Microstructure Investigation of Polymer Electrolyte Fuel Cell Catalyst Layers Containing Perfluorosulfonated Ionomer.

Perfluorosulfonated ionomers are the most successful ion-exchange membranes at an industrial scale. One recent, cutting-edge application of perfluorosulfonated ionomers is in polymer electrolyte fuel cells (PEFCs). In PEFCs, the ionomers are used as a component of the catalyst layer (CL) in addition to functioning as a proton-exchange membrane. In this study, the microstructures in the CLs of PEFCs were characterized by combined synchrotron X-ray scattering and transmission electron microscopy (TEM) analyses. The CL comprised a catalyst, a support, and an ionomer. Fractal dimensional analysis of the combined ultrasmall- and small-angle X-ray scattering profiles indicated that the carbon-black-supported Pt catalyst (Pt/CB) surface was covered with the ionomer in the CL. Anomalous X-ray scattering revealed that the Pt catalyst nanoparticles on the carbon surfaces were aggregated in the CLs. These findings are consistent with the ionomer/catalyst microstructures and ionomer coverage on the Pt/CB surface obtained from TEM observations.

Impact of the Composition of Alcohol/Water Dispersion on the Proton Transport and Morphology of Cast Perfluorinated Sulfonic Acid Ionomer Thin Films.

The dispersion of perfluorinated sulfonic acid ionomers in catalyst inks is an important factor that controls the performance of catalyst layers in membrane electrode assemblies of polymer electrolyte fuel cells. Herein, the effects of water/alcohol compositions on the morphological properties and proton transport are examined by grazing incidence small-angle X-ray scattering, grazing incidence wide-angle X-ray scattering, and electrochemical impedance spectroscopy. The thin films cast by a high water/alcohol ratio Nafion dispersion have high proton conductivity and well-defined hydrophilic/hydrophobic phase separation, which indicates that the proton conductivity and morphology of the Nafion thin films are strongly influenced by the state of dispersion. This finding is expected to further understand the morphology and proton transport properties of Nafion thin films with different water/alcohol ratios, which has implications for the performance of the Pt/Nafion interface.

Morphology Changes in Perfluorosulfonated Ionomer from Thickness and Thermal Treatment Conditions.

The morphological changes of Nafion thin films with thicknesses from 10 to 200 nm on Pt substrate with various annealing histories (unannealed to 240 °C) were systematically investigated using grazing incidence small-angle X-ray scattering (GISAXS) and grazing incidence wide-angle X-ray scattering (GIWAXS). The results revealed that the hydrophilic ionic domain and hydrophobic backbone in Nafion thin films changed significantly when the annealing treatment exceeded the cluster transition temperature, which decreased proton conductivity, due to the constrained hydrophilic/hydrophobic phase separation, and increased the crystalline-rich domain. This research contributed to the understanding of ionomer thermal stability in the catalyst layer, which is subjected to thermal annealing during the hot-pressing process.

Triboelectric charging of polytetrafluoroethylene antithrombotic catheters.

This study proposes that a polytetrafluoroethylene (PTFE) electret tube charged by frictional electricity can prevent the solidification of the indwelling catheter in blood vessels. Coagulation in intravascular indwelling catheters may discontinue the treatment because of thrombus-derived bacteria-adhesion infections or poor blood removal. Current commercially available intravascular catheters lack complete antithrombotic measures, even with heparin or urokinase antithrombotic coatings. Herein, we tested the effectiveness of an antithrombotic treatment that prevents coagulation using a static electric charge on the interior of the PTFE tube via the triboelectric effect by rubbing the tube's inner wall with a round glass rod. The anticoagulation properties were evaluated by enclosing a sample of blood in an electret tube and observing the coagulase adhering to the inner wall using a microscope. To confirm the effectiveness of this treatment, the charge-distribution on the inner surface of the electret tube was measured, surface irregularities were observed, and the elements on the surface were analyzed. The surface potential inside the electret tube was - 366.4 V, which proved effective for an antithrombotic treatment, as it discouraged coagulation, and the triboelectric charging process caused neither surface element denaturation nor significant surface irregularities. The nearly uniform negative surface charge on the inside of the tube was responsible for the antithrombotic effect because no surface irregularities or change in the surface element denaturation was observed. Triboelectrically charged PTFE electret tubes are highly useful for intravascular indwelling catheters.

Measurement of a new parameter representing the gas transport properties of the catalyst layers of polymer electrolyte fuel cells.

