research showed that the effect of mobile phase species on separation was significant for the determination of Esomeprazole and its related compounds. Successful separation of the drug from its related impurities and degradation products formed under different stress conditions was achieved using ammonium acetate buffer/ACN by a gradient elution. Compared with phosphate buffer/ACN, ammonium acetate buffer/ACN under same pH and gradient showed a great improvement in resolution due to the change of elution order. The drug was subjected to stress conditions including acidic, alkaline, oxidative, photolytic, and thermal conditions. Extensive degradation occurred in acidic and oxidative conditions, while mild degradation was observed in alkaline and photolytic conditions. Besides, it turned out the drug was extremely stable under thermal condition. The stability‐indicating LC–UV method was validated with respect to linearity, precision, accuracy, specificity, and robustness. The LC–MS method was also adopted for the characterization of degradation products. Based on the m/z values and fragmentation patterns, the degradation pathway of the drug has been proposed.     

Wang Resin Bound Addition Reactions Under Microwave Irradiation

The addition reaction process of Wang resin bound amines with isocyanates was monitored directly using a FTIR method. It showed that the reaction process was greatly enhanced under microwave irradiation.     

Hydrogen Peroxide–Promoted Transformation of Thioureas/Thiosemicarbazides to Related Ureas/Semicarbazides at Room Temperature via Grinding

A novel and environmentally benign synthetic method for ureas through hydrogen peroxide–promoted desulfurization of thioureas at room tepemperature via grinding is reported. As compared with the traditional method, this one is manipulatively simple and the oxidant is low cost, highly active, and environmentally friendly.