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

Spontaneous absorption of an accelerated hydrogen atom near a conducting plane in vacuum

We study, in the multipolar coupling scheme, a uniformly accelerated multilevel hydrogen atom in interaction with the quantum electromagnetic field near a conducting boundary and separately calculate the contributions of the vacuum fluctuation and radiation reaction to the rate of change of the mean atomic energy. It is found that the perfect balance between the contributions of vacuum fluctuations and radiation reaction that ensures the stability of ground-state atoms is disturbed, making spontaneous transition of ground-state atoms to excited states possible in vacuum with a conducting boundary. The boundary-induced contribution is effectively a nonthermal correction, which enhances or weakens the nonthermal effect already present in the unbounded case, thus possibly making the effect easier to observe. An interesting feature worth being noted is that the nonthermal corrections may vanish for atoms on some particular trajectories.Comment: 19 pages, no figures, Revtex

The role of trefoil factor family in apparently healthy subjects administrated gastroprotective agents for the primary prevention of gastrointestinal injuries from low-dose acetylsalicylic acid: a preliminary study

It is well-known that acetylsalicylic acid induces gastrointestinal complication. Recently, trefoil factor family has been reported as a mucosal protective factor. We focused on trefoil factor family as one of defensive system for gastrointestinal injuries. The aim of this trial was to evaluate trefoil factor family levels in the serum of healthy subjects with low-dose acetylsalicylic acid. Low-dose acetylsalicylic acid with placebo or proton pump inhibitor or rebamipide were administered in 30 healthy subjects. Transnasal endoscopy was performed at 0, 24 h, 3 and 7 day. Changing of trefoil factor family (1,2,3) and numbers of gastric injuries were evaluated. The numbers of gastric injuries were significantly increased in the placebo group at 3 and 7 days. Injuries in the proton pump inhibitor group were not induced, in the rebamipide group were slightly induced. Trefoil factor family level in the placebo group were decreased in 3 and 7 days compared with prior to starting the trial. Trefoil factor family may have an important association with acetylsalicylic acid-induced gastrointestinal damage. Proton pump inhibitor and rebamipide prevented low-dose acetylsalicylic acid-induced gastrointestinal complications compared with the placebo group

Spontaneous excitation of an accelerated multilevel atom in dipole coupling to the derivative of a scalar field

We study the spontaneous excitation of an accelerated multilevel atom in dipole coupling to the derivative of a massless quantum scalar field and separately calculate the contributions of the vacuum fluctuation and radiation reaction to the rate of change of the mean atomic energy of the atom. It is found that, in contrast to the case where a monopole like interaction between the atom and the field is assumed, there appear extra corrections proportional to the acceleration squared, in addition to corrections which can be viewed as a result of an ambient thermal bath at the Unruh temperature, as compared with the inertial case, and the acceleration induced correction terms show anisotropy with the contribution from longitudinal polarization being four times that from the transverse polarization for isotropically polarized accelerated atoms. Our results suggest that the effect of acceleration on the rate of change of the mean atomic energy is dependent not only on the quantum field to which the atom is coupled, but also on the type of the interaction even if the same quantum scalar field is considered.Comment: 11 pages, no figure

Enhancement and suppression of tunneling by controlling symmetries of a potential barrier

We present a class of 2D systems which shows a counterintuitive property that contradicts a semi classical intuition: A 2D quantum particle "prefers" tunneling through a barrier rather than traveling above it. Viewing the one particle 2D system as the system of two 1D particles, it is demonstrated that this effect occurs due to a specific symmetry of the barrier that forces excitations of the interparticle degree of freedom that, in turn, leads to the appearance of an effective potential barrier even though there is no "real" barrier. This phenomenon cannot exist in 1D.Comment: 10 pages and 7 figure

Mechanistic basis for the recognition of laminin-511 by α6β1 integrin

Mamoru Takizawa, Takao Arimori, Yukimasa Taniguchi, Yu Kitago, Erika Yamashita, Junichi Takagi and Kiyotoshi Sekiguchi, "Mechanistic basis for the recognition of laminin-511 by α6β1 integrin", Science Advances, Vol. 3, No. 9, e1701497, AAAS, 201

Brain2Music: Reconstructing Music from Human Brain Activity

The process of reconstructing experiences from human brain activity offers a unique lens into how the brain interprets and represents the world. In this paper, we introduce a method for reconstructing music from brain activity, captured using functional magnetic resonance imaging (fMRI). Our approach uses either music retrieval or the MusicLM music generation model conditioned on embeddings derived from fMRI data. The generated music resembles the musical stimuli that human subjects experienced, with respect to semantic properties like genre, instrumentation, and mood. We investigate the relationship between different components of MusicLM and brain activity through a voxel-wise encoding modeling analysis. Furthermore, we discuss which brain regions represent information derived from purely textual descriptions of music stimuli. We provide supplementary material including examples of the reconstructed music at https://google-research.github.io/seanet/brain2musicComment: Preprint; 21 pages; supplementary material: https://google-research.github.io/seanet/brain2musi