Polystyrene supported pyrazolinium Cr(VI) reagents: preparation and use in synthetic organic chemistry

Divinylbenzene (DVB) and ethyleneglycol dimethacrylate (EGDMA) crosslinked polystyrenes (2%) were functionalized to generate pyrazolinium chromate, chlorochromate and pyrazole–CrO₃ complex functionalities. These were found to oxidize primary and secondary alcohols to the corresponding carbonyl compounds in high yields. The influence of solvent, temperature, catalyst and molar excess of the reagent in these oxidation reactions was investigated to find out the optimum conditions for effective oxidation reactions. EGDMA crosslinked polystyrene supported reagents showed higher reactivity in terms of functional group capacity and percentage yield. Also, chlorochromate reagent was found to be very efficient in oxidizing alcohols to carbonyl compounds. The spent polymeric reagent after the oxidation step can be easily removed by filtration and can be regenerated many times. © 1998 SCI.     

Polyacenaphthylene supported t-butyl chromates: a new class of solid phase oxidizing reagents

Copolymers of acenaphthylene with divinylbenzene were functionalized by incorporating t-butyl chromate groups, and the resulting polymeric reagents were used to oxidize alcohols to carbonyl compounds. Primary and secondary alcohols were oxidized to the corresponding carbonyl compounds in quantitative yields. The extent of oxidation was found to depend on the various reaction parameters including the temperature, nature of the solvent, concentration of the reagent functions, duration of the reaction and the presence of catalyst. © 1998 SCI.     

Polymer-bound hydroxamic dithiobenzoic anhydride: a new heterogeneous photoinitiator

Poly(methylmethacrylate) resins crosslinked with divinyl benzene, ethyleneglycol dimethacrylate and N,N′-methylene-bis-acrylamide were functionalized to generate a photodissociable chromophore, S-benzoyl-o-dithiohydroxamate. These polymeric mixed anhydrides were found to be efficient heterogeneous initiators in the light-induced polymerization of acrylic and vinyl monomers. On UV irradiation, both homopolymers and graft polymers were obtained. Polymerization of MMA was followed at various time intervals and as a function of monomer and initiator concentrations. On varying the initiator concentration, the rate of polymerization passed through a maximum. © 1998 SCI.     

新型摆线传动的共轭啮合机理

分析了新型平动、滚动转换装置摆线机构的啮合机理,用等距曲线和摆线方程导出齿条廓线方程,研究了该机构的啮合特性,分析传动比和瞬心线后证明摆线齿条和滚柱的啮合符合齿形啮合基本定理,属于共轭啮合,发现滚轮齿条机构可实现双向零间隙传动,同齿轮齿条机构相比,传动距离更大,传动精度更高.     

纳米金属及其氧化物对污水生物处理系统中微生物的影响

微生物以其独特的生理生化特性,在市政污水处理中承担着去除有机物和脱氮除磷的重要作用,然而纳米金属及其氧化物的广泛应用提高了纳米材料进入污水处理厂的可能性,致使污水处理中的微生物暴露在风险环境中。文中从微生物聚集体存在形式角度出发,概述了纳米材料对微生物特性的影响,揭示了微生物在不利条件下的应对机制,为从群体感应角度深入探究微生物应对纳米材料等胁迫作用提供重要理论依据,并对曾处于胁迫下的微生物功能修复的可能性提出展望。     

Electrospraying the Triblock Copolymer SEBS: The Effect of Solvent System and the Embedding of Quantum Dots

