PAMAM体型缩聚物的制备及其性能研究

以分子末端带有多官能度活泼端基的PAMAM等为原料 ,通过缩聚反应制备了一类新型体型缩聚物 .借助X射线光电子能谱仪 (XPS)对制备的体型缩聚物进行分析 ,利用其化学分析电子光谱 (ESCA)中碳元素价态的拟合数据判断体型缩聚反应进行的程度 ,数据表明酯基碳 (—COO)拟合峰已基本消失 ,说明其与氨基缩合反应转化为酰胺基 (—CON) ,且反应进行的比较彻底 .通过体型缩聚物在乙醇、正己烷、甲苯、氯仿、异丙醇、乙酸、甲酸、去离子水中进行溶胀试验 ,发现其在甲酸作为溶剂体系中的溶胀比出现最大值 ,根据溶度参数的意义估测体型缩聚物的溶度参数约为δ2 =2 7 6 (MJ m3) 1 2 (即甲酸的溶度参数 ) .对原料PAMAM以及制备的体型缩聚物进行DSC分析 ,发现制备体型缩聚物的玻璃化转变温度 (Tg)有了较大提高 ,从初始原料PAMAM的负值提高到 4 8℃左右 .     

分光光度法快速测定乳链菌肽效价

为了解决琼脂扩散法测定乳链菌肽效价时间长的问题,引进了分光光度测定法.确定的测定工艺为藤黄微球菌接种接种龄为指数期的中后期、接种量为10%的,加入待检样品在温度33℃、转速150 r/min的摇床培养5 h,600 nm波长下测定吸光度值,通过乳酸菌肽浓度与检测菌吸光度之间的函数关系准确测量乳酸菌肽的效价.重复测定的最大相对误差在±5%以内.     

Preparation,characterization, and properties of poly(aryl ether sulfone) systems with double‐decker silsesquioxane in the main chains by reactive blending

A series of copoly(aryl ether sulfone)s containing double‐decker‐shaped silsesquioxane (DDSQ) in the main chain was prepared. Toward this end, a novel diphenol polyhedral oligomeric silsesquioxane macromer was synthesized by hydrosilylation between 3,13‐dihydro octaphenyl double‐decker silsesquioxane (denoted dihydro DDSQ) and eugenol. The poly(aryl ether sulfone)s were synthesized from diphenol DDSQ, bisphenol A (BPA), and 4‐fluorophenyl sulfone using a one‐step high‐temperature solution method. By adjusting the ratio of diphenol DDSQ to BPA, copolymers with variable DDSQ content in the main chains were obtained. With increased DDSQ content in the main chain, the glass transition temperature decreased based on differential scanning calorimetry, and anti‐degradation was enhanced based on thermogravimetric analysis. Moreover, the dielectric constant κ of pure polymer (3.19 at 1 MHz) initially increased to 4.04 (DDSQ molar ratio = 10%), and then decreased to 2.68 at 1 MHz (DDSQ molar ratio = 100%). Crystallization behavior, solubility, and surface hydrophobicity were also investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 780–788     

基于STC89C52单片机测量管道长度

采用STC89C52单片机,利用声音在管道内形成驻波,通过测量驻波发生时的共振频率,进而求得管道长度.文中对单片机实现的系统硬件结构、软件设计作了具体的说明,并给出了几个测量实例.     

Comparative study on thermal behaviors between micrites and thrombolites using thermogravimetric analysis

Journal of Thermal Analysis and Calorimetry - Although micrites (abiotic limestone) and thrombolites (typical biotic limestone), according to the sedimentation and biological action, can be...     

溶剂热处理对超顺磁性球形γ－Al2O3催化剂载体性能的影响

 在前期制备超顺磁性氧化铝催化剂载体的基础上，对采用油中成型（内凝胶）方法制备的磁性球形氢氧化铝的晶型、比表面积、孔体积、孔分布和磁性能等性质进行了研究．实验中发现，溶剂热处理过程不仅有利于油中成型的无定形氢氧化铝微球向拟薄水铝石转化，而且可以增大载体的比表面积和孔体积．通过控制溶剂热处理的温度和时间，可有效地调控载体的孔分布．实验中制备的磁性氧化铝载体的物理化学性能，达到了硝基苯和正己烯催化加氢反应所需的要求．     

Dynamics of a paraffin crystal

Recently it has become possible to make a series of simulations on a supercomputer of the molecular motion of a pentacontane (C₅₀H₁₀₂) crystal containing close to 10000 atoms. Such a crystal is big enough to serve as a model of a macroscopic crystal. It can also serve as a model for polyethylene. The large volume of detailed information on the structure and motion permits a new level of understanding. Information on crystal appearance, pseudo-symmetric crystal structures, picosecond time-scale formation of conformational defects and the beginning of the melting process is presented.     

盐酸超声提取-火焰原子吸收光谱法测定加热不燃烧卷烟烟丝中钾、钙、钠、镁的含量北大核心CSCD

加热不燃烧卷烟(HNB)烟丝样品经干燥、搅碎和过筛后,分取0.1 g置于锥形瓶中,加入0.05 mol·L^(-1)盐酸溶液50 mL,超声提取20 min,离心。分取5 mL上清液,定容至50 mL,采用火焰原子吸收光谱法(FAAS)测定其中钙和钠含量;分取1 mL上清液,用水定容至100 mL,用FAAS测定其中钾和镁含量。结果显示,钾、钙、钠、镁的质量浓度均在一定范围内与其对应的吸光度呈线性关系,检出限(3s/k)分别为0.50,0.08,0.02,0.02 mg·kg^(-1);对实际样品进行6次平行测定和3个浓度水平的加标回收试验,测定值的相对标准偏差(n=6)均小于5.0%,回收率为90.0%~104%。方法用于5种分别用造纸法、稠浆法、辊压法和干法制备的HNB烟丝样品的分析,发现不同工艺所制样品中4种元素含量差别较大。