A posteriori error indicators for Maxwell''s equations

In this paper we shall analyze a class of a posteriori error indicators for an electromagnetic scattering problem for Maxwell's equations in the presence of a bounded, inhomogeneous and anisotropic scatterer. Problems of this type arise when computing the interaction of electromagnetic radiation with biological tissue. We briefly recall existence and uniqueness theory associated with this problem. Then we show how a posteriori error indicators can be derived using an adjoint equation approach. The error indicators use both the jump in normal and tangential components of the field across faces in the mesh.     

Microchemical methods in radiochemical analysis : Determination of chemical yields by micro-coulometry

Methods are described for the micro-coulometric determination of several elements using the Reilley and Porterfield method of generating EDTA by electrolysis of its mercuric chelate. The determination is carried out in a volume of about 1 ml of electrolyte and polarized mercury electrodes are used to detect the end-point. 0.025–0.5 μequiv. of many elements can be determined using an ammoniacal electrolyte at pH 10.5 or an acetate buffer at pH 5.5. The method is designed for determining chemical yields of radiochemical procedures using 100–1000-μg amounts of carriers.     

Optical fiber-based biosensors

This review outlines optical fiber-based biosensor research from January 2001 through September 2003 and was written to complement the previous review in this journal by Marazuela and Moreno-Bondi. Optical fiber-based biosensors combine the use of a biological recognition element with an optical fiber or optical fiber bundle. They are classified by the nature of the biological recognition element used for sensing: enzyme, antibody/antigen (immunoassay), nucleic acid, whole cell, and biomimetic, and may be used for a variety of analytes ranging from metals and chemicals to physiological materials.     

Microanalysis of unusual compounds. II

Summary Methods are described for the determination of carbon, hydrogen and nitrogen in highly explosive organo-metallic nitrate and perchlorate salts using Coleman analysers. Under no circumstances should these samples be heated in the combustion furnace unless they are well mixed with copper oxide or cobalt oxide.

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Zusammenfassung Verfahren zur C-, H- und N-Bestimmung in hochexplosiven metallorganischen Nitraten und Perchloraten mit Hilfe eines Coleman-Analysators wurden beschrieben. Solche Proben dürfen unter keinen Umständen im Verbrennungsofen erhitzt werden, bevor man sie gut mit Kupferoxid oder Kobaltoxid vermischt hat.

     

Fabrication of gold microtubes and microwires in high aspect ratio capillary arrays

In this communication, we describe the sequential deposition of materials in capillaries as a means to produce self-assembled three-dimensional gold microtubes, hollow gold microwires, and microtube and microwire arrays with unprecedented aspect ratios. The initial application of this technique is the fabrication of an array of microwires within a silica capillary array. The physical characteristics of these microwires are characterized via SEM, electrochemistry, and electrogenerated chemiluminescence emission.     

The use of microchemical methods in radiochemical analysis

Techniques used at A.W.R.E. during the past 6 years for the radiochemical analysis of mixtures of active nuclides using 0.5- to 1-mg quantities of carrier are described and their advantages discussed. Micro-methods are listed for chemical yield determinations by spectrophotometry and micro-titration, and details are given for the micro-titration of a number of elements with EDTA, using a spectrophotometric end-point. A special fitment is described to enable the Unicam SP600 spectrophotometer to be used for micro-titrations. Some values are given for the coefficients of variation obtained in typical chemical yield methods and in overall radiochemical déterminations of ⁹⁹Mo, ¹¹¹Ag, ¹¹⁵Cd and ¹⁴⁰Ba.     

Superconvergence of finite element approximations to Maxwell's equations

We study superconvergence of edge finite element approximations to the magnetostatic problem and to the time-dependent Maxwell system. We show that in special discrete norms there is an increase of one power in the order of convergence of the finite element method compared to error estimates in standard Sobolev norms. Our results are restricted to an orthogonal grid in R ³, but the grid may be nonuniform. © 1994 John Wiley & Sons, Inc.