Redox-Active Hybrid Polyoxometalate-Stabilised Gold Nanoparticles

We report the design and preparation of multifunctional hybrid nanomaterials through the stabilization of gold nanoparticles with thiol-functionalised hybrid organic–inorganic polyoxometalates (POMs). The covalent attachment of the hybrid POM forms new nanocomposites that are stable at temperatures and pH values which destroy analogous electrostatically functionalised nanocomposites. Photoelectrochemical analysis revealed the unique photochemical and redox properties of these systems.     

On Visibility in the Afshar Two-Slit Experiment

A modified version of Young’s experiment by Shahriar Afshar indirectly reveals the presence of a fully articulated interference pattern prior to the post-selection of a particle in a “which-slit” basis. While this experiment does not constitute a violation of Bohr’s Complementarity Principle as claimed by Afshar, both he and many of his critics incorrectly assume that a commonly used relationship between visibility parameter V and “which-way” parameter K has crucial relevance to his experiment. It is argued here that this relationship does not apply to this experimental situation and that it is wrong to make any use of it in support of claims for or against the bearing of this experiment on Complementarity.     

The spectral order of accuracy: A new unified tool in the design methodology of excitation-adaptive wave equation FDTD schemes

We define a new concept, termed the spectral order of accuracy (SOoA), which is the spectral domain analogue of the familiar order of accuracy (OoA). The SOoA is pivotal in a refined version of a recently-introduced methodology for formulating excitation-adaptive wave equation FDTD (WE-FDTD) schemes, described below. This concept is the basis for a unified classification for both existing and new schemes. Both one- and two-dimensional cases are presented for boundless, source free, homogeneous, isotropic and lossless media. The 1-D and 2-D cases are developed in detail for the (3, 2M + 1) (temporal, spatial) and (3, 3) 2-D stencils, respectively. Stability analysis is built into the methodology in terms of either analytical conditions or “stability maps” defined herein. The methodology is seen as a generalization of many existing schemes that also provides a unified tool for a systematical design of WE-FDTD schemes subject to specific requirements in terms of the spectral content of the excitation. The computational efficiency for all schemes remains the same for a given stencil, since the core of the FDTD code is unchanged between schemes, the difference being only in the values of scheme coefficients.     

Measurement of high frequency linear viscoelastic functions of a nitrile‐butadiene rubber compound by ultrasound spectroscopy

The storage and loss components of the complex wave modulus, M*(ω), measured on a nitrile‐butadiene rubber compound (NBR‐DIN 53538) by ultrasound spectroscopy at a temperature of 293.2 K, were combined with the components of the complex shear modulus, G*(ω), measured on the same sample in a commercial Rheometric Scientific ARES instrument with torsion geometry at different frequencies and temperatures, and superposed in a master plot using the time–temperature superposition principle. From the combined measurements the components of the complex bulk modulus, K*(ω), were obtained by means of the exact formula M*(ω) = K*(ω) + (4/3)G*(ω). Some of the features of the complex bulk modulus reported in the literature for polymeric materials are confirmed for the NBR‐DIN mixture. The maxima in G″(ω) and K″(ω) are separated by more than one order of magnitude in the frequency scale and furthermore, the shapes of the peaks are different. The simple idea, that, for many polymers, the mechanisms for relaxation in shear and in bulk are of the same basic nature appears not to be supported by the present data. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 91–102, 2007     

The enantiomers of N,N-dimethylthiobenzamides: Chromatographic behaviour and rotational barriers

N,N-Dimethylthiobenzamides bearing hydrogen atoms in both orthopositions were shown by ¹H NMR in the presence of an optically active alcohol to have non-coplanar π-systems. The barrier to rotation about the C(sp²-C(sp²) bond amounts to 43 ± 2 kJ/mol. Liquid chromatography on triacetylcellulose served for the enrichment of enantiomers of 2-substituted thiobenzamides. In several cases considerable enantioselectivity (relative retention up to 8.7) was observed. The barriers to enantiomerization (Tables 3, 4 and 5), determined by thermal racemization, were discussed in terms of non-bonding interactions, electrostatic repulsions and buttressing effects in the transition state of rotation.     

On the observability of forbidden lines

The disappearance of forbidden lines for O III at intermidiate plasma densities may be due to background wing emission of the stronger allowed lines, rather than to Stark broadening of the forbidden lines as suggested recently. The general conclusion is supported that the classical explanation of quenching is erroneous, at least for O III.