Multiple bonding versus cage formation in organophosphorus compounds: the gas-phase structures of tricyclo-P3(CBu(t))2Cl and P≡C-Bu(t) determined by electron diffraction and computational methods

The gas-phase structures of tricyclo-P(3)(CBu(t))(2)Cl and P≡C-Bu(t) have been determined by electron diffraction and associated quantum chemical calculations. Efforts to obtain detailed solid-state data for tricyclo-P(3)(CBu(t))(2)Cl have been thwarted by inability to prepare suitable crystalline material. Additional calculations for another tricyclic isomer of P(3)(CBu(t))(2)Cl and for two phosphorus-containing cyclopentadiene derivatives with pseudo-planar five-membered rings show that the experimentally observed isomer is more stable by at least 52 kJ mol(-1). Calculations for the equivalent structures with P atoms replaced by CH fragments have demonstrated that a ring structure is more favourable by over 200 kJ mol(-1) compared to each of two cage structures.     

Scheduling patrol boats and crews for the Royal Australian Navy

The Royal Australian Navy's Patrol Boat Force carries out essential tasks in the surveillance, policing and defence of Australia's coastal waters. To help the Navy make efficient use of a new generation of boats, the authors have developed optimization procedures to schedule the activities of the boats and their crews. The procedures—embodied in a software system called CBM (‘Crews, Boats, Missions’)—use simulated annealing and specialized heuristic techniques within a multi-stage problem-solving framework. Tests show that CBM is reliable in terms of solution quality, and flexible with respect to the range of scheduling conditions applied. CBM has proved valuable to the Navy as an investigatory tool, and it is planned that it should be adapted for operational use, as part of a decision support system to aid in the ongoing management of patrol boat operations.     

High performance liquid chromatographic evaluation of artemisinin,raw material in the synthesis of artesunate and artemether

A barrier to the development of artemisinin derivative based combination treatment of malaria is the lack of defined specifications and purity test methods for the raw material artemisinin. An HPLC method previously published in the International Pharmacopoeia to evaluate purity of artemisinin as an active pharmaceutical ingredient is adapted for use. Excellent method precision and linearity are demonstrated along with observations of robustness. In support of the development of specifications major impurities are identified using high resolution HPLC–MS, isolation via preparative HPLC followed by NMR. The identified impurities differ from those previously claimed.     

Cardiac sarcoplasmic reticulum and sarcolemmal proteins separated by two-dimensional electrophoresis: surfactant effects on membrane solubilization

We evaluated the use of the alkyaryl amidosulfobetaine zwitterionic detergent, designated as C8psi, to facilitate the solubilization of cardiac subcellular, membrane-associated proteins. Hearts from 7-week-old male Sprague-Dawley rats were isolated, and the left ventricles dissected and subsequently homogenized. The sarcolemma (SL) and the sarcoplasmic reticulum (SR) were isolated from different homogenate preparations originating from rat hearts by ultracentrifugation methods. The isolated membrane preparations were solubilized and the proteins precipitated. After resuspension, protein separation was achieved in first-dimensional IEF using an immobilized (pH 4-7) gradient and in the second dimension using 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Gels were then stained, images analyzed, and protein spots excised for subsequent identification. Protein identification from both SR and SL samples did not identify any of the known major membrane-associated proteins. Solubilization of whole tissue lysates with C8psi resulted in no increase in the total number of proteins detected relative to samples solubilized in the presence of 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulforate (CHAPS). The data suggest the utility of newer surfactants such as C8psi to improve both the resolution of (2-D) protein profiles and increase the number of proteins extracted from subcellular organelle fractions.     

Solving Vehicle Routing Problems Using Constraint Programming and Metaheuristics

Constraint Programming typically uses the technique of depth-first branch and bound as the method of solving optimization problems. Although this method can give the optimal solution, for large problems, the time needed to find the optimal can be prohibitive. This paper introduces a method for using local search techniques within a Constraint Programming framework, and applies this technique to vehicle routing problems. We introduce a Constraint Programming model for vehicle routing, and a system for integrating Constraint Programming and local search techniques. We then describe how the method can be accelerated by handling core constraints using fast local checks, while other more complex constraints are left to the constraint propagation system. We have coupled our local search method with a meta-heuristic to avoid the search being trapped in local minima. Several meta-heuristics are investigated ranging from a simple Tabu Search method to Guided Local Search. An empirical study over benchmark problems shows the relative merits of these techniques. Investigations indicate that the specific long-term memory technique used by Guided Local Search can be used as a diversification method for Tabu Search, resulting in significant benefit. Several new best solutions on the Solomon problems are found in relatively few iterations of our algorithm.     

BUDI: A Software System for Bus Dispatching

A software system is described for the dispatching of buses of different types operated by a public transport organization. The system uses simulated annealing to improve the desirability of the total allocation while satisfying a number of ‘hard’ dispatching constraints.     

Nucleophilic substitution reactions of the tricyclic triphosphorus cage P3(CBu(t))2: a novel route to polyphosphorus phosphenium complexes

Substitution of Cl(-) in the tricyclic triphosphorus cage Cl(P(1))-P3(CBu(t))2 by a range of both anionic and neutral nucleophiles has been investigated. With anionic nucleophiles, reaction with fluoride and hydride anion was shown to afford F(P(1))-P3(CBu(t)) and H(P(1))-P3(CBu(t))2 respectively. Subsequent deprotonation of the latter results in the formation of the aromatic anion [1,2,4-P3(CBu(t))2]-. With neutral nucleophiles, addition of either PMe3 or PEt3 to Cl(P(1))-P3(CBu(t))2 in the presence of TlOTf results in the formation of the phosphine-phosphenium complexes [(R3P(P(1))-P3(CBu(t))2][OTf] (R = Me or Et): the structure of the methyl-substituted compound was determined by a single crystal X-ray diffraction study. The phosphine ligand in these complexes is extremely labile and addition of I2 to [(Me3P(P(1))-P3(CBu(t))2]+ results in the formation of I(P(1))-P3(CBu(t))2.