A new preparation of samarium dibromide and its use in stoichiometric and catalytic pinacol coupling reactions

A new convenient preparation of samarium dibromide in THF is reported. Pinacol coupling reactions using SmBr₂ in catalytic amounts together with mischmetall as a coreductant have been performed with a variety of carbonyl compounds.     

Response of circular plates to central pulse loading

An analysis is presented for the response of a clamped circular plate subjected to a rectangular pulse uniformly distributed over a central circular area. The plate is rigid-perfectly plastic with yielding according to the Johansen criterion and the associated flow rule. Bending is assumed to be the predominant response. Simple formulas are obtained for the permanent central deflection for all pressures and loaded areas.     

Spectrophotometric determination of calcium in soil extracts with calcichrome

A simple direct method is presented for the spectrophotometric determination of calcium in hydrochloric acid soil extracts. The chromugenic agent used is Calciehrome (self-coupled diazotized H-acid), and the method covers the range 4 to 175 μg of calcium. A comprehensive study of interferences has been carried out. and a cation-exchange procedure described for the preliminary separation of large amounts of phosphate.     

Polymeric particulates to improve oral bioavailability of peptide drugs

Oral administration remains the most convenient way of delivering drugs. Recent advances in biotechnology have produced highly potent new molecules such as peptides, proteins and nucleic acids. Due to their sensitivity to chemical and enzymatic hydrolysis as well as a poor cellular uptake, their oral bioavailability remains very low. Despite sophisticated new delivery systems, the development of a satisfactory oral formulation remains a challenge. Among the possible strategies to improve the absorption of drugs, micro- and nanoparticles represent an exciting approach to enhance the uptake and transport of orally administered molecules. Increasing attention has been paid to their potential use as carriers for peptide drugs for oral administration. This article reviews the most common manufacturing methods for polymeric particles and the physiology of particle absorption from the gastrointestinal (GI) tract. In a second part, the use of polymeric particulate systems to improve the oral absorption of insulin is discussed.     

Poisson integrals associated to Dunkl operators for dihedral groups

In this paper we study the boundary behavior of Poisson integrals associated to Dunkl differential-difference operators for dihedral groups and the boundary integral representations for functions on the unit disc of annihilated by the Laplace operator corresponding to these differential-difference operators.