Study on Interface between Sub—micron Particles and Matrix in Al2O3p／Al Composites

The microstructural characteristic of 1070Al matrix composites reinforced by 0.15μm Al2O3 particles whose volume fraction was 40% was investigated by TEM and HREM.The results showed that the interface between the matrix and reinforcements was clean and bonded well,without any interfacial reaction products.There were some preferential crystallographic orientation relationships between Al matrix and Al2O3 particle because of the lattice imperfection on the surface of Al2O3 particles.     

High-Speed TDM–WDM Techniques for Long-Haul Submarine Optical Amplifier Systems

Optical amplifier techniques have led to the installation of large-capacity submarine systems and further capacity increases seem likely. This paper reviews the FSA submarine system, which flexibly operates at both 2.5 and 10 Gb/s and offers maximum transmission capacity of 60 Gb/s for commercial use. The system configuration as well as its characteristics and upgradability will be introduced, including measurement results on time-division-multiplexing/wavelength-division-multiplexing (TDM–WDM) transmission at bit rates of 10 and 20 Gb/s using non-return-to-zero or soliton pulses. To further increase transmission capacity, TDM–WDM techniques that permit more than 10 Gb/s signal transmission in each data channel should be developed. Thus, pulse formats, which include non-return-to-zero, return-to-zero, or soliton pulses, and dispersion allocation in transmission fibers are significant issues. We introduce and discuss our recent results from high-speed (10 to 40 Gb/s) TDM–WDM signal transmission experiments with regard to the above aspects.     

Distal surface of the rat ruffle-ended ameloblasts at the stage of enamel maturation observed by scanning electron microscopy

Distal surface of the rat ruffle-ended ameloblasts was observed by high resolution scanning electron microscopy. Specimens fixed by perfusion with 0.5% formaldehyde and 0.5% glutaraldehyde were decalcified with ethylenediamine tetraacetic acid and freeze-fractured using dimethyl sulfoxide. They were treated with 0.1% osmium tetroxide for 96 hr to remove excess cytoplasmic matrices, dehydrated, and critical-point dried. The present method was useful for observing both surface and intracellular structures simultaneously. The dense lamina lining the distal surface of the ruffle-ended ameloblasts having been dissolved in this preparation, the surface was clearly demonstrated in three dimensions under SEM. The surface was characterized by a complex labyrinth formed by protrusion and invagination of the plasma membrane. At high magnification, two kinds of minute granules are visible: small and larger granules measured as 10-20 nm and 70 nm in diameter, respectively. The former were more numerous than the latter. Furthermore, microfibrils connecting the protrusions of the plasma membrane were observed on the distal surface. The small granules probably connect the dense lamina with the distal surface of the ameloblasts. In addition, a denuded area free from the granules was sometimes recognized on the distal surface. These surface structures of the distal end of the ameloblasts appeared to be concerned with the enamel maturation.     

A New Equation for Predicting the Dielectric Constant of a Mixture

The dielectric constant of a compound consisting of two different materials was simulated using the Monte Carlo and finite element methods. In the high concentration range of the higher dielectric constant material, the simulated value of the dielectric constant showed a "parallel-model"-like tendency. On the other hand, in the low concentration range of the higher dielectric constant material, the compound showed a "serial-model"-like behavior. Around 65% content of the higher dielectric constant material, it exhibited results similar to the logarithmic mixing rule. After careful consideration of these results, a new equation to predict the dielectric constant of the compound was derived. The agreement between the dielectric constant calculated by the new equation and the measured values was better than in any other case reported before.     

Surface hydrophilicity and enzymatic hydrolyzability of biodegradable polyesters: 1. effects of alkaline treatment

