Two Unusual Trimers of Diketene

Formation of two unknown, tricyclic trimers of diketene, 3 and 4 , was observed in diketene solutions containing (CH₃)₃SiCl/NaI or TsOH.     

Ribaucourtransformationen und sphärische Abbildung

Ohne Zusammenfassung     

Implicit finite element methods for two-phase flow in oil reservoirs

The equations governing immiscible, incompressible, two-phase, porous media flow are discretized by generalized streamline diffusion Petrov–Galerkin methods in space and by implicit differences in time. Systems of non-linear algebraic equations are solved by Newton–Raphson iteration employing ILU-preconditioned conjugate-gradient-like methods to the non-symmetric matrix system in each iteration. The resulting solution methods are robust, enable complex grids with irregular nodal orderings and allow capillary effects. Several numerical formulations are tested and compared for one-, two- and three-dimensional flow cases, with emphasis on problems involving saturation shocks, heterogeneous media and curved boundaries. For reservoirs consisting of multiple rock types with differing capillary pressure properties, it is shown that traditional Bubnov-Galerkin methods give poor results and the new Petrov–Galerkin formulations are required. Investigations regarding the behaviour of several preconditioned conjugate-gradient-like methods in these type of problems are also reported.     

Capillary gas chromatography of amines with ammonia as carrier gas

The use of ammonia as a carrier gas for the chromatography of aliphatic and aromatic amines has been investigated. As compared to nitrogen, ammonia gave drastically improved peak symmetry and lower capacity factors (k′) for primary and secondary amines on polar (Polyethylene glycol) and medium Polar (methylphenylcyanopropylsilicone) stationary Phases. The effect of ammonia was more Pronounced at low column temperatures. Considerably better detection limits of primary and secondary amines were obtained with ammonia as carrier gas than with nitrogen. No detrimental effects of using ammonia were observed on the gas chromatograph or on the columns over a period of about one year.