Catalytic dehydrofluorination of CF3CH3(HFC143a) into CF2CH2(HFC1132a)

The catalytic dehydrofluorination of CF₃CH₃ was studied over various metal phosphate catalysts in a fixed-bed reactor. The Mg₂P₂O₇ catalyst exhibited the moderate activity and high selectivity of CF₂CH₂, and it is the most suitable catalyst for the dehydrofluorination of CF₃CH₃. Deactivation did not take place during the 100 h reaction over the Mg₂P₂O₇ catalyst, and XRD patterns of the catalyst were unchanged after 100 h reaction. However, small amounts of F⁻ ions were present on the surface of the catalyst from results of XPS. The active sites for CF₂CH₂ formation are weak acid sites of the catalysts, and carbon deposition and/or polymerization take place on strong acid sites. Results of CF₃CH₃-TPD indicated that the dehydrofluorination proceeds through a

Full-size image

carbonium-ion mechanism over Mg₂P₂O₇ catalyst, and the rate-determining step is the cleavage of the C–F bond.     

Development of a liquid-xenon photon detector--towards the search for a muon rare decay mode at Paul Scherrer Institute

We are developing a new type of photon detector in preparation of an experiment to search for muons decaying into positrons and gamma rays. In the experiment, the photon detector will utilize liquid xenon (Xe) as the scintillation material because of its fast response, large light yield, and high density. The scintillation light emitted in liquid Xe will be observed directly by positioning photomultipliers (PMTs) in the liquid without using a transmission window. In order to determine proper experimental procedures and to study the detector response to gamma rays, we constructed a prototype utilizing a 100 l volume of liquid Xe. The current status and future prospects of detector development are reported in this article.     

Microstructure and elemental distribution of americium-containing uranium plutonium mixed oxide fuel under a short-term irradiation test in a fast reactor

In order to investigate the effect of americium addition in MOX fuel on the irradiation behavior, the ‘Am-1’ program is being conducted in the experimental fast reactor Joyo. The Am-1 program consists of two short-term irradiation tests of 10 min and 24 h irradiations and a steady-state irradiation test. The short-term irradiation tests were successfully completed and the post irradiation examinations (PIEs) are in progress. This paper reports on the results of PIEs for Am-containing MOX fuel irradiated for 10 min. MOX fuel pellets containing 3% or 5% Am were fabricated in a shielded air-tight hot cell using a remote handling technique. The oxygen to metal ratio (O/M) of these fuel pellets was 1.98. They were irradiated at peak linear heating rate of about 43 kW m⁻¹. Focus was being placed on migration behavior of Am during the irradiation. The ceramography results showed that structural changes such as lenticular pores and a central void occurred early, within the brief 10 min of irradiation. The results of electron probe microanalysis revealed that the concentration of Am increased in the vicinity of the central void.     

A pattern classification by dynamic tactile sense information processing

This paper describes pattern classification with an artificial tactile sense. In this method, an object's shape is determined by touching, groping and grasping it with an artificial hand with tactile sense.

A simplified experiment classifying cylinders and square pillars was performed by an artificial hand with on-off switches instead of pressure sensitive elements. Highly reliable results were obtained. In addition, results of a surface groping experiment are given.     

Oxide ion conductivity in La0.8Sr0.2Ga0.8Mg0.2−XNiXO3 perovskite oxide and application for the electrolyte of solid oxide fuel cells

Although hole conduction was present, it was found that doping with Ni was effective in improving the oxide ion conductivity in La_0.8Sr_0.2Ga_0.8Mg_0.2O₃ based perovskite oxides. Considering the ionic transport number and the electrical conductivity, the optimized composition for Ni doped samples was La_0.8Sr_0.2Ga_0.8Mg_0.13Ni_0.07O₃ (LSGMN). In this composition, electrical conductivity was found to be virtually independent of the oxygen partial pressure from 1 to 10^–21 atm. Consequently, the oxide ion conductivity was still dominant in this optimized composition. In agreement with the improved oxide ionic conductivity, the power density of the solid oxide fuel cell using LaGaO₃ as an electrolyte increased by doping with a small amount of Ni on the Ga site. In particular, the power density of 224 mW/cm² at 873 K, which is the maximum power density in the cells using LaGaO₃ based oxide as the electrolyte, was attained using LSGMN in spite of the use of electrolyte plates with a thickness of 0.5 mm. Therefore, LSGMN is highly attractive for the electrolyte material of low temperature operating SOFCs.     

