Design method of self-expanding stents suitable for the patient's condition

A medical device of mesh-shaped tubular structure, called a stent, is frequently used to expand the stenosis of a blood vessel. The stent normally has the structure of longitudinally repeated wavy wire parts and strut parts, and its mechanical properties, such as bending flexibility and rigidity in the radial direction, mainly depend on the shape of the wavy wire and the construction of the strut. This paper presents, a design support system for self-expanding stents that can design stent shape and evaluate stent performance as routine flow. A two-stage method for designing suitable stent shapes is built into this system. The mechanical properties of self-expandable stents are evaluated using a non-linear finite element method. The wire length of the stent and the wire width are adopted as design parameters, and the sensitivity of the mechanical properties to these parameters is obtained. When the patient's conditions, such as blood vessel type and the diameter of the blood vessel with stenosis, are given by medical examination, the performance of the stent in restoring blood flow has to be determined. Finally, a method is proposed for designing suitable stents with the desired performance on the basis of mechanical properties.     

Single-shot microscopic electron imaging of intense femtosecond laser-produced plasmas

A simple technique for single-shot microscopic electron imaging was demonstrated for the study of intense femtosecond laser-produced plasmas. Passed through a permanent magnet lens designed for 110-keV electrons, hot electrons emitted from the plasma produced by a single laser pulse of 0.8 mJ with intensity of 3 × 10(16) W/cm(2) were successfully imaged. Analyzing this image, we found that electrons were emitted from an area of 3 μm in diameter. At higher laser intensity of 10(18) W/cm(2), distinct structures were observed in and near the focal spot of the laser; that is, the electrons were emitted from several separate spots. These results show that laser-plasma electron imaging is promising for studying the interactions of femtosecond lasers with high-density plasmas.     

Synthesis and application of a silica nanocomposite filler using water glass and a resole‐type phenol resin

Composite plastics in which silica was dispersed homogeneously were prepared from a resole‐type phenol resin and a silica‐sol using water glass. The silica (10–50 nm) was dispersed into resin particles of 2–20 μm in size. The powder that was obtained (nanocomposite filler) and a curing reagent were then mixed, and the resulting mixture was processed by using heat and pressure to yield plastics containing nanocomposite fillers. The coefficients of friction factor of the resulting plastics composites decreased by half and the amount of wear that they suffered decreased to just one tenth of that of the unfilled material, while their wear‐resistance was greatly improved. The new plastics displayed good sliding properties, while also maintaining good fluidity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Asymmetric Half-Wave Plate Configuration of PLC Mach–Zehnder Interferometer for Polarization Insensitive DQPSK Demodulator

We propose a novel polarization dependent frequency shift (PDf) reduction method for fabricating a silica-based PLC DQPSK demodulator incorporating an asymmetrically positioned half-wave plate, and demonstrate error-free 43-Gbit/s demodulation for any incident SOP. The PDf has a detrimental effect on the demodulation performance of a DQPSK signal, and it is degraded by various kinds of PLC fabrication errors. In this paper, we focus on the polarization crosstalk in the coupler, which is one of the main causes of PDf. To eliminate such PDf, we controlled both the position of the half-wave plate in the MZI and the polarization of the propagated light. We describe the principle of this PDf reduction method in detail and provide a theoretical and experimental discussion. In addition, we describe a compact DQPSK demodulator composed of a single MZI based DQPSK demodulator with a 90-degree optical hybrid. This demodulator configuration can reduce the receiver's footprint. Finally we achieved a compact DQPSK demodulator with a low PDf of less than 0.10 GHz in the L-band.     

Reduction of Polarization Dependence of PLC Mach-Zehnder Interferometer Over Wide Wavelength Range

Differential phase shift keying are today considered key solutions for the WDM long-haul transmission infrastructure, and a Mach-Zehnder interferometer (MZI) for its demodulation needs to have very low polarization dependent frequency shift (PDf). MZIs based on silica-based planar lightwave circuits can offer a compact reliable demodulator, but it suffers from a large PDf. In particular, they exhibit a large wavelength dependence on the PDf. It results in a narrow wavelength range where the PDf is sufficiently low, and this limits the operating range of the demodulator. In this paper, we propose a novel method for reducing the PDf over a wide wavelength range. We reveal that the large wavelength dependence of the PDf is due to both the polarization crosstalk of the half-wave plate and the birefringence of the waveguide. Using a mathematical approach, we derived a way to suppress the PDf by controlling the birefringence and the direction of the optic axis of the half-wave plate in the MZI. We confirmed the effectiveness of our proposed method experimentally and achieved a low PDF of < 1% for an FSR of over 140 nm in the wavelength.     

