Simultaneous Measurements of an Ultrasound and a Torsional Oscillator for 4He in a Nanoporous Glass

Previously, we carried out ultrasonic measurements for liquid ⁴He filled in a nanoporous glass (Gelsil), and observed an increase in the sound velocity due to decoupling of the superfluid component. At zero pressure, the superfluid transition temperature T _C is suppressed to 1.4 K from the bulk lambda point, 2.17 K. This behavior is the same as torsional oscillator measurements by Yamamoto et al. (Phys. Rev. Lett. 93:075302, 2004). However, the pressure dependence of T _C and the temperature dependence of the superfluid fraction are very different from the torsional oscillator measurements. In order to clarify the origin of the difference, we have developed a new technique of simultaneous measurement of an ultrasound and a torsional oscillator, and the system successfully works for a nanoporous glass. Here, we compare decoupling of the superfluid component for ⁴He films between an ultrasound and a torsional oscillator.     

The Effects of Conventional Stabilizers and Phenol Compounds Used as Antioxidants on the Stabilization of Nitrocellulose

The thermal behavior of nitrocellulose (NC) containing diphenylamine (DPA), 2‐nitrodiphenylamine (2‐NO₂‐DPA), N‐nitrosodiphenylamine (N‐NO‐DPA), ethyl centralite (EC), akardite II (AKII), 1,1,3‐tri‐(2‐methyl‐4‐hydroxy‐5‐tert‐butyl‐phenyl)‐butane (BP_less), 3‐(3,5‐di‐tert‐butyl‐4‐hydroxy‐phenyl)‐propionic acid octadecyl ester (BP_hin), and 3‐(3‐tert‐butyl‐4‐hydroxy‐5‐methyl‐phenyl)‐propionic acid 2‐(9‐{2‐[3‐(3‐tert‐butyl‐4‐hydroxy‐5‐methyl‐phenyl)‐propionyloxy]‐1,1‐dimethyl‐ethyl}‐2,4,8,10‐tetraoxa‐spiro [5.5] undec‐3‐yl)‐2‐methyl‐propyl ester (BP_semi) was observed during isothermal storage at 393 K using a C80 microcalorimeter. The results indicate that each stabilizer decreased NC's maximum heat release rate and increased the induction period of heat release. We also observed that the maximum heat release rate and the induction period were dependent on the amount of stabilizer. DPA decreased the maximum heat release rate to the greatest extent, with the other stabilizers having similar effects on the decrease of maximum heat release rate. AKII prolonged the induction period of heat release most. The order of prolongation of the induction period was AKII>2‐NO₂‐DPA≈DPA>N‐NO‐DPA≈EC>BP_less≈BP_semi≈BP_hin.     

Identification of Pseudozyma graminicola CBS 10092 as a producer of glycolipid biosurfactants, mannosylerythritol lipids

A basidiomycetous yeast, Pseudozyma graminicola CBS 10092, was found to accumulate a large amount of glycolipids in the cultured medium when grown on soybean oil as the sole carbon source. Based on thin layer chromatography, the extracellular glycolipids gave spots corresponding to those of mannosylerythritol lipids (MELs), which are highly functional and promising biosurfactants. From the structural characterization by 1H and 13C NMR, the main product was identified as 4-O-[(4'-mono-O-acetyl-2', 3'-di-O-alka(e)noyl)-beta-D-mannopyranosyl]-D-erythritol, which is a highly hydrophilic derivative of MELs known as MEL-C. According to high-performance liquid chromatography analysis, the main product, MEL-C, comprised approximately 85% of all the MELs, and the total amount reached approximately 10 g/L for 7 days. The fatty acids of the present MEL-C consisted of mainly C6, C8 and C14 acids, considerably different from those of MEL-C produced by other Pseudozyma strains such as P. antarctica and P. shanxiensis. The observed critical micelle concentration (CMC) and the surface-tension at CMC of the MEL-C were 4.0 x 10(-6) M and 24.2 mN/m, respectively, while those of MEL-A, the most intensively studied MEL, were 2.7 x 10(-6) M and 28.4 mN/m, respectively. This implied that the MEL-C has higher hydrophilicity than conventional MELs hitherto reported. In addition, on a water-penetration scan, the MEL-C efficiently formed the lamella phase (Lalpha) at a wide range of concentrations, indicating its excellent self-assembling properties. From these results, the newly identified MELs produced by P. graminicola are likely to have great potential for use in oil-in-water type emulsifiers and/or washing detergents, and would thus facilitate a broad range of applications for the promising yeast biosurfactants.     

Synthesis and electronic property of platinum nanowire and nanoparticle in mesoporous silica template

Platinum nanowires and nanoparticles were selectively synthesized in mesoporous silicas FSM-16 and HMM-1. The nanowires are 3 nm in diameter and several hundred nm to μm in length with high crystallinity. Pt nanowires and nanoparticles can be isolated by dissolving silica matrix with HF. The Pt wires extracted from organosilica HMM-1 have a nanonecklace structure, while the wires from siliceous FSM-16 have a nanorod structure. The extracted Pt nanoparticles (3 nm in size) on HOPG show the Coulomb staircase phenomena in STM/STS analysis. The mechanism for formation of the Pt nanowires is based on the migration of Pt ions in the mesoporous channels.     

