Nucleobases,Nucleosides and Nucleotides Determination in Yeasts Isolated from Extreme Environments

Chromatographia - Nucleobases, nucleosides and nucleotides can act as chemical markers and immunnostimulants. Ultra-high-performance liquid chromatography with electrospray ionization and...     

Ultra‐high pressure LC for astaxanthin determination in shrimp by‐products and active food packaging

Nowadays, there is increasing interest in natural antioxidants from food by‐products. Astaxanthin is a potent antioxidant and one of the major carotenoids in crustaceans and salmonids. An ultra‐high pressure liquid chromatographic method was developed and validated for the determination of astaxanthin in shrimp by‐products, and its migration from new packaging materials to food simulants was also studied. The method uses an UPLC® BEH guard‐column (2.1 × 5 mm, 1.7 µm particle size) and an UPLC® BEH analytical column (2.1 × 50 mm, 1.7 µm particle size). Chromatographic separation was achieved using a programmed gradient mobile phase consisting of (A) acetonitrile–methanol (containing 0.05 m ammonium acetate)–dichloromethane (75:20:5, v/v/v) and (B) ultrapure water. This method was evaluated with respect to validation parameters such as linearity, precision, limit of detection, limit of quantification and recovery. Low‐density polyethylene films were prepared with different amounts of the lipid fraction of fermented shrimp waste by extrusion, and migration was evaluated into food simulants (isooctane and ethanol 95%, v/v). Migration was not detected under the tested conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

The regularized Benjamin-Ono and BBM equations: Well-posedness and nonlinear stability

Nonlinear stability of nonlinear periodic solutions of the regularized Benjamin-Ono equation and the Benjamin-Bona-Mahony equation with respect to perturbations of the same wavelength is analytically studied. These perturbations are shown to be stable. We also develop a global well-posedness theory for the regularized Benjamin-Ono equation in the periodic and in the line setting. In particular, we show that the Cauchy problem (in both periodic and nonperiodic case) cannot be solved by an iteration scheme based on the Duhamel formula for negative Sobolev indices.     

Spectral image cathodoluminescence,photoluminescence and Raman study of GaAs layers grown on Si substrates

GaAs layers grown on Si substrates by the conformal method were investigated by means of Raman, photoluminescence and cathodoluminescence spectroscopies. The combination of these optical techniques allows a better knowledge of the properties of these layers, with special emphasis on the stress distribution and the incorporation of dopants. In particular, samples intentionally doped, with alternate doped and undoped fringes, have been analyzed. The effective incorporation of Si atoms in the GaAs structure to produce n-type layers and the formation of Si complexes are determined by Raman and cathodoluminescence data. The lateral quasi-periodic stress distribution, typically observed in these layers, is shown to affect the Si incorporation.     

Mass Structured Systems with Boundary Delay: Oscillations and the Effect of Selective Predation

We study equilibrium and oscillatory solutions of a general mass structured system with a boundary delay. Such delays may be derived from systems with a separate egg class. Analytical calculations reveal existence criteria for non-trivial steady states. We further explore parameter space using numerical methods. The analysis is applied to a typical mass structured slug population model revealing oscillations, pulse solutions and irregular dynamics. However, robustly defined isolated cohorts, of the form sometimes suggested by experimental data, do not naturally emerge. Nonetheless, disordered, leapfrogging local maxima do result and may be enhanced by selective predation.     

Method for detecting and characterising actinide-bearing micro-particles in soils and sediment of the Fukushima Prefecture,Japan

An aqueous biphasic system has been used for selective extraction of U(VI) ions from Th(IV), Sm(III) and Ce(III). Role of different biomolecules like morin, catechin, hesperidin and 4-hydroxycoumarin have been studied. Morin serves as the best reagent when citrate ions are used as a masking agent. Citrate forms stronger complexes with the other metal ions than morin thereby restricting their extractions. Contrarily, U(VI) forms a stronger complex with morin than citrate and is selectively extracted under the same conditions. It was also observed that morin can act as a spectrophotometric reagent for ratiometric detection and analysis of U(VI) ions.

     

Fisher-Shannon plane and statistical complexity of atoms

Using the Hartree-Fock non-relativistic wave functions in the position and momentum spaces, the statistical measure of complexity C, due to López-Ruiz, Mancini, and Calbet for the neutral atoms as well as their monopositive and mononegative ions with atomic number Z=1-54 are reported. In C, given by the product of exponential power Shannon entropy and the average density, the latter is then replaced by the Fisher measure to obtain the Fisher-Shannon plane. Our numerical results suggest that in overall the Fisher-Shannon plane reproduces the trends given by C, with significantly enhanced sensitivity in the position, momentum and the product spaces in all neutral atoms and ions considered.     

Catalytic asymmetric hydrosilylation of acetophenone with new chiral thiourea ligands containing the (S)-α-phenylethyl group

New chiral thioureas 1–8 containing 1,2-ethylendiamine or trans-1,2-diaminocyclohexane as the carbon skeleton, and containing an (S)-α-phenylethyl group have been prepared (79–98% yield). Thioureas 1–8 were used as ligands for the zinc-based catalyzed asymmetric hydrosilylation of acetophenone with polymethylhydrosiloxane (PMHS). The best result was achieved with monothiourea 1 (up to 75% ee), in toluene and a catalyst load of 5 mol %.