Synthesis of (imidazo[1,2-C]pyrimidin-2-yl)phenylmethanones and 6-benzoylpyrrolo[2,3-D]pyrimidinones

4-Pyrimidinamines have been reacted with 3-bromo-1-phenylpropane-1,2-dione to give a series of (imidazo[1,2-c]pyrimidin-2-yl)phenylmethanones. The dione also reacted with ethyl amidinoacetate to yield ethyl 2-amino-5-benzoylpyrrole-2-carboxylate which was used to prepare a series of 6-benzoylpyrrolo[2,3-a]pyrimidines.     

An adaptive cut‐cell method for environmental fluid mechanics

In this work we present a numerical method for solving the incompressible Navier–Stokes equations in an environmental fluid mechanics context. The method is designed for the study of environmental flows that are multiscale, incompressible, variable‐density, and within arbitrarily complex and possibly anisotropic domains. The method is new because in this context we couple the embedded‐boundary (or cut‐cell) method for complex geometry with block‐structured adaptive mesh refinement (AMR) while maintaining conservation and second‐order accuracy. The accurate simulation of variable‐density fluids necessitates special care in formulating projection methods. This variable‐density formulation is well known for incompressible flows in unit‐aspect ratio domains, without AMR, and without complex geometry, but here we carefully present a new method that addresses the intersection of these issues. The methodology is based on a second‐order‐accurate projection method with high‐order‐accurate Godunov finite‐differencing, including slope limiting and a stable differencing of the nonlinear convection terms. The finite‐volume AMR discretizations are based on two‐way flux matching at refinement boundaries to obtain a conservative method that is second‐order accurate in solution error. The control volumes are formed by the intersection of the irregular embedded boundary with Cartesian grid cells. Unlike typical discretization methods, these control volumes naturally fit within parallelizable, disjoint‐block data structures, and permit dynamic AMR coarsening and refinement as the simulation progresses. We present two‐ and three‐dimensional numerical examples to illustrate the accuracy of the method. Copyright © 2008 John Wiley & Sons, Ltd.     

Surface Analysis of Pulverised Fuel Ash by Secondary Ion Mass Spectrometry and X-ray Photoelectron Spectroscopy

Samples of pulverised fuel ash (PFA) obtained both from power stations and from laboratory combustion experiments have been examined by SIMS (secondary ion mass spectrometry) and XPS (x-ray photo-electron spectroscopy). The elemental analysis is at present semi-quantitative and indicates presence of sulphur mainly as sulphate ion in the outer surface layer (5–10 nm) of some samples. Other elements, notably Mg, Fe, K and Ti appear at higher concentrations, up to ～ 10% once the outer 10–20 nm surface layers have been removed by ion etching.     

Electrochemical Characterization of Myoglobin‐Polylysine Films at a Temperature Range of 6–80 °C

This work demonstrated for the first time that myoglobin cross‐linked in polylysine films is electrochemically active at 6 °C. At 6 °C, these protein films exhibited reversible reduction/oxidation peaks which are characteristic of Fe^III/Fe^II redox couple. The estimated current function densities (J=1.6×10^?4 C/V cm²), surface concentrations (Γ_T=0.10 nmol/cm²) and standard electron transfer constant (k_s=13.86 s^?1) at 6 °C for the data taken at a scan rate of 0.1 V/s were similar to those which were obtained at 10, 15 and 23 °C. Basically, this study shows a possible electrocatalytic application of these myoglobin/polylysine films, for example in low temperature sensing applications.     

Enantioselective epoxide polymerization using a bimetallic cobalt catalyst

A highly active enantiopure bimetallic cobalt complex was explored for the enantioselective polymerization of a variety of monosubstituted epoxides. The polymerizations were optimized for high rates and stereoselectivity, with s-factors (k(fast)/k(slow)) for most epoxides exceeding 50 and some exceeding 300, well above the threshold for preparative utility of enantiopure epoxides and isotactic polyethers. Values for mm triads of the resulting polymers are typically greater than 95%, with some even surpassing 98%. In addition, the use of a racemic catalyst allowed the preparation of isotactic polyethers in quantitative yields. The thermal properties of these isotactic polyethers are presented, with many polymers exhibiting high T(m) values. This is the first report of the rapid synthesis of a broad range of highly isotactic polyethers via the enantioselective polymerization of racemic epoxides.     

Hydrogen Bonding in the Water Stabilized Structure of the Modified Unsymmetrically Substituted Viologen Chromophore, <Emphasis Type="Italic">N</Emphasis>-ethyl-<Emphasis Type="Italic">N</Emphasis>′-(2-phosphonoethyl)-4,4′-bipyridylium Dichloride

Abstract  

The crystal structure of the modified unsymmetrically N,N′-substituted viologen chromophore, N-ethyl-N′-(2-phosphonoethyl)-4,4′-bipyridinium dichloride 0.75 hydrate (1) has been determined. Crystals are triclinic, space group P−1 with Z = 2 in a cell with a = 7.2550(1), b = 13.2038(5), c = 18.5752(7) Å, α = 86.495(3), β = 83.527(2), γ = 88.921(2)°. The two independent but pseudo-symmetrically related cations in the asymmetric unit form one-dimensional hydrogen-bonded chains through short homomeric phosphonic acid O–H···O links [2.455(4), 2.464(4) Å] while two of the chloride anions are similarly strongly linked to phosphonic acid groups [O–H···Cl, 2.889(4), 2.896(4) Å]. The other two chloride anions together with the two water molecules of solvation (one with partial occupancy) form unusual cyclic hydrogen-bonded bis(Cl···water) dianion units which lie between the layers of bipyridylium rings of the cation chain structures with which they are weakly associated.     

Bond percolation on isoradial graphs: criticality and universality

In an investigation of percolation on isoradial graphs, we prove the criticality of canonical bond percolation on isoradial embeddings of planar graphs, thus extending celebrated earlier results for homogeneous and inhomogeneous square, triangular, and other lattices. This is achieved via the star–triangle transformation, by transporting the box-crossing property across the family of isoradial graphs. As a consequence, we obtain the universality of these models at the critical point, in the sense that the one-arm and $2j$ -alternating-arm critical exponents (and therefore also the connectivity and volume exponents) are constant across the family of such percolation processes. The isoradial graphs in question are those that satisfy certain weak conditions on their embedding and on their track system. This class of graphs includes, for example, isoradial embeddings of periodic graphs, and graphs derived from rhombic Penrose tilings.