New application of laser beam to failure analysis of LSI with multi-metal layers

A new technique for failure analysis of LSI with multi metal layers is described. There is a fabrication technique to form a big and optional window on upper layers using Nd-YAG laser without destroying any electrical function, and to approach the failure point through this window. The failure analysis procedure based on logical flow is presented. Fabrication technique is located in part of this procedure which consists of four steps. Two difficult reasons for approaching the failure point without fabrication technique are described. This difficulty results from line composition and line width. The fabrication procedure using Nd-YAG laser is reported. This procedure is to cover the chip surface with photo resist, and form a big and optional size window on upper layer with laser beam, and finally expose the purposed layer. Three failure analysis examples using this technique are introduced: unformed contact falure mode, Si-noduled failure mode, and isolation destroying failure mode.     

Electrical conductivity and domain structure in ferroelastic Tl2SeO4

We have carried out the optical observation, electrical conductivity and ²⁰⁵Tl NMR measurements, and subsequently investigated the origin of the large conductivity above ferroelastic phase transition temperature T_c (=661 K) on the basis of the domain structure and the crystal structure. Electrical conductivity exhibits the discontinuous increase around T_c with increasing temperature and becomes approximately 5 × 10⁻³ S m⁻¹ above T_c. Moreover, from the ²⁰⁵Tl NMR measurements, it is found that mobile Tl ions exist above T_c. Furthermore, from the analysis of the domain structure based on the crystal structure in the low-temperature ferroelastic phase, it is also found that the anomalously large fluctuations of SeO₄ tetrahedrons exist above T_c. It is deduced from these results that the high electrical conductivity above T_c is caused by the mobile Tl ions closely related to the anomalously large fluctuations of SeO₄ tetrahedrons accompanied by the ferroelastic phase transition.     

A simple and fast method to disperse long single-walled carbon nanotubes introducing few defects

A simple and fast dispersion method that incorporates heating is used to disperse long (more than 10 μm) single-walled carbon nanotubes (SWCNTs) with minimal defects. The method enables a dispersed solution of SWCNTs to be produced in less than 10 min in only three steps: (1) addition of the dispersant, (2) heating, and (3) grinding. The dispersion method does not require sonication, which shortens the SWCNTs and can generate surface defects. SWCNT films were prepared from the dispersed solution, and the films exhibited a resistance of 380 Ω/sq at a transparency of 64.8%. This dispersion method can be easily scaled up, making it useful for the preparation of dispersed SWCNTs for commercial and industrial applications.     

Remarkable enhancement in durability of Pd/H-ZSM-5 zeolite catalysts for CH4-SCR

Effect of second components on the catalytic performance of Pd/H-ZSM-5 zeolite (Pd: 0.4 wt.%) was evaluated by a durability test of NO reduction with CH₄ at a relatively high temperature of 500°C in the presence of water vapor for a prolonged period. The Pd/H-ZSM-5 showed high stable activity for this reaction without H₂O in the reactant feed, while immediate and irreversible deactivation was observed in the presence of H₂O, resulting in no activity after 7 h. The second components such as Co, Rh, Ag, Ce, and Fe introduced individually to the Pd/H-ZSM-5 enhanced the durability, and in particular the addition of 3.3 wt.% Co led to a stable NO conversion for more than 40 h in the presence of H₂O.     

Mixing mechanism of three‐tip kneading block in twin screw extruders

In recent years, twin screw extruders have been applied to various kinds of polymer processing. It has been important to find their optimum geometrical configurations and operational processing conditions for the best performance of extrusions and products. Many engineers have been evolving numerical and the experimental methods to characterize the mixing performance for twin screw extruders. We have carried out three‐dimensional flow simulations of kneading blocks in intermeshing co‐rotating twin screw extruders by using the finite element method to quantify their ability in distributive and dispersive mixing. We discuss their performance in distributive mixing for three different type of kneading blocks in terms of the residence time distribution and the nearest distance between markers at various periods of time, by using the marker tracking method. Those numerical techniques and applications of mixing indices have enabled us to quantify and evaluate their abilities in distributive mixing of kneading blocks in twin screw extruders.     

Effect of sweep gas species on tritium release behavior from lithium titanate packed bed during 14 MeV neutron irradiation

In a fusion reactor, the prediction of tritium release behavior from breeder blanket is important to design the tritium recovery system, but the amount of tritium generated is necessary information to do that. Hence, tritium generation and recovery studies on lithium ceramics packed bed have been started by using fusion neutron source (FNS) in Japan Atomic Energy Agency (JAEA). Lithium titanate (Li₂TiO₃) was selected as tritium breeding material, and its packed bed was enclosed by the beryllium blocks, and was kept at certain temperature during fusion neutron irradiation. During irradiation, the packed bed was purged with the sweep gas continuously, and tritium released was trapped in each gas absorber selectively by chemical form. In this work, the effect of sweep gas species on tritium release behavior was investigated. In the case of sweep by helium with 1% of hydrogen, tritium in water form was released sensitively corresponding to the irradiation. This is due to existence of the water vapor in the sweep gas. On the other hand, in the case of sweep by helium without water vapor, tritium in gaseous form was released first, and release of tritium in water form was delayed from gaseous tritium and was gradually increased.