An EXAFS study of dopant substitution in LiNbO3 and LiTaO3

Abstract

We report an EXAFS study of Co and Fe doped LiNbO₃ and LiTaO₃. Our results show that the dopant ions occupy Li sites in both materials.     

Theoretical analysis of dehumidification process in a desiccant wheel

A mathematical model based on the one-dimensional Navier–Stokes equation is described. The current model is capable of predicting the transient and steady-state transport in a desiccant wheel. It reveals the moisture and temperature in both the airflow channels and the sorbent felt, in detail, as a function of time. The predicted results are validated against the data taken from experimental results, with reasonable accuracy. Therefore, the numerical model is a practical tool for understanding and accounting for the complicated coupled operational process inside the wheel. Consequently, it is useful for parameter studies. As a demonstration of its utility, the model is employed to study the effect of felt thickness and passage shape on the performance of a desiccant wheel.     

New Reagents for the Reductive Quenching of Ozonolysis Reactions

3,3′-Thiodipropionic acid and its salts were found to be effective reductive quench reagents in the ozonolysis of olefins. They were as effective as methyl sulfide without its drawbacks. A polymer-bound form of 3,3′-thiodipropionic acid was also effective.     

Robotic solid phase extraction and high performance liquid chromatographic analysis of ranitidine in serum or plasma.

A fully automated assay for the analysis of ranitidine in serum and plasma, with and without an internal standard, was validated. It utilizes robotic solid phase extraction with on-line high performance liquid chromatographic (HPLC) analysis. The ruggedness of the assay was demonstrated over a three-year period. A Zymark Py Technology II robotic system was used for serial processing from initial aspiration of samples from original collection containers, to final direct injection onto the on-line HPLC system. Automated serial processing with on-line analysis provided uniform sample history and increased productivity by freeing the chemist to analyse data and perform other tasks. The solid phase extraction efficiency was 94% throughout the assay range of 10-250 ng/mL. The coefficients of variation for within- and between-day quality control samples ranged from 1 to 6% and 1 to 5%, respectively. Mean accuracy for between-day standards and quality control results ranged from 97 to 102% of the respective theoretical concentrations.     

Adsorption of water on clean aluminum by measurement of work function changes

Clean surfaces were produced on bulk aluminum samples by a new cutting procedure inside an ultra-high vacuum system. This cutting technique made it possible to stabilize the reference electrode of a vibrating capacitor by equilibration with the gas. Adsorption of water on the clean surfaces was studied by following changes in the work function of the surface at various temperatures and water vapor pressures. Water chemisorbed on the aluminum causing a work function change of − 1.4 V at one monolayer. The rate and amount of chemisorption were negatively dependent on temperature. The characteristics of the work function changes lead to the conclusion that the water chemisorbs by a precursor mechanism.