脳由来神経栄養因子（BDNF）を用いた非外科的歯周治療の基礎研究

内容の要約広島大学(Hiroshima University)博士(歯学)Doctor of Philosophy in Dental Sciencedoctora

Particle size and surface texturing effects on friction of magnetorheological fluids

MR fluids are produced by dispersing micron-sized ferrimagnetic particles in oil. Generally, the presence of foreign particles in a lubricant affects the sliding behavior of the lubricated surface. Accordingly, the dispersed particles in MR fluids should significantly affect the lubrication properties of the fluids. In this study, we investigated the lubrication properties of MR fluids through sliding tests and in situ observations, while focusing on the behavior of the dispersed particles. MR fluids containing dispersed particles of various diameters were tested. The results of the sliding tests suggested that the MR fluid with the smallest particles exhibited the best lubrication characteristics. Surface observations showed the presence of grooves on the lubricated surfaces after wear. It is assumed that the grooves are formed by the abrasive action of the dispersed particles and that they affect the behavior of the particles. In situ observations proved that, in the case of flat surfaces, the dispersed particles remained stationary during sliding. On the other hand, in case of grooved surfaces, they moved along the grooves. Given these results, it can be surmised that the grooves on the worn surface changed the behavior of the particles and improved the lubricity of MR fluids

Tribochemical Reactions of Halogen-Free Ionic Liquids on Nascent Steel Surface

Ionic liquids are expected to show applicability as novel lubricants. However, halogen anion-based ionic liquids cause severe corrosive wear. To preclude this, this chapter describes the use of halogen-free anion-based ionic liquids as lubricants. The study investigated the tribological performances and lubricating mechanisms of sulfur, phosphorus, and cyanoanion-based ionic liquids. Sulfur and phosphorus anion-based ionic liquids formed reaction films on worn surfaces; the sulfur- and phosphorus-containing films exhibited low-friction coefficients and specific wear rates, respectively. The steric hindrance of the ionic liquids affected their tribochemical reaction behaviors. Cyanoanion-based ionic liquids also showed low-friction coefficients; however, their values were higher than those of halogen anion-based ionic liquids. To achieve low friction, tribochemical reaction of the ionic liquids and adsorption of anions on the worn surface were required. The stability of the cyanoanion-based ionic liquids against the nascent steel surface was related to the thermal stability. These halogen-free anion-based ionic liquids and formed tribolayer films differ in physical and chemical properties. When these ionic liquids are applied as lubricants in the industry, it is important to choose ionic liquids depending on the sliding conditions

A DEVELOPMENT OF A MUA TO MAKE PICTOGRAPH MAIL FOR CHILDREN

In recent years, children have begun using computers actively. With this situation, they are beginning to learn how to operate a mail user agent (Hereafter, called MUA) to adaptation to an information society. However, the user interface of general MUAs is not designed with them in mind. Specifically, many unnecessary menu items exist on the user interface of general MUAs. Moreover, the menu text contains many difficult characters (called Kanji) in Japan. In this situation, it is difficult to say that children could learn how to operate the MUA without being confused by the complex user interface. We consider it to be important that even children who have not learned Kanji can use the user interface. To solve this issue, we have developed a MUA that has a simple user interface only represented in Hiragana. In order to create a simple user interface for child use, it is necessary to reduce the number of menu items. Along with this, the number of available functions on this MUA has decreased. However, we think it is rather important to prevent the confusion and unexpected behavior of children. It is also necessary to devise a function to make an e-mail to attract the interest of them. Therefore, we have implemented a function to generate pictograph mail easily.We are using the XML-based User Interface Language (Hereafter, called XUL) to build a user interface for children. It is a language used to build the user interface of Mozilla applications like Firefox and Thunderbird. By using it, we can customize the user interface of Thunderbird to fit any purpose. By these improvements, we think children will be able to use the MUA actively and with enjoyment without falling into confusion

Effectiveness of Surface Texturing for Improving the Anti-seizure Property of Copper Alloy

AbstractIt is well known that lead-bronze is widely used in the automotive industry owing to the high anti-seizure property. However, because of toxicity of lead, the automotive industry demands a lead-free copper alloy from the viewpoint of environment. Lead- free copper alloy, which has the anti-seizure property as high as lead-bronze, has not been yet well exploited. For this reason, the objective of this study is to improve the anti-seizure property of lead-free copper alloy using a laser surface texturing (LST). In this study, a ring-on-ring sliding friction tester was used to assess the effectiveness of LST on the anti-seizure property of lead- free copper alloy. The upper specimens were made of FCD700, while the textured bottom specimens were made of PBC2 (lead- free copper alloy). A Daphne Hydraulic Fluid 32 (Idemitsu) paraffinic oil was used as a lubricant. The sliding friction test was conducted with a running-in period for 10min at a load of 50N. Afterwards, the load was increased incrementally from 50N to 1600N, while the friction coefficient was measured simultaneously. The friction test results showed that the textured specimens have a better anti-seizure property compared to the non-textured specimens. Based on the obtained experimental results, it was concluded that the arrangement and area ratio of dimples play an important role in improving the anti-seizure property