Nafion®/(organically modified silicate) nanocomposites via polymer in situ sol–gel reactions: Mechanical tensile properties

A series of Nafion®/[organically modified silicate (ORMOSIL)] hybrid materials have been created by in situ sol–gel copolymerizations of tetraethylorthosilicate and semiorganic silicon alkoxide monomers. The trends in the mechanical tensile properties of these hybrid materials were largely rationalized in terms of the entrapment of the long sulfonic acid side chains in silicate or ORMOSIL structures. There is a significant increase in the mechanical strength relative to that of unfilled Nafion®, except in one case. Young's modulus is enhanced relative to that of unfilled acid form Nafion® in a number of cases, although the degree of ductility is reduced relative to that of unfilled Nafion®. The filler fractions are beneath a critical value that would reflect percolation of a glassy, direct load‐bearing silicate phase. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2237–2247, 2002     

Reactions of naphthalene in N2O5?NO3?NO2? air mixtures

The reactions of naphthalene in N₂O₅? NO₃? NO₂? N₂? O₂ reactant mixtures have been investigated over the temperature range 272–297 K at ca. 745 torr total pressure and at 272 K and ca. 65 torr total pressure using long pathlength Fourier transform infrared absorption spectroscopy. 2,3-Dimethyl-2-butene was added to the reactant mixtures at 272 K to rapidly scavenge the NO₃ radicals both initially present in the added N₂O₅ and formed from the thermal decomposition of N₂O₅ during the reactions. The data obtained in the presence and absence of added 2,3-dimethyl-2-butene showed that napthalene undergoes initial reaction with the NO₃ radical to form an NO₃-naphthalene adduct, which either rapidly decomposes back to the reactants (at a rate of ca. 5 × 10⁵ s^?1 at 298 K) or reacts exclusively with NO₂ to form products. When NO₃ radicals, N₂O₅ and NO₂ are in equilibrium, this overall process is kinetically equivalent to reaction of naphthalene with N₂O₅, and previous kinetic and product studies have indeed assumed the reactions of naphthalene and alkyl-substituted naphthalenes in N₂O₅? NO₃? NO₂? air mixtures to be with N₂O₅, and not with NO₃ radicals.     

Effects of Signal Spectrum Bandwidth on Different PMD Compensation Feedback Methods

We compared efficiencies of different PMD compensation feedback methods against transmission signal bandwidth,including NRZ, RZ, CRZ format under various duty cycles. We found that the critical factor determining the efficiency of PMD compensation is not the modulation format, but the spectral bandwidth of the transmission signal.     

Visualizing parameters from loglinear models

Summary  This paper presents a graphical display for the parameters resulting from loglinear models. Loglinear models provide a method for analyzing associations between two or several categorical variables and have become widely accepted as a tool for researchers during the last two decades. An important part of the output of any computer program focused on loglinear models is that devoted to estimation of parameters in the model. Traditionally, this output has been presented using tables that indicate the values of the coefficients, the associated standard errors and other related information. Evaluation of these tables can be rather tedious because of the number of values shown as well as their rather complicated structure, mainly when the analyst needs to consider several models before reaching a model with a good fit. Therefore, a graphical display summarizing tables of parameters could be of great help in this situation. In this paper we put forward an interactive dynamic graphical display that could be used in such fashion.     

Theoretical investigation of the Au/Si(1 1 1)-(5 × 2) surface structure

The atomic structure of the Au/Si(1 1 1)-(5 × 2) surface has been studied by density-functional theory calculations. Two structure models, proposed experimentally by Marks et al. and Hasegawa et al., have been examined on an equal ground. In our total-energy calculations, both models are found to be locally stable and energetically comparable. In our electronic-structure analyses, however, both models fail to reproduce the key features of angle-resolved photoemission spectra and scanning-tunneling-microscopy images, indicating that the considered models need to be modified. Suggestions for the modification are given based on the present calculations.     

Synthesis of novel conjugated polymer based on cyclopenta[def]phenanthrene and vinylene with strong interchain interaction

In this study, a novel conjugated polymer, poly(4,4‐bis(2‐ethylhexyl)‐4H‐cyclopenta[def]phenanthrene‐2,6‐vinylene) (PCPPV) has been synthesized and characterized. For the polymerization, Gilch's reaction was applied for the first time with the cyclopenta[def]phenanthrene system. The absorption and emission spectra of PCPPV are red‐shifted about 40–50 nm due to the vinylene units when compared with those of poly(2,6‐(4,4‐bis(2‐ethylhex‐yl)‐4H‐cyclopenta[def]phenanthrene)) (PCPP). The solid‐state fluorescence is significantly broadened, possibly due to π–π interactions introduced by the phenanthrene and vinylene moieties. In solution, as the concentration of polar solvent increased, the photoluminescence (PL) intensity decreased due to quenching and aggregation by the interchain interactions between the conjugated backbones. After annealing the film at 80 °C, the PL and electroluminescence (EL) emission spectra exhibited also the quenching and aggregation effects indicating the interchain interactions of PCPPV. The large number of aromatic rings in a unit and the increased planarity achieved through introduction of vinylene units are able to give interchain interactions stronger than fluorene or phenylene units. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5068–5077, 2009     

Boundary conditions in rational conformal field theories

We develop further the theory of Rational Conformal Field Theories (RCFTs) on a cylinder with specified boundary conditions emphasizing the role of a triplet of algebras: the Verlinde, graph fusion and Pasquier algebras. We show that solving Cardy's equation, expressing consistency of a RCFT on a cylinder, is equivalent to finding integer valued matrix representations of the Verlinde algebra. These matrices allow us to naturally associate a graph G to each RCFT such that the conformal boundary conditions are labelled by the nodes of G. This approach is carried to completion for sl(2) theories leading to complete sets of conformal boundary conditions, their associated cylinder partition functions and the A-D-E classification. We also review the current status for WZW sl(3) theories. Finally, a systematic generalisation of the formalism of Cardy–Lewellen is developed to allow for multiplicities arising from more general representations of the Verlinde algebra. We obtain information on the bulk–boundary coefficients and reproduce the relevant algebraic structures from the sewing constraints.