合成直链烷基苯的锆磷铝固体酸催化剂 I.催化剂合成及其影响因素

合成了一系列用于苯与直链烯烃烷基化反应的含有杂原子的磷铝分子筛固体酸催化剂 (MeZrAPO 5 ) ,同晶取代磷铝分子筛骨架中磷和铝的杂原子包括锆和至少一种选自硅、硼、镓、锗、铁、镁、锡等的元素。考察了晶化温度、晶化时间、杂原子种类、铝源等因素对催化剂合成的影响 ,探索了合成样品中模板剂脱除的最佳条件。结果表明 ,晶化温度高于 15 0℃、n(TEA) /n(Al2 O3 )≥ 1 5以及加入Zr原子都有利于直接生成MeZrAPO 5晶相 ;用小晶粒和高结晶度的铝源合成时 ,分子筛的结晶度高。     

Properties of Carbopol Solutions as Models for Yield-Stress Fluids

ABSTRACT: The effect of pH on the non-Newtonian viscosity (η)of aqueous Carbopol 940 solutions is presented with high resolution (pH increments about 0.4) between pH = 2.8 and 12.7. Aqueous NaOH was used to adjust pH of 1.48 wt % Carbopol solutions. A Contraves viscometer was used to measure steady-flow shear stress at known shear rate (γ) over the range γ= 8 to 195 s⁻¹. Yield stresses and shear-thinning η(γ) were observed. Data were fitted with a Herschel-Bulkley model, whose parameters (including yield stress) were expressed as functions of pH. Comparisons were made of η(γ) to the dynamic viscometric properties η'(ω) and η*(ω) for comparable ranges of γ and frequency (ω): A fairly close match was found between η and η* but η«η'. pH dependence included previously unreported extrema of h(pH) in the range of pH = 6.2 to 6.6. Because of sensitive control of rheological properties with pH, Carbopol solutions can be used to mimic a great range of shear-thinning and yield-stress behavior that should make them useful for model studies directed toward process and equipment design and evaluation.     

Cholesterol‐imprinted polymer receptor prepared by a hybrid imprinting method

A novel cholesterol‐imprinted polymer (CMIP‐H) was prepared by a hybrid method of covalent imprinting and non‐covalent imprinting. This approach involves the copolymerization of a template‐containing monomer, cholesteryl 2‐hydroxyethyl methacrylate carbonate, and a cross‐linker, followed by hydrolysis to afford a flexible guest‐binding site accompanied with the easy and efficient removal of a ‘sacrificial spacer’. The effect of solvent on the binding capacity of CMIP‐H towards cholesterol was studied, indicating that a good binding capacity towards cholesterol could be achieved in a less‐polar solvent. The binding experiments of CMIP‐H towards a series of structural analogues of cholesterol, including cholesterol acetate, progesterone and stigmasterol, were carried out in hexane. The results showed that CMIP‐H almost did not bind cholesterol acetate at all because the hydrogen‐bonding site is blocked. It exhibited a similar binding towards both cholesterol and stigmasterol, but much higher binding towards progesterone. Copyright © 2005 Society of Chemical Industry     

交联透明质酸的降解及其释药性能

用己二酸二酰肼（ADH）对透明质酸（HA）进行化学修饰，制备交联透明质酸（HA-ADH）薄膜。粘度法测试表明HA-ADH是一种可降解的生物材料，并且与HA相比，HA．ADH的降解速率减慢。在此基础上，研究了以疏水性的替硝唑（TDZ）和亲水性的头孢唑啉钠（CEZ）为模拟药物的HA-ADH药物载体薄膜的释药性能。紫外-可见（UV-Vis）吸收光谱检测表明，HA-ADH是一种疏水性药物TDZ的优良缓释制荆，这是由于TDZ的疏水性和HA-ADH薄膜的缓慢溶胀和降解性能的结合而得到的，药物的释放主要受扩散机制控制。     

Retaining maximum antioxidative potency of wheat germ oil refined by molecular distillation

A process of physical refining wheat germ oil using the technique of molecular distillation (MD) is presented in this work. Wheat germ oil was obtained from the germ by solvent extraction using hexane and also by cold pressing. The oil extracted with hexane was degummed and bleached before deacidification in order to modify the parameters of phosphorus and color. The goal in carrying out the stage of physical refining by MD was to preserve the maximum amount of original antioxidative potential obtained from extraction of the crude oil. The effect of evaporation temperature of one‐stage MD on the efficiency of free fatty acid elimination was studied. The antioxidant portion was followed by means of analytic determination of tocopherols by high‐performance liquid chromatography. Tocopherol retention up to 98% was achieved in the oil extracted by pressing, and yields of up to 96% were achieved in the oil extracted with hexane. Copyright © 2007 Society of Chemical Industry     

择形催化合成2,6-DMN的研究进展

介绍了2,6-二甲基萘(2,6-DMN)的制备方法,详细论述了萘、甲基萘在分子筛催化剂上择形催化合成2,6-DMN的研究进展,提出了择形催化合成2,6-DMN的研究方向。     

The Minimum PAPR Code for OFDM Systems

In this letter, a block code that minimizes the peak‐to‐average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals is proposed. It is shown that peak envelope power is invariant to cyclic shift and codeword inversion. The systematic encoding rule for the proposed code is composed of searching for a seed codeword, shifting the register elements, and determining codeword inversion. This eliminates the look‐up table for one‐to‐one correspondence between the source and the coded data. Computer simulation confirms that OFDM systems with the proposed code always have the minimum PAPR.     

影响道路沥青低温抗裂性能的因素

用弯曲梁流变仪、直接拉伸试验机对7种国内外油源沥青样品进行了低温抗裂性能的评价，从沥青的四组分、相对分子质量及其分布来分析其对沥青低温抗裂性能的影响，结果表明，沥青的相对分子质量分布宽，对沥青的低温抗裂性能有利。