Nachweis und Bestimmung des Bleis

Ohne Zusammenfassung     

Eine empfindliche Reaktion auf Phenol und Salizyls?ure

Ohne Zusammenfassung     

Reaction of triphenylphosphine with poly(ethylene terephthalate) and certain model compounds at elevated temperature

Triphenylphosphine and poly(ethylene terephthalate) react at 370°C to produce ethylene, triphenylphosphine oxide, carbon dioxide, benzoic acid, and terephthalic acid. The reaction proceeds by the initial formation of a zwitterionic species which then generates a phosphonium ylid and leads to the observed products. Any flame retardant activity from the use of triphenyl-phosphine may be attributed to the formation of triphenylphosphine oxide. The co-production of ethylene renders triphenylphosphine a less effective flame retardant than triphenylphosphine oxide.     

Survey of exact N-body decompositions of stochastic scalar-Jastrow–Hartree form

The quantum N-body dynamics problem with pairwise interactions can be exactly decomposed into the average of N stochastically evolving 1-body problems, thereby eliminating the usual exponential scaling of computational costs. Unfortunately, the variance in such averages can be large leading to slow Monte Carlo convergence. In addition, norm preserving decompositions are available only for identical fermions or bosons. Here we introduce a family of decompositions of scalar-Jastrow–Hartree form which can be applied to electronic structure and many molecular dynamics problems. We also discuss their convergence properties and test a few such methods on the vibrational stretching mode dynamics of CH₄. Finally, we explain how the Monte Carlo convergence problem can be completely eliminated via the introduction of a perfect control variate.     

Thermal degradation studies on PMMA–HET acid based oligoesters blends

Imparting thermal stability to polymethyl methacrylate (PMMA) without affecting its optical clarity is attempted by incorporating HET acid based oligoesters. Pure PMMA and PMMA containing five and 20 wt% of four different oligoesters are separately prepared using bulk polymerization. The thermal properties of the materials studied using DSC, TG, TG–FTIR and Pyr–GC–MS are presented. The main volatile degradation products identified are CO, HCl, CO₂, H₂O, hexachlorocyclopentadiene, hexachloroendomethylene tetrahydrophthalic acid/anhydride and methyl methacrylate. A detailed mechanism for the influence of the degradation products of HET acid based oligoesters on the thermal degradation of PMMA is also presented.