Reaction of benzyl alcohol over the hydrogen storage intermetallic compound Mg2Cu

The reaction of benzyl alcohol over the hydrogen storage intermetallics Mg₂Cu was studied in the temperature range of 573–773 K. Benzaldehyde and toluene, the major products, were produced by dehydrogenation and disproportionation reactions, respectively. Anthracene, stilbene and benzyltoluenes were also formed due to benzylation reaction. Since the benzylation course was strongly influenced by shape selectivity considerations, these were produced in minor amounts. Below 673 K, Mg₂Cu behaves like metals while above 673 K it behaves like oxide systems in its catalytic properties.     

Gauge technique and BCS theory of superconductivity

Summary The gauge technique in unbroken (exact) relativistic quantum electrodynamics is applied to the nonrelativistic BCS theory exhibiting spontaneously brokenU(1) gauge invariance. In addition to the BCS-type solution, we find an interestingnew solution forweak coupling exhibiting ahigh T _c. The authors of this paper have agreed to not receive the proofs for correction.     

High-temperature superconductivity in bismuth-copper oxides of the type Bi m M n Cu p O x (M=Mg,Ca, Sr,Ba, Bi)

Several oxides of the Bi _m M _n Cu _p O _x family (m=2, 3;n=2, 3, 4;p=1, 2, 3 and M=alkaline earth or Bi), possessing structures similar to the Aurivillius family of oxides, show highT _c superconductivity. Contribution No. 514 from the Solid State and Structural Chemistry Unit.     

A Monte Carlo ray tracing study of polarized light propagation in liquid foams

A Monte Carlo ray tracing scheme is used to investigate the propagation of an incident collimated beam of polarized light in liquid foams. Cellular structures like foam are expected to change the polarization characteristics due to multiple scattering events, where such changes can be used to monitor foam dynamics. A statistical model utilizing some of the recent developments in foam physics is coupled with a vector Monte Carlo scheme to compute the depolarization ratios via Stokes-Mueller formalism. For the simulations, the incident Stokes vector corresponding to horizontal linear polarization and right circular polarization are considered. It is observed that bubble size and the polydispersity parameter have a significant effect on the depolarization ratios. This is partially owing to the number of total internal reflection events in the Plateau borders. The results are discussed in terms of applicability of polarized light as a diagnostic tool for monitoring foams.     

Ruthenium(III)-catalyzed oxidation of amides by sodium N-bromobenzenesulphonamide in hydrochloric acid: a kinetic and mechanistic study

The kinetics of the RuIII-catalyzed oxidation of urea and substituted ureas namely: methylurea, ethylurea and propylurea, to the corresponding hydrazines by sodium N- bromobenzenesulphonamide or bromamine-B (BAB) in HCl medium has been studied at 303K. The reaction rate shows a first order dependence each upon [BAB], [amide] and [RuIII] and is dependent on [H+]. Addition of halide ions and benzenesulphonamide do not significantly affect the rate. Proton inventory studies were made in H2O-D2O mixtures for urea and methylurea. A Taft linear free energy relationship is observed for the reaction with *=–2.95 and =–0.25, showing that electron-donating groups enhance the rate. An isokinetic relation is observed with =370K, indicating that enthalpy factors control the rate; this result is also confirmed by Exner Criterion which showed a linear plot for the logarithms of rate constants at the highest and lowest temperatures employed. The protonation constant of monobromamine-B has been evaluated and equals 7.5. A mechanism consistent with the observed kinetic data has been proposed.     

Generalised mean spherical approximation and the thermodynamics of a classical one-component plasma

The generalised mean spherical approximation has been used in deriving the thermodynamics of a classical one-component plasma using the variational method. The free energy and the excess specific heat are calculated and compared with recent Monte-Carlo results. The agreement was found to be good.