Characterization and electrochemical properties of CF4 plasma-treated boron-doped diamond surfaces

The effect of CF₄ plasma etching on diamond surfaces, with respect to treatment time, was investigated using scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. SEM observations and Raman spectra indicated an increase in surface roughening on a scale of 10–20 nm, and an increase in crystal defect density was apparent with treatment time in the range of 10 s to 30 min. In contrast, alteration of the diamond surface terminations from oxygen to fluorine was found to be rather rapid, with saturation of the F/C atomic ratio estimated from XPS analysis after treatment durations of 1 min and more. The redox kinetics of Fe(CN)₆^3−/4− was also found to be significantly modified after 10 s of CF₄ plasma treatment. This behavior shows that C–F terminations predominantly affect the redox kinetics compared to the effect on the surface roughness and crystal defects. The double-layer capacitance (C_dl) of the electrolyte/CF₄ plasma-treated boron-doped diamond interface was found to show a minimum value at 1 min of treatment. These results indicate that a short-duration CF₄ plasma treatment is effective for the fabrication of fluorine-terminated diamond surfaces without undesirable surface damage.     

High-efficiency finishing process for metal mold by large-area electron beam irradiation

A new finishing process for metal molds by large-area electron beam (EB) irradiation is proposed in this study. In the large-area EB irradiation equipment used here, an EB with high-energy density is irradiated without focusing the beam, and so the EB with a maximum diameter of 60 mm can be used for melting or evaporating metal surface instantly. Experimental results show that the surface roughness decreases from 6 μmRz to less than 1 μmRz in just a few minutes under proper machining conditions. The corrosion resistance of metal mold surface also could be greatly improved by large-area EB irradiation. Furthermore, the surface roughness of tilting surface close to 90° could be well improved. Therefore, large-area EB irradiation method has a possibility to become a high-efficiency finishing process for metal molds.     

Synthesis of metal nitrides and carbide powders by a spark discharge method in liquid media

Metal nitrides and carbides powders were synthesized by the spark discharge method in liquid ammonia at 100 °C and 11 kV of the spark discharge voltage and in n-heptane at 25 °C and 7.5 kV using the pellets of aluminum, titanium, iron and chromium as the starting material. The main products were AlN, TiN_0.51, -Fe, -Cr₂N in liquid ammonia, and Al₄C₃, TiC, -Fe, Fe₂C and Cr₇C₃ in n-heptane. The agglomerated particle size decreased with increasing melting point of the metal used as the starting material.     

Residual amounts of chlorophylls and pheophytins in refined edible oils

The quantities of chlorophyll (CHL) A and B, and pheophytin (PHY) A and B in 10 kinds of refined edible oils were estimated by the fluorometric method. The results revealed that CHL and PHY were present in commercial edible oils. PHY A showed the highest content at ca. 67% in total pigments. Compositional ratios of CHL and PHY were similar in different kinds of plant oils. Through the analysis of rapessed oils at every refining step, we determined that PHY is not formed during oil refining. In the autoxidation of soybean oils to which various amounts of CHL mixtures had been added, the peroxide value of tested oils increased in proportion to the total chlorophyll content. In addition, the compositional changes of the 4 components during autoxidation were investigated.     

Antioxidant effects of chlorophyll and pheophytin on the autoxidation of oils in the dark. I. Comparison of the inhibitory effects

The effects of chlorophyll and pheophytin on the autoxidation of oils in the dark were investigated by oven tests. The results indicated that both chlorophyll and pheophytin show antioxidant activity when methyl linoleate is used as substrate. Furthermore, chlorophyll retarded the oxidative deterioration of triglycerides in rapeseed and soybean oils at 30 C. Among the four chlorophyll derivatives (chlorophylls a and b and pheophytins a and b), chlorophyll a showed the strongest antioxidant activity. The antioxidant effects of chlorophyll and pheophytin depended on the storage temperature and the kinds of oil used as substrate.     

Antioxidant effects of chlorophyll and pheophytin on the autoxidation of oils in the dark. II. The mechanism of antioxidative action of chlorophyll

To understand the mechanism of the antioxidant effect of chlorophyll on the autoxidation of oils in the dark, antioxidant activities of several derivatives of chlorophyll were compared. Antioxidant activities were observed in chlorophyll derivatives such as protopor-phyrin methyl ester and its magnesium chelated compound. Porphyrin seems to be an essential chemical structure for the antioxidant activity of chlorophyll. Chlorophyll did not decompose the hydroperoxides, but reduced free radicals such as 1,1-diphenyl-2-picrylhydrazyl. Electron spin resonance spectrum of the π-cation radical was recorded during the oxidation of chlorophyll in methyl linoleate solution. These observations suggest that chlorophyll may act as a hydrogen donor to break the chain reaction.     

