Solid-state single and triple-quantum 93Nb MAS NMR studies of ferroelectric Pb(Mg1/3Nb2/3)O3 and a related pyrochlore

Pb(Mg1/3Nb2/3)O3 (PMN), a well-known relaxor ferroelectric material, and a related pyrochlore phase have been studied by single- and triple-quantum 93Nb MAS NMR spectroscopy. The assignment of the NMR resonances has been attempted.     

Isothermal Vapor–Liquid Equilibria for the Ternary System 2-Propanol + Tetrahydrofuran + 1-Chlorobutane at 25°C

Isothermal vapor–liquid equilibria (VLE) for mixtures containing 2-propanol + tetrahydrofuran + 1-chlorobutane have been measured using a modified version of a Boublik–Benson still at 25°C. A test of thermodynamic consistency, like the McDermott–Ellis method was applied to the activity coefficients. Excess molar Gibbs free energies were calculated over the entire range composition. Different expressions existing in the literature were used to predict activity coefficients.     

Diastereoselective tandem 6-exo carbolithiation intramolecular ring opening in (-)-8-aminomenthol-derived perhydrobenzoxazines. A new synthesis of enantiopure 4-substituted tetrahydro isoquinolines and 2-azabenzonorbornanes.

Aryllithiums prepared by bromine-lithium interchange in chiral 2-(o-bromophenyl)-substituted perhydro-1,3-benzoxazines participate in the intramolecular 6-exo carbolithiation reaction with unactivated double bonds attached to the nitrogen substituent of the heterocycle. When the reaction time is extended or no TMEDA is used, the cyclized lithium intermediates react intramolecularly with the N,O-acetal system leading to 2-azabenzonorbornane derivatives. The reactions are highly stereoselective and constitute a high-yielding synthesis of enantiopure 4-substituted tetrahydroisoquinolines or 7-substituted 2-azabenzonorbornanes.     

Memetic self-adaptive evolution strategies applied to the maximum diversity problem

The maximum diversity problem consists in finding a subset of elements which have maximum diversity between each other. It is a very important problem due to its general aspect, that implies many practical applications such as facility location, genetics, and product design. We propose a method based on evolution strategies with local search and self-adaptation of the parameters. For all time limits from 1 to 300 s as well as for time to converge to the best solutions known, this method leads to better results when compared to other state-of-the-art algorithms.     

Production of Enzymes by Paenibacillus chitinolyticus and Paenibacillus ehimensis to Obtain Chitooligosaccharides

Obtaining oligosaccharides from chitosan has been the focus of several studies in the pharmaceutical, chemical, food, and medical areas, due to their functional properties. Here, we evaluated the production potential of biologically functional chitooligosaccharides using enzymes extracts produced by Paenibacillus chitinolyticus and Paenibacillus ehimensis. After 48 h of fermentation, these microorganisms were able to produce chitosanases, which generated oligomers with a degree of polymerization between dimers and hexamers. The maximum conversion of chitosan to oligomers was 99.2 %, achieved after 12 h incubation of chitosan with enzymes produced by P. ehimensis. The chitooligosaccharides generated were capable of scavenging the 2,2-diphenyl-1-picrylhydrazyl radical, reaching a maximum scavenging rate of 61 and 39 % when produced with P. ehimensis and P. chitinolyticus enzymes, respectively. The use of these enzymes in the crude form could facilitate their use in industrial applications.     

Selective Monophosphorylation of Aliphatic Diamines

This article describes an improved method to synthesize phosphoramidic acid aminoalkyl esters from diamines by the adaptation of industrial patents. Four mono-phosphorylated products having amino sites were obtained in good a yield. Such compounds have potential coordination properties with transition metals and also potential biological activity.