Novel method for site-controlled surface nanodot fabrication by ion beam synthesis

By using a Ga FIB system to spatially control the implantation of Ga into SiO(2) followed by vacuum annealing, we have fabricated self-assembled surface Ga nanodots with a high degree of control of nucleation location. The morphology of the Ga nanodots is closely related to Ga dose, showing a critical dose needed for nucleation that results in Ga nanodot formation just below the surface, while at higher doses Ga nanodots form on the surface as metallic Ga droplets. Possible applications include defining nucleation sites for subsequent growth, use as Ga source for GaN or GaAs quantum dots, or as catalyst for nanowire growth.     

Abnormal activation of lipoprotein lipase by non-equilibrating apoC-II: further evidence for the presence of non-equilibrating pools of apolipoproteins C-II and C-III in plasma lipoproteins

Using artificial triglyceride emulsions, we have demonstrated the presence of non-equilibrating pools of apolipoproteins C-II and C-III in human plasma lipoproteins. As the concentrations of acceptor triglycerides were increased, a greater fraction of both apoC-II and apoC-III shifted away from the native plasma lipoproteins to the artificial lipid emulsions. All of the apoC-II and apoC-III in very low density and high density lipoproteins (VLDL and HDL), however, could not be removed from native plasma lipoproteins. The percent of total plasma apoC-II and apoC-III that could be recovered in the VLDL and HDL density fractions varied when plasma from different individuals was used. When plasma samples from normotriglyceridemic subjects were used, HDL was the primary donor of apoCs. The percent of total plasma apoCs associated with HDL decreased from 60% to 25% for apoC-II and from 65% to 15% for apoC-III. When plasma samples from hypertriglyceridemic subjects were incubated with artificial lipid emulsions, VLDL was the primary donor of apoCs. HDL from hypertriglyceridemic subjects only accounted for 5-10% of total fasting plasma apoCs and did not contribute significantly to the final apoC contents of the artificial triglyceride emulsions. To evaluate the significance of the depletion of exchangeable apoCs from plasma HDL, we also examined the ability of control and apoC-depleted HDL to serve as activator for bovine milk lipoprotein lipase (LPL) in vitro. When HDL depleted of exchangeable apoCs were used as the source of plasma apolipoproteins for the activation of LPL in vitro, only 5-10% of the maximal activity obtained with native HDL was demonstrated. In fact, in the presence of comparable concentrations of HDL apoC-II, activation of LPL was the least with HDL which lacked exchangeable apoCs. Our data thus indicated that the presence of exchangeable apoC-II on HDL is necessary for the activation of LPL in vitro. This finding is consistent with our data that suggest that HDL from hypertriglyceridemic subjects do not stimulate LPL as well as HDL from normolipidemic subjects.     

Effect of a hepatocyte growth factor/heparin-immobilized collagen system on albumin synthesis and spheroid formation by hepatocytes

A hepatocyte growth factor (HGF)/heparin-immobilized collagen system was used as a synthetic extracellular matrix for hepatocyte culture. The albumin synthesis, nucleus numbers and morphology of the hepatocytes were determined separately to evaluate the hepatocyte number and hepatocyte-specific function under this system. The benefits of the HGF/heparin-immobilized collagen system for hepatocyte culture were confirmed by three types of culture methods in vitro, namely 2D film cultures, 2D gel cultures and 3D gel cultures. In 2D collagen film cultures, hepatocytes exhibited the highest albumin synthesis (1.42 μg/well/day) in HGF/heparin-immobilized collagen films at 7 days of culture. Heparin inhibited hepatocyte adhesion while HGF promoted hepatocyte migration, and spheroid formation was easily detected in HGF/heparin-immobilized collagen films. In 2D collagen gel cultures, albumin synthesis of around 15 μg/well/day was detected and maintained for more than 18 days on HGF/heparin-immobilized collagen gels. Similar findings were obtained in 3D HGF/heparin-immobilized collagen gel cultures, which exhibited albumin synthesis of up to 30 μg/well/day. The albumin synthesis by hepatocytes was two-fold higher in 3D gel cultures compared with 2D gel cultures, and was maintained for over 2 weeks compared with 2D film cultures using the HGF/heparin-immobilized collagen system. Taken together, the HGF/heparin-immobilized collagen system was effective for albumin synthesis by hepatocytes in both 2D film cultures and 3D gel cultures, and therefore shows good potential for tissue engineering use.     

Hydrolysis of Cellulose Selectively into Glucose Over Sulfonated Activated-Carbon Catalyst Under Hydrothermal Conditions

A sulfonated activated-carbon (AC-SO₃H) catalyst selectively hydrolyzes cellulose with β-1,4-glycosidic bonds into glucose in the catalytic hydrothermal reactions at temperatures around 423 K. The AC-SO₃H catalyst with the hydrothermal pre-treatment has the excellent catalytic properties attributed to the high hydrothermal stability and the strong acid sites of sulfo functional groups.     

