Equation Elucidating the Catalyst-Layer Proton Conductivity in a Polymer Electrolyte Fuel Cell Based on the Ionomer Distribution Determined Using Small-Angle Neutron Scattering.

The performance of a polymer electrolyte fuel cell can be enhanced by improving the proton conductivity of the catalyst layer, where the oxygen reduction reaction generates electrochemical power. Protons are conducted through the ionomer coatings on catalyst-supporting carbon particles, which form porous structures that facilitate oxygen diffusion during the reaction within the catalyst layer. Therefore, while a higher ionomer content in the catalyst layer is favorable, the proton conductivity is additionally governed by the type of carbon support. As the influence of the ionomer distribution is not fully understood, we introduce a novel proton conductivity model for use in simulating catalyst layers with various amounts of ionomers and different carbon types. This proton conductivity model considers that several ionomers occur as thin films with drastically suppressed proton conductivities. Although evaluating the thin-film ionomer fraction is challenging, proton-conducting ion clusters in thick-film ionomers have been detected by characterizing the catalyst layers via small-angle neutron scattering. Our model reveals that reducing the fraction of the thin-film ionomer or avoiding factors that suppress its proton conduction improves the performance of the catalyst layer.

The role of oxygen-permeable ionomer for polymer electrolyte fuel cells.

In recent years, considerable research and development efforts are devoted to improving the performance of polymer electrolyte fuel cells. However, the power density and catalytic activities of these energy conversion devices are still far from being satisfactory for large-scale operation. Here we report performance enhancement via incorporation, in the cathode catalyst layers, of a ring-structured backbone matrix into ionomers. Electrochemical characterizations of single cells and microelectrodes reveal that high power density is obtained using an ionomer with high oxygen solubility. The high solubility allows oxygen to permeate the ionomer/catalyst interface and react with protons and electrons on the catalyst surfaces. Furthermore, characterizations of single cells and single-crystal surfaces reveal that the oxygen reduction reaction activity is enhanced owing to the mitigation of catalyst poisoning by sulfonate anion groups. Molecular dynamics simulations indicate that both the high permeation and poisoning mitigation are due to the suppression of densely layered folding of polymer backbones near the catalyst surfaces by the incorporated ring-structured matrix. These experimental and theoretical observations demonstrate that ionomer's tailored molecular design promotes local oxygen transport and catalytic reactions.

Synthesis and Properties of Fluorocarbon-Hydrocarbon Hybrid Block Copolymers with Perfluorosulfonimide Acid.

Novel fluorocarbon-hydrocarbon hybrid block copolymer electrolytes were synthesized. The block copolymer electrolytes consist of poly(perfluoropropyl sulfonimide) (PC3SI) as a perfluorinated hydrophilic segment and poly(ether ether sulfone) as a hydrocarbon hydrophobic segment. The sulfonimide group of poly(perfluoropropyl sulfonimide) has superacidity, very low equivalent weight (EW = 293 g/equiv), and a proton conductivity of 1.2 × 10-2 S/cm under dry conditions and 25 °C, although soluble in water. The proton conductivity of the block copolymer was 1.7 × 10-3 S/cm at 20% relative humidity and 25 °C, which is three times as high as that of Nafion 112.

Protease-activated receptor-stimulated interleukin-6 expression in endometriosis-like lesions in an experimental mouse model of endometriosis.

The present study was undertaken to investigate the function of protease-activated receptor (PAR) in endometriotic lesions using a mouse model of endometriosis. Unilateral ovariectomy (uOVX) was performed on female nude mice followed by intraperitoneal transplantation of a suspension mixture of immortalized human endometrial epithelial cells (EM-1) and stromal cells (EtsT-499). Endometriosis-like lesions were observed mostly around the dissection site after transplantation. The expression of interleukin (IL)-6 and cyclooxygenase-2 in the lesions was enhanced in uOVX mice compared to non-uOVX animals. In non-uOVX mice, IL-6 mRNA levels were higher in lesions formed with cells that were pretreated with PAR1/2 agonists (thrombin, 10 U/ml and PAR2-activating peptide, 30 µM) compared to untreated, intact cells. Peritoneal IL-6 concentrations were also increased in the PAR1/2 agonists-treated group. IL-6 expression induced by PAR activation was blocked by the treatment of cells with serine protease inhibitors. In cultured endometrial cells, simultaneous treatment with PAR1 and PAR2 agonists significantly increased the expression of IL-6. These results suggest that peritoneal bleeding may accelerate IL-6 expression in endometriotic lesions in part through the activation of PAR.

Germylene and silylene complexes of molybdenum via E-H (E = Ge, Si) bond activations: steric influences on intramolecular MoH...E interactions.

Reactions of Cp*(dmpe)Mo(eta(3)-CH(2)Ph) with organogermanes (RR'GeH(2)) afforded germylene complexes Cp*(dmpe)Mo(H)GeRR' (RR' = Ph(2) (2), Et(2) (3), (Mes)H (4), ((t)Bu)H (5)). Compound 2 does not possess an intramolecular H...Ge interaction of the type exhibited by its silicon analogue and by 3. The existence of such interactions appears to depend on the steric properties of substituents on the Ge (or Si) atom. For comparison, a silylene complex was prepared by reaction of 9-silafluorene with 1, to give Cp*(dmpe)Mo(H)Si(C(12)H(8)), which on the basis of NMR spectroscopy does not possess a significant Si...H interaction.

Coordination chemistry of a kinetically stabilized germabenzene: syntheses and properties of stable eta6-germabenzene complexes coordinated to transition metals.

