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81.
Dynamic mechanical properties were studied for epoxy resin filled with porous silica microballoons with varying surface area, pore radius, pore volume and adsorbed water. The glass transition temperature (Tg) of the composites is 12–14°C lower than the Tg of the unfilled epoxy resin. This Tg depression is attributed to the preferential adsorption of curing agents on the porous silica microballoons. Tg of the composite increases with increase in the adsorbed water on fillers. The storage modulus has a distinct correlation with the Hg-surface area of silica microballoons, which corresponds to the sum of the surface area of pores with radii larger than about 4 nm. Tan δc tan δm decreases with increasing Hg-surface area. 相似文献
82.
Mototsugu Takemoto Mikio Kajiyama Hiroshi Mizumachi Akio Takemura Hirokuni Ono 《应用聚合物科学杂志》2002,83(4):726-735
A series of ethylene vinyl acetate copolymers (EVA) were blended with some tackifier resins that were made from wood extracts, and possible relations between their miscibility and properties as hot‐melt adhesives (HMA) were investigated. From our previous report on miscibility of various EVA‐based HMAs, we chose some blends that represent some of the typical miscibility types and investigated their peel strengths. When the blends were miscible at testing temperatures, the temperature at which the maximum value of peel strength was recorded tended to move toward higher temperature as tackifier content of blends increased. This result corresponds to the storage modulus of the blends whose curves tended to move toward higher temperature as tackifier content of blends increased when blend components were miscible as well as their maximum values of tan δ, or glass transition temperatures. It was characteristic for peel strength that there existed second peaks on peel strengths curves at ~ 100°C, which adhesive tensile strengths for the blends did not have. In terms of relationship between miscibility and HMA performances, we suggest that there are several factors other than miscibility that affect absolute values of peel strength more directly than miscibility; this idea has to be investigated further in the a future study. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 726–735, 2002 相似文献
83.
Wataru Mizutani Masatsugu Shigeno Kazuhiro Saito Naotake Morita Toru Yoshioka Masatoshi Ono Koji Kajimura 《Journal of microscopy》1988,152(2):547-556
As a sample for initial study on biological materials by using scanning tunnelling microscope (STM), we selected phosphoric acid consisting of phosphorous atoms which play biologically an important role. We measured polyphosphoric acid coated on HOPG by STM and scanning tunnelling spectroscopy (STS) in air. In order to identify molecules on STM images, local I-V curves were taken simultaneously. The averaged I-V curves and the normalized conductance spectra of graphite coated with the acid show characteristics different from those of clean graphite surface. Around a step of the substrate, we found domains where normalized conductance spectra were different from those of clean graphite surface and ascribable to that of the adsorbed molecules. 相似文献
84.
85.
Surface polyion complex (sPIC) gels were prepared with a nonionic hydrogel interior core, composed of poly(N‐vinylformamide and poly(N‐vinylacetamide), and a chemically bounded polyion complex layer on the outer surface, composed of poly(vinylamine) and poly(acrylic acid). The gels were investigated as controlled drug release models based on electrostatic interactions depending on pH. Methylene blue and allura red were employed as cationic and anionic drug models, respectively, and resulted in the selective adsorption depending on pH conditions. Monovalent and multivalent anionic drug models, allura red and 1,3,6‐naphthalenetrisulfonate were observed for their releasing behavior from the sPIC gel. The results indicated that the multivalent anionic drug effectively controlled release depending on pH conditions. We further investigated sPIC gels regarding their ability to control the release of ionic molecules as a function of pH‐driven changes in electrostatic interactions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42081. 相似文献
86.
Kandy Napan Dr. Shuwei Zhang Whitney Morgan Thomas Anderson Prof. Dr. Jon Y. Takemoto Prof. Dr. Jixun Zhan 《Chembiochem : a European journal of chemical biology》2014,15(15):2289-2296
Three key tailoring enzymes in pradimicin biosynthesis: PdmJ, PdmW, and PdmN, were investigated. PdmW was characterized as the C‐6 hydroxylase by structural characterization of the corresponding product, 6‐hydroxy‐G‐2A. The efficiencies of the C‐5 and C‐6 hydroxylations, catalyzed respectively by PdmJ and PdmW, were low when they were expressed individually with the early biosynthetic enzymes that form G‐2A. When these two cytochrome P450 enzymes were co‐expressed, a dihydroxylated product, 5,6‐dihydroxy‐G‐2A, was efficiently produced, indicating that these two enzymes work synergistically in pradimicin biosynthesis. Heterologously expressed PdmN in Streptomyces coelicolor CH999 converted G‐2A to JX137a by ligating a unit of D ‐alanine to the carboxyl group. PdmN has relaxed substrate specificity toward both amino acid donors and acceptors. Through combinatorial biosynthesis, a series of new pradimicin analogues were produced. 相似文献
87.
