Composition dependence of the photocatalytic activities of BiOCl(1-x)Br(x) solid solutions under visible light

We prepared BiOCl(1-x)Br(x) (x=0-1) solid solutions and characterized their structures, morphologies, and photocatalytic properties by X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, Raman spectroscopy, photocurrent and photocatalytic activity measurements and also by density functional theory calculations for BiOCl, BiOBr, BiOCl(0.5)Br(0.5). Under visible-light irradiation BiOCl(1-x)Br(x) exhibits a stronger photocatalytic activity than do BiOCl and BiOBr, with the activity reaching the maximum at x=0.5 and decreasing gradually as x is increased toward 1 or decreased toward 0. This trend is closely mimicked by the photogenerated current of BiOCl(1-x)Br(x) , indicating that the enhanced photocatalytic activity of BiOCl(1-x)Br(x) with respect to those of BiOCl and BiOBr originates from the trapping of photogenerated carriers. Our electronic structure calculations for BiOCl(0.5)Br(0.5) with the anion (O(2-), Cl(-), Br(-)) and cation (Bi(3+)) vacancies suggest that the trapping of photogenerated carriers is caused most likely by Bi(3+) cation vacancies, which generate hole states above the conduction band maximum.     

Random field Ising model and community structure in complex networks

We propose a method to determine the community structure of a complex network. In this method the ground state problem of a ferromagnetic random field Ising model is considered on the network with the magnetic field B_s = +∞, B_t = -∞, and B_i≠s,t=0 for a node pair s and t. The ground state problem is equivalent to the so-called maximum flow problem, which can be solved exactly numerically with the help of a combinatorial optimization algorithm. The community structure is then identified from the ground state Ising spin domains for all pairs of s and t. Our method provides a criterion for the existence of the community structure, and is applicable equally well to unweighted and weighted networks. We demonstrate the performance of the method by applying it to the Barabási-Albert network, Zachary karate club network, the scientific collaboration network, and the stock price correlation network. (Ising, Potts, etc.)     

Studies on the E7 liquid crystal orientations confined to perfluorinated carboxylic acid-treated cylindrical cavities of Anodisc membranes by FTIR spectroscopy

The orientation of E7 liquid crystal (LC) confined within 200 nm diameter cylindrical cavities of Anodisc membranes are investigated by FTIR dichroism techniques. The cavity walls of the confining pores were chemically modified with different length perfluorinated carboxylic acids (PCAs, C _n F_2n+1COOH, n = 3, 4, 5, 6) at 1, 3 and 5 mM concentrations. From the FTIR spectra of PCA-treated alumina Anodsic membranes, we found salt formation between the -COOH group of the PCAs and the Anodisc membranes. From the FTIR spectra of LC-filled Anodisc membranes, we found an abrupt alignment direction change, from parallel to perpendicular, of the LC molecules along the long axis of the cavities between n = 4 and n = 5 for the 1 mM concentration of PCA. However, for the 5 mM concentration of PCA, the parallel-to-perpendicular alignment direction of LC molecules changed between n = 3 and n = 4. These LC orientation changes for PCA-treated Anodisc membranes occurred at shorter length than for hydrocarbon carboxylic acid (HCA, C _n H_2n+1COOH)-treated Anodisc membranes. This change may be caused by the lower surface energy of the -(CF₂) _n CF₃ chain of PCA than that of the -(CH₂) _n CH₃ chain of HCA.     

Synthesis and photoluminescence study of benz[f]indene derivatives

The synthesis and optical properties of a series of benz[f]indenes as new building blocks for electronic and optoelectronic materials are described.     

Functionalized large ring crown ethers

Reactions of 3,6,9,12-tetraoxa-7-(benzyloxymethyl)-1,14-tetradecanediol with appropriate ditosylates followed by hydrogenolysis produce hydroxymethyl-27-crown-9 and hydroxy- methyl-30-crown-10. Alkali metal cation complexation by lipophilic dodecyl ether derivatives of these crowns is examined.     

Sol-gel transition of polyacrylonitrile/propylene carbonate solution

The thermoreversible gelation of polyacrylonitrile (PAN)/propylene carbonate (PC) solution was investigated by calorimetric, thermomechanical, optical, and rheological measurements. Two endothermic signals are observed for PAN/PC gels in DSC thermograms, and the peak temperature of the higher melting endotherm coincides with the gel melting temperature determined from the TMA thermogram. SEM micrographs show that the overall structure is separated into two phases and is composed of sperical domains, which may be formed upon passing through the thermodynamically unstable or metastable state via the liquid-liquid phase separation. The gelation rate increases with the aging temperature. This is also discussed on the basis of the elasticity theory of the fishnet gel. © 1994 John Wiley & Sons, Inc.     

The P-version of the mixed-finite element method for nonlinear second-order elliptic problems

The p-version of the mixed finite element method is considered for nonlinear second-order elliptic problems. Existence and uniqueness of the approximation are demonstrated and optimal order error estimates in L² are derived for the three relevant functions. Error estimates for the scalar function are also given in L^q, 2 ? q ? + ∞. © 1996 John Wiley & Sons, Inc.     

Synthesis of cryptands with one carbon and one nitrogen bridgehead atom

Two novel cryptands which each contains one carbon and one nitrogen atom at the bridgehead positions are synthesized and found to form strong complexes with lithium cations.     

A study of hadronic decays of the ϒ′

We present a detailed study of the decays ?′ → π⁺π^?? and ?′ → π⁰π⁰?, where the ? decays subsequently to e⁺e^? or μ⁺μ^?. The results are obtained from a sample of 146 000 ?′ decays observed with the CUSB detector at the Cornell Electron Storage Ring. We derive branching fractions of (18.9 ± 2.6)% for ?′ → π′π^?? and (10.3 ± 2.3)% for ?′ → π⁰π⁰?, and determined partial widths for these decays. Invariant mass and angular distributions of both the π⁺π^? and π⁰π⁰ systems are presented. We also set a limit on the branching fraction for ?′ → η? of less than 0.2% at the 90% confidence level.