The first stable eta6-germabenzene complexes, that is, [M(CO)3(eta6-C5H5GeTbt)] {M=Cr (2), Mo (3), and W (4); Tbt=2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}, have been synthesized by ligand-exchange reactions between [M(CO)3(CH3CN)3] (M=Cr, Mo, and W) and the kinetically stabilized germabenzene 1 and characterized by 1H and 13C NMR, IR, and UV/Vis spectroscopy. In the 1H and 13C NMR spectra of 2-4, all of the signals for the germabenzene rings were shifted upfield relative to their counterparts in the free germabenzene 1. X-ray crystallographic analysis of 2 and 4 revealed that the germabenzene ligand was nearly planar and was coordinated to the M(CO)3 group (M=Cr, W) in an eta6 fashion. The formation of complexes 2-4 from germabenzene 1 should be noted as the application of germaaromatics as 6pi-electron ligands toward complexation with Group 6 metals. On the other hand, treatment of 1 with [{RuCp*Cl}4] (Cp*=C5Me5) in THF afforded a novel eta5-germacyclohexadienido complex of ruthenium-[RuCp*{eta5-C5H5GeTbt(Cl)}] (9)-instead of the expected eta6-germabenzene-ruthenium cationic complex [RuCp*{eta6-C5H5GeTbt}]Cl (10). Crystallographic structural analysis of 9 showed that the five carbon atoms of the germacyclohexadienido ligand of 9 were coordinated to the Ru center in an eta5 fashion.

Photophysical and photochemical processes of 9,10-dihydro-9-silaphenanthrene derivatives: photochemical formation and electronic structure of 9-silaphenanthrenes.

Photophysical and photochemical processes of 9-methyl- and 9-phenyl-9,10-dihydro-9-silaphenanthrene derivatives have been studied at room temperature and 77 K in comparison with the carbon analogue, 9,10-dihydrophenanthrene. These 9,10-dihydro-9-silaphenanthrene derivatives show smaller fluorescence quantum yield and remarkably larger Stokes shifts than those of the carbon analogue. In contrast, their phosphorescence quantum yields are two times larger than those of the carbon analogue, although the absolute value is not so large (approximately 0.1). Reaction products and intermediates produced by the 266 nm light photolysis have been studied, and it has been confirmed that 9-methyl- and 9-phenyl-9-silaphenanthrenes have been photochemically formed in methylcyclohexane at 77 K, in addition to the formation of radical cations of 9,10-dihydro-9-silaphenanthrene derivatives and the carbon-centered radical: 9-hydro-9-silaphenanthrenyl radical.

Erythrocytosis due to an erythropoietin-producing large uterine leiomyoma.

BACKGROUND: Various etiologies of myomatous erythrocytosis syndrome (erythrocytosis associated with a uterine leiomyoma), one of which is altered production of erythropoietin, have been proposed. We report a case of erythrocytosis associated with a large uterine leiomyoma in which erythropoietin activity and immunostaining for erythropoietin in the leiomyoma were found. CASE: A 64-year-old woman, gravida 2, para 1, was referred to our department for treatment of a large uterine myoma and erythrocytosis with elevated levels of erythropoietin. Total abdominal hysterectomy with bilateral salpingo-oophorectomy was performed, and the results of the pathological examination confirmed the diagnosis of leiomyoma of the uterus, which weighed 920 g. The patient's postoperative course was satisfactory, and the levels of hemoglobin and erythropoietin were normalized and remained within normal ranges. The level of erythropoietin in the uterine leiomyoma measured by radioimmunoassay was elevated (372 mU/wet gram), and specific immunostaining for erythropoietin was found in the cytoplasm of leiomyoma cells. The levels of erythropoietin extracted from uterine leiomyomas of other patients who did not have erythrocytosis (control patients, n = 5) were lower (65 +/- 15.3 mU/wet gram), but specific immunostaining for erythropoietin was also found in the cytoplasm of leiomyoma cells from those patients. CONCLUSIONS: Our case was typical of myomatous erythrocytosis syndrome in which uterine leiomyoma was proved to produce erythropoietin. Our results also suggest that erythropoietin is produced in uterine leiomyomas of patients with and without erythrocytosis. Leiomyoma of the uterus may affect the production of erythropoietin and may develop into myomatous erythrocytosis syndrome when the level of erythropoietin exceeds the normal range.

Photochemical and thermal reactions of a kinetically stabilized 9-silaanthracene: the first spectroscopic observation of a 9,10-Dewar-9-silaanthracene isomer.

A kinetically stabilized 9-silaanthracene (1) underwent unique photochemical and thermal reactions to afford 9,10-Dewar-9-silaanthracene 2a and the head-to-tail [4 + 4] dimer 3, respectively. The structure of 2a was confirmed by 1H, 13C, and 29Si NMR spectra, and the kinetic parameters for the thermal reversion of 2a to 1 were obtained by the measurement of UV/vis spectra. The dimer 3 was thermally stable, and the molecular structure of 3 was determined by X-ray crystallographic analysis. It was experimentally demonstrated for the first time that 9-silaanthracene, as well as anthracene, can afford either the Dewar isomer or [4 + 4] dimer, depending on the reaction conditions.

Asymmetric synthesis of 1-aryl-1,2-ethanediols from arylacetylenes by palladium-catalyzed asymmetric hydrosilylation as a key step.

Double hydrosilylation of arylacetylenes with trichlorosilane catalyzed first by platinum and second by a chiral monophosphine-palladium complex generated the corresponding 1,2-bis(silyl)-1-arylethanes, the oxidation of which with hydrogen peroxide gave 1-aryl-1,2-diols of high enantiomeric purity (94-98% ee) in high yields.