Kouji Kawabata

Selective Protein Adsorption Property and Structure of Nano-Crystalline Hydroxy-Carbonate Apatite

The selective protein adsorption property and the local structure around carbonate ions of nanocrystalline hydroxy-carbonate apatite were examined in this study. Considerable change in the selectivity in the adsorption of BSA and β2-MG was observed due to the incorporation of thecarbonate ions in hydroxyapatite lattice. Since the protein adsorption property seems to be related to the surface charge density of hydroxyapatite due to the carbonation, the chemical states of the incorporated carbonate ions were examined by the 31C CP-MAS NMR spectroscopy. At least four peaks assignable to carbonate ions in A-site(OH-) and B-site(PO4 3-) were observed in 13C CP-MAS NMR spectrum. Thus, we must take into consideration that the surface charge distribution and the decrement of polar groups such as OH- groups due to the distribution of carbonate ions in both Aand B-sites of the hydroxyapatite lattice are particularly favorable for β2-MG adsorption rather than for BSA adsorption.

Preparation and Characterization of Boron-Containing Hydroxyapatite

Boron-containing hydroxyapatite (BHAp) particles were synthesized by the wet chemical processing method and subsequent thermal treatment at the temperature ranging from 700-1200°C, and examined the effect of boron introduction on the microstructure of BHAp. The local structure around boron and phosphorus in the BHAp was analyzed by solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The heat-treatment above 700°C induced the thermal decomposition of HAp to β-TCP and then the chemical reaction between HAp and B(OH)3 was induced above 900°C, resulting in the formation of boron-substituted HAp particles accompanied by the formation of β-TCP and its transformation to α-TCP above 1200°C.

NMR Structural Characterization of Mg-Containing Nano-Apatite

Nanometer scale Ca-deficient hydroxyapatite (nanoapatite) is a potential candidate as artificial bone substitute materials owing to its similarity to the bone with respect to composition, morphology and osteoclastic degradation or adsorbent materials for blood purification therapy to remove pathogenic substances. The initial biodegradation behaviors, the initial cell-material interaction and the protein adsorption properties of nanoapatite must depend on the microstructure. The purpose of this study is the preparation of nanoapatite particles and their structural characterization by using X-ray diffraction (XRD) and solid-state NMR spectroscopy. The nanoapatite particles were prepared by precipitation processing method, and the effects of magnesium ions on the precipitation of calcium phosphate were examined, because Mg ions are well-known to play a role of inhibition of crystal growth. The addition of Mg ions led to the precipitation of nanometer scale Ca-deficient apatite crystals having 1.33-1.63 of the molar ratio (Mg+Ca)/P. NMR analyses showed that the microstructure of Mg•HAp particles can be explained by a crystalline HAp core covered with a thin amorphous hydrated calcium phosphate layer.

Synthesis and Characterization of Mg-Containing Nano-Apatite

Nano-crystalline Mg-containing hydroxyapatite (Mg·HAp) were prepared by a wet chemical method, for which selective adsorption of proteins was examined, taking bovine serum albumin (BSA) and a pathogenic protein β2-microglobulin (β2-MG) as the model proteins. Increase in the Mg content led to smaller crystallites and larger specific surface area (SA) of Mg·HAps as well as zeta potential, while the amount both of BSA and β2-MG adsorption on Mg·HAp particles. It is thus concluded that the adsorption of BSA and β2-MG on Mg•HAp was associated with surface charges.

Towards the Visualization of Fuel Cavitation in a Nozzle of a Diesel Engine by Neutron Radiography

Preliminary study on the visualization of fuel cavitation in a nozzle of a Diesel engine by neutron radiography was presented. Various real metallic nozzles of the Diesel engines filled with fuel were visualized by neutron radiography. The fuel and the gas bubbles simulating the cavitation were well visualized. The multiplex exposures method by using a chopper with opening the electrical shutter of a CCD camera was carried out for the visualization of cavitation in a fuel nozzle of a Diesel Engine. Introduction It is supposed that the cavitation occurs inside the nozzle of a Diesel engine. The cavitation affects much on the fuel injection. The visualization of fuel cavitation has been required by the researchers of the Diesel engines. No visualization inside the nozzle of the Diesel engine has been reported. Neutron radiography is suitable for visualizing the fuel behaviors inside the metallic nozzle. Now the gasoline engine is used for many cars. It is said that it will be replaced by the fuel battery or the battery cars except special cars like sports cars in future since the gasoline engines need high quality oil and generate rather much CO2 and CO due to low fuel efficiency. While, it will have been used the Diesel engine for big trucks. Now, the fuel of the Diesel engine is light oil. Biological oils and recycle oils will be used for the Diesel engines in future. As the merits of the Diesel engine, the fuel efficiency is good. The amounts of CO and CO2 are small. The torque is high. Various fuels can be used. As the demerits, the Diesel engine exhausts a lot of NOx and PM (particles of materials). NOx and PM cause serious environmental problems. Therefore, improvement of the fuel injection in Diesel engine is an important engineering project. Cavitation is often called cold boiling. Boiling occurs due to the temperature increase up to the saturation temperature. While, cavitation occurs due to pressure decrease below the saturation pressure. In the fuel nozzle of the Diesel engine, the high pressure fuel (around several hundreds atmospheric pressure) is injected into the engine (around several tens atmospheric pressure). Rapid pressure decrease in the nozzle causes the cavitation and it may affect much on the fuel supply to the engine. Fig.1 shows the inside of the nozzle when it is open and close. The fuel is filled in the hatched area. This needle moves up and down with a revolution numbers of the engine from 600 rpm to 6000 rpm that is from 10ms to 100ms in period. Each area is called the nozzle chamber, the sac chamber and the nozzle hole as shown in the left figure. The conditions of the fuel outside the nozzle have been studied well by optical methods [1], but no one observed the conditions of the fuel Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vols. 270-273, pp 1349-1355 doi:10.4028/www.scientific.net/KEM.270-273.1349