On the upstream mobility scheme for two-phase flow in porous media

When neglecting capillarity, two-phase incompressible flow in porous media is modelled as a scalar nonlinear hyperbolic conservation law. A change in the rock type results in a change of the flux function. Discretizing in one-dimensional with a finite volume method, we investigate two numerical fluxes, an extension of the Godunov flux and the upstream mobility flux, the latter being widely used in hydrogeology and petroleum engineering. Then, in the case of a changing rock type, one can give examples when the upstream mobility flux does not give the right answer.Comment: A preprint to be published in Computational Geoscience

Arginine–glycine–aspartic acid functional branched semi-interpenetrating hydrogels

For the first time a series of functional hydrogels based on semi-interpenetrating networks with both branched and crosslinked polymer components have been prepared and we show the successful use of these materials as substrates for cell culture. The materials consist of highly branched poly(N-isopropyl acrylamide)s with peptide functionalised end groups in a continuous phase of crosslinked poly(vinyl pyrrolidone). Functionalisation of the end groups of the branched polymer component with the GRGDS peptide produces a hydrogel that supports cell adhesion and proliferation. The materials provide a new synthetic functional biomaterial that has many of the features of extracellular matrix, and as such can be used to support tissue regeneration and cell culture. This class of high water content hydrogel material has important advantages over other functional hydrogels in its synthesis and does not require postprocessing modifications nor are functional-monomers, which change the polymerisation process, required. Thus, the systems are amenable to large scale and bespoke manufacturing using conventional moulding or additive manufacturing techniques. Processing using additive manufacturing is exemplified by producing tubes using microstereolithography

Complexes of heterocyclic thiones and group 12 metals: part VI. Preparation and characterisation of complexes of cadmium(II) halides with 1-methylimidazoline-2(3H)-thione, 1,3-thiazolidine-2-thione and 1,3-benzothiazoline-2-thione. Crystal structures of polymeric (1,3-thiazolidine-2-thione)cadmium(II) chloride, bis(1,3-thiazolidine-2-thione)cadmium(II) iodide and monomeric bis(1-methylimidazoline-2(3H)-thione)cadmium(II) bromide

Reactions of 1-methylimidazoline-2(3H)-thione (meimz2SH), 1,3-thiazolidine-2-thione (tzdSH) and 1,3-benzothiazoline- 2-thione (bztzSH) with cadmium(II) halides in ethanol solutions result in the formation of 1:1 complexes for the chloride, both 1:1 and 2:1 complexes for the bromide, and only 2:1 complexes for the iodide. Spectroscopic evidence confirms the exocyclic sulfur atom to be the donor in all cases. Cadmium(II) acetate and the heterocyclic ligands in the presence of triethylamine form the insoluble deprotonated complexes. The structure of (tzdSH)CdCl2, consists of double halogen-bridged chains, linked into sheets via (NHCl)-Cl-... interactions and with the heterocycle coordinated to the metal via the exocyclic sulfur atom. Thus each cadmium is approximately octahedrally surrounded by one sulfur, 2 two-coordinate and 3 three-coordinate chlorine atoms. In contrast (tzdSH)(2)CdI2, forms chains via (IS)-S-... interactions; the metal is tetrahedrally coordinated by two sulfur and two iodine atoms. The structure of (meimz2SH)(2)CdBr2, consists of discrete complex molecules with essentially tetrahedrally coordinated Cd and no significant intermolecular interactions; the six molecules in the asymmetric unit are related by pseudo-symmetry and are very similar except for variation in the orientation of the heterocyclic substituents