Role of montmorillonite in flame retardancy of ethylene-vinyl acetate copolymer

The effects of non-treated (MMT), organophilic (OMM), and olefin/silicone polymer intercalated (IMM) montmorillonites on the thermal stability of ethylene-vinyl acetate copolymer (EVA) and on the flammability of magnesium hydroxide filled EVA were studied. The influence of various treatments on the delamination of montmorillonites in EVA was detected by rheological measurements and by Raman microscopy. The latter was a unique method for rapid detection of the dispersion also in highly filled EVA. Enhancement of thermo-oxidative stability of EVA and flame-retarded EVA could be observed by thermal analysis in the presence of variously treated montmorillonites. The flame-retardant efficiency of magnesium hydroxide was improved by simultaneous application of MMT and IMM. The increased performance of magnesium hydroxide was explained by the rheological effect of the IMM, catalytic effect of MMT and chemical interactions of montmorillonites with the metal hydroxide.     

Intrazeolite photooxygenation of chiral alkenes. Control of facial selectivity by confinement and cation-π interactions

Depending on the nature of the substituents on the stereogenic carbon atom, the ene reaction of singlet oxygen with several chiral alkenes by confinement within thionin-supported zeolite NaY, may exhibit significant changes on facial selectivity by comparison to their photooxygenation reaction in solution. It is proposed that, apart from the conformational consequences as a result of the alkene confinement within the zeolite cavities, a synergism between Na⁺-π interactions and singlet oxygen-Na⁺ interactions plays a significant role in the transition states of ene hydroperoxidation. Within NaY, the diastereoselectivity may significantly depend on the site selectivity, as probed through specific deuterium labelling of trisubstituted alkenes bearing a gem-dimethyl group. In certain cases, a remote stereogenic centre relative to the reacting double bond may induce enhanced diastereoselection and regioselectivity.     

The reaction of triptycene haloquinones with alkoxides. An unusual route to pentiptycene quinones

Triptycene haloquinones 3 react with sodium alkoxides in refluxing alcohol to afford, besides the expected substitution products, pentiptycene quinone 4. This approach to 4 is compared with a Diels-Alder strategy to the same compound.     

A finite difference scheme for computing inertial manifolds

A fully discrete method is presented for computing inertial manifolds of dissipative partial differential equations. In particular, only an approximate spectral decomposition of the dominant differential operator needs to be known. The first few of the smallest eigenvalues and eigenvectors of the discretized operator are approximated using the Lanczos algorithm. Numerical experiments are performed for an equation in one space dimension by discretizing the space variable on a sufficiently fine grid. The basic ideas and techniques are exemplified for selected bifurcation diagrams of an integrated form of the Kuramoto-Sivashinsky equation.This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) grant OGP0036901, NSERC and Schweizerischer Nationalfonds zur Förderung der Wissenschaften BEF 0150297, and Forschungsinstitut für Mathematik, ETH Zürich.     

Mehrstufiges Verfahren zur Herstellung von Deuteropropanon auf katalytischem Weg

A novel equipment for a multistep deuteration process of organic compounds was developed. As an example the deuteration of propanone by deuterium oxide over magnesia and thoria was examined. The degree of deuteration of the organic compound and of the catalysts was determined by on-line mass-spectrometry. Percentages of deuterium uptake of the organic compound up to 90% were found. These degrees of deuteration were higher than those measured at the catalysts' surface. This fact can be explained by the kinetic isotope effect.

     

SMART — An algorithm for reconstructing pictures from projections

A new algorithm — called SMART — is suggested for the reconstruction of digitized pictures from one-dimensional projections. The algorithm is shown to converge with a geometric rate to the least squares solution of minimal norm. Therefore the algorithm is applicable even to inconsistent systems which usually occur when the data are noisy.     

Antiproliferative Phenanthrenes from Juncus tenuis: Isolation and Diversity-Oriented Semisynthetic Modification

The occurrence of phenanthrenes is limited in nature, with such compounds identified only in some plant families. Phenanthrenes were described to have a wide range of pharmacological activities, and numerous research programs have targeted semisynthetic derivatives of the phenanthrene skeleton. The aims of this study were the phytochemical investigation of Juncus tenuis, focusing on the isolation of phenanthrenes, and the preparation of semisynthetic derivatives of the isolated compounds. From the methanolic extract of J. tenuis, three phenanthrenes (juncusol, effusol, and 2,7-dihydroxy-1,8-dimethyl-5-vinyl-9,10-dihydrophenanthrene) were isolated. Juncusol and effusol were transformed by hypervalent iodine(III) reagent, using a diversity-oriented approach. Four racemic semisynthetic compounds possessing an alkyl-substituted p-quinol ring (1–4) were produced. Isolation and purification of the compounds were carried out by different chromatographic techniques, and their structures were elucidated by means of 1D and 2D NMR, and HRMS spectroscopic methods. The isolated secondary metabolites and their semisynthetic analogues were tested on seven human tumor cell lines (A2780, A2780cis, KCR, MCF-7, HeLa, HTB-26, and T47D) and on one normal cell line (MRC-5), using the MTT assay. The effusol derivative 3, substituted with two methoxy groups, showed promising antiproliferative activity on MCF-7, T47D, and A2780 cell lines with IC₅₀ values of 5.8, 7.0, and 8.6 µM, respectively.