The structure of metallomicelles

The morphology of micelles formed by two novel metallosurfactants has been studied by small-angle neutron scattering (SANS) and small-angle-X-ray scattering (SAXS). The two surfactants both contain a dodecyl chain as the hydrophobic moiety, but differ in the structure of the head group. The surfactants are Cu(II) complexes of monopendant alcohol derivatives of a) the face-capping macrocycle 1,4,7-triazacyclanonane (tacn), and b) an analogue based upon the tetraazamacrocycle 1,4,7,10-tetraazacyclododecane. Here, neutron scattering has been used to study the overall size and shape of the surfactant micelles, in conjunction with X-ray scattering to locate the metal ions. For the 1,4,7,10-tetraazacyclododecane-based surfactant, oblate micelles are observed, which are smaller to the prolate micelles formed by the 1,4,7-triazacyclononane analogue. The X-ray scattering analysis shows that the metal ions are distributed throughout the polar head-group region, rather than at a well-defined radius; this is in good agreement with the SANS-derived dimensions of the micelle. Indeed, the same model for micelle morphology can be used to fit both the SANS and SAXS data.     

Novel properties from experimental charge densities: an application to the zwitterionic neurotransmitter taurine

The charge distribution of taurine (2-aminoethane-sulfonic acid) is revisited by using an orbital-based method that describes the density in a fixed molecular orbital basis with variable orbital occupation numbers. A new neutron data set is also employed to explore whether this improves the deconvolution of thermal motion and charge density. A range of molecular properties that are novel for experimentally determined charge densities are computed, including Weinhold population analysis, Mayer bond orders, and local kinetic energy densities, in addition to charge topological analysis and quantum theory of atoms-in-molecules (QTAIM) integrated properties. The ease with which a distributed multipole analysis can be performed on the fitted density matrix makes it straightforward to compute molecular moments, the lattice energy, and the electrostatic interaction energies of molecules removed from the crystal. Results are compared with high-level (QCISD) gas-phase calculations and band structure calculations employing density functional theory. Finally, the avenues available for extending the range of molecular properties that can be calculated from experimental charge densities still further using this approach are discussed.     

A study of methane activation by modified gallium- and zinc-based catalysts

The activation of CH₄ has been probed by studying CH₄ oxidation at ambient pressure over gallium- and zinc-based catalysts prepared by precipitation and modified with Au and Pt. The unmodified gallium- and zinc-based catalysts were both active for CH₄ oxidation. Modification of these catalysts by the addition of Au and Pt, alone and in combination significantly increased the rate of CH₄ oxidation. The 1% Pt/Ga₂O₃ catalyst was the most active of the gallium-based systems. The addition of Au to ZnO markedly increased the activity compared with unmodified ZnO, whilst for Au in combination with Pt the activity was further enhanced due to a synergistic effect of the metals.     

Vectorial Approach to Fast Correlation Attacks

A new, vectorial approach to fast correlation attacks on binary memoryless combiners is proposed. Instead of individual input sequences or their linear combinations, the new attack is targeting subsets of input sequences as a whole thus exploiting the full correlation between the chosen subset and the output sequence. In particular, the set of all the input sequences can be chosen as the target. The attack is based on a novel iterative probabilistic algorithm which is also applicable to general memoryless combiners over finite fields or finite rings. To illustrate the effectiveness of the introduced approach, experimental results obtained for random balanced combining functions are presentedMost of this work was done while he was with Rome CryptoDesign Center, Gemplus, Italy     

On the Motion of a Dynamic System with Minimal Dissipation

The motion of a holonomic scleronomic non-conservative mechanicalsystem with minimal dissipation is considered. As applicationsof the theory several problems are studied in detail.     

Polarizability anisotropies of cyano-substituted azulene,biphenyl, 2,2'- bipyridyl and naphthalene

The conformations of a number of cyano-substituted aromatic model mesogens with actual or potential application in liquid crystals have been obtained using density functional B-LYP/6-311G(d) methodology. Dipole polarizability tensors have been computed at Hartree-Fock and B3-LYP levels of theory using Spackman's recommended basis sets, in order to obtain polarizability anisotropies, and to compare them with those of the parent compounds. The results indicate that 6-cyanoazulene is a potentially important mesogenic component, having a polarizability anisotropy not much less than 4-cyano-2,2'-bipyridyl. Electric dipole transition moments and oscillator strengths to the lowest singlet and triplet excited states have also been estimated for the cyanoazulenes, using a Configuration-Interaction Singles CIS/6-311G(d) approximation.