Use of WDM technique in SDH networks

This paper proposes the introduction of the multiwavelength technique in the three layers of a SDH-based network. In the trunk layer, wavelength division multiplexing (WDM) takes advantage of the optical parallelism in a single fiber. Cross-connection can be achieved either passively (i.e., with tunable filters) or by means of wavelength converters. The latter solution, which offers high flexibility, was implemented in a 4 × 4 optical routing element. In the junction network the feasibility of a three-station WDM self-healing ring was demonstrated. Finally, in the access network, synchronous burst access and time and wavelength division multiplexing (T/WDM) switching is proposed to offer service flexibility to the subscribers.     

DPIV, HPTV and visualization study of a vortex ring–moving wall interaction

This paper presents an experimental study of the interaction between a vortex ring and a moving wall. This type of flow can be considered as modeling, in a simplified way, the interaction between a "typical eddy" and the viscous sublayer of a turbulent boundary layer. In the present study, the vortex ring is considered as a three-dimensional (3D) perturbation of a viscous Stokes layer. The interaction was first characterized by visualization. To obtain quantitative information, digital particle image velocimetry (DPIV) and holographic particle-tracking velocimetry (HPTV) were used. These different techniques led to a precise and detailed characterization of the vortex ring alone and of an interaction in which a hairpin vortex is generated in the Stokes layer. The results obtained show a good similarity between the observed vortex ring and the Oseen model. They also validate the Stokes layer model and show that in the present conditions, the hairpin vorticity is comparable to that of the Stokes layer. The holographic study, which was undertaken to obtain full 3D three-component (3D3C) velocity maps, showed the present limitations of HPTV.     

Immobilization of Thermomyces lanuginosus Lipase by Different Techniques on Immobead 150 Support: Characterization and Applications

Thermomyces lanuginosus lipase (TLL) was immobilized on native and modified Immobead 150, with epoxy groups removed by hydrolysis and oxidized to add aldehyde on its surface. Immobilizations on both supports were performed by adsorption, adsorption and cross-linking, covalent attachment, multipoint covalent attachment, and, for the modified support, multipoint covalent attachment using ethylenediamine. Biocatalysts were evaluated for thermal and solvent stabilities, and the best biocatalyst was also tested after incubation in ionic liquids and used in the synthesis of butyl butyrate and isoamyl butyrate. Multipoint covalent immobilized TLL on the native Immobead 150 (Emulti) showed a half-life of 5.32 h at 70 °C, being approximately 30 times more stable than its soluble form; it showed high stability in acetone, hexane, and isooctane. Its enzymatic activity was up to 40 % when incubated in ionic liquids. Ester synthesis produced yields of esterification above 60 % in 24 h. Of all immobilization protocols, the Emulti performed best concerning the thermal, solvent, and ionic liquids stabilities. Emulti was successfully applied to the synthesis of butyl butyrate and isoamyl butyrate, which are very important products for the food and beverage industries.     

XPS analysis of chitosan–hydroxyapatite biomaterials: from elements to compounds

Chitosan (Cs) and hydroxyapatite (Ha) were analysed by X‐ray photoelectron spectroscopy (XPS). Phosphorylated Cs microparticles and hybrid Cs/Ha microparticles were prepared and analysed by XPS before and after immersion in a solution 1.5 times more concentrated than a simulated body fluid (SBF). The accuracy of spectrum recording, peak decomposition and peak component assignment was insured by a post‐control of charge stabilization, and by the examination of correlations between spectral data guided by stoichiometry and charge balance. The concentration of organic oxygen was determined from the concentrations of the oxidized forms of carbon, allowing a sharper insight into speciation and O 1s peak shape. This indicated that the hydroxide ion of Ha, and hydrogenophosphate if present, give a contribution near 532.4 eV, which overlaps with organic oxygen. As a result of immersion in the 1.5*SBF solution, the formation of CaCO₃ and of Ha material occurred. A quantification could be made for the constituents of biomaterial interest, contaminating salts and paraffin oil residues from the microparticle manufacturing process. The uncertainties regarding the nature of the model calcium phosphate used and the best marker for calcium carbonate were addressed by comparing the possible effect on the output, which was facilitated by using ternary composition diagrams. Whatever their formulation, the native microparticles were found to be coated by a thick layer of paraffin oil. The induction of calcium carbonate and phosphate precipitation or the retention of precipitates by the microparticles was favored by the presence of phosphate in the initial formulation either by phosphorylation or by incorporation of Ha. Copyright © 2013 John Wiley & Sons, Ltd.     

Convergence of a step-doubling Galerkin method for parabolic problems

We analyze a single step method for solving second-order parabolic initial-boundary value problems. The method uses a step-doubling extrapolation scheme in time based on backward Euler and a Galerkin approximation in space. The technique is shown to be a second-order correct approximation in time. Since step-doubling can be used as a mechanism for step-size control, the analysis is done for variable time steps. The stability properties of step-doubling are contrasted with those of Crank-Nicolson, as well as those of more general extrapolated theta-weighted schemes. We provide an example computation that illustrates both the use of step-doubling for adaptive time step control and the application of step-doubling to a nonlinear system.