Effect of conditioning method on direct methanol fuel cell performance

We investigated the effect of the conditioning methods on improving the direct methanol fuel cell (DMFC) performance. The DMFC performance after the conditioning was measured using a newly developed single cell having an Ag/Ag₂SO₄ reference electrode, which is not influenced by methanol. As a result, we succeeded in developing an original two-step conditioning method in which the conditioning by fueling H₂ gas is conducted prior to a conventional DMFC conditioning. The anode and cathode characteristics after the two-step conditioning were measured with respect to a reference electrode. Based on the obtained i-E curves, the two-step conditioning is found to improve the methanol oxidation performance at the anode and also suppress the decline of the O₂ reduction performance at the cathode. The high DMFC performance based on the two-step conditioning is well explained by the anode and cathode characteristics.     

Characterization of nanocrystalline indium tin oxide thin films prepared by ion beam sputter deposition method

Indium tin oxide (ITO) thin films were deposited on glass substrates by ion beam sputter deposition method in three different deposition conditions [(i) oxygen (O₂) flow rate varied from 0.05 to 0.20 sccm at a fixed argon (1.65 sccm) flow rate, (ii) Ar flow rate changed from 1.00 to 1.65 sccm at a fixed O₂ (0.05 sccm) flow rate, and (iii) the variable parameter was the deposition time at fixed Ar (1.65 sccm) and O₂ (0.05 sccm) flow rates]. (i) The X-ray diffraction (XRD) patterns show that the ITO films have a preferred orientation along (400) plane; the orientation of ITO film changes from (400) to (222) direction as the O₂ flow rate is increased from 0.05 to 0.20 sccm. The optical transmittance in the visible region increases with increasing O₂ flow rate. The sheet resistance (R_s) of ITO films also increases with increasing O₂ flow rate; it is attributed to the decrease of oxygen vacancies in the ITO film. (ii) The XRD patterns show that the ITO film has a strong preferred orientation along (222) direction. The optical transmittance in the visible spectral region increases with an increase in Ar flow rate. The R_s of ITO films increases with increasing Ar flow rate; it is attributed to the decrease of grain size in the films. (iii) A change in the preferred orientations of ITO films from (400) to (222) was observed with increasing film thickness from 314 to 661 nm. The optical transmittance in the visible spectral region increases after annealing at 200 °C. The R_s of ITO film decreases with the increase of film thickness.     

Development of novel bioactive composites by electrophoretic deposition

Electrophoretic deposition (EPD), which is normally available on electric conductive materials, was applied to insulating materials. Wollastonite particles were deposited into the pores of porous alumina and porous ultrahigh molecular weight polyethylene (UHMWPE) substrates by EPD to yield alumina-wollastonite and UHMWPE-wollastonite composites, respectively. These composites were soaked in simulated body fluid (SBF) to evaluate their apatite-forming ability. Apatite was induced from the wollastonite particles, which grew on the surfaces and covered the entire composite surfaces. The bonding strength of the apatite layer to the substrates was as high as 8.9 MPa for alumina and 5.2 MPa for UHMWPE due to an interlocking effect. Thus, the formed alumina-wollastonite and UHMWPE-wollastonite composites should be useful as bone substitutes.     

Comparative Analysis of Single-Molecule Dynamics of TRPV1 and TRPV4 Channels in Living Cells

TRPV1 and TRPV4, members of the transient receptor potential vanilloid family, are multimodal ion channels activated by various stimuli, including temperature and chemicals. It has been demonstrated that TRPV channels function as tetramers; however, the dynamics of the diffusion, oligomerization, and endocytosis of these channels in living cells are unclear. Here we undertook single-molecule time-lapse imaging of TRPV1 and TRPV4 in HEK 293 cells. Differences were observed between TRPV1 and TRPV4 before and after agonist stimulation. In the resting state, TRPV4 was more likely to form higher-order oligomers within immobile membrane domains than TRPV1. TRPV1 became immobile after capsaicin stimulation, followed by its gradual endocytosis. In contrast, TRPV4 was rapidly internalized upon stimulation with GSK1016790A. The selective loss of immobile higher-order oligomers from the cell surface through endocytosis increased the proportion of the fast-diffusing state for both subtypes. With the increase in the fast state, the association rate constants of TRPV1 and TRPV4 increased, regenerating the higher-order oligomers. Our results provide a possible mechanism for the different rates of endocytosis of TRPV1 and TRPV4 based on the spatial organization of the higher-order structures of the two TRPV channels.     