Surface treatment using alkaline solutions was attempted to enhance the surface hydrophilicity and enzymatic hydrolyzability of hydrophobic poly(L ‐lactide) [ie poly(L ‐lactic acid) (PLLA) and poly(ε‐caprolactone) (PCL). The alkaline treatment was performed by immersing the PLLA and PCL films in 0.01 and 4 N NaOH solutions, respectively, for various periods of time. The effects of the alkaline treatment on the hydrophilicity of the films were monitored by dynamic contact angle measurements, while the enzymatic hydrolyzability of the PLLA and PCL films after the alkaline treatment were evaluated by weight losses in the presence of proteinase K and Rhizopus arrhizus lipase, respectively. With the alkaline treatment the hydrophilicity of the PLLA and PCL films was controllable in the advancing contact angle (θ_a) ranges of 84–108° and of 69–93°, respectively, by varying the alkaline treatment time. The enzymatic hydrolysis rates of the PLLA films became higher with decrease of the θ_a, irrespective of the crystallinity, strongly suggesting that the surface hydrophilicity or the surface molecular weight is crucial to determine their enzymatic hydrolyzability. In contrast, the enzymatic hydrolyzability of the PCL films remained unchanged even when the θ_a decreased from 93° to 73° by alkaline treatment for 4 h. However, prolonged alkaline treatment for periods of time exceeding 4 h, which insignificantly altered the θ_a but caused the formation of pores and cracks on the PCL film surface, accelerated the enzymatic hydrolysis of the PCL films. This indicates that the enzymatic hydrolyzability of the PCL film depends on the surface area per unit weight rather than the surface hydrophilicity. Copyright © 2003 Society of Chemical Industry     

Design and analysis of a mass spectrometer with superimposed magnetic and rotating electric fields

We planned to develop a small and inexpensive measurement device for determination of molecular concentration. The analysis process operates by superimposing a rotating electric field on a magnetic field. When the strength and frequency of the rotating electric field and the mass and speed of the ion are predetermined, the circular radius of the ion's trajectory is fixed. We designed a computer program to simulate ion movement in the electric field and magnetic field. It is possible to calculate the circular movement of the ion in the rotating electric field, and then calculate the circular movement in the superimposed state of the rotating electric field and magnetic field. The magnitude of the mass spectrometer conventionally determines resolution ability. Our definition of resolution is the fraction equal to the distance of separation divided by the distance of the attainment point. The resolution increases gradually at first, and then rises suddenly and dramatically to over 20 times the resolution of that of a spectrometer which does not use a superimposed field. We believe that the theory of ion movement in the rotating electric field and magnetic field could lead to the development of a small and inexpensive analysis machine. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(1): 15–26, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10113     

Solution copolymerization of ethylene with α-olefins by a MgCl2 supported TiCl4 catalyst

Summary Copolymerization of ethylene with -olefins, i.e. propylene, butene-1, 4-methyl-pentene-1(4-MP-1), was carried out by a MgCl₂ supported TiCl₄ catalyst in combination with Et₃Al at a temperature as high as 170 °C at which the polymerization system was homogeneous. This catalytic system showed very a high activity and produced copolymers having a density of 0.91–0.94 g/ml. Of these three kinds of comonomers, propylene showed the highest reactivity and caused most frequently the termination of a polymer growing by chain transfer reaction and produced copolymers having the broadest MWD.     

Studies on propylene polymerization with a highly active MgCl2 supported TiCl4 catalyst system

Summary Propylene polymerization was performed with a highly active MgCl supported TiCl₄ in conjunction with Et₃Al and ethyl benzoate (EB). The obtained polypropylene sample was separated into four fractions by successive extraction with pentane, heptane and trichloroethylene (trichlene). Yield, Mn, Tm and microtacticity of each fraction were determined, and the effects of the concentration of EB on these items of results were investigated. It has been found that EB enhances yield, Mn and stereospecificity of trichlene insoluble (the most stereospecific) fraction, and in contrast, it decreases rapidly yields of other three fractions without changing the character of the polymers. From these findings, the functions of EB to the active centers were discussed.     

NASICON-based solid-electrolyte cell as transducer for enzyme sensors

Enzyme sensors for glucose and uric acid have been developed based on a solid-electrolyte cell using NASICON (Na₃Zr₂Si₂PO₁₂). These potentiometric devices respond reversibly to glucose and uric acid over a concentration range of two orders of magnitude with sensitivities of −54 and −52 mV/decade, respectively. The sensors can be used for a batch-type as well as a flow-through-type measuring system. Primarily the sensors respond to the H₂O₂ that is produced by the enzymatic reactions. The role of the three-phase region, electrolyte solution, sensing electrode metal and NASICON has been investigated. The liquid electrolyte/sensing electrode metal interface is found to work as a potential-determining as well as a rate-determining interface for the enzyme sensor.