A variational approach to multi-phase motion of gas, liquid and solid based on the level set method

We propose a simple and robust numerical algorithm to deal with multi-phase motion of gas, liquid and solid based on the level set method [S. Osher, J.A. Sethian, Front propagating with curvature-dependent speed: Algorithms based on Hamilton-Jacobi formulation, J. Comput. Phys. 79 (1988) 12; M. Sussman, P. Smereka, S. Osher, A level set approach for capturing solution to incompressible two-phase flow, J. Comput. Phys. 114 (1994) 146; J.A. Sethian, Level Set Methods and Fast Marching Methods, Cambridge University Press, 1999; S. Osher, R. Fedkiw, Level Set Methods and Dynamics Implicit Surface, Applied Mathematical Sciences, vol. 153, Springer, 2003]. In Eulerian framework, to simulate interaction between a moving solid object and an interfacial flow, we need to define at least two functions (level set functions) to distinguish three materials. In such simulations, in general two functions overlap and/or disagree due to numerical errors such as numerical diffusion. In this paper, we resolved the problem using the idea of the active contour model [M. Kass, A. Witkin, D. Terzopoulos, Snakes: active contour models, International Journal of Computer Vision 1 (1988) 321; V. Caselles, R. Kimmel, G. Sapiro, Geodesic active contours, International Journal of Computer Vision 22 (1997) 61; G. Sapiro, Geometric Partial Differential Equations and Image Analysis, Cambridge University Press, 2001; R. Kimmel, Numerical Geometry of Images: Theory, Algorithms, and Applications, Springer-Verlag, 2003] introduced in the field of image processing.     

Buoyancy engine developed for underwater gliders

A buoyancy engine with a swashplate-type axial piston pump was developed. Its oil extrusion and drawing properties under high hydraulic pressure were evaluated. This buoyancy engine is now installed in an underwater glider that will achieve long-term monitoring of ocean environments up to 2100 m depth in a designated area with lower operational costs. This bidirectionally functioning pump can control the amount of oil in extrusion and draw operations. When drawing oil under high pressure, the hydraulic pump and the electric motor, respectively, act as a hydraulic motor and an electric generator. The generated electric power is absorbed by a damping resistor. The oil-drawing and extrusion properties were measured using a large hyperbaric chamber that is able to produce an almost identical environment to that of actual operations. Results confirmed stable oil extrusion operations up to 21 MPa. Regarding oil-drawing properties, although it was measured only up to 10 MPa in the hyperbaric chamber, it can be inferred that the system can draw the oil and can control the buoyancy precisely up to 21 MPa by replacing the two-way ball valve with an electromagnetic latching solenoid valve.     

Compact electrostatic levitator for diffraction measurements with a two axis diffractometer and a laboratory x-ray source

A compact electrostatic levitator was developed for the structural analysis of high-temperature liquids by x-ray diffraction methods. The size of the levitator was 200 mm in diameter and 200 mm in height and can be set up on a two axis diffractometer with a laboratory x-ray source, which is very convenient in performing structural measurements of high-temperature liquids. In particular, since the laboratory x-ray source allows a great amount of user time, preliminary or challenging experiments can be performed with trial and error, which prepares and complements synchrotron x-ray experiments. The present small apparatus also provides the advantage of portability and facility of setting. To demonstrate the capability of this electrostatic levitator, the static structure factors of alumina and silicon samples in their liquid phases were successfully measured.     

Further study on different dopings into PbWO4 single crystals to increase the scintillation light yield

Since we presented our preliminary result (Nucl. Instr. and Meth. A 486 (2002) 170) at SCINT2001, we have continued our efforts to increase the light yield (LY) of PbWO₄ scintillators by extending different dopings with an aim to find a possibility of using PbWO₄ successfully in Positron Emission Tomography (PET). Overall result obtained for single doping as well as double and tripple co-dopings are summarized, including decay characteristics and radiation hardness. The LY in non-doped PbWO₄ crystals with a size of 10×10×(20–30) mm³ is 25–35 photolectrons/MeV (phe/MeV) corresponding to 3–4% of the LY in BGO, when measured with a bialkali photomultiplier during a gate of 1 μs. The maximum LY increased to 49 phe/MeV for single doping with Mo⁶⁺, 80 phe/MeV for double co-doping of Mo⁶⁺+Sb⁵⁺, and 85 phe/MeV for tripple co-doping of Mo⁶⁺+Cd²⁺+Sb⁵⁺. The radiation hardness is larger than 10⁵ Gy for each of the samples co-doped with Mo⁶⁺+Sb⁵⁺ and Mo⁶⁺+Cd²⁺+Sb⁵⁺, while it is much poorer in PWO:Mo⁶⁺. In each of these co-doped samples, a medium-speed green emission in the microsecond range is created besides the fundamental fast (a few nanoseconds range) blue one, giving a peak at 500 nm in the radioluminescence spectrum similarly as in PWO:Mo⁶⁺.