Some design considerations in miniaturized electrokinetic separation systems

There is a great potential for miniaturized analytical separation systems, e.g. in process control, environmental monitoring, or clinical chemistry. Particularly, miniaturized electro-driven systems open many new possibilities. Most efforts in this area have been focused on cylindrical capillary columns. In the present paper, thin rectangular conduits are considered and comparisons with cylindrical tubes are made on the basis of theoretical models. A critical and limiting factor in electro-driven separations is the generation of heat. For a given cross-section, heat dissipation is more efficient in rectangular columns. Silicon is proposed as column material. Apart from the better thermal conductivity, monocrystalline silicon can be machined with an extraordinary precision when selective chemical etching procedures are employed. This precision is of central importance in the development of miniaturized high performance systems.     

Fast-neutron analysis at the Swedish Defence Research Agency

A fast-neutron analysis (FNA) system is being developed at the Swedish Defence Research Agency. The experimental set up, consisting of a SODERN Genie 16 (D-T) 14 MeV neutron generator, a HPGe-detector, a neutron monitor detector and related electronics, is described in some detail. Results from preliminary measurements on bulk samples containing mainly carbon and nitrogen are presented. Finally future objectives are discussed.     

A new approach to reduction of the Neumann problem in acoustic scattering to a non-hypersingular integral equation

The Neumann problem for the propagative Helmholtz equation inthe exterior of several bodies (obstacles) is studied in twoand three dimensions by a special modification of the boundaryintegral equation method. This modification can be called the'method of interior boundaries', because additional boundariesare introduced inside scattering bodies. The solution of theproblem is obtained in the form of a single layer potentialon the whole boundary. The density in the potential satisfiesthe uniquely solvable Fredholm equation of the second kind andcan be computed by standard codes. In fact our method holdsfor any positive wave numbers.     

Relaxation processes in supercooled confined water and implications for protein dynamics

We show that the viscosity-related main (alpha) relaxation of confined water vanishes at a temperature where the volume required for the cooperative alpha relaxation becomes larger than the size of the geometrically confined water cluster. This occurs typically around 200 K, implying that above this temperature we observe a merged alpha-beta relaxation, whereas below it only a local (beta) relaxation remains. This also means that such confined supercooled water does not exhibit any true glass transition, in contrast to other liquids in similar confinements. Furthermore, it implies that deeply supercooled water in biological systems, such as membranes and proteins, generally shows only a local beta relaxation, a finding of importance for low temperature properties of biological materials.     

Clinical use of laboratory thyroid tests and investigations.

Laboratory thyroid testing involves in vitro tests for autoimmune thyroid disease, thyroid dysfunction and neoplasia, in vivo investigations of thyroid function, and investigations of thyroid morphology. The authors describe, in tabular form, the diagnostic information carried by the tests and their clinical utility as well as clinically relevant interferences.     

A new approach to dynamic deactivation in capillary zone electrophoresis

This paper describes a simple means of obtaining high resolution separations of basic proteins at a pH below their pl. Small amounts of a cationic fluorosurfactant are added to the running buffer. A positively charged wall is thereby obtained which will repel positively charged proteins. The particular chemistry of fluorosurfactants is believed to enhance the efficiency of the deactivation. Examples are presented of the separation of some model proteins, including a human insulin-like growth factor (IGF-I), and a misfolded by-product of the growth factor.