Antibacterial effect of nanometer-size grafted layer of quaternary ammonium polymer on poly(ether ether ketone) substrate

Owing to its excellent physicochemical properties, poly(ether ether ketone) (PEEK) has been used clinically for medical implants. However, its surface properties should be improved to further enhance its compatibility with a living organism and infection resistance. Here, we examined the surface construction via a combined process, that is, the self-initiated photoinduced graft polymerization of N,N-dimethylaminoethyl methacrylate (DMA) on PEEK substrate followed by polymer quaternization using various bromoalkanes (Q-PDMA-g-PEEK). Using a Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, the grafting and quaternarization of poly(DMA) (PDMA) on the PEEK substrate was confirmed. The degree of quaternizations was at least 60% even when the various bromoalkanes were reacted. The Q-PDMA-g-PEEK with 1-bromooctane (BrC₈) (C₈-Q-PDMA-g-PEEK) substrate exhibited the highest ζ-potential of other Q-PDMA-g-PEEK substrates. However, no significant differences were observed in the degree of quaternization, thickness of the polymer layer, and hydrophilicity of all modified PEEK substrates. In addition, from antibacterial test with Escherichia coli, the C₈Q-PDMA-g-PEEK substrate exhibited the highest antibacterial rate (80%) among Q-PDMA-g-PEEK substrates examined. Therefore, we concluded that the surface ζ-potential is the one an important parameter for manufacturing PEEK substrates with bactericidal properties.     

Influence of Cu on nanostructure of Fe3O 4 particles

Cu is effective on the refinement of Fe₃O₄ rust particles but its mechanism is not clarified. In this study, the influence of Cu on the nanostructure of Fe₃O₄ particles was investigated through a detailed analysis of the characteristics of the artificially synthesized Fe₃O₄ particles formed with Cu²⁺ by various means. X‐ray absorption fine structure analysis showed that Cu is substituted for octahedral Fe and exists as Cu_xFe_(3‐x)O₄ in Fe₃O₄. The first‐principle calculation showed that lattice strain resulted around the substituted Cu. These results suggest that this lattice strain around substituted Cu inhibited the lattice growth and contributed to the refinement of Fe₃O₄ particles.     

Electrochemical and structural characterization of carbon-supported Pt-Pd bimetallic electrocatalysts prepared by electroless deposition

Electrochemical and structural characteristics of various Pt-Pd/C bimetallic catalysts prepared by electroless deposition (ED) methods have been investigated. Structural analysis was conducted by X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy (EDS). Monometallic Pt or Pd particles were not detected by EDS, indicating the ED methodology formed only bimetallic particles. The size of the Pt-Pd bimetallic particles was smaller than those of a commercially available Pt/C catalyst. The morphology of the Pt on Pd/C catalysts was identified and corresponded to Pd particles partially encapsulated by Pt.The electrochemical characteristics of the lowest Pd loading catalyst (7.0% Pt on 0.5% Pd/C) for the oxygen reduction reaction (ORR) have been investigated by the rotating ring disk electrode technique. The electrochemical activity was equal or lower than the commercially available Pt/C catalyst; however, the amount of hydrogen peroxide observed at the ring was reduced by the Pd, suggesting that such a catalyst has the potential to decrease ionomer degradation in applications. The Pt on Pd/C catalysts also show a higher tolerance to ripening induced by potential cycling. Therefore, catalyst suitability cannot be judged solely by its initial performance; information related to specific degradation mechanisms is also needed for a more complete assessment.     

Impact of Ground‐State Charge Transfer and Polarization Energy Change on Energy Band Offsets at Donor/Acceptor Interface in Organic Photovoltaics

The fullerene (C₆₀)/copper phthalocyanine (CuPc) interface is one of the widely used donor/acceptor (DA) interfaces for organic photovoltaics (OPVs), and information on the electronic structure at the interface is essential for fully understanding the energetics of excitons and carriers in OPVs. Here, an investigation into the energy levels at the C₆₀/CuPc interface is made using UV photoelectron, X‐ray photoelectron, and inverse photoemission spectroscopies. The vacuum level and core levels rise with C₆₀ deposition on the CuPc film, which indicates that the interfacial dipole is formed with the negative charge on the C₆₀ side. The interfacial dipole can be formed by the electron transfer from CuPc to C₆₀ in the ground state at the interface, which is indicated by the analysis of the UV–vis–NIR absorption spectrum of the CuPc/C₆₀ blended film. On the other hand, the highest occupied and lowest unoccupied molecular orbitals of CuPc and C₆₀ shift in opposite directions at the interface. This is attributed to the changes of the polarization energies of CuPc and C₆₀ at the interface. The formation of the interfacial dipole and the change of the polarization energy result in the anomalous energy band offsets at the C₆₀/CuPc interface, which are entirely different from those in inorganic p–n junctions.     

