Linear Relaxations of the Capacitated Warehouse Location Problem

The capacitated warehouse location problem consists of the well known transportation problem with the additional feature of a fixed charge associated with each warehouse which is put to use. The problem is usually solved as a special type of mixed integer programme, so that relaxation and lower bounding are a vital part of any algorithm. A deeper insight into the relaxation process may eventually lead to more efficient algorithms for the problem. It is shown here that the LP relaxation of the capacitated warehouse location problem can incorporate constraints of a much more general nature than those previously described.     

Diffusion of Methanol in Polydimethylsiloxane

The permeation and sorption of methanol in polydimethylsiloxane at 10 and 30°C. has been measured and the results analyzed to determine the concentration dependence of the steady-state diffusion coefficient D which is found to decrease as the total concentration C is increased. An analysis of the isotherms indicates that clustering of the methanol occurs in the polymer, becoming more predominant as the concentration is increased. A polymerization model used to describe the shape of the D versus C curve for water in polydimethylsiloxane has been modified and applied with some success to describe the shape of the isotherm and the D versus C curve for methanol. The linearity of the permeation rate with relative pressure in this and a number of water—polymer systems is briefly commented on.     

Engineered biosynthesis of novel spinosyns bearing altered deoxyhexose substituents

Novel spinosyns have been prepared by biotransformation, using a genetically engineered strain of Saccharopolyspora erythraea, in which the beta-D-forosamine moiety in glycosidic linkage to the hydroxy group at C17 is replaced by alpha-L-mycarose.     

On DABAL-Me3 promoted formation of amides

The range and utility of DABAL-Me₃ couplings of methyl esters and free carboxylic acids with primary and secondary amines under a variety of conditions (reflux, sealed tube, microwave) has been compared for a significant range of coupling partners of relevance to the preparation of amides of interest in pharmaceutical chemistry. Commercial microwave reactors promote the fastest couplings and allow the use of significantly sterically hindered amines (primary and secondary) and carboxylic acids derivatives. The influence of microwave energy on the reaction system was shown to be typically related to thermal effects (over-pressuring and superheating).     

Sorption of alkanediols by silicalite-1

Isotherms for the sorption of linear alkanediols HO(CH₂) _n OH (n = 2, 4, 6, 8) from aqueous solution by silicalite-1 at 25° are reported.     

Solid-state 27Al NMR studies of aluminophosphate molecular sieves. Enhanced resolution by quadrupole nutation and double-rotation.

Solid-state 27Al NMR spectra of several aluminophosphate molecular sieves have been recorded with conventional magic-angle spinning (MAS), double-rotation (DOR) and quadrupole nutation with fast MAS. Enhanced resolution was obtained in the quadrupole nutation experiment at certain radiofrequency pulse strengths. This extra resolution can be comparable to that attainable using DOR, and does not introduce spinning sidebands.     

Branch-and-Bound Algorithms for a Regional Water Authority Distribution Problem

A problem put forward recently by a Regional Water Authority differs from the well-known Capacitated Warehouse Location Problem only in that there are both weeks of normal demand levels and weeks of peak demand levels. We describe how Lagrangian relaxation based branch-and-bound algorithms have been adapted for the new problem. Computational results are given, enabling a comparison of the different approaches tried.     

The reaction of N-carboalkoxy reissert analogs with carboxylic acids

The reaction of N-carboalkoxy Reissert analogs in the presence of carboxylic acids yields the corresponding ester and heterocyclic base. Use of methoxy substituted benzoic acids yields, instead of the ester, the respective anhydride. Amides can also be prepared in a similar fashion.