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Pt is most useful metal for various electrochemical reactions as an electrocatalyst. In a direct methanol fuel cell, Pt performs a catalytic activity for both the methanol oxidation reaction and oxygen reduction reaction; therefore, a Pt-based catalyst is used as an anode and a cathode. For the coexistence of methanol and oxygen due to methanol crossover through an electrolyte membrane during the cell operation, the direct methanol fuel cell performance decreases. However, if a higher selective reaction electrocatalyst can be developed, the cell performance will not be suppressed. In this study, the reaction selectivities of seven types of Pt supported on carbon (Pt/C) electrocatalysts were evaluated using a porous microelectrode in the presence of methanol and oxygen. As a result, some Pt/C catalysts showed a methanol oxidation selectivity, while the other catalysts showed an oxygen reduction selectivity. It was found that the percentage of edge-atom in the Pt particle is related to the methanol oxidation selectivity or the oxygen reduction selectivity. Moreover, each current density decreases with the increasing chemical shift in the Pt binding energy.

Investigating the degradation mechanism of a polymer electrolyte fuel cell (PEFC) is indispensable for realizing a longer-lasting fuel cell. This report describes the research results that the cathode catalyst after a 9000 h cell operation has been removed to evaluate the O2 reduction reaction (ORR) and H2O2 generation amount during the ORR. First, the power generation performance of the prepared PEFC single cell was measured vs. the elapsed time of the long-term test operated at 80 °C at the constant current density of 200 mA cm−2. After the 9000 h operation, the power generation performance was confirmed to decrease. Subsequently, the cathode material containing the Pt–Co/C and the ionomer was removed from the cell and packed into the microcavity of the porous microelectrode (PME). By using the PME, ex situ electrochemical measurements were done in a sulfuric acid solution. The background cyclic voltammogram current of the 9000 h sample was one order of magnitude lower than that of the 0 h sample, suggesting that the electrochemical surface area had decreased. The diffusion-limiting ORR current decreased after the endurance test, however, the Tafel slopes were the same between the two in the same electrode potential region. This revealed that the endurance test does not affect the electron transfer mechanism of the ORR. By using the scanning electrochemical microscopy (SECM), the H2O2 yield assessed for the 9000 h sample at 0–0.7 V vs. RHE during the ORR was found to be 3–4 times higher than that for the 0 h sample. Based on the TEM observation, the high H2O2 yield after the 9000 h operation was considered to be due to the degradation of the ionomer incorporated in the cathode layer with the Pt–Co/C catalyst.

During the O2 reduction reaction (ORR) at the Pt cathode of a polymer electrolyte fuel cell (PEFC), a slight amount of H2O2 is produced as a by-product. The generated H2O2 degrades the polymer electrolyte membrane and Pt electrode due to its corrosive nature. It is reported that a relationship exists between the amount of H2O2 and an amount of ionomer used in an electrocatalyst layer. To clarify the relationship, we employed a Pt microdisk electrode so that the Nafion-coated thickness could be uniformly controlled. The H2O2 amount was then investigated with respect to the overcoated Nafion thickness. The generated H2O2 at the Nafion-coated Pt generator during the ORR is oxidized at a Pt detector of the scanning electrochemical microscope. As a result, the H2O2 detection current increased with the increasing Nafion thickness up to 0.16 μm. The current then decreased in the thicker Nafion region. The H2O2 increase at the thin Nafion/Pt can be explained by a decrease in the number of Pt–Pt pair-sites for the ORR. For the H2O2 decrease in the thicker region, a low diffusion coefficient of H2O2 in the Nafion layer makes it difficult to spread out.

The reaction selectivity of Pt loading carbon electrocatalysts (Pt/C) having different Pt particle sizes was electrochemically evaluated in the presence of methanol and O2. The electrochemical measurement of these electrocatalysts was performed using a porous microelectrode technique without any binder resin. In this study, we found an electrocatalyst which exhibits a reaction selectivity during the competitive reactions of methanol oxidation and O2 reduction. For the Pt/C of O2 reduction, the desired electrocatalyst is required to retain a low Pt loading amount irrespective of Pt particle size. For the methanol oxidation, the electrocatalyst having a Pt particle size around 4 nm is effective.

We report a case of a 59-year-old Japanese man with a black tumor on his right sole with satellite lesions. We diagnosed it as malignant melanoma (pT4aN0M0, stage III) . In December, 1997 he received wide resection and excision of the right inguinal lymph nodes. 3 courses of DAV-Feron chemotherapy were performed. In August, 1991 there was repeated local recurrence of in-transit lesions. We did simple excision and performed chemotherapy. 4 years and 6 months after the operation, the metastases were limited to in-transit lesions and evidence of distant metastasis was not noted. [Skin Cancer (Japan) 2002; 17: 230-233]

Stewart-Treves syndrome is a relatively rare malignant tumor. It develops in chronic lymphedema of the upper extremities after treatment for breast cancer. We report here an additional case of a 55-year-old female.Twenty-two years ago, she was treated with mastectomy and axillary lymph node dissection and radiotherapy for a left breast cancer. After that she had chronic lymphedema of the left upper extremity. One month before admission, she noticed a subcutaneous nodule on left cubital region. A biopsied specimen from the lesion showed angiosarcoma and the cells were positive for CD31 and CD34 immunohistochemically. The patient received a forequarter amputation. But, the tumor cells were found to have invaded to the stump, and she received radiotherapy. She is under careful follow up now. [Skin Cancer (Japan) 2004; 19: 178-180]

dyn/cm in the vicinity of the electrocapillary maximum. Additional electrocapillary curves taken during the scans in Figure 3 are shown in Figure 5. The interfacial tension over the entire potential range is lowered considerably by the presence of dodecylammonium ion, which is expected from its surface active behavior. This is most apparent in the potential region in which dodecylammonium ion transfer is the predominant process, i.e., at approximately -0.75 V vs. the TMA reference electrode. The electrocapillary maximum shifts positively, indicating interfacial adsorption of these cations. This study demonstrates the feasibility of obtaining electrocapillary curves rapidly at the ITIES. Complete 100-point curves were obtained in less than 10 min each, though fewer points and less time are needed to define potential regions of interest. Future work in this area will involve determination of the composition of the interfacial region by measuring (1) charge densities via the dependence of y on potential a t fixed activity and (2) surface excesses via the dependence of y on activity a t fixed potential. These would include not only various alkylammonium ions currently under study and related electroactive species used in liquid membrane ion selective electrodes but also chelates in presence and absence of metal ions in order to determine the role of their interfacial properties in an overall extraction mechanism.

The Huggins constant k′ in the expression for the viscosity of dilute nonelectrolytic polymer solutions, η = η(1 + [η] c + k′[η]2c2 + …), is calculated. For polymers in the theta condition, k′ is estimated to be 0.5 < kθ′ ≤ 0.7. For good solvent systems, the Peterson-Fixman theory of k′ has been modified; the equilibrium radial distribution function in the original theory is replaced with a parametric distribution for interpenetrating macromolecules in the shear force field. Comparison of the modified theory with experimental k′ for polystyrenes and poly(methyl methacrylates) of different molecular weights in various solvents shows good agreement. An empirical equation which correlates the Huggins constant k′ and the viscosity expansion factor αη for polymers has been found to coincide well with the modified theory.