A One-Pot Entry to a Novel 3-H-benzo[d]pyrazolo[1,5-b]isothiazole Ring System

Summary The phosphorus ylide obtained from the reaction between 2-aminobenzo[d]isothiazol-3-one and dimethyl acetylenedicarboxylate in the presence of triphenylphosphine undergoes a smooth intramolecular Wittig-type reaction to produce, in a one-pot reaction, 3-H-benzo[d]pyrazolo[1,5-b]isothiazole-2,3a-dicarboxylic acid dimethyl ester, a novel functionalized heterocyclic compound.     

Non-destructive characterization of compositional and textural properties of Etruscan bronzes: a multi-method approach

A combination of conventional analytical techniques, such as X-ray fluorescence (XRF) and scanning electron microscopy-electron probe microanalysis (SEM-EPMA), with novel applications of neutron scattering were employed for a non-destructive study of 6th century BC Etruscan bronze plates discovered almost two centuries ago in a princely chamber tomb in Umbria, Italy. The pieces were used to richly decorate a ceremonial carriage, two war chariots and some furniture. Analytical investigations have been carried out to provide the essential information to correctly assign several fragments in order to recompose the original plates. Analytical responses from XRF and SEM-EPMA, although indicative, were strongly affected by surface alteration and contamination. Rietveld analysis of neutron diffraction profiles emerged for its powerful capability to provide extensive non-destructive, high sensitivity information on bulk alloy composition and phase quantification allowing meaningful comparison among the pieces for the reconstruction of the original plates. In addition, strain and texture analyses demonstrated the capability of the technique to achieve a non-invasive characterization of manufacturing procedures. PACS 61.12.Ld; 81.40.Ef; 81.05.Bx     

Viscoelastic flow in a two-dimensional collapsible channel

We compute the flow of three viscoelastic fluids (Oldroyd-B, FENE-P, and Owens blood model) in a two-dimensional channel partly bounded by a tensioned membrane, a benchmark geometry for fluid–structure interactions. The predicted flow patterns are compared to those of a Newtonian liquid. We find that computations fail beyond a limiting Weissenberg number. Flow fields and membrane shape differ significantly because of the different degree of shear thinning and molecular extensibility underlying the three different microstructural models.     

Beta-functionalised polythiophenes as microelectrode modifiers in low conductive media

A study on polythiophene coated microelectrodes is reported, the goal being that of checking the capability of these electrochemical systems to work in low conductive media. The possibility of electrochemically p-doping the polymer in the presence of very low concentrations or even in the absence of supporting electrolyte in the solution is ascertained, opening the way to the use of similar systems in pure solvent media. This result is obtained in such conditions that the presence of residual charges--and corresponding counterions--trapped inside the film coating can be reasonably hypothesised.     

Isotropy breaking magnetoelastic behavior in highly magnetostrictive compounds

Two distinct acoustic shear modes are observed to propagate in otherwise isotropic rare earth-iron compounds when a magnetic field is applied. The field dependence of the velocities of the two modes are reported and the results interpreted using linear magnetoelastic theory.     

Hysteresis of charge tunneling in assemblies of carboxylic acid-modified gold nanoparticles

We report on charge transport measurements through laterally contacted assemblies of Au nanoparticles capped with 11-mercaptoundecanoic acid ligands. Both alternating- and direct-current data indicate that although the nanoparticles behave as electrically isolated metallic islands, there is a significant influence from the nanoparticle environment, indicating the existence of a slow reorganization process linked to charge transport. On the basis of the observation of temperature-dependent hysteresis of charge tunneling, we propose that this process is due to proton transfer between the carboxylic acid tails of the ligands.     

Valence-bond crystal in a pyrochlore antiferromagnet with orbital degeneracy

We discuss the ground state of a pyrochlore lattice of threefold orbitally degenerate S=1/2 magnetic ions. We derive an effective spin-orbital Hamiltonian and show that the orbital degrees of freedom can modulate the spin exchange, removing the infinite spin-degeneracy characteristic of pyrochlore structures. The resulting state is a collection of spin-singlet dimers, with a residual degeneracy due to their relative orientation. This latter is lifted by a magnetoelastic interaction, induced in the spin-singlet phase space, that forces a tetragonal distortion. Such a theory provides an explanation for the helical spin-singlet pattern observed in the B spinel MgTi2O4.     

Critical thermodynamics of the two-dimensional +/-J Ising spin glass

We compute the exact partition function of 2d Ising spin glasses with binary couplings. In these systems, the ground state is highly degenerate and is separated from the first excited state by a gap of size 4J. Nevertheless, we find that the low temperature specific heat density scales as exp(-2J/T), corresponding to an "effective" gap of size 2J; in addition, an associated crossover length scale grows as exp(J/T). We justify these scalings via the degeneracy of the low lying excitations and by the way low energy domain walls proliferate in this model.