Occurrence and behavior of butyltins in intertidal and shallow subtidal surface sediments of an estuarine beach under different sampling conditions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

VCD to determine absolute configuration of natural product molecules: secolignans from Peperomia blanda

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Montmorillonite (MMT) effect on the structure of poly(oxyethylene) (PEO)-MMT nanocomposites and silica-PEO-MMT hybrid materials

In this work we report the effects of incorporation of variable amounts (0.5-25%w/w) of montmorillonite in poly(oxyethylene) based materials in order to decrease the polymer crystallinity. Two different classes of materials were studied: silica-poly(oxyethylene)-montmorillonite hybrids prepared by the sol-gel route and poly(oxyethylene)-montmorillonite nanocomposites prepared by mixing the dry clay or the clay aqueous suspension into the melt poly(oxyethylene). The effects of monternorillonite loading on the poly(oxyethylene) crystallization control and on the nanostructural features were investigated by X-ray powder diffraction, small-angle X-ray scattering and differential scanning calorimetry. Experimental results show that free montmorillonite layers coexist with open aggregates and tactoids in the poly(oxyethylene)-montmorillonite nanocomposites, with different features depending on the filler proportion and preparation route. The intercalation of polymer chains in montmorillonite galleries markedly hinders the crystallization of the poly(oxyethylene) matrix. For hybrids materials the silica phase favors the exfoliation of montmorillonite tactoids, so that samples are predominantly constituted by dispersed platelets. (c) 2006 Elsevier B.V. All rights reserved.

Mercury Redox Chemistry in the Negro River Basin, Amazon: The Role of Organic Matter and Solar Light

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

APPLICATIONS OF ARTIFICIAL-INTELLIGENCE IN ORGANIC-CHEMISTRY .17. NEW PROGRAMS IN THE SISTEMAT PROJECT

This work describes the new improvements of the SISTEMAT project, one system for structural elucidation mainly in the field of Natural Products Chemistry. Some examples of the resolution of problems using C-13 Nuclear Magnetic Resonance and Mass Spectroscopy are given. Programs to discover new heuristic rules for structure generation are discussed. The data base contains about 10000 C-13 NMR spectra.