Removal of sample background buffering ions and myoglobin enrichment via a pH junction created by discontinuous buffers in capillary electrophoresis

Traditional CE sample stacking is ineffective for samples containing a high concentration of salt and/or buffer. We recently reported the use of a discontinuous buffer system for protein enrichment that was applicable to samples containing millimolar concentrations of salt. In this paper, the technique was investigated for samples containing unwanted buffering ions, including TRIS, MES, and phosphate, which are commonly used in biological sample preparation. Using myoglobin as a model protein, the results demonstrated that background buffering ions can be effectively removed or separated from the enriched protein. The key is to use either the acid or the base of the discontinuous buffers to adjust the pH of the sample, such that the net charge of the unwanted buffering ions is near-zero. The successful isolation and enrichment of myoglobin from up to 100 mM TRIS and 50 mM MES was demonstrated. The enrichment factors remained at approximately 200. Removal of phosphate was more challenging because its net charge was anionic in both the acid and the base of the discontinuous buffers. The enrichment was only achievable up to 30 mM of sodium phosphate, the enrichment factors observed were significantly lower, below 50, and the process was delayed due to the higher ionic strength resulted from phosphate. The migration of phosphate during enrichment was studied using a UV-absorbing analogue, phenyl phosphate. In addition, Simul 5.0 was used to simulate the discontinuous buffers in the absence and presence of TRIS and phosphate. The stimulated TRIS and phosphate concentration profiles were generally in agreement with the experimental results. The simulation also provided a better understanding on the effect of phosphate on the formation of the pH junction.     

Small Form Factor Fiber Optic Transceiver Module for High-end SONET/SDH Application

2.5Gb/s SONET/SDH applications with reach up to 80km in standard SMF fiber, is presented. Introduction Due to the trend towards higher port densities in high-capacity communication systems,Small Form Factor (SFF) Transceivers are becoming popular [1]. Originally, SFF transceivers were designed to address short reach (2km) and intermediate reach(15km) applications using PIN receivers [2]. We have developed SFF transceivers for the high-end SONET/SDH space (2.5Gb/s speed for 40km and 80km reach). This part of the SONET/SDH space is unique due to the need for Avalanche Photo Diode (APD) based receiver within a SFF footprint, and still maintaining a good transceiver performance is a real challenge.     

An efficient method of analysis for the drained and undrained behaviour of an elastic soil

In this paper a method of analysis for the drained and undrained behaviour of a saturated soil with an elastic anisotropic skeleton is proposed. The method depends upon embedding the problem in a series of problems depending upon a parameter, then expanding the solution in terms of that parameter. The method has the advantage that both the drained and undrained behaviour can be found simultaneously and the problems of a singular stiffness matrix usually associated with undrained behaviour of an elastic soil is avoided.     

The divergence from Gaussian of peak shapes in gamma-ray spectra observed with germanium detectors

A formula for the fitting of gamma-ray peaks produced from solid state detectors is suggested, which takes account of possible distortion from a pure Gaussian shape. Comparative analyses of peaks using the formula, and an assumed Gaussian shape are presented showing the improvement in the fitting. When accurate peak energies are required in order to identify unknown nuclides, it is recommended that the expression provided is used, since the calculated peak positions are influenced by the extent of the distortion present.     

Quadratic class numbers and character sums

We present an algorithm for computing the class number of the quadratic number field of discriminant . The algorithm terminates unconditionally with the correct answer and, under the GRH, executes in steps. The technique used combines algebraic methods with Burgess' theorem on character sums to estimate . We give an explicit version of Burgess' theorem valid for prime discriminants and, as an application, we compute the class number of a 32-digit discriminant.

     

Elasto-plastic consolidation of soil

A theory of the behaviour of an ideal mass of two-phase soil is developed. This theory unites the usually separately considered aspects of analytical soil mechanics of settlement and deformation; time dependent consolidation; and yielding leading to collapse of the mass. The theory assumes the soil to be an elasto-plastic permeable material and a finite element approximation of the resulting equations is derived through the principle of virtual work. Two example problems are treated numerically.