Toshiyuki Kawai Mitsuru Takemoto Shunsuke Fujibayashi Masashi Neo Haruhiko Akiyama Seiji Yamaguchi Deepak K. Pattanayak Tomiharu Matsushita Takashi Nakamura Tadashi Kokubo 《Journal of materials science. Materials in medicine》2012,23(12):2981-2992
The effects of surface treatment on the bone-bonding properties of Ti metal were examined by both mechanical detaching test and histological observation after implantation into rabbit tibiae for various periods ranging from?4 to?26?weeks. The bone-bonding ability of Ti metal, which is extremely low as it is abraded, was hardly increased by simple heat treatment at 600?°C or treatment with H2SO4/HCl mixed acid alone, but was markedly increased by the heat treatment after the acid treatment. Even Ti metal that had been previously subjected to NaOH treatment showed considerably high bone-bonding ability after acid and heat treatments. Such high bonding abilities were attributed to their high apatite-forming ability in the body environment. Their high apatite-forming abilities were attributed to a high positive surface charge, and not to the type of crystalline phase or specific roughness of their surfaces. The present study has demonstrated that acid and subsequent heat treatments are effective for conferring stable fixation properties on Ti metal implants. 相似文献
88.
Li-Ngee Ho Hiroshi Nishikawa Naohide Natsume Tadashi Takemoto Koichi Miyake Masakazu Fujita Koyu Ota 《Journal of Electronic Materials》2010,39(1):115-123
The properties of electrically conductive adhesives (ECAs) filled with Cu and Cu alloy fillers (with alloy elements Ag, Ge,
Mg, and Zn) were investigated in terms of electrical conductivity, thermal stability, and the effects of the trace alloy elements
on the oxidation resistance of the metallic fillers. Oxidation of metallic fillers under high-temperature exposure at 125°C
was considered as the main reason that led to degradation of electrical conductivity in the ECAs. Cu fillers alloyed with
a trace amount of Ag and Mg, respectively, had significant effects on the electrical conductivity and thermal stability of
the ECAs as the electrical resistivity was substantially suppressed and a consistently high electrical conductivity could
be maintained even after aging for 1000 h at 125°C. 相似文献
89.
Masatsugu Yaguchi Takashi OgataTakayuki Sakai 《International Journal of Pressure Vessels and Piping》2010
Internal pressure creep tests as well as uniaxial creep tests were conducted on 9Cr and 12Cr steels welded joints in order to evaluate creep strength of the high chromium steels welded parts under multiaxial stress conditions, where a welding direction of the internal pressure specimen was longitudinal one. Except under high stress conditions, cracks occurred at fine grained HAZ region for both materials, i.e., the type IV mode fracture. Regarding creep voids distribution along thickness direction of the internal pressure specimens, the creep voids were predominantly observed in the middle of the thickness at the HAZ region while they might be negligible in outer and inner surface of the specimen. Finite element analysis which considers HAZ and weld metal properties revealed that the principal stress (hoop stress) and the stress multiaxiality are the largest in the middle of the thickness at the HAZ region under the internal pressure creep conditions. It was suggested that the creep voids remarkably occurred inside the specimens at the HAZ region due to the severe stress state conditions. 相似文献
90.
Significance of saturated clays seams for the stability of rainfall-induced landslides 总被引:2,自引:0,他引:2
Hideki Ohta Thirapong Pipatpongsa Sokbil Heng Seiya Yokota Masaru Takemoto 《Bulletin of Engineering Geology and the Environment》2010,69(1):71-87
This paper reviews the analyses of several slope failures in Japan associated with clay seams and assesses the significance
of ground water level. Constant-volume shear box tests were used to obtain the strength parameters. The research considered
the significance of capillary forces in the clay mass in the development of a laboratory-established cohesion. It was concluded
that the laboratory-obtained apparent cohesion may not be applicable in actual site conditions and that a more realistic value
can be obtained using submerged/saturated samples in the constant-volume direct shear test. The practical implications of
this are demonstrated with a review of the Guinsaugon rockslide, South Leyte, Philippines. 相似文献