Initial oxidation kinetics of copper (1 1 0) film investigated by in situ UHV-TEM

Previous studies of the initial stage of oxidation on clean single crystal of Cu(1 0 0) have been extended to the case of the Cu(1 1 0) surface. The dynamic observation of the nucleation and growth of Cu oxide by means of in situ ultra high vacuum transmission electron microscopy (UHV-TEM) shows a highly enhanced oxidation rate on Cu(1 1 0) surface as compared to Cu(1 0 0). The kinetic data on the nucleation and growth of the three-dimensional oxide islands agree well with our heteroepitaxial model of surface diffusion of oxygen.     

Linearized Stability of Charged Thin-Shell Wormholes

The linearized stability of charged thin shell wormholes under spherically symmetric perturbations is analyzed. It is shown that the presence of a large value of charge provides stabilization to the system, in the sense that the constraints onto the equation of state are less severe than for non-charged wormholes.     

Study of a vibrating plate: comparison between experimental (ESPI) and analytical results

Real-time electronic speckle pattern interferometry (ESPI) was used for tuning and visualization of natural frequencies of a trapezoidal plate. The plate was excited to resonant vibration by a sinusoidal acoustical source, which provided a continuous range of audio frequencies. Fringe patterns produced during the time-average recording of the vibrating plate—corresponding to several resonant frequencies—were registered. From these interferograms, calculations of vibrational amplitudes by means of zero-order Bessel functions were performed in some particular cases. The system was also studied analytically. The analytical approach developed is based on the Rayleigh–Ritz method and on the use of non-orthogonal right triangular co-ordinates. The deflection of the plate is approximated by a set of beam characteristic orthogonal polynomials generated by using the Gram–Schmidt procedure. A high degree of correlation between computational analysis and experimental results was observed.     

X-ray diffraction study of some mesogenic copper, nickel and vanadyl complexes

We present a comparative study of various metallomesogenic complexes, using X-ray diffraction methods. For a given ligand linked to different metal atoms (Cu, Ni, VO), the nature of this central atom influences mainly the magnetic susceptibilities of the mesophases. With different ligands, which keep the close neighbourhood of the metal atom unchanged, the apparent length of the mesogenic unit is longer for short ligands than for longer ones. This unexpected behaviour is qualitatively well explained by taking into account the global shape of the different complexes.     

Thermal and dilute-solution properties of zwitterionic copolymers

We report the synthesis, characterization, thermal and dilute-solution properties of zwitterionic copolymers of the sulfobetaine type, where the proportion of ionic groups is varied over a wide range. Two different structures are considered: poly (2-vinyl pyridine sulfopropyl betaine) and poly (4-vinyl pyridine sulfopropyl betaine). Synthesis is carried out to obtain random copolymers which are further characterized and their ionic content determined. At low proportions of ionic groups, the behavior is similar to that observed in ionomers, with substantial differences between the two structures, Increased interaction among the zwitterionic groups at higher charge densities is evidenced, which leads to the formation of clusters and agglomerates. An increase in the intrinsic viscosity with salt content in aqueous solutions is also observed. This behavior is analogous to that of homopolymers with 100% ionic content, but with particular features of interest.     

The influence of the liquid crystalline core geometry on the mesogenicity of novel chiral 2-(4-substituted-phenoxy)propanonitriles

The synthesis and characterization of seven novel (R)-2-(4-substituted-phenoxy)propanonitriles are described. The propanonitriles were prepared to evaluate their potential use as thermochromics and ferroelectric dopants, as well as to determine their twist sense properties. The materials exhibit smectic and chiral nematic phases of high thermal stability; the mesogenic behaviour of the nitriles is directly related to the type of two-ring core unit employed. The effects of the different molecular geometries and polarizabilities of the liquid crystalline cores on mesophase stability are discussed, particularly in relation to other members of this series. The chiral nematic phase of the propanonitriles is assigned as having a left-handed twist sense from contact preparation studies, and this is in agreement with rules relating absolute configuration and molecular structure to helical twist sense.     

Boundaries for algebras of holomorphic functions

Let A_u(B_G) be the Banach algebra of all complex valued functions defined on the closed unit ball B_G of a complex Banach space G which are uniformly continuous on B_G and holomorphic in the interior of B_G, endowed with the sup norm. A characterization of the boundaries for A_u(B_G) is given in case G belongs to a class of Banach spaces that includes the pre-dual of a Lorentz sequence space studied by Gowers in Israel J. Math. 69 (1990) 129-151. The non-existence of the Shilov boundary for A_u(B_G) is also proved.