Combined Theoretical and Experimental Studies of Sodium Battery Materials

Owing to developments in theoretical chemistry and computer power, the combination of calculations and experiments is now standard practice in understanding and developing new materials for battery systems. Here, we briefly review our recent combined studies based on density functional theory and molecular dynamics calculations for electrode and electrolyte materials for sodium‐ion batteries. These findings represent case studies of successful combinations of experimental and theoretical methods.     

Dilemma game structure hidden in traffic flow at a bottleneck due to a 2 into 1 lane junction

Following Yamauchi’s study [A. Yamauchi, J. Tanimoto, A. Hagishima, H. Sagara, Dilemma game structure observed in traffic flow at a 2-to-1 lane junction, Physical Review E 79 (2009) 036104], we find that several social dilemma structures are represented by n-person Prisoner’s Dilemma (n-PD) games in certain traffic flow phases at a bottleneck caused by a lane-closing section. In this study, the stochastic Nishinari-Fukui-Schadschneider (S-NFS) model was adopted as a cellular automaton traffic model. In the system, two classes of driver-agents coexist: C-Agents (cooperative strategy) always driving in the first lane, and D-Agents (defective strategy) trying to drive in a lower-density lane, whether the first or the second lane. In relatively high-density flow phases, such as the metastable phase and the high-density phase, we found n-PD games, where D-Agents’ interruption into the first lane from the second just before the lane-closing section creates a heavier traffic jam, which reduces social efficiency. This could be solved by decreasing the interruption probability, which can be realized by a provision where drivers in the first lane firmly refuse interruptions.     

Enhanced magnetization and ferrimagnetic behavior of normal spinel ZnFe2O4 thin film irradiated with femtosecond laser

We report on spatially selective change of magnetism from paramagnetic to ferrimagnetic-like behaviors in normal spinel ZnFe₂O₄ thin film under irradiation with 780 nm femtosecond laser pulses. The distribution of Zn²⁺ and Fe³⁺ ions in the irradiated region on the film surface becomes disordered because of local heating to high temperatures, and the metastable phase of ZnFe₂O₄ is frozen in by the rapid quenching after irradiation, resulting in the formation of the ferrimagnetic phase. The ferrimagnetic phase reverts to the paramagnetic state by annealing at 800°C. The present technique is useful for two-dimensional patterning of magnetic thin films.     

Tetrahedron Equation and Quantum R Matrices for Spin Representations of {B^{(1)}_n}, {D^{(1)}_n} and {D^{(2)}_{n+1}}

It is known that a solution of the tetrahedron equation generates infinitely many solutions of the Yang-Baxter equation via suitable reductions. In this paper this scheme is applied to an oscillator solution of the tetrahedron equation involving bosons and fermions by using special 3d boundary conditions. The resulting solutions of the Yang-Baxter equation are identified with the quantum R matrices for the spin representations of ${B^{(1)}_n}$ , ${D^{(1)}_n}$ and ${D^{(2)}_{n+1}}$ .     

Does “game participation cost” affect the advantage of heterogeneous networks for evolving cooperation?

Masuda [N. Masuda, Participation costs dismiss the advantage of heterogeneous networks in evolution of cooperation, Proceedings of the Royal Society B 274 (2007) 1815-1821] reported that a game participation cost (expressed by adding same negative values to all four elements in a 2 × 2 payoff matrix) affects the advantage of heterogeneous networks in the evolution of cooperation. We show that this finding is not always true depending on the features of the network, indicating that participation costs help cooperation in certain situations rather than destroy it. In a weaker dilemma game on a scale free network derived from the Barabasi & Albert algorithm with a larger average degree, game participation cost helps rather than destroy the network reciprocity.     

Binary mass diffusion in smectic C and CA phases as observed by forced Rayleigh scattering

Abstract

We have observed the diffusion constants of a dye in several liquid crystals by forced Rayleigh scattering. In a liquid crystal which has a standard phase sequence of N-S_A-S_C, the diffusion anisotropy changes at the N-S_A phase transition and increases with decreasing temperature in S_A and S_C phases. The diffusion constants exhibit a rather smooth decrease with decreasing temperature except an anomaly at the S_A-S_c phase transition. In a liquid crystal which has the antiferroelectric S_CA phase, however, the diffusion constants show discontinuous increase and decrease at the S_A-S_c and the S_c-S_cA phase transition temperatures, respectively: the diffusion constant in S_C is larger than that in the higher temperature S_A phase. Anomalous signal increase and profile were observed at the phase transition temperatures, and were ascribed to the complementary transient grating due to the coexistence of two phases.     

Long-Range Electron Transfer in Rigid 310-Helical Oligopeptides Containing Redox Cyclic a-Amino Acids

Intrahelical photoinduced electron transfer processes (ET) in conformationally restricted oligopeptides have been studied by nanosecond time-resolved transient spectroscopy. The helical peptides were constructed from sterically hindered alpha-aminoisobutyric acid (Aib) and two cyclic alpha-amino acids (Aib class) bearing electron acceptor and donor side chains (DkNap, ThQx). This helical backbone design provides high conformation stability, as previously demonstrated, and yields reliable 3(10)-helical architectures in solution. The forward ET between ThQx and 3DkNap is followed by a slow back ET thus giving rise to an accumulation of the charge-separated ion pairs for hundreds of nanoseconds. We demonstrate the modulation of electronic interactions by the number of intervening Aib residues separating acceptor-donor side chains and propose modifications of the peptide framework by inclusion of a non-Aib amino acid residue. These well-defined and sterically stable frameworks are suited for the precise evaluation of intrahelical electron transfer processes mediated by peptides.