Novel evaluation method for degradation rate of polymer electrolytes in fuel cells

A simple and new method has been developed to evaluate the degradation rate of polymer electrolytes caused by the cross-leakage of H₂ or O₂ in PEFCs. Mixed gas of H₂ and air with a constant composition was supplied to a sample powder suspended in water, e.g., consisting of Pt supporting carbon black coated with a perfluorosulfonated acid electrolyte. Fluoride ion released from the electrolyte into the water was quantitatively analyzed as a function of time. The electrolyte was decomposed only when H₂, O₂, and Pt coexisted. The present method enables to compare the durability of different electrolyte polymers directly under the same controlled environment within a short period.     

Possible generation of electric multipole radiation from solid state quantum rings

The self-organized crystal growth of semiconductor quantum rings has opened a new possibility to study and exploit optical transitions between ring-shaped quantum states. In such states, orbital angular momenta of particle envelope functions are well-defined. We investigate theoretically the intraband interlevel transitions between such states and examine the possibility of electrical multipole radiations (EMRs). Selections rules due to envelope function quantum numbers are deduced. To enhance the EMR efficiency, we propose a novel coupled dot–ring structure, by which the lowest allowed EMR can be selected and manipulated, allowing the efficient radiation of multipole photons.     

Optical signal processing using nonlinear fibers

Ultra-fast optical signal processing is a promising technology for future photonic networks. This paper describes possible applications of nonlinear fibers to optical signal processing. The third-order optical nonlinearities in a fiber are discussed by analyzing the interaction of co-propagating optical waves. The properties of a nonlinear fiber are then considered in terms of optimizing the dispersion for achieving phase matching and decreasing walk-off. A highly nonlinear fiber (HNLF) is a practical candidate for an ultra-high-speed signal processor. Using HNLF, the following experiments are successfully demonstated: ultra-broadband wavelength conversion/optical phase conjugation by four-wave mixing, 160 Gb/s optical 3R-regeneration, and optical switching up to 640 Gb/s using a parametric amplified fiber switch. Steps for further improvements are also discussed.     

Inter­actions of thia­mine with polymeric halogenocadmate anions in the organic–inorganic hybrid compound (thia­minium)[Cd3Br4.4Cl3.6]

The structure of poly[3‐[(4‐amino‐2‐methylpyrimidin‐1‐ium‐5‐yl)meth­yl]‐5‐(2‐hydroxy­ethyl)‐4‐methyl­thia­zolium octa‐μ‐bromo/chloro­(4.4/3.6)‐tricadmate(II)], {(C₁₂H₁₈N₄OS)[Cd₃ Br_4.41Cl_3.59]}_n consists of hydrogen‐bonded thia­mine mol­ecules and polymeric cadmium bromide/chloride anions in an organic–inorganic hybrid fashion. The one‐dimensional anion ribbons are formed by edge‐sharing octa­hedra and vertex‐sharing tetra­hedra. Thia­mine mol­ecules adopting the S conformation are linked to anions via three types of inter­actions, namely an N(amino)—H⋯anion⋯thia­zolium bridging inter­action, an N(pyrimidine)—H⋯anion hydrogen bond and an O(hydr­oxy)—H⋯anion hydrogen bond.     

Effect of Quantum Well Width Reduction for GaInNAs/GaAs Lasers

We investigated the function of the quantum well (QW) width for laser characteristics especially for reduction of the well width. We pointed out that such reduction has almost no influence on the optical gain or the carrier overflow for a large conduction band offset system, such as GaInNAs QWs. A thin QW is advantageous for suppression of the carrier overflow to the higher quantized energy levels which results in good temperature and gain characteristics. Thin GaInNAs QWs is a good candidate for an active layer structure of the lasers utilized in the next optical communication systems.     

Brewster Anomalies in Opaque Random Amorphous Multilayers a-Si:H/a-Si3N4+x:H

Reflectance anomalies of random amorphous multilayers are shown to be different dependence on the incident angle for s- and p-polarized light by simulation. Disappearance of these anomalies has especially been observed for p-polarized light propagation at a certain incident angle. It is shown that this incident angle is the extended Brewster angle defined for opaque materials. This phenomenon, i.e., the disappearance of reflectance anomalies, is the Brewster anomaly in random amorphous multilayers made with absorbent materials. Preliminary results of experiments are also presented.     

Levels of146Ce studied through the decay of high-spin isomer of146La

The decay of 10.0 s high-spin isomer of¹⁴⁶La to levels of¹⁴⁶Ce has been studied using the on-line isotope separator KUR-ISOL. Gamma-ray singles,γ -γ coincidence and conversion-electron spectra have been measured. A level scheme containing 90 levels and 206γ-ray transitions has been constructed for¹⁴⁶Ce, populated in the decay of the high-spin isomer of¹⁴⁶La. Among these, 39 levels are reported for the first time. Spins and parities for some levels are proposed on the basis ofγ-decay mode, logft values and conversion-electron measurements. The band structure of the low-lying levels in¹⁴⁶Ce is discussed.     

Katz Correspondence for Quasi-Unipotent Overconvergent Isocrystals

Let k be a field and X = Spec (k[t,t ^-1 ]). Katz proved that a differential equations with coefficients in k((t ^-1 )) is uniquely extended to a special algebraic differential equation on X when k is of characteristic 0. He also proved that a finite extension of k((t ^-1 )) is uniquely extended to a special covering of X when k is of any characteristic. These theorems are called canonical extension or Katz correspondence. We shall prove a p-adic analogue of canonical extension for quasi-unipotent overconvergent isocrystals. As a consequence, we can show that the local index of a quasi-unipotent overconvergent is equal to its Swan conductor.