A numerical method for junctions in networks of shallow-water channels

There is growing interest in developing mathematical models and appropriate numerical methods for problems involving networks formed by, essentially, one-dimensional (1D) domains joined by junctions. Examples include hyperbolic equations in networks of gas tubes, water channels and vessel networks for blood and lymph in the human circulatory system. A key point in designing numerical methods for such applications is the treatment of junctions, i.e. points at which two or more 1D domains converge and where the flow exhibits multidimensional behaviour. This paper focuses on the design of methods for networks of water channels. Our methods adopt the finite volume approach to make full use of the two-dimensional shallow water equations on the true physical domain, locally at junctions, while solving the usual one-dimensional shallow water equations away from the junctions. In addition to mass conservation, our methods enforce conservation of momentum at junctions; the latter seems to be the missing element in methods currently available. Apart from simplicity and robustness, the salient feature of the proposed methods is their ability to successfully deal with transcritical and supercritical flows at junctions, a property not enjoyed by existing published methodologies. Systematic assessment of the proposed methods for a variety of flow configurations is carried out. The methods are directly applicable to other systems, provided the multidimensional versions of the 1D equations are available

Synthesis and reactivity of half-sandwich (η 5 -C 5 Me 5 )Ir(iii) complexes of a cyclometallated aryl phosphine ligand

Reaction of the Ir(iii) dimer [(η 5 -C 5 Me 5 )IrCl 2 ] 2 with PMeXyl 2 (Xyl = 2,6-C 6 H 3 Me 2 ), in the presence of the poorly coordinating base 2,2,6,6-tetramethyl piperidine, gives a chloride complex 1-Cl, resulting from hydrogen chloride elimination involving one of the phosphine benzylic hydrogen atoms and concomitant cyclometallation. Related compounds containing other halide or pseudohalide ligands, 1-Br, 1-Cl, 1-SCN, can be made, the latter featuring S-coordination of the ambidentate thiocyanate to the soft Ir(iii) Lewis acid centre, as suggested by IR data and demonstrated by X-ray crystallography. Hydride 2-H, and alkyl derivatives 3 (Me) and 4 (CH 2 SiMe 3 ) can also be prepared from 1-Cl and appropriate hydride and alkylating reagents. An interesting H/D exchange chemistry that occurs in the presence of CD 3 OD has been disclosed for 1-Cl, 1-Br and 2-H. For the halide derivatives, deuterium incorporation takes place into the methylene and methyl sites of their cyclometallated ligand, whereas for 2-H only the hydride and methylene (Ir-CH 2 ) protons participate in the exchange, which is strikingly accelerated by catalytic amounts of acids.Ministerio de Ciencia e Innovación CTQ2010-17476Consolider-Ingenio2010 CSD2007-0000Junta de Andalucia FQM-119, P09-FQM-483

Removal of the cyanobacterial toxin microcystin -Lr by biofiltration: Identification of toxin-degrading bacteria and effects of backwashing

The removal of the cyanobacterial toxin microcystin-LR by slow and rapid drinking water biofilters, the presence of the microcystin-degrading bacteria in operating biofilters, the impact of backwashing on the removal of microcystin by biofiltration, and the prediction of microcystin-LR removal using a nonsteady-state biofilm model were investigated. A newly recognized microcystin-LR degrader, Morganella morganii, exists in Lake Mead and operating active biofilters. The results of the biodegradation tests indicated that addition of a carbon source, in the form of biodegradable NOM, significantly delayed the degradation of microcystin-LR. The biofiltration experiments demonstrated that at steady-state, biofiltration may be a potential technology for the removal of microcystin-LR under slow and rapid conditions. However, the impact of backwashing on microcystin removal, points out some limitations for this treatment process. The results of biofilm model prediction using estimated biofilm thickness indicated a better agreement with the TOC experimental data than with the microcystin\u27s data

Visibility, Functionality and Proactivity: Visions for the Future of Public Folklore

Challenge