Glass microfluidic devices with thin membrane voltage junctions for electrospray mass spectrometry

In this study a novel glass membrane was prepared for conducting high voltage (HV) to solution in the channel of a microfabricated device for generation of liquid electrospray. Taylor cone formation and mass spectra obtained from this microdevice confirmed the utility of the glass membrane, but voltage conduction through the membrane could not be successfully explained based solely on the conductivity of the glass itself. This novel method for developing a high-voltage interface for microdevices avoids direct metal/liquid contact eliminating bubble formation in the channel due to water hydrolysis on the surface of the metal. Further, this arrangement produces no dead volume as is often found with traditional liquid junctions. At the same time, preliminary investigations into the outlet design of glass microdevices for interfacing with electrospray mass spectrometry, was explored. Both the exit shape and the use of hydrophobic coatings at the channel exit of the microdevice electrospray interface were evaluated using standard proteins with results indicating the utility of this type of design after further optimization.     

Attitudes and Perceptions Relating to Implementation and Success in Operational Research

This paper presents a study of a group of O.R. projects. The major emphasis of the research was on a comparison of both the managers' and the O.R. practitioners' perceptions and attitudes. The results show a large amount of agreement between the two groups, and the main disagreement concerned their confidence in the solution. A principal component analysis of the data followed by an orthogonal rotation produced a set of eight principal factors. These were then used for a regression analysis having implementation and success as dependent variables. The results indicate that major differences are seen in the relationship of the dependents to the factors when analysed separately for managers and practitioners. Most of the variance in the implementation score of practitioners is ‘explained’ by attitudinal variables, but this is not true for managers. Implications of the research for this Churchman/Schainblatt concept of "mutual understanding" are suggested.     

Synthesis and application of phosphonothioates,phosphonodithioates, phosphorothioates,phosphinothioates and related compounds

Methods for the preparation of phosphonothioates, phosphonodithioates, phosphorothioates, phosphinothioates and related compounds are reviewed. The application of these compounds as synthetic intermediates is also discussed.     

Developments in the Coordination Chemistry of Dicoordinate Phosphenium Ion Ligands

Abstract

Phosphenium ion ligands display synergic [sgrave]-donor, σ-acceptor properties which resemble other small molecules and the coordination chemistry of X₂P⁺ ligands is compared here with NO and SO₂.     

Solving free surface fluid flow problems by the minimal kinetic energy functional

In this paper a more accurate minimization technique, namely the minimal kinetic energy method, is developed and used to investigate the free surface fluid flow caused by an obstacle on the bottom of a channel whose exact shape and location are unknown a priori. The fluid flow is assumed to be two‐dimensional, steady, inviscid, incompressible, irrotational and under the effect of the gravitational force. The minimization technique is based on the combination of the boundary integral method and the variational principle technique. This technique is extensively used in identifying unknown bottom surfaces. To illustrate this technique the free surface profile to be applied in the inverse analysis has been generated following a direct formulation when the solid bottom boundary possesses a double hump/double depression, a hump in front of a step, and a depression and a hump in front of a step. For all problems considered, the numerical results are in excellent agreement with the known analytical solution. In fact the computed profiles for both the bottom and free surfaces are graphically indistinguishable from the analytical results. Copyright © 2001 John Wiley & Sons, Ltd.     

Rotating ellipses of varying shape

This article describes an investigation carried out while the second author was an undergraduate. The article gives an account of the way the work evolved, to give insight into the learning processes, as well as the mathematical issues encountered.     

Transient Free Convection from a Horizontal Surface in a Porous Medium Subjected to a Sudden Change in Surface Heat Flux

This paper presents an analytical and numerical study of transient free convection from a horizontal surface that is embedded in a fluid-saturated porous medium. It is assumed that for time steady state velocity and temperature fields are obtained in the boundary-layer which occurs due to a uniform flux dissipation rate q ₁ on the surface. Then, at the heat flux on the surface is suddenly changed to q ₂ and maintained at this value for . Firstly, solutions which are valid for small and large are obtained. The full boundary-layer equations are then integrated step-by-step for the transient regime from the initial unsteady state ( ) until such times at which this forward marching approach is no longer well posed. Beyond this time no valid solutions could be obtained which matched the final solution from the forward integration to the steady state profiles at large times .