Measurement of the radial temperature distribution in the central part of an arc burning through a polyethylene tube

The radial temperature distributions in the central part of arcs burning through polyethylene (PE) tubes are estimated by measuring the half-width of Hα line spectrum and using the electron density versus Stark half-width and the electron density versus temperature characteristics. Estimation is carried out for various tube inner diameters (2 and 4 mm) and dc arc currents (5, 10 and 15 A). The result shows that the temperature at the arc center is around 10,000 K, and it tends to increase as the tube inner diameter becomes narrow and/or the arc current increases. The overall temperature distributions from the arc axis to the tube wall are obtained by combining these inner temperature distributions with outer temperature distributions which have been derived from C₂ spectra. They are found to take a form of typical two-temperature distributions of ablation stabilized arcs. The electric field strengths of PE arcs are evaluated from the temperature distributions and the electrical conductivity versus temperature characteristics of thermally decomposed polyethylene vapor gas. The results agree well with experimental values.     

Structures and catalytic behavior of some niobium oxides

On niobium oxide catalysts, induction period was observed during 1-butene isomerizatlon, because surface strong adsorption sites for 1-butene existed. With sodium-loading on Nb₂O₅/Al₂O₃, new and weak basic sites such as Nb-O-Na-OH were formed. Nb₂O₅ supported on TlO₂ functioned as a sensor for oxygen and nitrogen monoxide.     

Integrated self-scanning light-emitting device (SLED)

The fabrication of monolithically integrated self-scanning light-emitting device (SLED) on a GaAs substrate and its performance are described. The SLED consists of integrated light-emitting thyristors whose turn-on voltages interact with each other through coupling diodes or resistors. Light-emitting states are automatically transferred by input clock pulses without using external shift registers. The resistors are made of a Cr-SiO cermet film, and the coupling diodes are made in part with p-n layers of thyristors. The integrated SLED is fabricated in eight photolithographic steps. High-speed operation, more than 10 MHz, can be achieved due to its simple structure and high-density packaging. It is expected that this SLED will be a key device in future large-scale optoelectronic integrated circuits     

MR of childhood-onset dentatorubral-pallidoluysian atrophy

MR findings in a 14-year-old boy with progressive myoclonic epilepsy, who was diagnosed as having dentatorubral-pallidoluysian atrophy by DNA analysis, were compared with those of his father, who had adult-onset dentatorubral-pallidoluysian atrophy. Besides showing severe brain atrophy, especially of the brain stem tegmentum and cerebellum, MR showed diffuse periventricular hyperintensity on T2-weighted images. As compared with the proband, the father had a mild case.     

Formation of CuxMo6S8−y thin film on an MoS2 substrate by a chemical transport technique

Thin films of Cu_xMo₆S_8?y were produced by transport of a gaseous copper compound onto an MoS₂ substrate by using a chemical transport technique. The films with thichness of about 10 to 30 μm were always grown on the substrate, and it was found that the thickness of the film may be estimated by that of the initial MoS₂ substrate. The micro-structure of the films was investigated by using both the x-ray diffraction and the scanning electron microscope techniques. It was found that the Cu_xMo₆S_8?y lattice growth preferred the hexagonal c-axis direction on the substrate. The copper content of the bulk specimen was determined by the atomic absorption method and the gradient of copper composition in the film was investigated by the electron probe micro-analysis. No concetration gradient of copper was observed within the product film.     

3.0 ps switching operation in all-Nb Josephson logic gates

A high-speed logic delay of 3.0 ps/gate in a resistor-coupled Josephson logic (RCL) gate chain is attained using a new Nb Josephson integrated circuit technology. Lift-off, Nb stress control and planarisation techniques are used for fabricating high-quality Nb/AlOx/Nb trilayer junctions and reliable Nb wiring. Pd, which is stable during etching, is used as a resistor material.     

The paramagnon model and some properties of superfluid 3He

The paramagnon model for the BCS-type state of superfluid ³He is applied to calculate the following properties in the ABM and BW states: the pressure dependence of the initial slope of the normalized superfluid mass density vs. 1 – T/T _c; the pressure dependence of the normalized specific heat jump at T _c; and the temperature dependence of the superfluid mass density at P = 20.7 and 27.6 bar. We also calculate the temperature dependence of the normalized nuclear spin susceptibility in the BW state. We compare our results with the experimental data on the A and B phases of superfluid ³He.Supported in part by grant No. A4630 of the National Research Council of Canada.For a preliminary version of this work see Ref. 1.On leave from the Institute for Solid State Physics, University of Tokyo, Roppongi, Tokyo, Japan.     

Porous properties of poly(glycidyl methacrylate‐co‐trimethylolpropane trimethacrylate) resins synthesized by suspension polymerization

Porous copolymer beads of 2,3‐epoxypropyl methacrylate (glycidyl methacrylate, GMA) crosslinked with 2‐ethyl‐2‐(hydroxymethyl)‐propan‐1,3‐diol trimethacrylate (trimethylolpropane trimethacrylate, TRIM) were prepared with toluene and octan‐2‐one as porogens by suspension polymerization. With an increase in the ratio of porogen to monomer, the total pore volume of poly(GMA‐co‐TRIM) increases significantly, whereas the surface area hardly changes. The total pore volume also depends on the nature of the porogen, exhibiting a maximum at the larger GMA contents in the monomer mixture of 50% v/v with octan‐2‐one and of 60% v/v with toluene, compared to that at the GMA content of 25% v/v with a 9/1 v/v mixture of cyclohexanol and dodecan‐1‐ol [Verweij, P. D.; Sherrington, D. C. J Mater Chem 1991, 1 (3), 371]. The surface area decreases significantly with an increase in the ratio of GMA to TRIM, almost regardless of the nature of the porogen. The porous properties of poly(GMA‐co‐TRIM) was well explained on the basis of phase separation, particularly taking into account not only the solubility parameters of the resulting polymer network and porogen but also the rigidity of TRIM. The porous poly(GMA‐co‐TRIM) may be a promising polymer matrix of novel materials for separation of boron isotopes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2374–2381, 2002