{N‐[2‐(η5‐Cyclopentadienyl)ethyl]‐4‐toluenesulfonamido‐N,O}(tetrahydrofuran‐O)bis(trifluoromethanesulfonato‐O)titanium(II)

The title compound, [Ti(CF₃O₃S)₂(C₁₄H₁₅NO₂S)(C₄H₈O)], contains a unique ligand system in which the Ti ion is bound to the N and O atoms of a 2‐p‐toluene­sulfon­amide ligand, which is linked by an ethyl group to a coordinated cyclo­penta­diene moiety. The distorted octahedral geometry about the Ti ion is completed by two tri­fluoro­methane­sulfonate ligands and a tetra­hydro­furan mol­ecule. Comparison with related compounds shows that both the Ti—N and Ti—O bonds of the sulfon­amide, although longer than normal values, indicate significant bonding interactions.     

Optimal superconvergent one step quadratic spline collocation methods

We formulate new optimal quadratic spline collocation methods for the solution of various elliptic boundary value problems in the unit square. These methods are constructed so that the collocation equations can be solved using a matrix decomposition algorithm. The results of numerical experiments exhibit the expected optimal global accuracy as well as superconvergence phenomena. AMS subject classification (2000)  65N35, 65N22     

Analysis of kinetic mechanism performance in conditional moment closure modelling of turbulent,non-premixed methane flames

This paper presents results obtained from the application of a first-order conditional moment closure approach to the modelling of two methane flames of differing geometries. Predictions are based upon a second-moment turbulence and scalar-flux closure, and supplemented with full and reduced chemical kinetic mechanisms, ranging from a simple 12-step to a complex 1207-step mechanism. Alongside analysis of the full kinetic schemes' performance, is an appraisal of the behaviour of their derivatives obtained using mechanism-reduction techniques. The study was undertaken to analyse the practicality of incorporating kinetic models of varying complexity into calculations of turbulent non-premixed flames, and to make comparison of their performance. Despite extensive studies of the predictive ability of such schemes under laminar flame conditions, systematic evaluations have not been performed for turbulent reacting flows. This paper reflects upon the impact that selection of chemical kinetics has upon subsequent calculations and concludes that, although application of reduced schemes is more than adequate to reproduce experimental data, selection of the parent mechanism is of paramount importance to the prediction of minor species. Although widely used schemes are well documented and validated, their performances vary considerably. Thus, careful consideration must be made to their application and origins during the evaluation of combustion models.     

Porous conducting polymer/heteropolyoxometalate hybrid material for electrochemical supercapacitor applications

A porous conducting polymer/heteropolyoxometalate hybrid material that displays high specific capacitance and low ionic resistance has been prepared for electrochemical supercapacitor applications. Polypyrrole/phosphomolybdate composite films were chemically synthesized in tetrahydrofuran in the presence of sodium sulfate, which acts as a porogen. While the phosphomolydic acid could be removed from the film upon rinsing with pure tetrahydrofuran or acetone, rinsing with water or methanol resulted in retention of the heteropolyoxometalate at a level high enough to easily observe its electrochemistry. The retained phosphomolybdate exhibits fast and reversible redox behavior, adding a significant amount of pseudocapacitance to the polymer. Porous films were obtained by leaching out the sodium sulfate porogen from the films using water. The morphology obtained using this method is altered by varying the monomer-to-porogen ratio. Increasing the porosity increases the rate at which the hybrid material can be charged/discharged (i.e., oxidized/reduced) by increasing the ionic conductivity and in turn lowering the resistor-capacitor time constant of the material. The ability to tune the porosity of the material allows the optimization of performance characteristics for use in supercapacitor applications. Impedance measurements indicate that the ionic conductivity of these porous structures can be increased more than an order of magnitude over that observed for standard conducting polymer films and that the hybrid material displays peak specific capacitance of around 700 F/g as well as excellent reversibility and cyclability.     

Exterior cloaking with active sources in two dimensional acoustics

We cloak a region from a known incident wave by surrounding the region with three or more devices that cancel out the field in the cloaked region without significantly radiating waves. Since very little waves reach scatterers within the cloaked region, the scattered field is small and the scatterers are for all practical purposes undetectable. The devices are multipolar point sources that can be determined from Green's formula and an addition theorem for Hankel functions. The cloaking devices are exterior to the cloaked region.     

UV light‐mediated alkylation of inorganic selenium

In the presence of low molecular weight organic acids (formic, acetic, propionic and malonic), inorganic selenium(IV) is converted by UV irradiation to volatile selenium carbonyl, dimethylselenide and diethylselenide, depending on the acid used. Gas chromatography–mass spectrometry analysis of the volatile products shows that, in 0.7 M formic acid solution, approximately 60–70% (v/v) SeH₂ and 30–40% (v/v) SeCO are formed. The presence of nitrate ion appears to increase threefold the formation of SeCO while completely suppressing formation of SeH₂. Copyright © 2003 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.     

Outputs and time lags for linear bioreactors

Linear systems of convection reaction-diffusion equations for bioreactors are shown to have a structure which allows a geometric factorization of steady state problems giving a significant reduction in their dimensionality. Moreover, convection dominated linear systems with quasisymmetric reaction terms may be further simplified by matrix transformations, which uncouple the differential equations. The boundary conditions are also uncoupled when the diagonal diffusivity matrix D governing diffusion in the bioparticle is a scalar multiple of the corresponding matrix H describing the diffusivity characteristic of the fluid boundary layers around the bioparticles. The dominant transient behaviour of the systems may be handled by establishing an analogous system of time independent equations for mean action time variables and higher moments. These equations have the same amenable structure. Outputs, time lags and various mean residence and first passage times, associated with establishing steady outputs from a concentration free initial state, can be expressed in terms of the steady state solutions and mean action time variables.     

Experimental investigation of an axisymmetric,impinging turbulent jet. 1. Velocity field

Mean and fluctuating velocities and shear stresses in an air jet impinging on a flat surface have been obtained by particle image velocimetry. A recirculation zone is revealed within the flow that carries material from the periphery of the wall jet back to its initial regions. Results within the wall jet agree with earlier data from laser Doppler anemometry, although significant differences occur with probe measurements. Data on the mixing characteristics of the flow are presented in a companion paper.