Development of porous plug phase separator and superfluid film flow suppression system for the Soft X-ray Spectrometer onboard ASTRO-H

ASTRO-H is the sixth Japanese astronomy satellite scheduled for launch in 2014. The Soft X-ray Spectrometer instrument is onboard ASTRO-H. This is a 6 × 6 array of X-ray microcalorimeters with an energy resolution of <7 eV at 0.5–10 keV. Superfluid liquid helium is utilized as a part of the cooling system. To retain the liquid helium in the tank under zero-gravity, a porous plug phase separator made of sintered stainless is used. Since the vapor mass flow rate is only 29 μg/s, any additional superfluid film loss influences the lifetime of the liquid helium. Therefore, a film flow suppression system consisting of an orifice, a heat exchanger, and knife edge devices is adopted based on the design used for the X-ray Spectrometer onboard Suzaku. The film flow will be suppressed to <2 μg/s, sufficiently smaller than the vapor flow rate. In the present investigation, the design and ground experiments of a helium vent system composed of the porous plug and film flow suppression system are presented. The results show that the phase separation and the film flow suppression are satisfactorily achieved.     

Fabricating transparent waveguide for wireless communication

The high frequency characteristics of hybrid structures made from indium tin oxide (ITO) films and very fine gold (Au) lines were theoretically and experimentally investigated to develop invisible coplanar waveguide (CPW) structures for microwave and millimeter-wave applications. After optimizing the Au/ITO hybrid structures, we achieved fabrication of an invisible CPW structure showing both high transmission and low reflection characteristics in the GHz range. Electromagnetic simulations by using a finite elements method explained the reason for the improved characteristics of the optimized Au/ITO hybrid CPW.     

Experimental and numerical studies of portable PEMFC stack

The objective of this work is to establish the design principles of a proton exchange membrane (PEM) fuel cell (FC) stack for portable applications. A combination of experiments and numerical simulations were carried out and the results analyzed to enhance understanding of the behavior of this portable PEMFC stack. A three-dimensional (3D) computational fluid dynamics (CFD)-based methodology was used to predict such as the current and temperature distributions of this portable PEMFC stack. The results show how the baseline operation and original design of this stack impact the local temperature, water content, water transport, and kinetic variables inside the individual cells. The outcome of this work will pursue the development of universal heuristics and dimensionless numbers correlated to portable PEMFC stack design.     

利用LC自动进样器来降低样品过载

本文介绍了一种新型自动进样器,能够将收集到的样品直接进样到色谱柱,而不用任何流路转换装置或额外的管路连接。除了需要常规自动进样器的六通切换阀,还设计了一个直接进样阀（DIV）用于自动进样器。六通阀和DIV的同步协调运行使得建立一个简单的样品流路和连续流体经过分离柱的系统成为可能。这种自动进样器的结构具有减小样品引入造成的谱带展宽和防止样品过载的特点。     

An analysis of reliability in the early stages of photovoltaic systems in Japan

In order to disseminate Photovoltaic (PV) technologies into the energy network, the cost down is not only important, but also improving the performance of the PV system is significant issues. Long‐term reliability is one of the most important issues in terms of PV system performance. Previous researches were mainly focused on the reliability of PV modules, but the PV system is composed of a power conditioner, wiring, junction box, and so on. To improve the reliability of PV systems, it is important to accumulate trouble cases focused on all components of PV system. In this paper, we aim at evaluation of the reliability for the PV system on the early stages of PV system's lifetime by using large number of Japanese PV systems' data from the field Test in Japan. New Energy and Industrial Technology Development Organization has been running the “Field test project in Japan” from 1992. In this project, PV system users have cooperated with the collection of monitoring data and reported on the information of maintenance and certain failures of PV systems for 4 years after installation of PV system. Using those reports each year of installation, we evaluated reliability of PV systems by means of parameters such as Mean Time Between Failure, Mean Time To Repair, and the suspension time of PV system. As a result, the main trouble of PV systems was related power conditioner, and a few trouble of PV module was caused by typhoon. Moreover, the trend of the failure rate before FY 2000 of installation was demonstrated as the trend of initial failure in “bathtub curve;” however, the trend of its after FY 2001 of installation was indicated as the accidental failure in “bathtub curve.” Further, the operator simply forgot to restart the power conditioner after maintenance or suspensions of PV system in many trouble cases, and the user did not notice that it had been suspended for a while. These trouble cases can be avoidable easily through the effective alarm such as error message of power conditioner systems with monitoring systems. Thereby, monitoring with the evaluation method of PV systems is one of the important technologies due to the long‐term reliability and stable operation. Copyright © 2010 John Wiley & Sons, Ltd.