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N M Jones

Publications and source records attributed to N M Jones.

20 records · Page 2Linked to original sources
PubMedDate not supplied

A meta-analysis of clinical trials involving different classifications of response into ordered categories.

Statistical methods are available for performing a meta-analysis when the response variable of interest is the same in each study. Problems arise when studies exploring a common therapeutic question use different patient response types. This article presents statistical methods for combining studies which involve different classifications of response into ordered categories. The assumptions required for the stratified proportional odds model, on which the analysis is based, are discussed. The approach is illustrated using results from a series of studies investigating the prevention of gastrointestinal damage induced by non-steroidal anti-inflammatory drugs.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMedDate not supplied

Comparison of methods for extraction of tobacco alkaloids.

Ultrasound and microwave techniques were used to extract tobacco alkaloids, and response surface methodology was used to optimize extraction conditions. Ultrasonic technique factors were temperature, 30-85 degrees C; time, 3-45 min; solvent volume, 8-80 mL. Microwave extraction factors were pressure, 15-75 psi; time, 3-40 min; power, 30-90% of the maximum magnetron power of 650 W. Soxhlet and solvent AOAC-modified extraction methods were also applied after some improvements. Nicotine, nornicotine, anabasine, and anatabine were quantified by gas chromatography. A steam distillation International Standards Organization method for total alkaloid evaluation was used as reference. The results obtained by the different methods were compared using a least squares deviation test. The ultrasonic and the proposed modified-AOAC extraction method were the more convenient with regard to practicability and precision. The relative deviations (n = 5) were as follows: For the ultrasonic method in low-level alkaloid tobaccos, 0.7% nicotine and 1.4-14% minor alkaloids; in high-level alkaloid tobaccos, 2.4% nicotine and 4.5-5.1% minor alkaloids. For the modified AOAC method in low-level alkaloid tobaccos, 0.9% nicotine and 2.4-11.6% minor alkaloids; and in high-level alkaloid tobaccos, 1.7% nicotine and 2.0-2.4% minor alkaloids.

Alkaloids↗