Two new diastereomeric chiral stationary phases (CSPs) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as a chiral tethering group and a Π-basic chiral unit such as (R)-1-(1-naphthyl)ethylamine (CSP 1) or (S)-1-(1-naphthyl)ethylamine (CSP 2) were prepared. The two CSPs were applied to the enantiomeric separation of N-(3,5-dinitrobenzoyl)-1-phenylalkylamines and N-(3,5-dinitrobenzoyl)-α...

PURPOSE To evaluate the dimensional accuracy of several impression methods including agar alginate combined impression in vivo; the marginal accuracy of stone dies was determined using a new electroformed master crown technique. MATERIALS AND METHODS Cast cores with knife-edge and chamfer margins and electroformed master crowns were fabricated for 3 patients. Five impressions were taken of ea...

A facile procedure is described for the preparation of [ "C]epicholesterol from [ '*C]cholesteroL Cholesterol is first converted to cholesteryl mesylate, which is treated with cesium acetate and 18-crown-6 in refluxing toluene to give epicholesteryl acetate. The latter is hydrolyzed, without isolation, with potassium hydroxide in tetrahydrofuran-methanol to give epicholesterol, which is obtaine...

UNLABELLED The failures of root canal preparation are due to some anatomical deviation (canal in "C" or "S") and some technique errors. The technique errors are usually present in canal root cleansing and shaping stage and are the result of endodontic treatment objectives deviation. OBJECTIVES Our study was made on technique errors while preparing the canal roots with hand ProTaper. METHODO...