This work reports on ABA triblock copolymer microparticles encoded with CdSe/CdS core–shell quantum dots (QDs) realized by electrospraying. This method allows for simple but efficient embedding of QDs in polymer beads while retaining the fluorescent properties of the original QDs. The creation of poly(styrene‐ethylene‐butylene‐styrene) (SEBS) monodisperse spherical microparticles with a tunable morphology for applications of the final QD‐loaded product is attainable via solvent variation. By varying the selectivity of the solvent for one of the distinct blocks in the polymer, the final particle morphology can be selectively altered while maintaining the same overall process conditions, allowing to tailor the particles from homogeneously flat in a nonselective solvent to dense spherical particles in an endblock selective solvent system. The mechanism responsible for this transition in morphology can be related to differences in mass transfer in the droplets and thus solvent evaporation rates arising from particular microphase structures. Finally, fluorescence characteristics of the final QD‐embedded polymer particles and photodegradation stability are investigated by spectrophotometry and are compared to the temporal evolution of the original QDs, indicating significant stability improvement and well‐dispersed QDs in an optimized polymer matrix morphology.     

聚合物阵列微针及其在透皮给药系统的应用

阵列微针作为一种新型透皮给药方式,能够避免皮肤角质层的屏障作用,实现亲水性药物和生物大分子药物的高效透皮吸收,具有无痛、微创、高效等优点。聚合物阵列微针的制备材料和制备方法多种多样,其不仅具有其他阵列微针的优点,还具有生物相容性好、安全性高、载药量精确可控及制备成本低廉等优势,是目前研究最为广泛且最具应用前景的一类阵列微针。系统地综述了目前聚合物阵列微针的主要制备方法及其在透皮给药系统中的最新研究进展。     

葡萄和葡萄酒中聚合色素的测定

采用蛋白质沉淀和传统二氧化硫脱色分析方法测定聚合色素中单分子花色素。葡萄和葡萄酒中两种聚合色素：小分子色素(SPP)与蛋白质不产生沉淀，而大分子色素(LPP)则产生沉淀。分析成熟期和采摘期赤霞珠、西拉葡萄浆果内的聚合物色素成分，其果粒中含有的聚合色素比相应的葡萄酒少。在葡萄酒中找到的多数大分子聚合色素是在葡萄酒酿造过程中产生的。通过对照，葡萄酒和其果粒中小分子色素含量相比较是不稳定的、变化的，西拉中SPP降低，赤霞珠SPP增加，黑比诺SPP变化很小。蛋白质沉淀和二氧化硫漂白分析研究得出，葡萄汁和葡萄酒中的单宁酸和聚合色素有相同的结论。     

一种高分子表面活性剂的合成及其乳化AKD的应用研究

设计并合成了一种高分子表面活性剂,当软硬单体m（St）m/（ODA）为2.5,亲水性单体AM质量分数为24%,阳离子单体DMC质量分数为24%,合成的高分子表面活性剂能很好地乳化和分散AKD,m（高分子表面活性剂）/m（AKD）为0.23时,制备的高分子基AKD乳液的平均粒径为398.2 nm,具有理想的贮存稳定性和极佳的施胶效果,综合性能优于市售传统AKD乳液。     

Protein–lipid interactions in gluten elucidated using acetic acid fractionation

Protein–lipid interactions in dough have an important impact on the quality of bakery products. Understanding of protein–lipid interactions in gluten can enhance the development of technological solutions to improve the breadmaking quality of flour as well as the functional properties of gluten. In this study, acetic acid at two different concentrations was used for treating and fractionating gluten. The impact of these procedures on the distribution of lipid components was measured. Acetic acid was able to dissociate non-polar lipids from the gluten protein matrix. Upon fractionation monomeric proteins (predominantly gliadins) and phospholipids were high in the 0.01 M acetic acid soluble fraction. The subsequent fractionation step using 0.1 M acetic acid resulted in an increased amount of high-molecular-weight glutenin subunits (HMW-GS) in the soluble fraction, along with more non-polar lipids and glycolipids in both the free and bound lipid extracts. The distribution of lipid classes demonstrates that non-polar lipids are either associated with the glutenin polymeric network through hydrophobic interactions or entrapped within the gluten matrix. The results also indicate that in gluten, glycolipids are likely to be associated with glutenins through both hydrophobic interactions and hydrogen bonds whilst phospholipids preferentially interact with gliadins and lipid binding proteins.