Polymerization of Methacrylamide Initiated by Ceric Ion-Citric Acid Redox System

Homogeneous polymerization of methacrylamide initiated by the ceric ammonium sulfate-citric acid (CA) redox pair has been investigated and reported at 35 ± 0.2°C under nitrogen atmosphere. The initiation was caused by the free radical generated by the decomposition of the complex formed between ceric ion and citric acid. The rate of monomer disappearance was found to be proportional to [CA]^0.4, [Ce^0.4+]^0.65, and [Monomer]¹ The rate of ceric ion disappearance was directly proportional to the ceric ion concentration but independent of the monomer concentration. The initial rate was independent of [H₂SO₄]. The activation energy of the system was found to be 21.4 kJ/mol.     

Integrating liquid crystal based optical devices in photonic crystal fibers

Liquid crystal photonic bandgap fibers form a versatile and robust platform for designing optical fiber devices, which are highly tunable and exhibit novel optical properties for manipulation of guided light. We present fiber devices for spectral filtering and polarization control/analysis.     

Painleve analysis for a semi-linear parabolic equation arising in smectic liquid crystals

This article presents a systematic method, employing a Painlevéanalysis for obtaining static and travelling wave solutionsto a semi-linear parabolic equation which frequently arisesin the smectic liquid crystal literature. The equation consideredhas sinusoidal non-linearities and shares some of the featuresof the double sine-Gordon equation; a brief discussion of therelationship of this equation to liquid crystals is also given.     

Multiple-view fluorescence optical tomography reconstruction using compression of experimental data

We report on the experimental demonstration of a fast reconstruction method for multiview fluorescence diffuse optical tomography by using a wavelet-based data compression. We experimentally demonstrate that the use of data compression combined with the multiview approach makes it possible to perform a fast reconstruction of high quality. A structured illumination approach, guided by the compression scheme, has been adopted to further reduce the acquisition time. The reconstruction algorithm is based on the finite element method, and hence is suitable for samples of any arbitrary shape.     

Spectral p‐multigrid discontinuous Galerkin solution of the Navier–Stokes equations

Discontinuous Galerkin (DG) methods are very well suited for the construction of very high‐order approximations of the Euler and Navier–Stokes equations on unstructured and possibly nonconforming grids, but are rather demanding in terms of computational resources. In order to improve the computational efficiency of this class of methods, a high‐order spectral element DG approximation of the Navier–Stokes equations coupled with a p‐multigrid solution strategy based on a semi‐implicit Runge–Kutta smoother is considered here. The effectiveness of the proposed approach in the solution of compressible shockless flow problems is demonstrated on 2D inviscid and viscous test cases by comparison with both a p‐multigrid scheme with non‐spectral elements and a spectral element DG approach with an implicit time integration scheme. Copyright © 2010 John Wiley & Sons, Ltd.     

Growth regimes in pulsed laser deposition of aluminum oxide films

Alumina is technologically exploited in several forms, ranging from compact hard films as protective coatings to open microstructures of high specific area as supports for catalysts. Currently, various production processes are used to deposit the different forms. PLD has the potential of obtaining not only the different forms, but also a continuous modulation of properties, by tuning of the process parameters. This work investigates the relationship between the process parameters and the resulting film morphology, structure and properties for PLD performed with an alumina target in a background oxygen atmosphere. Three distinct growth regimes are found, leading, respectively, to compact homogeneous films, columnar structures and open microstructures. These structures are quantitatively characterized, and the ranges of the process parameters corresponding to the three regimes are identified. An empirical scaling law is proposed, which can be exploited as a guide for the design of growth processes aimed at obtaining specific film properties.     

Stoffwechselprodukte von Mikroorganismen. 218. Mitteilung. Versuche zur Strukturaufklärung von Niphimycin, 1. Teil. Reinigung und Charakterisierung der Niphimycine Iα und Iβ sowie Abbau mit Salpetersäure

On the Structure Elucidation of Niphimycin, Part I. Purification and Characterization of the Niphimycins Iα and Ib?; Degradation by Nitric Acid From a sample of niphimycin the pure components, niphimycin Iα and Ib?, were isolated by column chromatography and droplet counter-current chromatography. They were characterized by UV., IR., ¹H-NMR. (300 MHz) and ¹³C-NMR. spectra. A vigorous degradation of niphimycin with nitric acid, followed by esterification with diazomethane, gave a complex mixture, from which many components could be isolated and identified. Several of the degradation products were synthesized, one of them (dimethyl 2,4-dimethyladipate) in a stereospecific manner, establishing the configuration of two of the centers of chirality of niphimycin. Niphithricin was identified with copiamycin and yielded with nitric acid a degradation mixture very similar to that from niphimycin. The structures of the degradation products are in good agreement with a macrolide-type structure of niphimycin and copiamycin. Further work for structure elucidation of niphimycin and copiamycin is in progress.