Physical Factors Determining Thermal Conductivities of Isotropic Conductive Adhesives

The thermal conductivities of a typical isotropic conductive adhesive (ICA) composed of an epoxy-based binder containing flake-shaped and spherical Ag particles have been studied. The ICA specimens exhibit anisotropy in their thermal conductivities between the vertical and in-plane directions. In addition, their thermal conductivities apparently depend on their thermal history during the curing and subsequent annealing processes, even if they are fully cured during the preliminary curing stage. The thermal conductivities tend to increase with decreasing electrical resistivities. The experimental values for the thermal conductivities of the ICA specimens were apparently higher than␣those predicted using Bruggemann’s equation. Analysis using the Wiedemann–Franz (W–F) law indicates that their thermal conductivities increase with increasing contribution from electrical conduction. In order to discuss the thermal conductivities of ICA specimens that exhibit relatively low electrical resistivities (below 10⁻³ Ω cm), the contribution of the conducting electrons must be included.     

Effect of Zr on microstructure of metallic glass coatings prepared by gas tunnel type plasma spraying

Metallic glass is one of the most attractive advanced materials, and many researchers have conducted various developmental research works. Metallic glass is expected to be used as a functional material because of its excellent physical and chemical functions such as high strength and high corrosion resistance. However, the application for small size parts has been carried out only in some industrial fields. In order to widen the industrial application fields, a composite material is preferred for the cost performance. In the coating processes of metallic glass with the conventional deposition techniques, there is a difficulty to form thick coatings due to their low deposition rate. Thermal spraying method is one of the potential candidates to produce metallic glass composites. Metallic glass coatings can be applied to the longer parts and therefore the application field can be widened. The gas tunnel plasma spraying is one of the most important technologies for high quality ceramic coating and synthesizing functional materials. As the gas tunnel type plasma jet is superior to the properties of other conventional type plasma jets, this plasma has great possibilities for various applications in thermal processing. In this study, the gas tunnel type plasma spraying was used to form the metallic glass coatings on the stainless-steel substrate. The microstructure and surface morphology of the metallic glass coatings were examined using Fe-based metallic glass powder and Zr-based metallic glass powder as coating material. For the mechanical properties the Vickers hardness was measured on the cross section of both the coatings and the difference between the powders was compared.     

Experimental study on geometric structure of isolated mixing region in impeller agitated vessel

Isolated mixing region in agitated vessel with rotated two-bladed paddle impeller and no baffle was visualized experimentally and its structural property was investigated in detail. A set of thin filaments spirally wrapping around the core of the toroidal isolated mixing region is observed under low Reynolds number conditions, which is smaller than 60. Three-dimensional geometrical structure of filament in isolated mixing region depends on the periodical perturbations caused by the rotating impeller. We have succeeded in the determination of three-dimensional geometrical structure of filament in isolated mixing region based on relation between the movement of fluid particle and filament numbers and/or wire turns. Interestingly, the wire turns of filaments are opposite to movements of fluid particles.     

Controlling the microadsorption structure of porphyrin dye assembly on clay surfaces using the "size-matching rule" for constructing an efficient energy transfer system

The microadsorption structure of two kinds of porphyrin molecules on an anionic clay surface was investigated by photochemical energy transfer reaction. Three procedures were examined for the preparation of the clay/porphyrin complexes: (i) coadsorption (CA) method, (ii) sequential adsorption (SA) method, and (iii) independent adsorption (IA) method as described in the text. Efficient and moderate energy transfer reactions were observed in the CA and SA complexes, respectively. On the contrary, the energy transfer did not occur in the IA complex. These results indicate that the microadsorption structure of the two kinds of porphyrin on the clay mineral surface resulting from the sample preparation methods, affects the energy transfer efficiency. As a result, it was revealed that (i) the adsorbed porphyrins can move on the clay mineral surface but cannot move from one clay surface to another clay sheet, and (ii) the integration structure of two kinds of porphyrin is more stable than the segregation structure in the present system. This unusual structure originated from an extremely strong electrostatic interaction between the porphyrin and the clay mineral as a result of a "size-matching rule". These unique strongly fixed dye assemblies on the clay mineral surface, in which the aggregation and segregation of dyes are suppressed, is very promising and attractive for constructing efficient photochemical reaction systems.     

Suppression of Potential Oscillations in PEFCs by Using Anode Catalyst Prepared by Polygonal Barrel‐Sputtering Method

In this study, we investigated the suppression of potential oscillations that occur while feeding H₂ gas including a large amount of CO to polymer electrolyte fuel cells. A carbon‐supported Pt–Ru alloy (Pt–Ru/C) sample was prepared by the polygonal barrel‐sputtering method. Electrochemical measurement was conducted in 1 N H₂SO₄ electrolyte solution saturated with H₂ gas including CO of 1,000 ppm. From the measurement, it was found that the prepared Pt–Ru/C sample showed higher CO tolerance than a commercially available sample, and therefore, potential oscillations in the case of the prepared sample occurred for slightly longer intervals. Additional samples were prepared by sputtering different amounts of Ru on the prepared Pt–Ru/C sample, and it was observed that the average interval of potential oscillations increased with the amount of Ru. This result suggests that in the case of the polygonal barrel‐sputtering method, Ru plays an important role in suppressing potential oscillations and influences the CO tolerance of Pt–Ru/C.