Application of electrospray mass spectrometry in the detection and determination of Remazol textile dyes.

The electrospray (ES) behaviour of selected Remazol textile dyes, their hydrolysis products and the latters' reaction, following elution from a strong anion-exchange cartridge, with 30% concentrated HCl in MeOH, is studied and applied to the direct analysis of dye containing effluent. For unambiguous identification and determination of these textile dyes in effluents, it is necessary to resort to ES utilising MS-MS and MS3. Further, a tabular review of recent applications of HPLC-ES-MS and, to a lesser extent, CE-ES-MS with reference to drug and pesticide analysis is presented.     

A comparative study of inflow conditions for two‐ and three‐dimensional spatially developing mixing layers using large eddy simulation

A series of spatially developing mixing layers are simulated using the large eddy simulation (LES) technique. A hyperbolic tangent function and data derived from boundary layer simulations are used to generate the inflow condition, and their effects on the flow are compared. The simulations are performed in both two and three dimensions. In two‐dimensional simulations, both types of inflow conditions produce a layer that grows through successive pairings of Kelvin–Helmholtz (K–H) vortices, but the composition ratio is lower for the hyperbolic tangent inflow simulations. The two‐dimensional simulations do not undergo a transition to turbulence. The three‐dimensional simulations produce a transition to turbulence, and coherent structures are found in the post‐transition region of the flow. The composition ratio of the three‐dimensional layers is reduced in comparison to the counterpart two‐dimensional runs. The mechanisms of growth are investigated in each type of simulation, and amalgamative pairing interactions are found in the pre‐transition region of the three‐dimensional simulations, and throughout the entire computational domain of those carried out in two‐dimensions. The structures beyond the post‐transition region of the three‐dimensional simulations appear to behave in a much different manner to their pre‐transition cousins, with no pairing‐type interactions observed in the turbulent flow. In order to accurately simulate spatially developing mixing layers, it is postulated that the inflow conditions must closely correspond to the conditions present in the reference experiment. Copyright © 2007 John Wiley & Sons, Ltd.     

A hybrid metaheuristic approach to the university course timetabling problem

This paper describes the development of a novel metaheuristic that combines an electromagnetic-like mechanism (EM) and the great deluge algorithm (GD) for the University course timetabling problem. This well-known timetabling problem assigns lectures to specific numbers of timeslots and rooms maximizing the overall quality of the timetable while taking various constraints into account. EM is a population-based stochastic global optimization algorithm that is based on the theory of physics, simulating attraction and repulsion of sample points in moving toward optimality. GD is a local search procedure that allows worse solutions to be accepted based on some given upper boundary or ‘level’. In this paper, the dynamic force calculated from the attraction-repulsion mechanism is used as a decreasing rate to update the ‘level’ within the search process. The proposed method has been applied to a range of benchmark university course timetabling test problems from the literature. Moreover, the viability of the method has been tested by comparing its results with other reported results from the literature, demonstrating that the method is able to produce improved solutions to those currently published. We believe this is due to the combination of both approaches and the ability of the resultant algorithm to converge all solutions at every search process.     

Crystal structure of 1-methyl-1,3,5,7-tetraazaadamantan-1-ium ammonium sulfate hydrate,a double salt containing puckered layers of hydrogen-bonded NH 4 + and SO 4 2− groups

The double salt [(CH₂)₆N₄CH₃](NH₄)SO₄·H₂O crystallizes in space groupP2₁/a, witha=12.994(2),b=6.319(1),c=15.082(2) Å, =93.78(2)^o, andZ=4. The structure was solved by the heavy-atom method and refined toR _F ²=0.051 for 2478 MoK data. The ammonium and sulfate ions are cross-linked by hydrogen bonds to form puckered layers disposed about the (001) family of planes. Each water molecule bridges a [(CH₂)₆N₄CH₃]⁺ ion and a sulfate group, so that the organic cations lying on both sides of a puckered layer have their methyl groups pointing inward and fitting into depressions. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82063 (18 pages).Carried out, in part, under contract DE-AC02-76CH00016 with the U.S. Department of Energy, Office of Basic Energy Sciences.