Long-wavelength luminescence from GaSb quantum dots grown on GaAs substrates

Self-assembled GaSb quantum dots (QDs) with a photoluminescence wavelength longer than 1.3 μm were successfully grown by suppressing the replacement of As and Sb on the surface of the GaSb QDs. This result means that GaSb can thus join InAs or GaInAs as a suitable material for QD lasers for optical communications.     

Parametrization of calcium binding site in proteins and molecular dynamics simulation on phospholipase A2

The empirical energy parameters for a calcium ion and its ligands in proteins were determined within a pairwise additive framework. The interaction energies of Ca²⁺-water, Ca²⁺-peptide group and Ca²⁺-carboxyl group systems were calculated using the ab initio molecular orbital method with basis sets of double zeta quality including polarization or diffuse functions. The resulting potential energy surfaces served as references for the determination of the nonbonded parameters in the empirical energy function. The nonadditive corrections for the Ca²⁺-ligand pair potentials are incorporated implicitly in the nonbonded paremeters by treating three-body (1:2 complex) or seven-body (1:6 complex) systems in reference calculations. Ligand polarizations induced by Ca²⁺ are estimated from the partial atomic charges of two-body (1:1 complex) systems. The charge sets were determined by scaling so as to reproduce the reference potential energy surfaces. The newly determined parameter set was used in a stochastic boundary molecular dynamics simulation of phospholipase A₂. The solvated structure of the Ca²⁺-binding site obtained from an X-ray crystallographic study is well reproduced by the parameter set.     

Numerical simulation of cyclic voltammetry for reversible systems with complex stoichiometry

Reversible waves of voltammetry with complex non-unity stoichiometry are studied here based on theory. Numerical simulations were performed for various stoichiometric systems in which coefficients m and q were independently varied from 1 to 4 in a general reaction scheme, mO + ne⁻ ai qR. The calculation results indicate that the peak current function at complex stoichiometry differs from that at simple unity stoichiometry. The relation between the half-wave potential and the formal potential has been partially corrected from that previously reported in the literature. Parameters in the relation between the peak potential and the half-wave potential are unique for each stoichiometric system. The parameter in the relation between the peak potential and the half-peak potential is also presented here.     

Preparation of a colloidal array of NaTaO3 nanoparticles via a confined space synthesis route and its photocatalytic application

The confined space synthesis method has been applied to the preparation of sodium tantalate (NaTaO(3)); hydrothermal reaction of NaOH and Ta(2)O(5) was carried out in the pores of a three-dimensional mesoporous carbon, which was replicated by the colloidal array of silica nanospheres (SNSs) 20 nm in size. This approach led to the formation of a colloidal array of NaTaO(3) nanoparticles 20 nm in size with a surface area of 34 m(2) g(-1). The photocatalytic performance of the colloidal array of NaTaO(3) nanoparticles for overall water splitting under UV irradiation (λ > 200 nm) was evaluated after loading a NiO cocatalyst onto NaTaO(3) samples. The NiO-loaded NaTaO(3) nanoparticles showed photocatalytic activity for overall water splitting more than three times as high as non-structured bulk NaTaO(3) particles.     

Thermal vibration in superionic conducting glass 5Agl–3Ag2O–2V2O5

The X-ray diffraction measurement for superionic conducting glass 5Agl–3Ag₂O–2V₂O₅ was carried out at 12, 100, 200 and 290 K. The temperature dependence of structure factor S(Q) of 5Agl–3Ag₂O–2V₂O₅ has been discussed based on the theoretical treatment that includes thermal vibration of atoms in noncrystalline materials. The effective overall Debye–Waller temperature parameter B increases with the increase of temperature.     

Phase Transition of CuITe

The phase transition and the crystal structures of CuITe were investigated by differential thermal analysis and X-ray powder diffraction measurements in the temperature range between 300 and 683 K. The new phase transition in CuITe was observed at 592 K. The enthalpy of transition is ΔH=0.125 kJ mol^-1. The new phase above 592 K belongs to tetragonal system with the space group I4₁ /amd. This revised version was published online in August 2006 with corrections to the Cover Date.     

The structure of AgI-Ag2O-V2O5 glasses

Structures of 10AgI-3Ag₂O-2V₂O₅, 3AgI-3Ag₂O---2V₂O₅ and 2AgI---2Ag₂O-V₂O₅ glasses have been investigated by neutron diffraction experiments. The characteristic features of observed structure factors S(Q) in 10AgI-3Ag₂O-2V₂O₅ glass is similar to those of other superionic conducting glasses and molten AgI. From the standpoint of the pair distribution functions, it is clarified that the Ag-I and I-I correlation strength and Ag---Ag correlation length increase with increasing AgI concentration. Observed results suggest that the local AgI structure accompanied by the re-arrangement of silver ions is formed with highly doped iodide ions.     

Optical characteristics of one-dimensional photonic crystals composed of high-aspect-ratio Si walls fabricated on V-grooved wafer

We demonstrate optical properties of one-dimensional photonic crystals (PC), which are fabricated using high-aspect-ratio etching on a V-grooved silicon wafer. The measured transmission spectrum has an obvious band gap; the suppression is over 30 dB. The quite small insertion loss of 1.9 dB is achieved by induced coupled plasma (ICP) cryogenic etching and direct coupling to the optical fiber aligned in the V-groove. We also successfully observed peaks originating from a localized cavity mode. Such a microcavity enables control of the light, which qualifies photonic crystal as a fundamental structure of optical functional devices. These results lead to achievement of integrated Si-based photonic circuits.     

Discrete Dynamical Systems with W(A (1) m−1 × A (1) n−1) Symmetry

We give a birational realization of affine Weyl group of type A ⁽¹⁾ _m–1 × A ⁽¹⁾ _n–1. We apply this representation to construct some discrete integrable systems and discrete Painlevé equations. Our construction has a combinatorial counterpart through the ultra-discretization procedure.