Structural order for one-scale and two-scale potentials

We perform molecular dynamics simulations to investigate the relationship between structural order and waterlike dynamic and thermodynamic anomalies in spherically symmetric potentials having either one or two characteristic length scales. Structural order is characterized by translational and orientational order parameters. We find that (i) dynamic and thermodynamic anomalies exist for both one-scale and two-scale ramp potentials, and (ii) waterlike structural order anomalies exist only for the two-scale ramp potential. Our findings suggest that the waterlike relationship between structural order and anomalies is related to the presence of two different length scales in the potential.     

Geometrical and Topological Properties of Real Polynomial Fibres

We establish a Gauss—Bonnet type formula for a smooth fibre of a nonproper real polynomial of ⁿ . For this we need to study topological properties of a generic hyperplane section of this fibre.     

Glass-transition temperature of water: a simulation study

We report a computer simulation study of the glass transition for water using the extended simple point charge potential. To mimic the difference between standard and hyperquenched glass, we generate glassy configurations with different cooling rates, and we calculate the temperature dependence of the specific heat on heating. The absence of crystallization phenomena allows us, for properly annealed samples, to detect in the specific heat the simultaneous presence of a weak prepeak ("shadow transition") and an intense glass transition peak at higher temperature. Our results support the view-point that the glass transition temperature is higher than the conventionally accepted value 136 K. We also compare our simulation results with the Tool-Narayanaswamy-Moynihan phenomenological model.     

Nonperturbative renormalization-group study of reaction-diffusion processes

We generalize nonperturbative renormalization group methods to nonequilibrium critical phenomena. Within this formalism, reaction-diffusion processes are described by a scale-dependent effective action, the flow of which is derived. We investigate branching and annihilating random walks with an odd number of offspring. Along with recovering their universal physics (described by the directed percolation universality class), we determine their phase diagrams and predict that a transition occurs even in three dimensions, contrarily to what perturbation theory suggests.     

Tensor Gauge Fields in Arbitrary Representations of GL(D, ℝ). Duality and Poincaré Lemma

Using a mathematical framework which provides a generalization of the de Rham complex (well-designed for p-form gauge fields), we have studied the gauge structure and duality properties of theories for free gauge fields transforming in arbitrary irreducible representations of GL(D, ). We have proven a generalization of the Poincaré lemma which enables us to solve the above-mentioned problems in a systematic and unified way.     

A four-electron O(2)-electroreduction biocatalyst superior to platinum and a biofuel cell operating at 0.88 V

O2 was electroreduced to water, at a true-surface-area-based current density of 0.5 mA cm-2, at 37 degrees C and at pH 5 on a "wired" laccase bioelectrocatalyst-coated carbon fiber cathode. The polarization (potential vs the reversible potential of the O2 /H2O half-cell in the same electrolyte) of the cathode was only -0.07 V, approximately one-fifth of the -0.37 V polarization of a smooth platinum fiber cathode, operating in its optimal electrolyte, 0.5 M H2SO4. The bioelectrocatalyst was formed by "wiring" laccase to carbon through an electron conducting redox hydrogel, its redox functions tethered through long and flexible spacers to its cross-linked and hydrated polymer. Incorporation of the tethers increased the apparent electron diffusion coefficient 100-fold to (7.6 +/- 0.3) x 10-7 cm 2 s-1. A miniature single-compartment glucose-O2 biofuel cell made with the novel cathode operated optimally at 0.88 V, the highest operating voltage for a compartmentless miniature fuel cell.     

In situ EPR spectroscopy of aromatic diyne cyclopolymerization

Electron paramagnetic resonance (EPR) spectroscopy was successfully used for the first time to follow the Bergman cyclization of bis-ortho-diynyl arene (BODA) compounds. Five BODA monomers with different spacer (X) and terminal groups (R) were compared. In situ polymerization via EPR spectroscopy yielded first-order rate expressions. Monomers with spacer -O- or -C(CF(3))(2) and terminal group R = Ph exhibited similar kinetic behavior upon thermal polymerization, whereas monomers with pyridine and thiophene terminal groups gave significantly higher rates of polymerization over phenyl-terminated derivatives. A model compound, 1,2-bis(phenylethynyl)benzene, was used to probe the polymerization mechanism, and radical intermediates were found to be stable indefinitely at room temperature.     

Planarized star-shaped oligothiophenes with enhanced pi-electron delocalization

[structure: see text] Planarized star-shaped oligothiophenes 1 have been synthesized by connecting short-chain oligothiophenes on a benzo[1,2-b:3,4-b':5,6-b' ']trithiophene central core. Their electrochemical and optical properties have been characterized by cyclic voltammetry and UV-visible spectroscopy, respectively. These results associated with theoretical calculations show the advantage of benzotrithiophene as a central core in terms of pi-electron delocalization.