Flow characteristics of a small moving bed downcomer with an orifice under negative pressure gradient

Behaviour of gas-solid mixtures in a small moving bed downcomer operating under negative pressure gradient has been investigated experimentally, because flow characteristics in a downcomer are important factors in powder handling processes, such as a multi-stage spouted bed or a circulating fluidized bed. In this study, a small downcomer in which the moving bed height could be controlled was employed with the intention of using a downcomer as a connecting tube in a multi-stage spouted bed. Based on experimental observation, the moving bed flow changed from smooth flow (Region(I)) to slip-stick flow (Region(II)) and then changed from slip-stick flow to intermittent flow (Regime(III)), as the gas pressure gradient in the downcomer was increased. In this study, the critical point for steady-state (Region(I)) operation was also examined experimentally and theoretically, by using eight kinds of solid particles (Geldart B, D and A powders) and six different orifice sizes which were used to restrict solids flow at the base of the downcomer. As a result, a correlation of solids flow rate in the stable moving bed downcomer under negative pressure gradient was derived and the critical point between stable and unstable flow was explained by the proposed model.     

The selective thermal cis-trans isomerization of 1,2-diphenylsulfonyl ethylene in the presence of carbon dioxide

The selective isomerization of cis-1,2-diphenylsulfonyl ethylene to trans-1,2-diphenylsulfonyl ethylene proceeded in supercritical carbon dioxide above 393 K without an addition of catalyst. The product yield increased with increasing temperature and was almost constant against carbon dioxide density. The 73% of product yield was obtained at 493 K and 10 MPa of carbon dioxide pressure for 60 min. The product yield obtained in supercritical carbon dioxide was larger than those obtained in organic solvents. The supercritical carbon dioxide was a dilute solvent compared with organic solvent, which probably reduced the suppression of the reaction by dense solvent. Further, only cis-sulfonyl ethylenes isomerized among several cis-ethylene derivatives. The sulfonyl group played an important role for the isomerization.     

Effect of gamma radiolysis on pit initiation of zircaloy-2 in water containing sea salt

In spent fuel pools at the Fukushima Daiichi Nuclear Power Station (1F), seawater was injected for cooling purposes after the tsunami disaster in March 2011. It is well known that the chloride in the seawater has the potential to cause localized corrosion (e.g., pitting corrosion) in metals. In this study, we evaluated the pitting potentials of zircaloy-2, the material used in the fuel cladding tubes in 1F, as a function of chloride concentration. To accomplish this, we used artificial seawater under gamma-ray irradiation and investigated the effect of radiolysis on pit initiation of zircaloy-2 in water containing sea salt. Changes in the composition of water containing sea salt were analyzed as well, both before and after gamma-ray irradiation. The characteristics of the resultant oxide films formed on zircaloy-2 were evaluated by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The experimental results showed that the pitting potential under irradiation was slightly higher than that under conditions in which no radiation was present, and that the pitting potential decreased with increasing chloride concentration in the presence as well as the absence of radiation. Solution analyses for water containing sea salt showed that hydrogen peroxide was generated by irradiation. The oxide film was composed of zirconium oxide and was made thicker during the irradiation. The higher pitting potential could thus be explained by the capacity of hydrogen peroxide to oxidize the surface and enhance oxide film formation. Under gamma-ray irradiation, the zircaloy-2 surface with an oxide film formed by radiolysis products was found to be resistant to pitting in the presence of chloride.     

Identification of plant model of linear induction motors for a traction system intended for use in a high‐performance controller

A linear induction motor (LIM) is suitable for use in trains. The motor can be used in both wheel‐suspended and contact‐less types such as the Linear Metro and HSST trains in Japan. The LIM has end winding as well as asymmetrical winding. The end effect is a major problem in the LIM, and it makes the analysis, design, and control of motors difficult. This paper describes a method that combines numerical analysis and the equivalent circuit for the LIM in order to design a high‐performance controller for the LIM that includes the end effect. A sample basic field‐oriented control scheme that is based on the plant model is applied to the LIM in order to check the control performance. The theory of rotary induction motors is used for verification. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(2): 44–54, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21171     

Thermal degradation characteristics of oil‐filled cable joint with extremely degraded tan δ oil

Much of oil‐filled (OF) cable has been used for a long time as 66‐ to 500‐kV extrahigh‐voltage cable. Sometimes we can see extremely degraded tan δ oil (several tens of percent of tan δ, for example) in joint boxes, etc. The values of tan δ calculated by a simple combination model of paper/oil show that the oil‐impregnated paper with such a high tan δ oil likewise has an extremely high tan δ, which must result in thermal breakdown. However, such an event has not taken place up to the present in actually operated transmission lines. This fact suggests that some mechanism for the suppression of tan δ has acted in the paper insulation impregnated with degraded tan δ oil. Therefore, we investigated in detail the tan δ characteristics of paper impregnated with extremely high tan δ oil. In addition, based on the investigation results, we developed a method for simulation of heat generation by dielectric loss in an OF cable joint (which has degraded tan δ oil). © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(1): 1–10, 2012; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21184