The optimization of the catalyst layers is necessary for obtaining a better fuel cell performance and reducing fuel cell cost. Although the ionomer coverage of the Pt catalyst is said to be a key parameter in this regard, the proportion of Pt either directly or indirectly covered by the ionomer is thought to be an important parameter with regard to gas transport (indirectly covered Pt: its gas transport paths are completely blocked by the ionomer even if it does not directly cover Pt). In this study, a new technique has been developed for evaluating the proportion of Pt covered indirectly or directly by the ionomer, which is defined as the "capped proportion", based on the carbon monoxide (CO) adsorption properties at different temperatures. The validity of the method was thoroughly examined by identifying the CO adsorption properties of the components of the catalyst layers. The capped proportion and oxygen transport resistance in the catalyst layers showed a good correlation, indicating that the capped proportion is a dominant factor of oxygen transport resistance. This technique thus enables the evaluation of the dominant factor of the gas transport properties of the catalyst layers. The method has another significant advantage in that it does not require a membrane electrode assembly, let alone electrochemical measurement, which should be helpful for catalyst layer optimization.

Dispersion of Rod-like Particles of Nafion in Salt-Free Water/1-Propanol and Water/Ethanol Solutions.

The dispersion of perfluorinated sulfonic acid ionomers in catalyst inks is an important factor controlling the performance of catalyst layers in membrane electrode assemblies of proton exchange membrane fuel cells (PEMFCs). The effect of water/alcohol composition on the dispersion of H-Nafion in water/1-propanol and water/ethanol solutions was studied by dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and (19)F nuclear magnetic resonance ((19)F NMR) spectroscopy. Hydrodynamic radii calculated from DLS decay profiles and the radii and interparticle distance of rod-like particles derived from SAXS profiles showed almost the same dependence on alcohol concentration. 1-Propanol was more effective than ethanol to induce changes in the characteristic lengths of the rod-like particles. The motional narrowing in the (19)F NMR spectra by addition of 1-propanol indicates selective solvation of the rod-like particles. We suppose this might have decreased their radii and induced their elongation, which eventually led to extension of the ordered regions as observed in the hydrodynamic radii. Our study helps to clarify the dispersion of Nafion in aqueous alcohol solutions, which has implications for the performance of PEMFCs.

A new spectroelectrochemical cell for in situ measurement of Pt and Au K-edge X-ray absorption fine structure.

A new spectroelectrochemical cell to investigate the structure of Pt/Au nanoclusters using Pt and Au K-edge X-ray absorption fine structure (XAFS) measurements under the electrochemical conditions is developed. K-edge XAFS measurements for Pt and Au require a sample as thick as 1-2 cm, which prevents homogeneous potential distribution. We can measure in situ Pt and Au K-edge XAFS spectra and determine reasonable electrochemical surface areas using our developed spectroelectrochemical cell. This work provides a new approach to analyze Pt/Au core-shell nanoclusters. The new cell is designed to be applied to both spectra with high absorption-edge energies such as the K-edge of Pt and Au and those with low absorption-edge energy such as Pt L-edge.

Effect of binocular stereopsis on surgical manipulation performance and fatigue when using a stereoscopic endoscope.

We compared performance in three kinds of endoscopic tasks -- a pegboard, incision, and suturing - under the monoscopic (2D) and stereoscopic (3D) visual conditions conducted for 1 hour in total. We also evaluated the degree of fatigue from the aspects of subjective and objective consciousness using the critical flicker frequency (CFF) test together with a questionnaire of fatigue. A total of eight subjects showed higher performance when using the 3D display than the 2D display in all three tasks and, simultaneously, improvement in performance as a result of learning effect. No difference of fatigue was found depending on the display conditions both in the CFF test and questionnaire.

Influence of perioperative blood transfusion on the prognosis of patients with gastric cancer receiving anticancer chemotherapy.

BACKGROUND: The deleterious effect of blood transfusions on survival has been reported in patients with cancers of various organs. However, it remains unclear whether there is any adverse effect of blood transfusion when the patients are administered anticancer drugs after surgery for gastric cancers.METHODS: Data from patients with gastric resection for advanced gastric cancer were retrospectively analyzed to determine the influence of perioperative blood transfusion on the survival rate. All patients were administered anticancer drugs (mitomycin C [MMC] and tegafur-uracil [UFT]). Sixty-nine (33%) of 208 patients received blood transfusion perioperatively, while 139 patients (67%) did not receive transfusion. Multivariate analysis of clinicopathologic prognostic factors, including blood transfusion, was performed. Lymphocyte subsets were measured to investigate the immunosuppressive effect of blood transfusion.RESULTS: The 5-year survival rate was 48.8% in the 69 transfused patients and 66.9% in the 139 non-transfused patients ( P < 0.01). Cox's multiple regression analysis showed that, when patients received anticancer drugs, perioperative blood transfusion was not a significant factor affecting survival after the gastric cancer surgery. However, the CD4/CD8 ratio at 3 months after the surgery was significantly lower in the transfused group than in the non-transfused group.CONCLUSION: Blood transfusion did not affect the survival of operated patients who received postoperative adjuvant chemotherapy. However, the finding that the ratio of CD4/CD8 after surgery was significantly higher in the non-transfused group than in the transfused group supports the notion that transfusion causes broad-spectrum immunosuppression.