Synthesis of poly(sorbitan methacrylate) hydrogel by free-radical polymerization

Hydrogels are materials with the ability to swell in water through the retention of significant fractions of water within their structures. Owing to their relatively high degree of biocompatibility, hydrogels have been utilized in a host of biomedical applications. In an attempt to determine the optimum conditions for hydrogel synthesis by the free-radical polymerization of sorbitan methacrylate (SMA), the hydrogel used in this study was well polymerized under the following conditions: 50% (w/v) SMA as monomer, 1% (w/w) alpha, alpha'-azo-bis(isobutyro-nitrile) as thermal initiator, and 1% (w/w) ethylene glycol dimethacrylate as cross-liking agent. Under these conditions, the moisture content of the polymerized SMA hydrogel was higher than in the other conditions. Moreover, the moisture content of the poly(SMA) hydrogel was also found to be higher than that of the poly(methyl methacrylate [MMA]) hydrogel. When the Fourier transform-infrared spectrum of poly(SMA) hydrogel was compared with that of poly(MMA) hydrogel, we noted a band at 1735-1730/cm, which did not appear in the Fourier transform-infrared spectrum of poly(MMA). The surface of the poly(SMA) hydrogel was visualized through scanning electron microscopy, and was uniform and clear in appearance.     

Wuweizidilactones A-F: novel highly oxygenated nortriterpenoids with unusual skeletons isolated from Schisandra chinensis

A phytochemical study of secondary metabolites produced by Schisandra chinensis has led to the isolation of six novel highly oxygenated nortriterpenoids, wuweizidilactones A-F (1-6). Compounds 3-6 possess an unprecedented 3,4-seco-18(13-->14)-abeo-artane skeleton. Interestingly, structures 3-6 have a beta-oriented methyl group at the C-14 position. This structural feature corroborates the biogenetic pathway proposed for the formation of 18-norschiartane-type compounds 1 and 2. The structures of these novel metabolites were established on the basis of their detailed spectroscopic analysis. The structure of 1 was also confirmed by single-crystal X-ray diffraction analysis. For the first time, the absolute configuration of these nortriterpenoids was determined by using a modified Mosher method.     

Resolution of infrared matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using glycerol; enhancement with a disperse laser beam

Some experimental factors affecting the resolution in glycerol infrared matrix-assisted laser desorption/ionization (IR-MALDI) time-of-flight (TOF) mass spectrometry were investigated. Loading the sample inside a cavity covered with a grid was found to improve the resolving power as reported previously, although not to the extent attainable in UV-MALDI using the same instrument. The resolving power improved as the laser spot area at the sample position got larger, becoming almost comparable with that in UV-MALDI when the spot area was a little larger than the cavity size. Reduced concentration of the ablated materials in the acceleration region with the use of the grid and large irradiation area may be responsible for the enhanced resolution. In addition, the threshold laser fluences measured in this work were lower than those reported in the literature and tended to decrease more rapidly as the irradiation area increased than predicted previously. The implication of similar threshold fluences for matrix and analyte ions is discussed in relation to the analyte ion formation mechanism.     

Diastereoselective Prins-type reaction of cycloalkenylcyclopropanol silyl ethers and alpha,beta-unsaturated aldehyde acetals

Electrophilic addition of 1-(1-cyclohexenyl)-1-cyclopropanol trimethylsilyl ether to alpha,beta-unsaturated aldehyde acetals under Lewis acidic conditions proceeds with good to excellent diastereoselectivity to afford spirocyclobutanones containing three contiguous stereocenters. A convenient entry to enantioselective syntheses is available by use of a nonracemic C2-symmetric acetal. Elaboration of the resulting adducts provides ready access to medium-sized carbocycles.     

脲基氨基甲酸酯化合物的合成及应用研究

在轿车发动机的燃烧室中以及发动机进气系统的汽油喷嘴上,汽油往往因高温及废气的酸性物质作用而产生沉积物,尤其是在喷油嘴上会产生结焦,甚至堵塞喷油嘴,使汽车不能启动运行［'－'j．采用优化发动机设计的办法,对改善沉积物和结焦作用不大,而在汽油中加人汽油清净分散剂却能产生较好的效果．目前,美国加人清净分散剂的汽油已占90％,深入研究新型、高效的清净分散剂已成为研究的热点．按化学结构汽油清净分散剂大致分为两类"－'：（l）小分子胺类,如N一苯硬脂酷胺、单丁二醋亚胺、双丁二酚亚胺和1,3一三甲撑二胺类等;（2）低聚…     

Electrocatalytic Behavior of Metalloporphyrins(Ⅶ)——Kinetic Study of Cysteine Oxidation on Heat-Treated Cobalt Tetramethoxyphenyl Porphyrin Adsorbed on Graphite

The metnoas or rotating ring-disc electrode(RRDE) ana cyclic voltammetry were used to study the oxidation of cgsteine on heat-treated cobalt tetramethoxyphenyl porphyrin adsorbed on graphite(Co-TMPP/graphite) in solutions of various pH.Experimental results showed that Co-TMPP/graphite exhibits significant catalytic activity for cysteine oxidation in solutions with various pH.The current efficiency of cysteine oxidation on Co-TMPP/graphite in basic media is more than 90%.It was found that the kinetics of cysteine oxidation on Co-TMPP/graphite is a simple irreversible reaction controlled by rate of charge transfer.The standard rate,constants(k) of cysteine oxidation were calculated and the reaction mechanism of this reaction in solutions of various pH wes discussed.     

Solvent-Processible Polymer Membrane-Based Reference Electrodes for Miniature Chemical Sensors

We have recently developed a new type of liquid junction-free reference electrode that is suited for fabrication of miniature ion sensor devices. The proposed reference electrode system employs a solvent-processible polymer membrane, and the best performance membrane so far is formulated with an aromatic type polyurethane,synthesized with 4,4'- methylenebis(phenyl isocyanate) and poly(tetramethylene ether glycol).     

光敏络合催化光解水析氢的电化学模拟

Durham等^[1]曾利用Pt(黑)|lN HCl‖Ru(bipy)₃²⁺、MV²⁺、EDTA(pH=9)|Pt(网)电池模拟光解水析氢反应。但该装置的左、右二半电池中溶液的pH值相差9以上,相当于外加0.5V以上的偏压,因此,不能真实地模拟自发的光解水析氢过程。     

Effect on Intensity Correlation Time by Input Signal in a Single-Mode Laser with Bias Signal Modulation

The effect on intensity correlation time T by input signal is studied for gain-noise model of a single-mode laser driven by colored pump noise and colored quantum noise with colored cross-correlation with a bias signal modulation in this paper. By using the linear approximation method, we detect that there exists maximum (i.e., resonance) in the curve of the intensity correlation time T upon bias-current i0 when the noise correlation coefficient λ is positive; and there exists minimum (i.e., suppression) in the T-i0 curve when λ is negative. And when λ is zero, T increases monotonously with increasing i0. Furthermore, the curve of T upon the signal frequency Ω is also studied. Our study shows that no matter what the value ofλ is, there exists minimum (i.e., suppression) in the T-Ω curve.