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

Occlusogramを用いたIndividualized finishing arch wireの作製

The purpose of this study was to test the premise that by tracing occlusograms at the pretreatment stage, one can construct a precise finishing arch wire. The sample consisted of 22 male and 20 female dental students with skeletal Class I and near-normal occlusion. Occlusograms were taken for all plaster dental casts with 0.018 x 0.025 slot edgewise pre-an-gulated and pre-torqued brackets attached to all teeth. Futhermore, our method was applied clinically and an illustrative case is presented. Three different arches (A-arch; a smooth line drawn through the contact points of anterior and posterior teeth, B-arch; constructed by drawing a smooth curve through the cusp tips and incisive edges and C-arch; represented the 0.016 nitinol arch wire) showed a close fit as determined by the fourth degree polynomial equation, with r＾2 of 0.99

THREE-DIMENSIONAL FLOW FIELD AND LEG MOTION DURING UNDULATORY UNDERWATER SWIMMING

This study described swimmers’ leg motions and the three-dimensional flow field around their legs during undulatory underwater swimming (UUS). We used the particle image velocimetry (PIV) method and a three-dimensional motion capture system. Seven male swimmers participated and we acquired EMG data of one male swimmer during UUS after the previous experiment. After the downward kick motion that includes the legs’ lateral rotation and the ankles’ dorsal flexion, water’s backward momentum was observed. During the upward kick motion, backward flow velocity decreased, but flow occurred in a vertical, upward direction. This suggested that UUS could demonstrate great propulsion power by generating jet flow through the downward kick motion that might be assisted by upstream flow from the upward kick motion

A Selective Accumulation of Some Leaf Xanthophylls in Hen Egg Yolk and Its Manner.

ニワトリにおける緑葉カロテノイドの吸収と体組織分布について部分的に明らかにするとともに,とくに卵黄へのルテインの集中選択的蓄積に関する知見を得た. 投与した緑葉カロテノイド各々のみかけ吸収率は50～65%とカロテノイドによる差は認められないが,卵黄への蓄積量及び蓄積率はキサントフィルが高く,なかでもルテインはそのみかけ吸収量の25%が卵黄に蓄積している.これに対し,β－カロチンはみかけ吸収量のわずか0.6%しか蓄積せず,卵黄全カロテノイドに占める割合もルテインの約85%に対し1%である. 3日間の短期投与による緑葉カロテノイドの肝,卵巣,血液への正味蓄積量において,ルテインは肝よりも卵巣に6倍以上の速度で蓄積するのに対し,他のキサントフィル及びβ－カロテンは肝に多く蓄積する傾向がある.このことは緑葉カロテノイドのうちルテインがとくに卵黄に蓄積しやすいことを示すものである