Self-bonding in an amorphous polymer below the glass transition: A T-peel test investigation

Films of amorphous polystyrene (PS) with a weight-average molecular weight (M_w) of 225 × 10³ g/mol were bonded in a T-peel test geometry, and the fracture energy (G) of a PS/PS interface was measured at the ambient temperature as a function of the healing time (t_h) and healing temperature (T_h). G was found to develop with (t_h)^1/2 at T_h = T_g-bulk − 33 °C (where T_g-bulk is the glass-transition temperature of the bulk sample), and log G was found to develop with 1/T_h at T_g-bulk − 43 °C ≤ T_h ≤ T_g-bulk − 23 °C. The smallest measured value of G = 1.4 J/m² was at least one order of magnitude larger than the work of adhesion required to reversibly separate the PS surfaces. These three observations indicated that the development of G at the PS/PS interface in the temperature range investigated (<T_g-bulk) was controlled by the diffusion of chain segments feasible above the glass-transition temperature of the interfacial layer, in agreement with our previous findings for fracture stress development at several polymer/polymer interfaces well below T_g-bulk. Close values of G = 8–9 J/m² were measured for the symmetric interfaces of polydisperse PS [M_w = 225 × 10³, weight-average molecular weight/number-average molecular weight (M_w/M_n) = 3] and monodisperse PS (M_w = 200 × 10³, M_w/M_n = 1.04) after healing at T_h = T_g-bulk − 33 °C for 24 h. This implies that the self-bonding of high-molecular-weight PS at such relatively low temperatures is not governed by polydispersity. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1861–1867, 2004     

我国AB股双重上市公司经营业绩变化的实证分析

本文以46家在上海和深圳同时上市AB股的公司的样本,分析了公司实行双重上市前1年及其后4年的经营业绩的变化趋势以及股权结构和上市顺序对它的影响。研究表明,双重上市当年及其后4年经营业绩显著下降;股权结构和上市顺序对公司经营业绩影响明显。最后,文章提出了改善AB股公司经营业绩的对策建议。     

Hydrophilic core-shell microspheres: a suitable support for controlled attachment of proteins and biomedical diagnostics

Functional hydrophilic microspheres (latex particles) have found various applications in life sciences and in medicine - particularly in latex diagnostic tests. This paper presents a comprehensive review of studies on latex particles with a hydrophilic interfacial layer composed of various hydrophilic polymers with reactive groups at the ends of macromolecules or at each monomeric unit along the chain. Typical examples of these hydrophilic polymers are poly(2-hydroxyethyl methyl methacrylate), poly(acrylic acid), poly(N,N-dimethylacrylamide), polysaccharides, poly(ethylene oxide) and polyglycidol. Hydrophilic microspheres with different morphologies (uniform or core-shell, see Figure) have been synthesized by emulsion and dispersion polymerizations. The chemical structure of polymers which constitute the interfacial layer of microspheres has been investigated using a variety of instrumental techniques (such as XPS, SSIMS and NMR) and analytical methods based on specific chemical reactions suitable for the determination of particular functional groups. Microspheres are exposed to contact with proteins in the majority of medical applications. This paper presents examples of studies on the attachment of these biomacromolecules to microspheres. The relation between the structure of the interfacial layer of microspheres and the ability of these particles for the covalent binding of proteins is discussed. Several examples of diagnostic tests, in which hydrophilic microspheres with adsorbed or covalently immobilized proteins were used as reagents, are presented. The paper also contains a short review of the application of magnetic hydrophilic particles for protein separation. Examples of hydrophilic latex particles used for hemoperfusion or heavy metal ion separation are presented. Hydrophilic microspheres with uniform or core-shell morphologies.     

一类利用回归关系的计量指标抽样方案

在产品质量判定的抽样检验问题中,当目标指标需用破坏性试验才能得其值时,更为常用的是用非破坏性试验可得量值的协变指标量来预报它。但在产品抽样验收问题上,未能形成理论较为严密的方法,这是由于预报误差这个关键问题的处理尚未解决得好,即给不出抽样方案的功效计算的正确或是近似性较好的公式。本文通过建立合理的数学模型,把对目标指标的质量要求化为对协变指标量的统计要求,从而利用两者的回归关系,结合两种复杂的抽样方案,给出功效函数的计算公式和计算方法,并进行了分析。     

孔梯度陶瓷纤维复合膜管的制备及特性

陶瓷过滤管具有孔隙率高、耐腐蚀、耐高温、机械强度高、便于清洗、使用寿命长等优点,是高温烟尘处理用的高效过滤元件.本文研制了一种具有梯度孔结构堇青石陶瓷纤维复合膜过滤元件,该过滤元件是由多孔支撑体、过渡层和分离膜层组成.其中支撑体、过渡层和分离层的气孔率分别为35～40;、50～60;和60～70;.文中主要分析了孔梯度陶瓷纤维复合膜管的材料结构和抗热震性能,同时对复合膜管进行含尘气体过滤的冷态模拟试验.对于烟气中粒径大于或等于0.1μm的颗粒,复合膜管的截留率达到99.8;以上.     

