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Kobayashi, Y.,Sato, M.,Taguchi, H.,Koike, S.,Nakatsuji, H.,Tanaka, K. Asian Australasian Association of Animal Productio 2004 Animal Bioscience Vol.17 No.3
Seventy-six animals including cattle, sheep, horses, 6 species of zoo animals were employed for collection of fresh feces in order to detect verotoxigenic Esherichia coli (VTEC) by safe, quick and sensitive PCR-based molecular methods. Bacterial cell disruption with bead-beating followed by bacterial DNA purification with hydroxyapatide chromatography and gel filtration allowed DNA preparation from animal feces with high recovery and purity. A mountain goat was firstly shown by PCR and sequencing to shed verotoxin 2 gene (vt2) that was used to generate vt2 probe and second primer set for nested PCR to attempt more sensitive detection. Most sensitive nested PCR revealed that 45% of tested cattle and 47% of tested zoo animals were VTEC-positive, while least sensitive normal PCR detected VTEC from none of these animals except a mountain goat. Moderately sensitive detection by PCR in combination with hybridization suggested that the VTEC density varied between the VTEC-positive cattle.
Kobayashi, Koichi,Suzuki, Masato,Dung, Le Anh,Yun, Hyun-do,Rokugo, Keitetsu Elsevier 2018 Construction and Building Materials Vol.178 No.-
<P><B>Abstract</B></P> <P>SHCC mixtures with various water cement ratios and different types of fiber (PVA and PE) were tested with an aim to clarify the properties of cracked SHCC. After examining the mechanical performances of the composites, chloride penetration and rebar corrosion tests were conducted on cracked SHCC specimens.</P> <P>PE fiber, PVA fiber, and a mixture of PE and PVA were added in SHCC. Part of the cement was replaced with limestone powder in some mixtures to vary the water cement ratio of the mortar matrix. For SHCC mixtures containing PVA fiber, which has lower strength and Young's modulus, the water cement ratio had to be increased to obtain a strain hardening property. The chloride penetration test revealed that chloride could penetrate into SHCC through fine cracks and that the width of the fine cracks had no bearing on the amount of chloride accumulated in the crack fracture surfaces. On the other hand, chloride penetration through cracks into the mortar matrix was affected by the number of cracks and water cement ratio. As a result, the corrosion area on rebar in cracked SHCC was also largely dependent on the number of cracks and water cement ratio. However, the corrosion area was smaller than that of ordinary mortar. When the strain is in a small range, the corrosion prevention performances of PE-SHCC and PVA-SHCC were more or less the same.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Rebar corrosion protection performances of cracked SHCCs were investigated. </LI> <LI> Chloride penetration through cracks into SHCC was affected by the number of cracks. </LI> <LI> It was also affected by W/C of mortar matrix. </LI> <LI> The corrosion prevention performances of PE-SHCC and PVA-SHCC were comparable. </LI> <LI> Even SHCC with low ductility can enhance the durability of RC structures. </LI> </UL> </P>
Self-assembly of Fine Particles Applied to the Production of Antireflective Surfaces
Kobayashi, Hayato,Moronuki, Nobuyuki,Kaneko, Arata Korean Society for Precision Engineering 2008 International Journal of Precision Engineering and Vol.9 No.1
We introduce a new fabrication process for antireflective structured surfaces. A 4-inch silicon wafer was dipped in a suspension of 300-nm-diameter silica particles dispersed in a toluene solution. When the wafer was drawn out of the suspension, a hexagonally packed monolayer structure of particles self-assembled on almost the complete wafer surface. Due to the simple process, this could be applied to micro- and nano-patterning. The self-assembled silica particles worked as a mask for the subsequent reactive ion etching. An array of nanometer-sized pits could be fabricated since the regions that correspond to the small gaps between particles were selectively etched off. As etching progressed, the pits became deeper and combined with neighboring pits due to side-etching to produce an array of cone-like structures. We investigated the effect of etching conditions on antireflection properties, and the optimum shape was a nano-cone with height and spacing of 500 nm and 300 nm, respectively. This nano-structured surface was prepared on a $30\;{\times}\;10-mm$ area. The reflectivity of the surface was reduced 97% for wavelengths in the range 400-700 nm.
Synthesis of metallic copper nanoparticles and metal-metal bonding process using them
Kobayashi, Yoshio,Nakazawa, Hiroaki,Maeda, Takafumi,Yasuda, Yusuke,Morita, Toshiaki Techno-Press 2017 Advances in nano research Vol.5 No.4
Metallic copper nanoparticles were synthesised by reduction of copper ions in aqueous solution, and metal-metal bonding by using the nanoparticles was studied. A colloid solution of metallic copper nanoparticles was prepared by mixing an aqueous solution of $CuCl_2$ (0.01 M) and an aqueous solution of hydrazine (reductant) (0.2-1.0 M) in the presence of 0.0005 M of citric acid and 0.005 M of n-hexadecyltrimethylammonium bromide (stabilizers) at reduction temperature of $30-80^{\circ}C$. Copper-particle size varied (in the range of ca. 80-165 nm) with varying hydrazine concentration and reduction temperature. These dependences of particle size are explained by changes in number of metallic-copper-particle nuclei (determined by reduction rate) and changes in collision frequency of particles (based on movement of particles in accordance with temperature). The main component in the nanoparticles is metallic copper, and the metallic-copper particles are polycrystalline. Metallic-copper discs were successfully bonded by annealing at $400^{\circ}C$ and pressure of 1.2 MPa for 5 min in hydrogen gas with the help of the metalli-ccopper particles. Shear strength of the bonded copper discs was then measured. Dependences of shear strength on hydrazine concentration and reduction temperature were explained in terms of progress state of reduction, amount of impurity and particle size. Highest shear strength of 40.0 MPa was recorded for a colloid solution prepared at hydrazine concentration of 0.8 M and reduction temperature of $50^{\circ}C$.