Computer-assisted method development and optimization in high-performance liquid chromatography

This paper reports the use of DryLab, a computer simulation software package, to assist in the development and optimization of a reversed-phase high-performance liquid chromatographic (HPLC) method for the separation of a model drug candidate and its degradation products. Prior to the optimization process, columns with various bonded phases are evaluated for their chromatographic performance using the sample of interest. Simultaneous optimization of two separation variables and the use of resolution maps to predict the optimal conditions are illustrated. Options to optimize column conditions (column length and flow-rate) to further reduce run time are briefly discussed. The accuracy of DryLab-predicted retention times and resolution is compared with experimental values. The DryLab software used in this study provided satisfactory predictions for the selected model, with average errors of less than 3.5 and 11.8% for retention time and resolution, respectively.     

Measurements of two-dimensional densities for a bistable device driven by colored noise

We have constructed an electronic circuit which accurately mimics the dynamics of a nonequilibrium, bistable flow driven by additive, exponentially correlated, Gaussian noise. The noise voltage and voltages representing the velocity and displacement were measured, digitized and then assembled into the stationary, statistical densitiesW(V _n ,X) andW for several noise intensities and correlation times. Our measurements are in good agreement with the theoretical results of Jung and Risken described in the preceeding paper.     

A review of III-nitride research at the Center for Quantum Devices

In this paper, we review the history of the Center for Quantum Devices’ (CQD) III-nitride research covering the past 15 years. We review early work developing III-nitride material growth. We then present a review of laser and light-emitting diode (LED) results covering everything from blue lasers to deep UV LEDs emitting at 250 nm. This is followed by a discussion of our UV photodetector research from early photoconductors all the way to current state of the art Geiger-mode UV single photon detectors.