Evaluation of Water Ammonium Ion Test Kit and Its Feasibility for the Analysis of Protein in Food

The traditional method for the determination of protein in food needs the operations of digestion, distillation, absorption, and titration; therefore, it is complicated and time-consuming and requires professional personnel. Is there a more convenient and faster detection method that can directly determine the ammonium ions in protein digestion solution to obtain the protein content of food and avoid the distillation–absorption–titration process? The feasibility of water ammonium ion test kits for food protein rapid detection was discussed here. After digestion, the protein in food transforms into ammonium ions in the digestion solution. Because of the variety of food, there are many different inorganic ions left in the food digestion solution, and at the same time, digestion agents are added in the digestion process and become potential interference factors in ammonium determination. Therefore, the detection accuracy of ammonium test kits needs to be evaluated first, including their anti-interference ability. The standard curve of ammonium was established by the test kit. When the ammonium concentration was 0.00–2.50 mg/L, the absorbance at 620 nm was linearly related to the ammonium concentration, the determination coefficient R² was 0.9995, and the detection limit of this method was 0.01 mg/L. The influences of temperature, pH value, and reaction time on the test kit method were discussed. The precision was 0.90–3.33%; the repeatability was 1.71–4.86%; and the recovery rate of tap water, river water, and sea water was controlled within 90–103%. The anti-interference ability of the evaluated test kit was better than that of the national standard detection method. The test kit, combined with sample pretreatment and protein conversion formula, was used to detect protein in different types of food (milk powder, rice flour, wheat flour, soy, banana, milk, fish food, chicken food, and dog food). The results showed that there were no significant differences (ρ > 0.05) between the national method and the test kit method. The ammonium ion test kit method shortened the determination time and had higher sensitivity, showing its potential for the rapid determination of food protein.     

综合微光测试系统的总体设计

描述一种微光像增强器综合测试系统的总体设计。设计采用了组合结构，使系统只用单一的光源就可以测试微光像增强器九项光量子类和几何类的参数，具有以往几台常规测试仪器功能的总和。系统对各参数测量的不确定度２～４％。     

强激光装置中玻璃疵病在线检测的光学系统设计

介绍了一种用于玻璃疵病在线检测的近摄工作距成像光学系统,其光组结构形式采用了光阑后置的准远心结构形式,主要光学参量为f′=14 mm;在物像距为250 mm约束条件下,物方视场达到90 mm（对角线）;F/number=3.56;光谱适应范围为400~800 nm,对应的空间分辨率为100 lp/mm时,调制传递函数大于0.29.     

Characterization and Bioavailability of Vitamin C Nanoliposomes Prepared by Film Evaporation-Dynamic High Pressure Microfluidization

Vitamin C nanoliposomes were prepared by combining a conventional method (film evaporation) with dynamic high pressure microfluidization. Their physicochemical characterizations (antioxidant activity, particle size, entrapment efficiency, morphology, in vitro drug release, and storage stability) and skin permeation behavior were investigated. The results showed that vitamin C nanoliposomes, having equivalent DPPH (2, 2-diphenyl-1-picrylhydrazyl) free radical scavenging capacity of pure vitamin C solution without loss of their biological activity, exhibited better storage stability at 37°C for 24 hours and at 4°C for 60 days, a more excellent sustained drug release as well as higher skin penetration rate than vitamin C liposomes.     

Tensile Characterization of FRP Rods for Reinforced Concrete Structures

The application of FRP rods as an internal or external reinforcement in new or damaged concrete structures is based on the development of design equations that take into account the mechanical properties of FRP material systems.The measurement of mechanical characteristics of FRP requires a special anchoring and protocol, since it is well known that these characteristics depend on the direction and content of fibers. In this study, an effective tensile test method is described for the mechanical characterization of FRP rods. Twelve types of glass and carbon FRP specimens with different sizes and surface characteristics were tested to validate the procedure proposed. In all, 79 tensile tests were performed, and the results obtained are discussed in this paper. Recommendations are given for specimen preparation and test setup in order to facilitate the further investigation and standardization of the FRP rods used in civil engineering.