Development of self-vibration/detection AFM probe using quartz tuning fork

We present a novel type of quartz tuning-fork probe, which oscillates and detects its own probe deformation, for atomic force microscopy (AFM) systems. The quartz tuning-fork structure was fabricated using anisotropic wet etching, and a sharp tip was formed on a beam using a focused ion beam (FIB) system. We evaluated the vibration properties of the fabricated tuning fork with the tip structure in an anti-phase vibration mode and obtained a Q-factor value of 2.5 to 2.8 × 10³. This value was one order larger than that of a conventional Si probe. We experimentally clarified that the tuning-fork probe measured a 100-nm step of the Si surface, as well as the debris with a thickness of a few tens of nanometers on the surface by self-vibration and self-detection in cyclic-contact mode AFM. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Software reliability assessment tool based on object-oriented analysis and its application

In general, the software testing-efforts which are spent in large-scale software development account for a half of the total amount of the development effort. Therefore, the management of fault-detection and fault-correction activities in the testing phase is very important to efficiently and economically develop a highly-reliable software product. In this paper, a software management tool which aids the quality/reliability assessment and testing-progress control in the testing phase is developed. This tool consists of several sub-systems that analyze software fault-detection data and assess software quality/reliability and testing-progress based on adopted software reliability growth models. Also, we use JAVA language to implement the tool. The JAVA language is widely known as an object-oriented and platform-free programming language. These characteristics are suitable for constructing our tool, because the tool will be revised to adopt new software reliability growth models and/or new testing-control techniques. This revised version was published online in June 2006 with corrections to the Cover Date.     

A Numerical Verification Method of Solutions for the Navier-Stokes Equations

A numerical verification method of the solution for the stationary Navier-Stokes equations is described. This method is based on the infinite dimensional fixed point theorem using the Newton-like operator. We present a verification algorithm which generates automatically on a computer a set including the exact solution. Some numerical examples are also discussed.     

Spontaneous Remission of Primary Aldosteronism with Mineralocorticoid Receptor Antagonist Therapy: A Review

In this review, we describe previous basic and clinical studies on autonomous aldosterone production. Over the past decades, mineralocorticoid receptor antagonists (MRAs) have been found to concentration-dependently inhibit steroidogenesis in different degrees. However, many studies have proven the suppressive effects of MRAs on the activities of hormone synthase. The probable factors of cytochrome P-450 reduction, both in microsomes and mitochondria, have also been considered: (1) one of the spironolactone metabolite forms had destructive function, except canrenone, (2) 7α-thio-spironolactone was an obligatory intermediate in the spironolactone-induced CYP450 decrease, and (3) the contributing steroids should have 7α-methylthio or 7α-methylsulfone groups. In previous clinical research, spironolactone-body-containing cells showed a type II pattern of enzyme activity (i.e., enhanced 3β-hydroxysteroid dehydrogenase, glucose-6-phosphate, and NADP-isocitrate dehydrogenase activities and weaken succinate dehydrogenase activity), and the subcapsular micronodules composed of spironolactone-body-containing cells also exhibited a type II pattern and excess aldosterone secretion, indicating that the subcapsular micronodules might be the root of aldosterone-producing adenoma. Moreover, combined with the potential impeditive function to aldosterone secretion, a few cases of spontaneous remission of primary aldosteronism, with normal ranges of blood pressure, plasma potassium, plasma renin activity, and aldosterone renin ratio, have been reported after long-term treatment with MRAs.     

Micromachined pyramidal shaped biodegradable microneedle and its skin penetration capability

A biodegradable pyramidal shaped microneedle array made of hyaluronic acid-based material was fabricated by anisotropic wet etching and a molding process. First, pyramidal shaped needles were fabricated on a Si wafer by anisotropic wet etching as an original master and then a mixture of two biodegradable materials, hyaluronic acid and a collagen, were replicated with the same shape as the original Si needle by a molding process. The height and pitch of the needle were 0.21 and 0.62 mm, respectively. The tip radius in the replicated biodegradable needle became 0.005 mm. The penetration capability of the needle arrays was evaluated by applying the load to skin multiple times. Results showed that both the Si and biodegradable needle arrays could successfully penetrate silicone rubber sheets with the applied load of 100 g. The developed biodegradable needle arrays also successfully penetrated mouse skin with the load of 50 g.