Shear band formation in IF steel during cold rolling at medium reduction levels

The mechanisms of shear band formation in IF steel after cold rolling to ～50% reductions have been investigated using transmission electron microscopy. The observations revealed that shear bands were always parallel to a second set of microbands, where these exist, and contained within individual crystals, indicating that shear banding is controlled by orientation. Crystallographic analysis revealed that shear banding involves two mechanisms, dislocation glide and rigid-body rotation. In the first step, dislocation glide causes a rotation about the 〈211〉 axis to produce the so called ‘S’ band, which gives the shear band its crystallographic character. In the second step, when the most heavily stressed slip plane parallel to the shear band is of the form {110}〈111〉, rigid-body rotation continues about the 〈211〉 axis in the sheared zone and, then, a rotation about the transverse direction (TD) is promoted by the geometry of the sample. Using rigid-body matrix theory, the calculated orientations of shear bands are shown to be in agreement with experimental observations. The process outlined is capable of explaining how slip processes in grains that contain microbands, using either {110} or {112} slip planes, can produce crystallographic shear bands.     

Hydrogenic systems,frequency standards and fundamental constants

Hydrogenic (two-body) systems are the only atomic systems for which uncertainties in calculations of the energy levels approach the current state of the art in frequency measurement. This article discusses progress in the theory and measurement of transition frequencies in hydrogenic systems. These studies have relevance to the determination of fundamental constants and the testing of physical theories, especially quantum electrodynamics. A set of high accuracy calculable frequency standards could also be realized by using hydrogenic systems.     

Dual extremum principles and the hypercircle for biharmonic problems

The canonical Euler-Hamilton theory is used to establish the connection between extremum principles and the hypercircle for a class of biharmonic problems. An illustration of the results is provided by calculations for a clamped plate.     

Direct sample fraction deposition using electrospray in narrow-bore size-exclusion chromatography/matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for polymer characterization

A direct sample fraction deposition method was developed for off-line size-exclusion chromatography (SEC)/matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry. By using electrospray, the SEC eluent, together with a suitable matrix solution added coaxially, was directly deposited on the MALDI plate. Owing to the formation of very small droplets in electrospray, solvent evaporation is much faster. The fractionation volume in narrow-bore SEC, which can directly be collected in one MALDI spot, can easily be optimized in the range of a few microlitres. In addition, fairly homogeneous sample spots were obtained. The possible influence of composition variation of the SEC effluent on the analytical results using direct fraction deposition was investigated; no substantial effects were observed. The applicability of the method was demonstrated by characterizing a broad poly(methyl methacrylate) sample. Copyright 2000 John Wiley & Sons, Ltd.     

Quantification of raf antisense oligonucleotide (rafAON) in biological matrices by LC-MS/MS to support pharmacokinetics of a liposome-entrapped rafAON formulation

An LC-MS/MS method was developed to quantify an antisense oligonucleotide against Raf-1 expression (rafAON) in monkey and mouse plasma and in mouse tissue homogenates from animals dosed with a liposome-entrapped rafAON easy-to-use formulation (LErafAON-ETU) intended for use as an antineoplastic agent. RafAON was extracted from mouse and monkey plasma using solid-phase extraction. Tissues were homogenized and sample cleanup was achieved by protein precipitation. RafAON and the internal standard (IS) were separated on a Hamilton PRP-1 column and quantified by tandem mass spectrometry using an electrospray source in negative ion mode. The total run time was 4.0 min. The peak areas of two rafAON transitions were summed and plotted against the peak area of an IS transition to generate the standard curve. In monkey plasma the linear range was 50-10,000 ng/mL, and in mouse plasma it was 25-5000 ng/mL. The lower limit of quantification was 500 ng/mL (10 microg/g tissue) in heart, kidney, liver, lung and spleen homogenates, and the standard curve was linear up to 10,000 ng/mL. Accuracy, precision and stability were evaluated and found to be acceptable in all three matrices. The assay was used to support pharmacokinetics and tissue distribution studies of LErafAON-ETU in mice and monkeys.