In situ study of oxidation states of platinum nanoparticles on a polymer electrolyte fuel cell electrode by near ambient pressure hard X-ray photoelectron spectroscopy

We performed in situ hard X-ray photoelectron spectroscopy (HAXPES) measurements of the electronic states of platinum nanoparticles on the cathode electrocatalyst of a polymer electrolyte fuel cell (PEFC) using a near ambient pressure (NAP) HAXPES instrument having an 8 keV excitation source. We successfully observed in situ NAP-HAXPES spectra of the Pt/C cathode catalysts of PEFCs under working conditions involving water, not only for the Pt 3d states with large photoionization cross-sections in the hard X-ray regime but also for the Pt 4f states and the valence band with small photoionization cross-sections. Thus, this setup allowed in situ observation of a variety of hard PEFC systems under operating conditions. The Pt 4f spectra of the Pt/C electrocatalysts in PEFCs clearly showed peaks originating from oxidized Pt(II) at 1.4 V, which unambiguously shows that Pt(IV) species do not exist on the Pt nanoparticles even at such large positive voltages. The water oxidation reaction might take place at that potential (the standard potential of 1.23 V versus a standard hydrogen electrode) but such a reaction should not lead to a buildup of detectable Pt(IV) species. The voltage-dependent NAP-HAXPES Pt 3d spectra revealed different behaviors with increasing voltage (0.6 → 1.0 V) compared with decreasing voltage (1.0 → 0.6 V), showing a clear hysteresis. Moreover, quantitative peak-fitting analysis showed that the fraction of non-metallic Pt species matched the ratio of the surface to total Pt atoms in the nanoparticles, which suggests that Pt oxidation only takes place at the surface of the Pt nanoparticles on the PEFC cathode, and the inner Pt atoms do not participate in the reaction. In the valence band spectra, the density of electronic states near the Fermi edge reduces with decreasing particle size, indicating an increase in the electrocatalytic activity. Additionally, a change in the valence band structure due to the oxidation of platinum atoms was also observed at large positive voltages. The developed apparatus is a valuable in situ tool for the investigation of the electronic states of PEFC electrocatalysts under working conditions

RESEARCH ARTICLE Decreased Frequency of Intestinal Regulatory CD5+ B Cells in Colonic Inflammation

Background CD5+ B cells are a type of regulatory immune cells, though the involvement of this B cell subset in intestinal inflammation and immune regulation is not fully understood. Methods We examined the distribution of CD5+ B cells in various mouse organs. Expression levels of CD11b, IgM, and toll-like receptor (TLR)-4 and-9 in B cells were evaluated. In vitro, TLR-stimulated IL-10 production by colonic lamina propria (LP) CD5+ and CD5- B cells was mea-sured. In vivo, mice with acute or chronic dextran sulfate sodium (DSS)-induced colonic injury were examined, and the frequency of colonic LP CD5+ B cells in those was assessed by flow cytometry. Results The expression level of TLR9 was higher in colonic LP CD5+ B cells as compared to CD5- B cells. Colonic LP CD5+ B cells produced greater amounts of IL-10 following stimulation with TLR ligands, especially TLR9, as compared with the LP CD5- B cells. Acute intestinal inflammation transiently decreased the frequency of colonic LP CD5+ B cells, while chronic inflammation induced a persistent decrease in colonic LP CD5+ B cells and led to a CD5- B cell-dominant condition. Conclusion A persistent altered mucosal B cell population caused by chronic gut inflammation may be involved in the pathogenesis of inflammatory bowel diseases

A case report of malaria in a foreign sailor in Japan

A foreign soilor who had arrived by ship from Goa, India, was found to be infected with both Plasmodium falciparum and P. vivax. Although the P. vivax was a chloroquine-resistant type, Fansidal Ⓡ was effective and the patient recovered. As it was the season for proliferation of mosquitoes in Japan, the patient was isolated so as not to become a source of secondary infection. Knowing the place where a patient with high grade fever comes from is of great help in diagnosing malaria, which is seldom seen in Japan