New derivatives of poly-hexafluoropropylene oxide from the corresponding alcohol

Poly-hexafluoropropylene oxide (poly-HFPO) alcohol was prepared by the reduction of the corresponding methyl ester using NaBH_4, NaBD₄, or LiAlH₄ (LAH). This alcohol is a versatile starting material for the preparation of additional interesting compounds. Because of its expected poor nucleophilicity, before attempting additional reactions, we have found it advantageous to prepare a corresponding salt. We have found that the resulting salt behaved like a normal hydrocarbon alkoxide. The reaction of this salt with either acetyl chloride or allyl chloride (or bromide) gave the expected products which proved to be normal nucleophilic substitutions. In addition, the bromination of the allyl ether was studied using NMR and GC/MS techniques.     

Zur volumetrischen Bestimmung des Broms neben Chlor und Jod

Ohne Zusammenfassung     

Transitive parabolic unitals in semifield planes

Every semifield plane with spread in PG(3,K), where K is a field admitting a quadratic extension K⁺, is shown to admit a transitive parabolic unital. The author gratefully acknowledges helpful comments of the referee in the writing of this article.     

Large quartic groups on translation planes,II—Even order: Characterization of the Ott‐Schaeffer planes

A general theory of collineation groups generated by quartic groups of even order is considered. Applications are given to collineation groups generated by ‘large’ quartic groups. © 2005 Wiley Periodicals, Inc. J Combin Designs 13: 195–210, 2005.     

A Quantitative Method for Determining Proper Job Rotation Intervals

Job rotation is a useful tool that can be used in many work settings to produce task variety for workers and to reduce worker fatigue and injuries. Developing a job rotation plan requires determining the set of jobs to be included in the rotation, the rotation sequence, and the proper length of the rotation interval. Previous research has considered both the jobs to include in a rotation plan and how to sequence the rotation plan but no work has been conducted to quantitatively examine different rotation interval lengths. Using different rotation interval lengths may result in different stresses for the workers performing a particular set of tasks and therefore affect the quality of the job rotation implementation. This paper proposes a quantitative method based on mathematical programming to obtain a proper job rotation interval length. The merit of the method is determined by examining its effectiveness in reducing worker stress and the potential for injury as well as its applicability for use in real settings.