Phase separation in polymer blends comprising copolymers: 6. Effect of molecular architecture of block copolymers

To study the effect of the molecular architecture of a copolymer on its miscibility with corresponding homopolymers a series of block copolymers of styrene and isoprene with diblock, triblock and four-arm star architectures have been prepared and the morphologies of the blends of the copolymers and polyisoprene with different molecular weights have been examined by electron microscopy. The results show that miscibility varies in the sequence diblock>triblock>four-arm star copolymers. This sequence is in the opposite direction to the variation of the architectural complexity of the block copolymers, i.e. the more complex is molecular architecture, the greater is conformation restriction in microdomain formation and the less is solubility of homopolymer in corresponding domains.     

纳米稀土复合固体超强酸催化合成乙酸苄酯

采用共沉淀法制备了纳米稀土复合固体超强酸SO4^2-／ZrO2-2％Nd2O3催化剂，电镜分析表明，催化剂颗粒直径在25nm左右，比表面积测定：71．03m^2／g。酸强度-12．70〈Ho〈-11．99。并对合成乙酸苄酯的最佳反应条件进行了研究。研究表明：当苯甲醇与乙酸的物质的量比为1：2，反应时间为5h，反应温度为120℃，催化剂用量为6％苯甲醇的质量时，酯化率可达92．04％。研究发现，该催化剂可重复使用并可活化再生。     

Study of different effect on foaming process of biodegradable bionolle in supercritical carbon dioxide

Microcellular foaming of biodegradable Bionolle in supercritical CO₂ has been produced. The effects of a series of variable factors, such as saturation temperature, saturation pressure, and depressurization time and step on the foam structures and density, were studied through measurement of density and SEM observation. The experimental results show that higher saturation temperatures lead to an increase in bulk densities; and different depressurization time and step result in different product cell morphology. In addition, at some saturation temperature, the orientation of the cells can be found in the product morphology. XRD experimental results show that the foaming treatment with SC CO₂ increased the crystallinity of Bionolle. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2901–2906, 2006     

Isolation and characterization of ganglioside 9-O-acetyl-GD3 from bovine buttermilk

Bovine buttermilk contains a unique ganglioside, 9-O-acetyl-GD₃. In order to isolate large quantities of this ganglioside, a simplified isolation scheme which consists of several ion-exchange and silica gel column chromatographic procedures was devised. The isolated 9-O-acetyl-GD₃ was characterized on the basis of its thin-layer chromatographic behavior, its immunoreactivity with a specific monoclonal antibody, JONES, and by conversion to authentic GD₃ by mild base treatment.     

MACD与K线图技术在证券投机中的实证研究

利用MACD趋势指标与K线形态图进行相互验证技术,改进一般的基于MACD的证券买卖准则。实证结果表明,基于改进后的MACD买卖准则进行证券投机,几乎能使投机者捕捉到每一波段行情,从而获取较高收益。     

Analysis of junction temperatures in high-power GaN-based LEDs

We presented the analysis of the incomplete conduction in bonding medium in high power GaN-based light-emitting diode (LED) packages. A numerical study was carried out with parametric model to understand the junction temperature variation due to bonding medium defects. Transient thermal measurement was performed to evaluate LED’s junction temperature. Thermal resistance from chip to lead frame was 20 K/W in our sample LED. It was suggested that only 60% of the surface area of the bonding medium was involved...     

Preparation of micro-patterned surfaces of Si-N-O films and their influence on adhesion behavior of endothelial cells

Microgrooves were prepared on Si(100) surface by photolithography and wet etching.Subsequently,Si-N-O films were deposited on the microgrooves by unbalanced magnetron sputtering(UBMS) and micro-patterned surfaces of Si-N-O films were obtained.The size of the micropatterns was measured by surface profilometer.The chemical composition of Si-N-O films were characterized by X-ray photoelectron spectrometry(XPS) and the wettability of the micropatterned surfaces was evaluated by contact angle measurement.The beh...     

Fuel combustion test in constant volume combustion chamber with built-in adaptor

Combustion tests of pre-mixture of methane and air in constant volume combustion chamber(CVCC) have been carried out by means of flame propagation photo and gas pressure measurement,the effects of CVCC body temperature,intake pressure of pre-mixture of methane and air,equivalence ratio and location of the built-in adaptor have been investigated.The whole combustion chamber can be divided into two parts,i.e.the upper combustion chamber and the lower combustion chamber,by the built-in adaptor with through hol...     

Dynamic equivalent method of interconnected power systems with consideration of motor loads

The existing equivalent methods usually only deal with static load models and neglect the dynamic characteristics of loads such as induction motors.This paper presents a dynamic equivalent method which considers motor dynamics.At first,the clustering criterion of motor loads is given.The motors with similar dynamic characteristics are classified into one group.Then,reduction of motors in the same group is carried out.Finally,parameters of the equivalent motor are calculated and the equivalent system is thus...