Effect of orientation of two-dimensional filler on dynamic mechanical properties of cured epoxy resin

Dynamic mechanical properties of cured epoxy resin filled with mica flake, as two-dimensional filler, were investigated over the temperature range from room temperature to 200°C. Two series of composite specimens were examined. One is series RM, containing ill-oriented mica flakes, and another is RMB, containing mica flakes oriented in the direction parallel to the specimen surface. Both tensile and shear moduli for RMB series were determined by dynamic mechanical experiments. The tensile modulus for RMB series was always higher than that for RM series over the whole temperature range. The shear modulus for RMB series was low, compared with that of the tensile modulus in the rubbery state. The behavior of the modulus reinforcement, observed both in the glassy and rubbery states, was compared with recently proposed theories of Wu and Padawer and Beecher. In the glassy state, the tensile modulus of RM series follows Wu's theory, while that of the RMB series agrees with Padawer and Beecher's theory. In the rubbery state, the tensile modulus of each series cannot be well explained by either theory. It was proposed that the tensile stress applied to the specimen was converted to shear stress in a thin resinous layer sandwiched by two mica flakes. The modulus behavior of the RMB series can be fully explained by this model.     

An explanation of the wetting and the mutual diffusion mechanisms of liquid metals using ab-initio atomic orbital calculation

In this report, in order to clarify fundamentally the wetting phenomenon between pure material surfaces, we propose a new method for the experimental evaluation and consider quantitatively the wetting mechanism from the microscopic standpoint of the chemical reaction between interfacial atoms. Ab-initio molecular orbital calculation was performed to explain the wetting and the mutual diffusion mechanisms. It was found that the calculated binding energies were in good agreement with the interaction energies estimated from measured contact angles, and it was also cleared that the hybridization of the interfacial d-orbitals was one of the most important elements of the mutual diffusion.     

新型压电驱动机构

介绍了所研制的新型压电流体泵、多自由度压电马达、压电超声减摩机构等新型压电驱动机构的基本原理、试验样机的结构及研究现状。     

Dynamic Assembly/Disassembly of Staphylococcus aureus FtsZ Visualized by High-Speed Atomic Force Microscopy

FtsZ is a key protein in bacterial cell division and is assembled into filamentous architectures. FtsZ filaments are thought to regulate bacterial cell division and have been investigated using many types of imaging techniques such as atomic force microscopy (AFM), but the time scale of the method was too long to trace the filament formation process. Development of high-speed AFM enables us to achieve sub-second time resolution and visualize the formation and dissociation process of FtsZ filaments. The analysis of the growth and dissociation rates of the C-terminal truncated FtsZ (FtsZt) filaments indicate the net growth and dissociation of FtsZt filaments in the growth and dissociation conditions, respectively. We also analyzed the curvatures of the full-length FtsZ (FtsZf) and FtsZt filaments, and the comparative analysis indicated the straight-shape preference of the FtsZt filaments than those of FtsZf. These findings provide insights into the fundamental dynamic behavior of FtsZ protofilaments and bacterial cell division.     

水/水乳液的形成、稳定及功能特性研究进展

水/水乳液是一种新型胶体分散体系，目前已成为胶体与界面科学领域的研究热点。本文综述水/水乳液的形成机制、影响因素和特性，归纳总结典型天然高分子的水/水乳液体系；介绍利用颗粒、嵌段聚合物、聚电解质等3种物质稳定水/水乳液的方法，其中，重点介绍颗粒稳定水/水乳液的机理和影响因素，以及水/水乳液在活性物质荷载和淀粉消化中的应用。指出水/水乳液的未来发展方向，特别是应开发更多的食品级水/水乳液体系，以拓展在食品中的应用范围。     

Survey of PCB and organochlorine pesticide residues in meats and processed meat products collected in Osaka, Japan

Residues of PCB and organochlorine pesticides in meats (beef, pork and poultry) and processed meat products collected in Osaka, Japan were surveyed. For 35 years from 1970 to 2004, the concentrations of PCB, HCH isomers, DDT analogues and dieldrin in all meats appeared to decline with each passing year. The concentration of each isomer of HCH in all meats declined rapidly from the early to the late 1970's and showed a gentle decline thereafter; beta-HCH showed the highest residue rate of the isomers in all the time periods surveyed, except for pork and poultry samples in the early 1980's. The concentrations of DDT analogues in all meats also showed sharp declines from the late 1970's to the early 1980's, followed by a smaller decrease thereafter; the main residues were pp'-DDD, p,p'-DDE and p,p'-DDT, and the residue rate of p,p'-DDE increased over the years. The residue levels of organochlorine pesticides in processed meat products (raw materials: beef, pork, poultry and mixture of ground beef and pork) were surveyed for 15 years (from 1990 to 2004) and there were no significant differences in the values among the materials. The concentrations of each pesticide in processed meat products tended to be lower than those of the corresponding meat samples, respectively.     

The gelatinization and retrogradation of cornstarch gels in the presence of citric acid

The effects of citric acid on the gelatinization and retrogradation for 20 wt% cornstarch gels were studied by differential scanning calorimetry (DSC) measurements, uniaxial compression tests and dynamic viscoelastic measurements. The pH value of cornstarch dispersion was adjusted to between 5.0 and 3.0 by adding citric acid. The pH of gels without citric acid (control) was 6.3. The cornstarch gels with pH value adjusted to 3.0 were brittle, while the values of Young’s modulus and dynamic viscoelasticity were higher than those of other samples. It is thought that hydrolysis of amylose and amylopectin chains by adding citric acid occurred and the length of elastically active chains decreased, also leading to the formation of new networks. It was found that when cornstarch gels with added citric acid were stored, they became brittle, but became hard to deform against small deformation. However, when cornstarch gels with or without citric acid were stored for longer time at 5 °C, the retrogradation ratio estimated by thermal analysis was not affected by the presence of citric acid.     

New insight in characterization of red wine astringency using soft tribology method

The variation of friction coefficient (μ) of model wine and model saliva mixtures with entrainment speed (V_R) on simulated oral surfaces was evaluated by oral tribology. Combined with techniques of dynamic light scattering (DLS), atomic force microscopy (AFM), rheometer, and quartz crystal microbalance with dissipation monitoring (QCM-D), the correlation between characteristics of the model wine and model saliva mixtures (particle size and morphology, suspension viscosity, adsorption film thickness, and viscoelasticity) and the oral lubrication loss was established. The results showed that the higher the concentration of tannin in the model wine, the larger the size of the complexes with the model saliva, and the higher the thickness, viscoelasticity, and roughness of the adsorption film formed, which resulted in the increase of friction coefficient in the boundary lubrication regime. Different from previous results, it is found that the maximum value of the friction coefficient (μ_max) in the boundary regime has the best positive correlation with the astringency perception intensity of the model wine accordingly.