Effects of Organic Sulfur and Phosphor Compounds Used as Antioxidants on the Thermal Behavior of Nitrocellulose and its Decomposition Mechanism

The effects of 3‐dodecylsulfanyl‐propionic acid 3‐(3‐dodecylsulfanyl‐propionyloxy)‐2,2‐bis‐(3‐dodecylsulfanyl‐propionyl‐oxymethyl)‐propyl ester (SO), 3,9‐bis‐octadecyloxy‐2,4,8,10‐tetraoxa‐3,9‐diphospha‐spiro[5,5]undecane (POf), and 3,9‐bis‐(2,6‐di‐tert‐butyl‐4‐methyl‐phenoxy)‐2,4,8,10‐tetraoxa‐3,9‐diphospha‐spiro[5,5]undecane (POp), which are used as antioxidants for polymers, on the degradation of nitrocellulose (NC) were investigated under isothermal storage conditions at 393 K with a microcalorimeter. The result indicated that SO/NC and POf/NC accelerated the heat release when compared with NC without an antioxidant, whereas the heat release behavior of NC/POp was similar to that of NC without an antioxidant. In the case of SO/NC and POf/NC, the heat release was observed in the presence of O₂, whereas it was not observed in a N₂ atmosphere. The SO content in SO/NC and PO content in POf/NC increased with the storage time. According to this behavior, it can be explained that sulfuric acid or phosphoric acid, which originates from SO or POf, accelerates the autoxidation of NC.     

Steam reforming of dimethyl ether promoted by surface protonics in an electric field

The catalytic steam reforming of dimethyl ether (DME) in an electric field was carried out and the effects of proton hopping induced by the electric field on a Pd-supported CeO₂ catalyst surface were investigated. The hydrolysis of DME was promoted even on Pd/CeO₂ catalyst by the application of the electric field at low temperatures (in the range of 423–623 K), while the direct decomposition of DME was suppressed. The apparent activation energy in this temperature range was much lower with (17.2 kJ mol^?1) than without (79.0 kJ mol^?1) the electric field. Kinetic analyses demonstrated that the effect of the reactant partial pressures was also markedly different with and without the electric field. The effect of the partial pressure of water and electrochemical impedance spectra strongly suggest that surface proton hopping promotes the steam reforming of DME in an electric field at low temperatures.     

Automated flow quantification for spin labeling MR imaging

Objective

The Time-Spatial Labeling Inversion Pulse (Time-SLIP) technique enables tracing of regional fluid flows without the use of contrast medium. The objective of this study is to quantify automatically slow and complex fluid flows using the Time-SLIP technique.

Materials and methods

Series images were acquired with a 1.5-T MRI scanner using the Time-SLIP technique with half-Fourier fast spin-echo (FSE) and balanced steady-state free precession (bSSFP) sequences. In this method, labeled fluid regions in images were automatically detected based on image processing techniques for a given point. The flow velocity of the labeled fluid region was calculated using regression fitting for the region’s position. To evaluate our method, constant and non-constant laminar flows in a water phantom were studied. In addition, volunteer experiments were conducted to quantify the flow of cerebrospinal fluid.

Results

In the constant flow experiments the correlation factor r ² between the flow velocity calculated from our method and the laminar peak velocity calculated from the volumetric flow rate was 0.9992 for the FSE sequence and 0.9982 for the bSSFP sequence. In the non-constant flow study, the flow velocity was calculated accurately for any period inversion time even when the flow velocity was changed, and the quantification error was negligible. In the volunteer experiments, r ² between the flow velocity calculated by the proposed method and that obtained by manual annotation was 0.9383.

Conclusion

The experimental results showed that our proposed method can quickly and accurately provide information on flow velocities especially for slower and complex flows. Our method is, therefore, expected to be useful in diagnostic support systems.     

Oxygen non-stoichiometries in (Th0.7Ce0.3)O2−x

Oxygen non-stoichiometry in (Th_0.7Ce_0.3)O_2−x oxide solid solutions was investigated from the viewpoint of Ce reduction. The oxygen non-stoichiometry was experimentally determined by means of thermogravimetric analysis as a function of oxygen potential at 1173, 1273 and 1373 K. Features of the isotherms of oxygen non-stoichiometry in (Th_0.7Ce_0.3)O_2−x similar to those in oxygen non-stoichiometric actinide and lanthanide dioxides were observed. The oxygen non-stoichiometry in (Th_0.7Ce_0.3)O_2−x was compared with those of CeO_2−x and (U_0.7Ce_0.3)O_2−x. It was concluded that the Ce reduction has some relation to defect forms and their transformations in the solid solutions.